Implementation of GIS to Palm Oil Plantation Management in Indonesia
Abstract
Palm oil plantations are a major commodity producer with Indonesia currently being the world’s second-largest producer of crude palm oil (CPO) after Malaysia. Together these two countries account for 84% of total world production and 88% of global exports (Guerin 2006). The demand for palm oil is increasing significantly, both locally and for export resulting in further land clearing and conversion of existing plantations over extensive areas of Sumatra and Kalimantan. Typically, palm oil plantations include production areas requiring supporting infrastructure such as buildings, roads and services. To better control the associated resources and assets, GIS is considered to be an essential tool for effective management. The implementation of this technology is only slowly emerging in the Indonesian plantation industry. This paper considers the information requirements of plantation management, and GIS integration to include the following: mapping, infrastructure, production planning, and control analysis for several plantations at various stages of development. Due to the dynamic nature of plantation development, information needs change during the life cycle of the crop and this has been taken into account in this paper. Reference is made to the success of applying GIS technologies to several plantation projects in Sumatra, Indonesia.
INTRODUCTION
This study investigates the implementation of GIS to palm oil plantation management in Indonesia. The benefits of GIS for resource management are relatively well known when discussing the applications of this technology and this paper focuses on GIS applications in a specialised sector within resource management – palm oil plantations. This study involves the development of a GIS for several palm oil estates with the aim of improving plantation and production management.
GIS was applied to three plantations in Sumatra, Indonesia. Two estates are located in North Sumatra, Kwala Pasilam Lat 3.88295° Long 98.39210° and Balai Gajah Lat 3.94478° Long 98.40240° and Rimba Sawang Lat 4.12212° Long 98.00160° in Aceh Tamiang, Aceh. The palm oil plantation industry is a significant resource in Indonesia. In 2004 palm oil plantations covered 5.2 million Ha and many predict that to date the total area of palm oil has exceeded 6 million Ha (Ardiansyah 2006). It is estimated that Sumatra accounts for 70% of the total planted area (Savitry). Indonesia is currently the world's second-largest producer of crude palm oil (CPO) after neighbouring Malaysia. Together, the two Southeast Asian countries account for 84% of total world production and 88% of global exports (Guerin 2006). The increasing demand for palm oil has placed pressure on land conversion of existing plantations, increasing production yields, and further land clearing of new areas. Although Malaysia produces the majority of world exports of CPO, Indonesia is projected to become the number one producer in the next few years. Demand for this commodity continues to rise due to the unparalleled productivity of the oil palm seed, the most productive of all oil seeds in the world, combined with its multiple uses and its biofuel potential.
Palm oil is used for a variety of purposes, as an ingredient in food products, engine lubricants, as a base for cosmetics and in the manufacture of high grade soaps and detergents. Palm oil is a source of one of the raw materials in biodiesel, a diesel-equivalent processed fuel derived from biological sources which can be used in unmodified diesel-engine vehicles. With soaring crude oil prices and few harmful emissions compared to petroleum based fuels, Asian palm oil producers see huge opportunities for the future as global demand for biofuels surge.
NEED FOR A GIS SYSTEM
Geo-Information Technologies (GIT) provide an important tool for the management of plantations. Prior to the introduction of global positioning systems and geographic information systems, data obtained in the field was difficult to obtain and in many cases inaccurate. Typical examples include plantation boundaries varying from government permits, and applied production areas different from actual. This has been a result of the problems in measurement and mapping of difficult terrain and remote, inaccessible locations. Furthermore, plantation management has to consider the changing nature of an estate that extends from initial land clearing, the production stage and finally the re-planting or conversion phase. GIS differs from traditional methods to provide alternative tools which can monitor and analyse data. By creating a GIS, plantation and production can be more efficiently and effectively managed to increase profitability.
Mapping :
Estate boundaries :- typically boundaries are not well defined and mapped. Traditional mapping used the optical distance method. This is now considered to be unsuitable because of the inaccuracies in this form of measurement and is being replaced by GPS systems. With the availability of the latter equipment, accurate verification of estate boundaries can be made, typically revealing discrepancies and areas occupied by others.
Divisions, blocks (planting) :- Plantation management requires accurate information of estate divisions (afdeling), blocks (planting areas) for control purposes. Typically, budgets and production estimates are determined based on division and block areas. Subsequently, accurate data for production areas is necessary.
Infrastructure, (roads, bridges, buildings) :-.The location of infrastructure is essential for planning and logistical purposes. Palm plantations require extensive road networks for collection of production. In the development stage, access roads and culverts to bridge streams are required to be built. GIS is used to effectively manage these facilities.
Spatial Management :
Mapping of an estate is fundamental to the GIS system. Following mapping of the estate, data can be analysed to quantify and qualify plantation resources. This data can easily be classified into year of planting, age, type of crop, administrative zones and size with the GIS software.
Data Management :
Due to the dynamic nature of a plantation site, from initial land clearing, growing stage through to replanting, it is important for the information database to be current. Changes to the spatial information have to be easily modified in the GIS.
Beyond the essential parts of basic GIS applications, there are a number of advanced GIS analyses that can provide benefits to executive and estate level management. GIS technologies have the capability of providing information to improve fertilisation programs, optimum crop life cycle, production prediction and income. Additional GIS analyses can be guided by the requirements of the individual plantation companies and expertise of the GIS specialist.
Fertilisation Programs :
By incorporating laboratory and field results from soil and leaf sampling analyses into a GIS, managers can spatially assess overall plantation health and identify areas of low nutrients and/or poor soil conditions. Appropriate action to improve conditions in the less productive areas of an estate can be planned. Furthermore, data on low-nutrient areas can be cross analysed with crop yield data to assess effects on production yields.
Optimum Crop Life Cycle :
During the lifetime of a plantation, production yields increase with age, plateau and thereafter decline. Managers need to decide on the optimum time to convert aged rubber crops to palm oil or, when existing palm oil crops must be cleared to make way for new replanting. Trends in crop yields can be analysed and forecasted to assist management in deciding when crop blocks have reached the end of their productive life, or when blocks are under performing and should be converted.
Production Prediction & Forecasting Income :
GIS can efficiently summarise actual production yield data to look at monthly and yearly trends. Such information can assist management in planning labour and equipment requirements, work plans and schedules as well as monthly expenditure budgeting. Actual production can be monitored and graphed; production can be predicted based on crop age and additional agronomic information. By predicting production, management can forecast income based on CPO price trends. This valuable information can assist management in future organisational planning and potential enterprise expansion.
METHOD
Mapping Process The equipment used for mapping was a Magellan ProMark 3 Differential Global Positioning System (PM3). This is a L1 system having centimetre survey and decimetre mapping accuracy capability. Mapping was referenced to the WGS84 datum and Universal Transverse Mercator (UTM) projection. A base station was established on site from a national geodetic point, or by an averaged position. The mapping of an estate was fixed to this base station position.
