ORGANIC FARMING : A BOON FOR OUR FARMERS
Dr. N.G. Hegde
BAIF Development Research Foundation
Warje, Pune
Indian Agriculture
India is a leading developing country, making economic progress through agricultural development. Farming is the major source of employment and livelihood in rural areas, where about 65-70% of the people are living. However, the agricultural production has not reached the expected stage because of lack of resources such as water, nutrients, good quality planting material, plant protection and post harvest management. Over 75% of the farmers hold less than 2 ha. land and about 72% of the area under agriculture is dependent on rainfall, whereby return on investment is not assured due to failure of rains and other calamities. These small and marginal farmers who spend over 85% of their income on food alone have no opportunity to make any savings. In the absence of cash reserves, the poor farmers are unable to procure necessary inputs for crop production. As against the world average of 172 kg/ha chemical fertilisers, Indian agriculture consumes only about 70 kg/ha. The average fertiliser consumption is even lower, if fertilisers applied for three important crops like paddy, wheat and sugarcane are not considered in the average.
Thus a majority of the crops suffer from nutritional deficiency. Under such conditions, organic farming can be a boon, as the farmers can enrich their soil and manage their crops better, without depending on expensive external inputs. Organic farming can also help to avoid environmental pollution, while keeping the cost of food production under control. With the modernisation of agriculture in the developed countries, expensive agro-chemicals are being deployed for enhancing the crop yields. However, it is necessary to maintain a balance of various inputs with proper monitoring of soil fertility and crop health to optimise the benefits. This implies tillage and water management as well. These technologies when transferred to developing countries, fail to deliver similar results because of untimely application of inputs, inefficient equipment and tools and inadequate supervision. In the absence of adequate drainage system, the agro-chemicals percolate down and pollute the soil and ground water. The chemical fertilisers and pesticides when applied in heavy doses particularly at a later stage of crop growth are absorbed by leaves, fruits and seeds and pollute the food commodities, thereby causing health hazards. Thus organic farming is helpful for production of safe food at low cost. There are many components of organic farming, which can reduce the cost of production and ensure a clean environment. These include use of farmyard manure, composts, green manure, organic mulches, vermicomposts, algae and biofertilisers, which can enrich the soil and support the crop growth and yields. Many botanicals having pesticidal and fungicidal properties can be substituted for plant protection chemicals. Certain micro organisms which are harmless to human and plants but capable of destroying insects can also be used effectively for crop protection. Microbes such as mycorrhizae have been helpful in overcoming the stress from drought and diseases, while improving the availability of P. Thus integration of various biological measures can reduce the cost of agricultural production, while ensuring healthy food and a clean environment.
Organic Sources of Nutrients
As a part of organic farming, nutrients should be supplied from organic sources such as farmyard manure (FYM) or compost. FYM contains about 0.5% nitrogen, 1.0% phosphorus apart from other nutrients and humus. FYM also improves the soil productivity by improving water retention capacity and promoting beneficial micro-organisms. However the recommended dose of FYM, even for common food crops is in the range of 15-20 tons/ha which is bulky. It is also difficult to procure large quantities of FYM to meet the entire nutritional requirements particularly when the land holding is large or soil productivity is low. Hence it may be worthwhile to produce other forms of organic manure, such as NADEP, compost, green manuring, vermicompost and biofertilisers to reduce the dependence on chemical fertilisers.
Composts
Compost is prepared by degeneration of agricutural and other organic waste materials. It is an age old practice to dig a shallow pit of 75-90 cm depth and 1.0 m width and then spread the wastes in the pit as and when generated. The material gets decomposed over 4-6 months. This practice also helps to keep the environment clean. However, as the process is slow and the output in normal course is very small, farmers have not been taking keen interest in this activity.
NADEP is the modified method of composting. NADEP is named after its inventor. This method advocates the use of aerated tank of 3.66 m x 1.5 m x 0.90 m, constructed with brick or any other material. Bamboo and palm leaves can also be used to reduce the cost of the tank. The ground should be made compact with mud and dung to reduce seepage. This tank can accommodate 1350 kg agricultural waste, 90 kg cow dung, 1675 kg fine soil and 1350 litres water. All these materials should be kept ready and the tank should be filled within 1-2 days by spreading first layer of agricultural waste, second layer of water and dung mixture followed by a layer of sand. This can be repeated several times to fill the tank in 12-14 layers. The top of the tank should be covered with 7.5 cm thick layer of clay soil mixed with dung.