Position of boundary corners, planted areas and features etc was determined by a second [rover] unit. The rover unit was located over the required point and measurement taken over a 30 second period. Roads were recorded in line measurement mode with the rover unit located on a moving vehicle. At the end of the measurement session the rover and base data were downloaded and processed simultaneously to correct errors such as multipath and atmospherics, to achieve decimetre accuracy standard. The rover unit of the PM3 has the ability to receive raster and vector maps, which gives a real time map position of the GPS
receiver. Also the PM3 uses feature file libraries to format data entry at the time of data collection. This has been useful when measuring planted areas, where planted year, type of crop data can be added, and in the recording of bridge positions where size of pipe, span and width information can be typed in to a formatted page directly at the time of measurement. Following processing of site measurements from the GPS software, data was then imported into an AutoCAD format drawing. Drawing of polygons and lines were done in the drawing software format prior to importing to the ArcGIS.
All data was stored, processed and displayed in ArcGIS 9 (ArcMap Version 9.2) (ESRI 2006) referenced to the WGS84 datum with a Universal Transverse Mercator (UTM) projection, zone 47 North.
Once drawing files were imported and converted into an ArcGIS geodatabase. All individual crop polygons were combined into one shapefile. The crop attribute table was edited to include additional fields for estate, year of planting, ID (e.g. A, B, C etc), type of crop (e.g. rubber, palm), afdeling (administrative division within the estate), code (based on estate, year planted and ID) and crop area (hectares).
To forecast production an additional field for tree age was calculated. Tabular data of expected production against palm oil tree age (Buana et al) was imported into ArcGIS and joined with the crop attribute table. For each crop polygon of varying size, production was calculated giving yield (ton/year) for years 2007 – 2012.
RESULTS
From the implementation of GIS to palm oil plantation and production management, certain elements became apparent. Firstly, accurate mapping was necessary. This formed the basis of the data required for the GIS. By accurately mapping the plantation boundary and divisions, it appeared that discrepancies existed between applied plantation records and actual results. Secondly, GIS proved to be a valuable tool in the management of the spatial data and the display of areas of interest. Thirdly, GIS could be used effectively for the purposes of prediction.
DISCUSSION
Applying Geo Information Technologies in the palm oil plantation industry has not been without difficulties. The initial mapping problem involved collecting data from the field to produce maps, which required survey information to be identified by plantation staff. Mapping of crop areas was usually done with the division assistant, because of the difficulty in differentiating areas. Satellite imagery may in some cases be suitable for plantation boundaries, however in the case studies tree coverage hindered boundary, divisional and block demarcations, especially when adjoining boundaries had similar crop type and/or encroachments.
Plantation companies have some awareness of GPS, and attempt to survey areas with consumer GPS units, which give positional accuracy of +/-10m. Difficulties are encountered when transferring information from GPS units [usually in the form of waypoints] to mapping or GIS software. Plantation staff typically do not have the software, hardware or knowledge to successfully complete this operation. This is one of the factors restricting the implementation of a GIS. Another factor is the general lack of knowledge concerning GIS and its potential benefits by management. Few plantation companies in Sumatra, Indonesia have survey departments and very few organisations, if any, have a GIS department. In this industry there are only a few consultants operating, and this may explain why GIS is not more widely applied. No tertiary educational facilities were found in Sumatra to offer undergraduate courses in GIS.
Caution should be given to the resources allocated for field collection of data and preparation of GIS database. Considerable time is required in verifying field data and design of the GIS database. However once this phase is complete, mapping and graphical data display can easily be generated to suit the needs of management. The process of keeping data up to date should not be overlooked as results produced directly relate to the accuracy of the database.
CONCLUSION
When GPS and GIS technologies were applied, information was accurate, reliable and repeatable. These technologies were welcomed by plantation management, as GIS technology established a dependable basis on which to make decisions. GIS enables the effective management, analysis and display of information in a clear and structured manner. Plantation companies involved in the case studies considered that the application of GIS would lead to greater efficiencies and therefore greater profitability. Use of this technology and its application advantages are not widely known by the plantation industry. Further education and industry exposure is necessary to bring greater awareness of GIT to the palm oil plantation industry.
Saturday, August 28, 2010
Friday, August 27, 2010
Tuesday, January 5, 2010
CABBAGE cultivation
Some people, who desire to lose weight quickly, utilize the well-known Cabbage soup diet and this is how they make this vegetable grow. The cabbage is a tough vegetable that grows well when planted in fertile soils. Various shades of green cabbages are available. But there are also purple or red types. The shape of the cabbage head varies from the typical round to pointed or flattened. Most varieties of cabbage have smooth leaves. However, the leaves of Savoy types are crinkly textured.
Cabbage Varieties
Cabbage can be grown easily if you choose suitable varieties and observe correct insect management and proper culture. Cabbage has always been regarded as a very good source of vitamins and has disease-preventive properties.Cabbage varieties are enumerated below, with their respective properties:1. Green Cabbage-perhaps the most common.2. Cheers - have solid round heads; can be harvested in 75 days and are tolerant to black rot and trips.3. Early Jersey Wakefield - have pointed headstand is harvested in 63 days. It stands well and resists splitting.4. King Cole - have large, firm and extremely uniform heads and can be harvested in 74 days.5. Savoy King - takes 85 days to harvest with dark green color and have very uniform heads.6. Savoy Queen - harvested in 88 days and weighs 5 pounds it has deep green color and is tolerant to heat.7. Red Meteor - takes 75 days to harvest its firm and good for all seasons.8. Ruby Ball - harvested in 71 days and can weigh 4 pounds, they are slow to burst and resists both cold and heat.
Planting Cabbage
Early cabbages are transplanted soon enough so they will mature before the heat of summer. They are easily transplanted from either cell-pack-grown or bare-root plants. Late cabbages should be started during mid-summer. However, its main head develops during fall. It can either be seeded directly in the garden or transplanted. Whenever possible, seedbeds or seed flats are put in places protected from the sun. This is the normal way of planting cabbage:1. Plants are spaced 12 to 24 inches apart from each other in the row. The space primarily depends upon the variety and the size of the head.2. Sow the cabbage seed 1/4 to 1/2 inch deep in the soil and keep it thin and most or transplant the seedling to the spacing desired.3. Starter fertilizer is used when transplanting while for plants that are already half grown, they are side-dressed with nitrogen fertilizer.4. To keep the weeds down, shallow cultivation is done. Sufficient soil moisture is essential throughout the growing season.Another important factor in growing cabbages is irrigation. This will help the young plants endure the intense sunlight and summer heat and will supply them will sufficient water. There is really no particular time when the cabbages can be harvested, for as long their heads are already formed and solid and firm to hand pressure. However, they must be harvested before their heads crack or split. Good cabbages are essential for a good Cabbage Soup Diet.
Cabbage Varieties
Cabbage can be grown easily if you choose suitable varieties and observe correct insect management and proper culture. Cabbage has always been regarded as a very good source of vitamins and has disease-preventive properties.Cabbage varieties are enumerated below, with their respective properties:1. Green Cabbage-perhaps the most common.2. Cheers - have solid round heads; can be harvested in 75 days and are tolerant to black rot and trips.3. Early Jersey Wakefield - have pointed headstand is harvested in 63 days. It stands well and resists splitting.4. King Cole - have large, firm and extremely uniform heads and can be harvested in 74 days.5. Savoy King - takes 85 days to harvest with dark green color and have very uniform heads.6. Savoy Queen - harvested in 88 days and weighs 5 pounds it has deep green color and is tolerant to heat.7. Red Meteor - takes 75 days to harvest its firm and good for all seasons.8. Ruby Ball - harvested in 71 days and can weigh 4 pounds, they are slow to burst and resists both cold and heat.