Any cracks developed in due course can be sealed with mud paste. The top of the tank should be protected from direct sunlight and heavy rains by covering organic mulch or by erecting a shed. This tank will produce 2.5 tons of fine compost in 3-4 months. Green manuring is another age old practice for producing organic matter in the field itself. This can be done by growing a short crop of green manure by sowing seeds of sunhemp, denicha, horse gram or beans and turn it in the soil, at 8-10 weeks age. The type of crop depends on the soil type, moisture availability season and cost of seed. The other method is to grow shrubs and trees on field bunds or in other areas and top branches from time to time for green manure. Such branches can also be used as mulch particularly in fruit orchards. The mulch conserves soil moisture in the initial stage and subsequently turns into organic manure. When the volume of dried leaves (litter) is high, such material can be used directly in orchards as mulch instead of using for manure. Availability of green and dry foliage is the major constraint for adoption of this practice on a wider scale.
Vermicompost
It is an extension of composting having added benefits. Earthworms constitute more than 80% of the soil invertibrate biomass. They play a significant role in maintaining the soil productivity. Earthworms enhance the decomposition of organic matter and they also contribute 20-100 kg nitrogen per ha per year, besides other mineralised nutrients and plant growth factors. Earthworms help the growth of beneficial bacteria and actinomycetes by providing optimum conditions of temperature, moisture, aeration and phosphate. Worms also produce several enzymes which split complex polymers in wastes into simple molecules which are further utilised by the soil micro-organisms.
Worms assimilate some of the micro-organisms as their food. Hence more the microbial biomass in the soil, more will be the worm biomass. Worms enrich the soil with oxygen, thus encouraging aerobic micro-organisms. These are useful micro-organisms which perform several important functions like nitrogen fixation, nitrification, production of enzymes, antibiotics, growth hormones, etc. In normal soils, where the microbial biomass content acting in the top 30 cm is active, earthworms can enhance the quantity upto 10 tonnes/ha in addition to their own population of 1 ton.They also control parasitic nematodes and enhance the crop yields. Although they are present in the soil, deliberate attempts to enhance their population in the soil through application of vermicompost will be beneficial.
Biofertilisers : Rhizobia and Azotobacter
Use of biofertilisers carrying Rhizobium and Azotobacter for crop production is in practice since a long time. These micro-organisms fix atmospheric nitrogen and supply it to plants. Hence biofertilisers can substitute chemical fertilisers to some extent. However these products did not become popular until recently, because of inadequate awareness, lack of marketing outlets and insignificant results in the field. Biofertilisers produced with out-dated technology by small research laboratories had no marketing expertise to launch these products in the field. Hence the biofertilisers could not establish their superiority before a well planned marketing network of the fertiliser industry. The poor quality carrier used for production affected the shelf life. These problems have now been solved through the application of biotechnology combined with a marketing strategy to sell through fertiliser marketing network, without any competition. Moreover, the focus for promoting biofertilisers has shifted from more intensive crops like groundnut, wheat, paddy and sugarcane to other crops where farmers have not been applying adequate doses of fertilisers. This has helped the farmers to improve the crop yields while reducing the cost of production. Those who have realised these benefits are now coming forward to purchase biofertilisers.
Blue-green Algae
Blue-green algae belonging to genera Nostoc and Anabaena, fixes atmospheric nitrogen in symbiotic association with waterfern belonging to Azolla species. Azolla-Anbaena association can contribute over 100 kg nitrogen per ha per crop like paddy under lowland conditions. Hence algae is an excellent association to supply nitrogen in low lying areas.
Phosphate Solubilising Micro-organisms (PSM)
Soils having high pH have the problem of phosphorus availability for plants. In such a situation, phosphate solubilising micro-organisms (PSM) can be useful to reverse this process. PSM is a group of heterotrophic micro-organisms capable of solubilising inorganic P from insoluble sources. These include the following bacteria, fungi and yeast. There are :
Bacteria: Bacillus megaterium, B.circulans, B.subtilis, Pseudomonas straita, P.rathonis;
Fungi: Aspergillus awamori, Penicillium digitatum, Trichoderma sp.
Yeast: Schwanniomyces occidentails.
The solubilisation of P by these micro-organisms is attributed to excretion of organic acids like citric, glutamic, succinic, lactic, oxalic, glyoxalic, maleic, fumaric, tartaric and Ketobutyric. These micro-organisms weather rock phosphate and tricalcium phosphate by decreasing the particle size, reducing it to nearly amorphous forms. In addition to P-solubilisation, these micro-organisms can mineralise organic P into a soluble form.