Planting Cabbage
Early cabbages are transplanted soon enough so they will mature before the heat of summer. They are easily transplanted from either cell-pack-grown or bare-root plants. Late cabbages should be started during mid-summer. However, its main head develops during fall. It can either be seeded directly in the garden or transplanted. Whenever possible, seedbeds or seed flats are put in places protected from the sun. This is the normal way of planting cabbage:1. Plants are spaced 12 to 24 inches apart from each other in the row. The space primarily depends upon the variety and the size of the head.2. Sow the cabbage seed 1/4 to 1/2 inch deep in the soil and keep it thin and most or transplant the seedling to the spacing desired.3. Starter fertilizer is used when transplanting while for plants that are already half grown, they are side-dressed with nitrogen fertilizer.4. To keep the weeds down, shallow cultivation is done. Sufficient soil moisture is essential throughout the growing season.Another important factor in growing cabbages is irrigation. This will help the young plants endure the intense sunlight and summer heat and will supply them will sufficient water. There is really no particular time when the cabbages can be harvested, for as long their heads are already formed and solid and firm to hand pressure. However, they must be harvested before their heads crack or split. Good cabbages are essential for a good Cabbage Soup Diet.
MUSHROOM cultivation
Mushroom (Agarics Bosporus), the paddy-straw mushroom (Volvariella vovvacea) and the oyster mushroom (Pleurotus sajor-caju). Of these, A. Bosporus is the most popular and economically sound to grow and is extensively cultivated throughout the world. However, due to its low temperature requirement, its cultivation is restricted to the cool climatic areas and to the winter in the plains of Northern India. In summer, the tropical paddy-straw mushroom is suitable for growing in most parts of India. Even then it is less attractive commercially owing to very low yield per unit weight of the substrate and an extremely short shelf-life. But, as a kitchen-garden crop it is preferred because it is very delicious and nutritious.Oyster mushroom can grow at moderate temperature ranging from 220 to 280C. therefore, it is suitable for most of the places of India. It is a familiar item in the menu of most hotels in Bangalore where it is being grown commercially.In north India, the climate conditions prevailing during different seasons can be exploited for growing mushroom throughout the year.
CULTIVATION
1. Selection of StrainsFor successful mushroom production, it is necessary for each grower to produce as economically and efficiently as possible the highest quality of mushrooms. This can be accomplished among other requirements, by selecting the best strains which should be high yielding , visually attractive, having desirable flavour, and resistance to adverse climate and pests and diseases. Presently, there are many strains of white, cream and brown varieties in cultivation. The brown variety is the natural mushroom and considered to be the most vigorous form. It tolerates and adverse conditions better than the white variety. A snow white mushroom first appeared amongst a bed of mushroom in the USA and ever since the variety has dominated the mushroom industry throughout the world, although it has a very high limited shelf-life. Where growing conditions tend to be on the dry side and humidity cannot be correctly controlled the brown mushroom should be grown. New superior strains are through selection, hybridization and induced mutations continually introduced by mushroom research laboratories and spawn makers. In India, S 11, S 649 and S791 are the good strains available. These strains were originally introduced from reowned commercial spawn makers, Somycel and darlington. Now these strains are well adapted in the Indian climate and are very popular with the growers.
2. Maintenance of Strains.Three methods are known by which strains can be propagate. these are multispore culture, tissue culture and mycelium transfer. By periodic subculturing of the mycelium on a suitable agar medium, the span strains can be kept for many years in a fairly good state. However, the frequent subculturing of the strain may result in its degeneration. Maintenence of strain by multisporous culture is only possible if new multispore cultures are compared with the original strain before the original multisporous culture would show much genetic variation. In the tissue culture, small pieces of fruit bodies are cut under sterile conditions and inoculated on a nutrient medium. Mycelium growing out of these tissue can provide the starting point for subsequent spawn production. However, it is commonly observed that tissue cultures often give lower yields than the original cultures. Of these 3 methods, mycelium transfer is most reliable but it is essential that the performance of the mycelium is continually checked in order to detect any degeneration-like slow-growing matted mycelium or fluffy mycelium with abnormal growth rate.
SpawnThe propogating material used by the mushroom growers for planting beds is called spawn. The spawn is equivalent to vegetative seed of higher plant. Quality of spawn is basic for the successful mushroom cultivation.At present, the pure culture spawn has been the basis of modern spawn production units all over the world. The manufacture of the pure culture spawn is done under scientifically controlled conditions which demand a standard of hygiene as in a hospital operation theatre. Equipment and substrate used for spawn are autoclaved and filtered air is passed during the inocluation ensures complete freedom from contamination.(a) Manure spawnBoth composted horse-dung or synthetic compost may be used. The composted manure is thoroughly washed to remove such substance in compost which retard growth. The excess water is squeezed out and moisture content adjusted to 60%. The manure is packed in half-litre milk bottles or heat-resistant polypropylene bags os suitable size. The bottles or bags plugged with non-absorbant cotton-wool and sterlized in an autoculave at 1210C for 2 hr or on 2 consecutive days for an hour each. They are then inoculated with a large bit of agar-containing mycelium and incubated at 220-240C in a dark place. the spawn can be used to inoculate fresh bottles or bags to obtain the second generation spawn.(b) Grain spawnTen kilograms of wheat grains are boiled for 15 min in 15 litres of water and then allowed to soak for another 15 min without heating. the excess water is drained off and the grains are colled in sieves. Turn the grains several times with a spoon for quick cooling. The colled grains, are mixed with calcium carbonate. the gypsum (CaSO4.2H2O) and 30 g fo calcium carbonate. The gypsum prevents the grains from sticking together and calcium carbonate is necessary to correct the pH. the prepared grains are filled into half-litre milk bottles or polypropylene bags (at the rate of 150-200 g per bottle or bag) and autocalved for 2 hr at 1210C. After sterlization, the material should have a pH value of 6.5 to 6.7. the bottles are inoculated with grains spawn or with bits of agar medium colonized with mycelium and incubated at 220-240C in a dark place. the mycelium completely permeates the grains in about 2 weeks. Other grains like sorghum and pearlmillet can also be used for spawn making.(c)Perlite spawnThis was developed by Lemke (1971). Perlite is a mineral which expands at temperature more than 10000C. The ingredients, of the spawn are : Perlite (1,450 g), wheat-bran (1,650 g), gypsum (200 g), calcium carbonate (50 g), and water (665 cc). The gredients are mixed, filled in bottles and sterlized. Thereafter, the process is the same as for grain spawn. Perlite spawn is easy to disperse and can be produced at a cheaper cost. This spawn can be stored for a long time.
SUNFLOWER cultivation
Grow good maize crops are generally suitable for sunflower. In undeveloped regions, however, there are large areas basically suitable for sunflower on which the crop is not sown, and even though local growers may have produced poor crops, breeders are frequently able to select within local or known varieties a strain which will be more productive on these soils.
Soils with an appreciable sand content have produced higher yields than more clayey soils in the same area under similar standards of husbandry.