The P-solubilisers also produce fungistatic and growth-promoting substances which influence plant growth. The performance of these micro-organisms is affected by availability of a carbon source, P concentration, particle size of rock phosphate and other factors like temperature and moisture. PSM will be a boon for the farmers where the soil pH is high.
Vesicular-Arbuscular Mycorrhizae (VAM)
The symbiotic association between plant roots and fungal mycelia is termed as mycorrhiza and it belongs to the following orders :
Order / Sub-order / Family / Genus1. Endogonales / Endogonaceae / Endogone
2. Glomales / 1. Glominae / i. Glomaceae
ii. Acaulosporaceae / Glomus sclerocystis
Entrophosphora acaulospora
2. Gigasporinae / i. Gigasporaceae / Gigaspora scuttellispora
These fungi are found to be associated with a majority of agricultural crops. VAM occur over a broad ecological range from aquatic to desert environments. VAM have been associated with increased plant growth and enhanced accumulation of plant nutrients, mainly P, Zn, Cu and S through greater soil exploration by mycorrhizal hyphae. It has also been reported that VAM stimulate plant growth by physiological effects other than by enhancement of nutrient uptake or by reducing the severity of diseases caused by soil pathogens.
The survival and performance of VAM fungi is affected by the host plant, soil fertility, cropping practices, biological and environmental factors. Maximum root colonization and sporulation occur in low fertility soils. The results of field trials conducted in India indicate that VAM inoculations increased yields significantly and the response varied with soil type, soil fertility and VAM cultures. The major constraint for field trials with VAM has been the inability to produce `clean pure' inoculum on a large scale as the fungi are obligate symbionts and have to be maintained and multiplied on living host plants. In such a situation, until suitable methods are evolved to multiply on a large scale, it is better to concentrate on crops normally grown in nursery beds where they can be easily inoculated with selected strains and then transplanted.
Plant Protection
Application of eco-friendly organic farming technologies for plant protection have been gaining popularity during recent years. Spraying of Bacillus thuringiensis, a pathogen capable of attacking several lepedopteran insects has been successfully adopted in many countries to control pests on many crops. However, in India this has not been tried, due to the fear of damage caused to silkworms. Scientists in USA have inserted genes coding the toxin of B.thugingiensis into Pseudomonas fluorescence, a bactorium that inhabits the roots of crop plants, thereby enabling corn plant to withstand cutworm attack. It is learnt that similar efforts have been made to control the insects of cotton crop.
Commercial production of biopesticides containing different bacteria, fungi and viruses have also been undertaken for control of certain insects. These biopesticides are developed by culturing the pathogens found in the insect species. With the environmental restrictions on chemical pesticides, these alternatives are gaining popularity in the West. There is good scope to promote such products. Breeding of sterile insects is another technique for pest control. When a particular insect is damaging the crop, sterile males of some species are bred in the laboratory and released in the field. These insects compete with the normal ones for survival and breeding and control the multiplication.
Many botanicals have the properties to control pests and diseases of plants. Extracts of neem, pongamia, custard apple, callophyllum (undai) seeds can control a wide range of insects, bacteria, fungi and virus. Botanical pesticides are not only eco-friendly but also economical. Farmers can easily prepare their own pesticides from these seeds, although commercial products are sold in the market. Popularisation of such practices can promote the cultivation of these species on wastelands.
Promotion of Organic Farming
Organic farming being an eco-friendly, low cost technique using locally available inputs, it has good scope for wider replication. Promotion of organic farming should be a regular campaign as a part of social marketing at par with the marketing of agro-chemicals, through publicity and field demonstration. To enhance the benefits of organic farming and to compensate for the low yield particularly during the initial stages, special marketing efforts should be made to sell the products at premium prices. Formation of consumer network for distribution of organic products can facilitate easy marketing.
Adequate literature on the techniques and benefits of organic farming should also be made available to farmers through various outlets and public communication systems for better adoption of this technology.
The success of organic farming is dependent on soil fertility and regular monitoring of soils and crop growth. It is advisable to shift gradually from normal cropping practices to organic farming where soil productivity is poor and procurement of organic manure is difficult. The organic crop yields are likely to be lower as compared to the crops grown with agrochemicals. Such losses in crop-yields are compensated by low cost of inputs, higher price recovery and pollution free environment. Above all, the poor farmers do not have to depend on the high cost of external inputs.
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