Whatever soil type is available, good drainage is more important than basic fertility, for it is usually easier to supply nutrients than improve drainage.
Sunflower grows well on neutral to moderately alkaline soils, with a range of pH 6.5 – 8.0, but dislikes acid conditions.
Wild varieties are tolerant of poor drainage but cultivated varieties are unsuited to such conditions, which increase susceptibility to fungal disease and lodging from lack of support.
Salinity affects plant growth, development and some seed characteristics, usually oil content, and also influences nutrient uptake.
Where salt concentrations are low to moderate, the first visual symptom is often a thin stem and stunted growth.
Salinity can also reduce disease resistance, for example to Macrophominia in Tunisia and charcoal rots. Varietal differences to salinity are becoming increasingly reported, a very valuable characteristic, since the proportion of salt affected soils in the irrigated areas of the world continues to increase, and selection of varieties suited to these conditions is becoming more important.
The use of micro elements in fertilizer mixtures can assist in increasing salt tolerance, for the growing of sunflower in these regions would add a valuable cash crop, or be an addition to local diets. There are indications that sunflower roots play an important role in the plant's tolerance of salinity, in that they may act as accumulators of sodium rather than as a barrier to its assimilation.
In India, an exchangeable sodium percentage higher than 16 delayed germination, and later delayed the development of flower heads. Reduction in germination or emergence caused by salinity. Soils containing 0.2 per cent salts decreased yields by nearly 40 per cent.
The depressing effect of high salinity levels on emergence is also related to temperature at this period, but there would also appear to be varietal differences in this response.
Some cultivars are adversely affected by high soils temperatures some by low, while others emerge well at a high or low temperature, but poorly in the mid range.
The degree of salinity also affects the rate of, and total emergence at different temperatures.
It would thus appear that there is considerable scope for increasing salt tolerance in sunflower.
Avoid acid, salime and ill-drained soils for sunflower cultivation.
For rainfed sunflower heavy clays or clay loams are more suitable since they are highly water retentive.
Deep soils always preferable at least 15-20 cm.
To cultivate this crop in rabi season with residual moisture select only heavy soils. Light soils are well suited for this crop where irrigation is not a limiting factor.
Sunflower is grown from 400S to 550N, but greatest production is between latitudes 20 and 500N and 20 - 400S. it will grow from sea level to 2500m, but generally gives highest yield of oil per hectare below 1,500m.
Day length influences time to flowering it does so in the period from emergence to budding. After this there was no apparent effect. However, for all practical purposes, sunflower can be considered day neutral, and within any large geographical area. Under controlled environmental conditions it has been shown that development was more rapid at 12 hours daylight equivalent than at 16 hours of longer. However, as noted, high temperature is more likely to reduce the time to maturity. Frost will damage sunflower to some degree at all sages of growth, although mature plants are more resistant to low temperature than soyabean or maize.
Young plants in the four to six leaf stage can apparently withstand temperatures of 5 to 60C for short periods. However, a hard frost after floral initiation, about the eight leaf stage, will usually reduce yield by affecting head development, although visual damage, may appear slight.
Frost will also damage immature seed and substantially reduce viability, but mature seed is less affected. This may be of little concern to commercial oilseed producers, but can influence the choice of site for seed production. A frost free period of about 120 days is recommended where sunflowers are to be grown on a commercial scale. Sunflower grown well within a temperature range of 20 - 250C, although controlled environment tests indicate that 27 - 280C would appear to be the optimum.
A range of 8 - 340C is tolerated without significant yield reduction, indicating adaptation to regions with warm days and cold nights. A major visual effect of temperature is on the rate of development, with prolonged high temperature reducing the time to maturity, in some instances by nearly 50 per cent Temperature is known to affect seed oil content, seed and oil characteristics, but its effects on plants growing in the field are often masked or modified by other environmental factors.
In general, temperature which remains above 250C at flowering is believed to reduce seed yield and seed oil content. As temperature during development decreased there was an increase in linoleic acid in the range 49 - 74 per cent. The contrary produced an increase in oleic acid content. The marked reduction in linoleic acid is believed to due to temperature acting on the desaturase enzymes, responsible for the conversion of oleic to linoleic acid.
It may thus be necessary to relate time of sowing to temperature at flowering when a particular type of oil is required. The effect of temperature is not limited to its direct influence on seed oil constituents, since the basically different types of oil produced can directly influence local manufactures and their produce range. Sunflower is considered to be drought resistant and while this may be so, oil yield is substantially reduced if plants are allowed to become stressed during the main growth period and at flowering.
A major symptom of moisture stress in the vegetative phase is a reduction in the number and size of leaves.
Should a water shortage continue, lower leaves are shed and plant height will be substantially less than normal.
One of the mechanisms employed by sunflower or resist moisture stress is by wilting, since it has been shown in controlled trials that in limp leaves water loss was reduced to a greater extent than photosynthesis.
Plants can be independent of rainfall to a large extent, and good crops produced with as little as 500mm of irrigation water only, provided the subsoil moisture is adequate.
Sunflower will produce a moderate yield on rainfall down to 300mm, but at this level of production is unlikely to be commercially viable as a mechanized crop.
In the field, the relationship between low rainfall and seed yield is often almost linear from 200 to 500 mm, with 1t / ha usually achieved around 300 - 350mm.
As a guide, the yield which can reasonably be expected from rain grown sunflower in more arid areas is approximately half that of a local sorghum crop.
It should be noted, however, that in arid conditions seed oil content is adversely affected.
Between 500 and 750 mm of rain, and some of this may be stored soil moisture, evenly spread over the growing period and ceasing just before main flowering and seed filling, will normally produce excellent crops.
Losses from disease and lodging can be severe when rainfall is above, 1,000 mm unless the soil is free draining, especially if there are heavy falls when plants are fully grown.
Various methods have been developed to assist growers to select suitable areas or soils.
Because of their height, sunflower are susceptible to damage by high wind from when they are half grown, more so when irrigated as moist soil gives less support.
There is considerable variation in the ability to resist wind damage basically related to root development, and this should influence selection when choosing varieties to be grown in windy locations.
Hail can be extremely damaging to young seedlings which seldom recover if the terminal shoots are destroyed.
Full grown or mature plants are little affected, even though leaves may appear shredded or badly holed.
Based on the climate requirements discussed above sunflower can be grown throughout the year.
However, the sowing time should be determined based on three aspects.
There should not be moisture deficit between bud stage to flowering.
The crop should not be caught in rains during pollination period
Pollination period should not coincide with the period of high temperatures since the honey bee activity is negligible when high temperature are prevailed and thus poor seed setting.
Hence, under Andhra Pradesh conditions sowings should not be done beyond 15th February.
Soils with an appreciable sand content have produced higher yields than more clayey soils in the same area under similar standards of husbandry.
Whatever soil type is available, good drainage is more important than basic fertility, for it is usually easier to supply nutrients than improve drainage.
Sunflower grows well on neutral to moderately alkaline soils, with a range of pH 6.5 – 8.0, but dislikes acid conditions.
Wild varieties are tolerant of poor drainage but cultivated varieties are unsuited to such conditions, which increase susceptibility to fungal disease and lodging from lack of support.
Salinity affects plant growth, development and some seed characteristics, usually oil content, and also influences nutrient uptake.
Where salt concentrations are low to moderate, the first visual symptom is often a thin stem and stunted growth.
Salinity can also reduce disease resistance, for example to Macrophominia in Tunisia and charcoal rots. Varietal differences to salinity are becoming increasingly reported, a very valuable characteristic, since the proportion of salt affected soils in the irrigated areas of the world continues to increase, and selection of varieties suited to these conditions is becoming more important.
The use of micro elements in fertilizer mixtures can assist in increasing salt tolerance, for the growing of sunflower in these regions would add a valuable cash crop, or be an addition to local diets. There are indications that sunflower roots play an important role in the plant's tolerance of salinity, in that they may act as accumulators of sodium rather than as a barrier to its assimilation.
In India, an exchangeable sodium percentage higher than 16 delayed germination, and later delayed the development of flower heads. Reduction in germination or emergence caused by salinity. Soils containing 0.2 per cent salts decreased yields by nearly 40 per cent.
The depressing effect of high salinity levels on emergence is also related to temperature at this period, but there would also appear to be varietal differences in this response.
Some cultivars are adversely affected by high soils temperatures some by low, while others emerge well at a high or low temperature, but poorly in the mid range.
The degree of salinity also affects the rate of, and total emergence at different temperatures.
It would thus appear that there is considerable scope for increasing salt tolerance in sunflower.
Avoid acid, salime and ill-drained soils for sunflower cultivation.
For rainfed sunflower heavy clays or clay loams are more suitable since they are highly water retentive.
Deep soils always preferable at least 15-20 cm.
To cultivate this crop in rabi season with residual moisture select only heavy soils. Light soils are well suited for this crop where irrigation is not a limiting factor.
Sunflower is grown from 400S to 550N, but greatest production is between latitudes 20 and 500N and 20 - 400S. it will grow from sea level to 2500m, but generally gives highest yield of oil per hectare below 1,500m.
Day length influences time to flowering it does so in the period from emergence to budding. After this there was no apparent effect. However, for all practical purposes, sunflower can be considered day neutral, and within any large geographical area. Under controlled environmental conditions it has been shown that development was more rapid at 12 hours daylight equivalent than at 16 hours of longer. However, as noted, high temperature is more likely to reduce the time to maturity. Frost will damage sunflower to some degree at all sages of growth, although mature plants are more resistant to low temperature than soyabean or maize.
Young plants in the four to six leaf stage can apparently withstand temperatures of 5 to 60C for short periods. However, a hard frost after floral initiation, about the eight leaf stage, will usually reduce yield by affecting head development, although visual damage, may appear slight.
Frost will also damage immature seed and substantially reduce viability, but mature seed is less affected. This may be of little concern to commercial oilseed producers, but can influence the choice of site for seed production. A frost free period of about 120 days is recommended where sunflowers are to be grown on a commercial scale. Sunflower grown well within a temperature range of 20 - 250C, although controlled environment tests indicate that 27 - 280C would appear to be the optimum.
A range of 8 - 340C is tolerated without significant yield reduction, indicating adaptation to regions with warm days and cold nights. A major visual effect of temperature is on the rate of development, with prolonged high temperature reducing the time to maturity, in some instances by nearly 50 per cent Temperature is known to affect seed oil content, seed and oil characteristics, but its effects on plants growing in the field are often masked or modified by other environmental factors.
In general, temperature which remains above 250C at flowering is believed to reduce seed yield and seed oil content. As temperature during development decreased there was an increase in linoleic acid in the range 49 - 74 per cent. The contrary produced an increase in oleic acid content. The marked reduction in linoleic acid is believed to due to temperature acting on the desaturase enzymes, responsible for the conversion of oleic to linoleic acid.
It may thus be necessary to relate time of sowing to temperature at flowering when a particular type of oil is required. The effect of temperature is not limited to its direct influence on seed oil constituents, since the basically different types of oil produced can directly influence local manufactures and their produce range. Sunflower is considered to be drought resistant and while this may be so, oil yield is substantially reduced if plants are allowed to become stressed during the main growth period and at flowering.
A major symptom of moisture stress in the vegetative phase is a reduction in the number and size of leaves.
Should a water shortage continue, lower leaves are shed and plant height will be substantially less than normal.
One of the mechanisms employed by sunflower or resist moisture stress is by wilting, since it has been shown in controlled trials that in limp leaves water loss was reduced to a greater extent than photosynthesis.
Plants can be independent of rainfall to a large extent, and good crops produced with as little as 500mm of irrigation water only, provided the subsoil moisture is adequate.
Sunflower will produce a moderate yield on rainfall down to 300mm, but at this level of production is unlikely to be commercially viable as a mechanized crop.
In the field, the relationship between low rainfall and seed yield is often almost linear from 200 to 500 mm, with 1t / ha usually achieved around 300 - 350mm.
As a guide, the yield which can reasonably be expected from rain grown sunflower in more arid areas is approximately half that of a local sorghum crop.
It should be noted, however, that in arid conditions seed oil content is adversely affected.
Between 500 and 750 mm of rain, and some of this may be stored soil moisture, evenly spread over the growing period and ceasing just before main flowering and seed filling, will normally produce excellent crops.
Losses from disease and lodging can be severe when rainfall is above, 1,000 mm unless the soil is free draining, especially if there are heavy falls when plants are fully grown.
Various methods have been developed to assist growers to select suitable areas or soils.
Because of their height, sunflower are susceptible to damage by high wind from when they are half grown, more so when irrigated as moist soil gives less support.
There is considerable variation in the ability to resist wind damage basically related to root development, and this should influence selection when choosing varieties to be grown in windy locations.
Hail can be extremely damaging to young seedlings which seldom recover if the terminal shoots are destroyed.
Full grown or mature plants are little affected, even though leaves may appear shredded or badly holed.
Based on the climate requirements discussed above sunflower can be grown throughout the year.
However, the sowing time should be determined based on three aspects.
There should not be moisture deficit between bud stage to flowering.
The crop should not be caught in rains during pollination period
Pollination period should not coincide with the period of high temperatures since the honey bee activity is negligible when high temperature are prevailed and thus poor seed setting.
Hence, under Andhra Pradesh conditions sowings should not be done beyond 15th February.
POTATO
Introduction
Potato is most widely grown vegetable crop in the country with a share of 25.7 per cent. The area under potato cultivation is 1.4Million ha with total production of 25 MT. The main varieties of potato grown in the country are Kufri Chandramukhi, Kufri Jyoti, Kufri Badshah, Kufri Himalani, Kufri Sindhuri, Kufri Lalima etc.
Uttar Pradesh is the leading potato growing state in the country followed by West Bengal and Bihar. In Karnataka potato is considered as a important commercial crop in uttar Karnataka region It is widely cultivated in Belgaum and Dharwad districts. The area under potatoe cultivation in these areas is around 20,000 Ha.
Classification
Potato is the most useful and important member of the family Solonaceae and it belongs to genus Solanum which consists of 7 cultivated and about 154 wild species but the commercially viable potato has only 2 species.
Solanum Andigenum
The plants of the species are characterized with thin and long stems, small and narrow leaflets having profuse flowering and long stolons. It is not very common.
The tubers are mostly covered with deep sunken eyes on them. The yielding potential is very low and, therefore, it is not grown on large scale.
Solanum Tuberosum
It is more common plants have shorter and thicker stem, larger and wider leaflets. In addition to the above-mentioned species Solanum Lemissum and Solanum Stenotonum are also of some importance as they are resistant to some form of virus and diseases, but they are also not being cultivating commercially.
Crop Rotations And Intercropping
Potato is grown in rotation with other crops, usually to maintain desirable soils texture and state of fertility
To build up organic matter
To reduce crop loss from insect and plant disease
To increase per unit productivity per unit area and time
To improve the quality of produce
Potato, being a fast growing crop, fits well in different rotations and inters cropping systems. It can very successfully be grown in the following sequences.
Maize – Potato – Wheat
Paddy – Potato – Wheat
GM - Potato - Wheat
For successful cultivation of these rotations, the following time schedule needs to be considered.
Maize and paddy sowing should be done in early June
Grow short duration early maturing varieties
Grow potato in October
Prefer late sown varieties of wheat viz. PBW373, PBW138, Raj 3765 in the end of December and early January
Green manuring is done during rainy season
Green manure should be ploughed in the field at least 15 days before potato planting
Green manure improves the soil fertility
The potato crop is also grown in different inter-cropping such as
Sugarcane + Potato
Maize + Potato
Potato is most widely grown vegetable crop in the country with a share of 25.7 per cent. The area under potato cultivation is 1.4Million ha with total production of 25 MT. The main varieties of potato grown in the country are Kufri Chandramukhi, Kufri Jyoti, Kufri Badshah, Kufri Himalani, Kufri Sindhuri, Kufri Lalima etc.
Uttar Pradesh is the leading potato growing state in the country followed by West Bengal and Bihar. In Karnataka potato is considered as a important commercial crop in uttar Karnataka region It is widely cultivated in Belgaum and Dharwad districts. The area under potatoe cultivation in these areas is around 20,000 Ha.
Classification
Potato is the most useful and important member of the family Solonaceae and it belongs to genus Solanum which consists of 7 cultivated and about 154 wild species but the commercially viable potato has only 2 species.
Solanum Andigenum
The plants of the species are characterized with thin and long stems, small and narrow leaflets having profuse flowering and long stolons. It is not very common.
The tubers are mostly covered with deep sunken eyes on them. The yielding potential is very low and, therefore, it is not grown on large scale.
Solanum Tuberosum
It is more common plants have shorter and thicker stem, larger and wider leaflets. In addition to the above-mentioned species Solanum Lemissum and Solanum Stenotonum are also of some importance as they are resistant to some form of virus and diseases, but they are also not being cultivating commercially.
Crop Rotations And Intercropping
Potato is grown in rotation with other crops, usually to maintain desirable soils texture and state of fertility
To build up organic matter
To reduce crop loss from insect and plant disease
To increase per unit productivity per unit area and time
To improve the quality of produce
Potato, being a fast growing crop, fits well in different rotations and inters cropping systems. It can very successfully be grown in the following sequences.
Maize – Potato – Wheat
Paddy – Potato – Wheat
GM - Potato - Wheat
For successful cultivation of these rotations, the following time schedule needs to be considered.
Maize and paddy sowing should be done in early June
Grow short duration early maturing varieties
Grow potato in October
Prefer late sown varieties of wheat viz. PBW373, PBW138, Raj 3765 in the end of December and early January
Green manuring is done during rainy season
Green manure should be ploughed in the field at least 15 days before potato planting
Green manure improves the soil fertility
The potato crop is also grown in different inter-cropping such as
Sugarcane + Potato
Maize + Potato
VEGETABLE crops
Fertilizer Management for Vegetables
In Asian countries where fertilizer is relatively cheap in relation to the value of the crop, farmers tend to apply too much fertilizer. This is particularly true of vegetables, since they are a high-value crop. For the farmer, this represents a type of insurance against crop losses due to nutrient deficiencies. However, overuse of fertilizer is not only wasteful, but is damaging to both crop quality and the environment.
Furthermore, vegetables tend to be a short-term crop which are grown as part of a multiple cropping system. In intensive tropical systems with vegetables, and also in temperate systems where protective structures are used, it is common for a number of crops to be grown each year on the same piece of land.
This means that the nutrient supply of each crop is affected by the fertilizer which was applied to previous crops. Efficient fertilizer use means matching the supply of nutrients to those required by the crop. Rather than managing the nutrients for separate successive crops, vegetable production involves managing the nutrient supply and requirements of the total cropping system.
Patterns of Vegetable Production
There seem to be two main patterns of vegetable production in Asia. One is intensive vegetable production, in areas either specially suited to vegetables or near large population centers. The second is a vegetable/cereal cropping system, in which vegetables are usually the subsidiary crop. Combined vegetable/cereal systems can in turn be divided into vegetable production on raised beds in paddy fields after rice, and vegetables grown as an intercrop or relay crop with corn, wheat etc. in rainfed uplands.
Sustainable vegetable production for each of these two systems will take a different course, but in each case there must be a positive nutrient balance. Since N fertilizer rates for vegetables are generally fairly high, there is usually a positive N balance in cereal/vegetable systems. However, this may not be true of all nutrients. For example, boron deficiency is fairly common in the vegetable production area around Chiang Mai, Thailand.
Maintaining the Long-Term Fertility of Vegetable Fields
Intensive vegetable production involves a large volume of output _ 30 mt/ha/crop of Chinese cabbage would be quite a normal yield. Vegetable-producing soils are constantly being mined of nutrients with every harvest. This massive removal must be compensated by a large volume of inputs, either of chemical fertilizer, organic materials, or a mixture of both. While farmers attempt to compensate for nutrients removed by applying the same level of nutrients in fertilizer, it is difficult for them to achieve a proper nutrient balance, especially if they use only chemical fertilizers.
In many other countries, there is a gap between cereal and vegetable yields from farmers' fields and those from research stations. Often in the case of cereals, the gap is caused by underuse of fertilizer, while in the case of vegetables, it may be due to fertilizer overuse. Many soils used for vegetables show accumulation of nutrients over time, rather than depletion. Farmers in Sri lanka even try to reclaim the soil of vegetable fields by removing the topsoil, and adding fresh soil brought in from uncultivated land.
Soil testing is necessary to identify nutrient deficiencies. There is a need for an expanded soil testing service, and for simple and quick testing procedures. In areas where rural transport is difficult, a mobile service which collected samples for testing might be very useful.
Utilization of Organic Wastes
Applied compost and other organic materials are known to have a beneficial effect on soil productivity, and on the control of pests and diseases. Vegetables tend to receive higher applications of organic fertilizer than any other type of crop, the main limits being the cost and availability of compost.
Not only do organic materials benefit the soil and crop but, as one paper presentation pointed out, composting should be seen as part of solid waste management. In most industrialized countries, it is becoming increasingly difficult and expensive to find landfill sites. In the United States in 1993, only 3.1% of municipal solid wastes were composted. The majority of wastes (62.3%) were used as land fill, with the remainder being incinerated or recycled. Raising the proportion of composted wastes would make a large savings in landfill costs. However, effective recycling of municipal wastes needs some preliminary sorting at a household level, so that wastes are already sorted into organic materials, plastic etc. at the point of collection.
The point was also made that organic materials do not necessarily always give higher yields than synthetic ones. Experiments with green pepper in the United States showed that yields were higher when polyethylene mulch was used, compared to organic mulches. However, the fruit were larger when they were grown with organic mulch. Interestingly, the same effect was seen in the following crop of squash, in that the squash were larger in the organic mulch plot, although the overall yield was not any higher. While organic mulches can sometimes give yields comparable to those from plastic ones, this depends on the type and rate of organic mulch used, its effect on soil microorganisms, and the type of vegetable being grown.
Fertilizer, Crop Yields and Nitrate Levels
In some long-term fertilizer experiments at five sites in Taiwan where vegetables had been grown for at least ten years, chemical fertilizers have been applied according to conventional recommendations, together with a small percentage of organic fertilizer. Crops showed a marked response to fertilization, to the extent that if fertilizer was discontinued for only one crop, there was a fall in yield of 20-35%. There was also a fall in the quality of the vegetables. Since large quantities of irrigation water were used in this system, good fertilizer management depended on suitable water management, to minimize leaching.
There was a linear and highly significant relationship between the plant uptake of N, P and K, and the crop yield. There was also a linear and significant relationship between the N content of the plant, and the eventual yield. However, there was a negative relationship between the yield and the P content of the plant, while there was no significant relationship between yield and the plant K content. This perhaps reflects the high levels of available P and K in these soils, all of which had been used for long-term vegetable production.
There was also a correlation between N levels and nitrate levels in the plant. Thus, any reduction in nitrogen applications to reduce nitrate levels tended to result in a fall in crop yield.
Crop Selection and Fertilizer Efficiency
There is a considerable difference between different types of vegetable, in terms of their efficiency of nitrogen use. Data presented at the seminar showed that spinach and leek, for example, both use nitrogen inefficiently. Such crops may have nitrogen leaching losses of more than 200 kg N/ha, compared to losses of 30-40 kg N/ha for cabbage. Reducing the rate of losses for crops such as leek would mean a great increase in fertilizer efficiency.
A further interesting point made is that some crop combinations make more efficient use of fertilizer than others. For example, combinations of rice-green pepper and rice-tomato are extremely inefficient in their use of N, with an N recovery rate of only 27%. In contrast, a combination of rice-mungbean-corn showed highly efficient N use, with a recovery rate of 56%. Another efficient combination, in terms of N use, was rice-garlic-sweet potato.
This shows the importance of treating the fertilizer requirements of the total cropping system, rather than of the separate crop components. The relative fertilizer efficiency of crop combinations needs to be taken into account when fertilizer recommendations are being made.
Appropriate crop combinations sometimes allow a vegetable crop to be grown in a cereal-based system without any additional fertilizer. In India before the 1960s, when indigenous cereal varieties were grown, little fertilizer was used, and legume pulses were grown in rotation or as intercrops. With the introduction of high-yielding varieties and chemical fertilizers, cereals began to dominate the cropping system at the expense of legumes. Nowadays, there is a return to something like the traditional pattern, since short-duration varieties make it possible to grow mungbean as an intercrop or as an interim crop. Mungbean yields are about 0.2-1.0 mt/ha, and the production potential of the following crop is sustained or even improved, especially if the mungbean straw is incorporated into the soil. If the previous crop has been given the recommended fertilizer applications, no more fertilizer is needed for the mungbean. Thus the production potential of the farm is increased, at a relatively low cost.
Conclusion
It is generally agreed today that an ideal agricultural system must be not only productive but sustainable. Some types of vegetable production are presumably more sustainable than others, but to define which these are, we need indicators of sustainability. It is still diffiocult to define these indicators, especially in quantitative terms. General indicators of sustainability have been suggested, including productivity (yield), stability (yield over time), protection of the resource base, viability (whether a system is economically profitable) and social acceptability (to both farmers and the general public). The problem is to apply such criteria to give quantified results.
It is clear that many improvements are possible in fertilizer efficiency. These include improved water management, efficient crop combinations, and improved formulations such as slow-release fertilizers to synchronize nutrient availability with crop needs. The timing of fertilizer applications is also important, not only to minimize leaching losses, but also to maximize yield. Vegetables are very sensitive to nutrient deficiencies during the early growth period. Unlike cereals, any deficiency suffered by a vegetable crop early on is not compensated during later growth stages.
Because of the high levels of nutrients removed with the crop, and because vegetables are a high-value crop, vegetables often receive very heavy fertilizer applications. Unbalanced fertilizer use and micronutrient deficiencies are common problems. There is a widespread need among the region's vegetable farms for more soil testing, including perhaps a mobile service specially adapted to the needs of small-scale farmers.
Planning and implementation of research should follow an integrated approach, with input from economists, plant pathologists and soil scientists as well as agronomists. Farmers should also be included, not just to evaluate new technology, but also to contribute from their own experience and traditional knowledge. Models are likely to play an increasingly important role, not just in research but also in extension with the development of DSS (Decision Support System) models.
Sustainable agriculture must take into account the long-term impact of agricultural production on environment. However, environmentally friendly methods may involve some sacrifice of yield, in which case there is the question, Who should pay the cost of this? Fertilizer recommendations for vegetables based on maximum yield usually involve some cost to the environment. Conversely, environmentally optimum application rates can result in a substantial loss of yield
In Asian countries where fertilizer is relatively cheap in relation to the value of the crop, farmers tend to apply too much fertilizer. This is particularly true of vegetables, since they are a high-value crop. For the farmer, this represents a type of insurance against crop losses due to nutrient deficiencies. However, overuse of fertilizer is not only wasteful, but is damaging to both crop quality and the environment.
Furthermore, vegetables tend to be a short-term crop which are grown as part of a multiple cropping system. In intensive tropical systems with vegetables, and also in temperate systems where protective structures are used, it is common for a number of crops to be grown each year on the same piece of land.
This means that the nutrient supply of each crop is affected by the fertilizer which was applied to previous crops. Efficient fertilizer use means matching the supply of nutrients to those required by the crop. Rather than managing the nutrients for separate successive crops, vegetable production involves managing the nutrient supply and requirements of the total cropping system.
Patterns of Vegetable Production
There seem to be two main patterns of vegetable production in Asia. One is intensive vegetable production, in areas either specially suited to vegetables or near large population centers. The second is a vegetable/cereal cropping system, in which vegetables are usually the subsidiary crop. Combined vegetable/cereal systems can in turn be divided into vegetable production on raised beds in paddy fields after rice, and vegetables grown as an intercrop or relay crop with corn, wheat etc. in rainfed uplands.
Sustainable vegetable production for each of these two systems will take a different course, but in each case there must be a positive nutrient balance. Since N fertilizer rates for vegetables are generally fairly high, there is usually a positive N balance in cereal/vegetable systems. However, this may not be true of all nutrients. For example, boron deficiency is fairly common in the vegetable production area around Chiang Mai, Thailand.
Maintaining the Long-Term Fertility of Vegetable Fields
Intensive vegetable production involves a large volume of output _ 30 mt/ha/crop of Chinese cabbage would be quite a normal yield. Vegetable-producing soils are constantly being mined of nutrients with every harvest. This massive removal must be compensated by a large volume of inputs, either of chemical fertilizer, organic materials, or a mixture of both. While farmers attempt to compensate for nutrients removed by applying the same level of nutrients in fertilizer, it is difficult for them to achieve a proper nutrient balance, especially if they use only chemical fertilizers.
In many other countries, there is a gap between cereal and vegetable yields from farmers' fields and those from research stations. Often in the case of cereals, the gap is caused by underuse of fertilizer, while in the case of vegetables, it may be due to fertilizer overuse. Many soils used for vegetables show accumulation of nutrients over time, rather than depletion. Farmers in Sri lanka even try to reclaim the soil of vegetable fields by removing the topsoil, and adding fresh soil brought in from uncultivated land.
Soil testing is necessary to identify nutrient deficiencies. There is a need for an expanded soil testing service, and for simple and quick testing procedures. In areas where rural transport is difficult, a mobile service which collected samples for testing might be very useful.
Utilization of Organic Wastes
Applied compost and other organic materials are known to have a beneficial effect on soil productivity, and on the control of pests and diseases. Vegetables tend to receive higher applications of organic fertilizer than any other type of crop, the main limits being the cost and availability of compost.
Not only do organic materials benefit the soil and crop but, as one paper presentation pointed out, composting should be seen as part of solid waste management. In most industrialized countries, it is becoming increasingly difficult and expensive to find landfill sites. In the United States in 1993, only 3.1% of municipal solid wastes were composted. The majority of wastes (62.3%) were used as land fill, with the remainder being incinerated or recycled. Raising the proportion of composted wastes would make a large savings in landfill costs. However, effective recycling of municipal wastes needs some preliminary sorting at a household level, so that wastes are already sorted into organic materials, plastic etc. at the point of collection.
The point was also made that organic materials do not necessarily always give higher yields than synthetic ones. Experiments with green pepper in the United States showed that yields were higher when polyethylene mulch was used, compared to organic mulches. However, the fruit were larger when they were grown with organic mulch. Interestingly, the same effect was seen in the following crop of squash, in that the squash were larger in the organic mulch plot, although the overall yield was not any higher. While organic mulches can sometimes give yields comparable to those from plastic ones, this depends on the type and rate of organic mulch used, its effect on soil microorganisms, and the type of vegetable being grown.
Fertilizer, Crop Yields and Nitrate Levels
In some long-term fertilizer experiments at five sites in Taiwan where vegetables had been grown for at least ten years, chemical fertilizers have been applied according to conventional recommendations, together with a small percentage of organic fertilizer. Crops showed a marked response to fertilization, to the extent that if fertilizer was discontinued for only one crop, there was a fall in yield of 20-35%. There was also a fall in the quality of the vegetables. Since large quantities of irrigation water were used in this system, good fertilizer management depended on suitable water management, to minimize leaching.
There was a linear and highly significant relationship between the plant uptake of N, P and K, and the crop yield. There was also a linear and significant relationship between the N content of the plant, and the eventual yield. However, there was a negative relationship between the yield and the P content of the plant, while there was no significant relationship between yield and the plant K content. This perhaps reflects the high levels of available P and K in these soils, all of which had been used for long-term vegetable production.
There was also a correlation between N levels and nitrate levels in the plant. Thus, any reduction in nitrogen applications to reduce nitrate levels tended to result in a fall in crop yield.
Crop Selection and Fertilizer Efficiency
There is a considerable difference between different types of vegetable, in terms of their efficiency of nitrogen use. Data presented at the seminar showed that spinach and leek, for example, both use nitrogen inefficiently. Such crops may have nitrogen leaching losses of more than 200 kg N/ha, compared to losses of 30-40 kg N/ha for cabbage. Reducing the rate of losses for crops such as leek would mean a great increase in fertilizer efficiency.
A further interesting point made is that some crop combinations make more efficient use of fertilizer than others. For example, combinations of rice-green pepper and rice-tomato are extremely inefficient in their use of N, with an N recovery rate of only 27%. In contrast, a combination of rice-mungbean-corn showed highly efficient N use, with a recovery rate of 56%. Another efficient combination, in terms of N use, was rice-garlic-sweet potato.
This shows the importance of treating the fertilizer requirements of the total cropping system, rather than of the separate crop components. The relative fertilizer efficiency of crop combinations needs to be taken into account when fertilizer recommendations are being made.
Appropriate crop combinations sometimes allow a vegetable crop to be grown in a cereal-based system without any additional fertilizer. In India before the 1960s, when indigenous cereal varieties were grown, little fertilizer was used, and legume pulses were grown in rotation or as intercrops. With the introduction of high-yielding varieties and chemical fertilizers, cereals began to dominate the cropping system at the expense of legumes. Nowadays, there is a return to something like the traditional pattern, since short-duration varieties make it possible to grow mungbean as an intercrop or as an interim crop. Mungbean yields are about 0.2-1.0 mt/ha, and the production potential of the following crop is sustained or even improved, especially if the mungbean straw is incorporated into the soil. If the previous crop has been given the recommended fertilizer applications, no more fertilizer is needed for the mungbean. Thus the production potential of the farm is increased, at a relatively low cost.
Conclusion
It is generally agreed today that an ideal agricultural system must be not only productive but sustainable. Some types of vegetable production are presumably more sustainable than others, but to define which these are, we need indicators of sustainability. It is still diffiocult to define these indicators, especially in quantitative terms. General indicators of sustainability have been suggested, including productivity (yield), stability (yield over time), protection of the resource base, viability (whether a system is economically profitable) and social acceptability (to both farmers and the general public). The problem is to apply such criteria to give quantified results.
It is clear that many improvements are possible in fertilizer efficiency. These include improved water management, efficient crop combinations, and improved formulations such as slow-release fertilizers to synchronize nutrient availability with crop needs. The timing of fertilizer applications is also important, not only to minimize leaching losses, but also to maximize yield. Vegetables are very sensitive to nutrient deficiencies during the early growth period. Unlike cereals, any deficiency suffered by a vegetable crop early on is not compensated during later growth stages.
Because of the high levels of nutrients removed with the crop, and because vegetables are a high-value crop, vegetables often receive very heavy fertilizer applications. Unbalanced fertilizer use and micronutrient deficiencies are common problems. There is a widespread need among the region's vegetable farms for more soil testing, including perhaps a mobile service specially adapted to the needs of small-scale farmers.
Planning and implementation of research should follow an integrated approach, with input from economists, plant pathologists and soil scientists as well as agronomists. Farmers should also be included, not just to evaluate new technology, but also to contribute from their own experience and traditional knowledge. Models are likely to play an increasingly important role, not just in research but also in extension with the development of DSS (Decision Support System) models.
Sustainable agriculture must take into account the long-term impact of agricultural production on environment. However, environmentally friendly methods may involve some sacrifice of yield, in which case there is the question, Who should pay the cost of this? Fertilizer recommendations for vegetables based on maximum yield usually involve some cost to the environment. Conversely, environmentally optimum application rates can result in a substantial loss of yield
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