In this article we will discuss about:- 1. Definition of Conservation Agriculture 2. Effects of Conservation Agriculture 3. Constraints.
Definition of Conservation Agriculture:
Conservation agriculture was defined in the First World Congress on Conservation Agriculture as the practice to promote the infiltration of rainwater, where it falls and its retention in the soil as well as a more efficient use of soil water and nutrients leading to higher and more sustainable productivity.
Nowadays, in most the countries the conservation agriculture has been successfully implemented with very promising results on economic benefits as well as in improving of water resources. Conservation agriculture is also very conducive to modify the soil-water plant environment.
Under conservation agriculture the following practices can be undertaken:
i. Crop residue management for developing a good porosity in the soil media.
ii. Weed control by using suitable farm machines/implements.
iii. Development of soil covers for checking the soil erosion/soil loss.
iv. Minimum soil disturbance for sowing the seeds, using zero till seed drill.
v. Use of crop rotation practices.
In conservation agriculture the possibility of soil damage is reduced, and recuperation of soil architecture is very quickly gained to that of the unimproved fallow system. An appropriate crop rotation is important for development of soil cover, which is effective to check soil erosion.
The residue-based zero tillage practices are preferred to follow on structurally damaged soils. For which, the tillage operation can be done to break the underlying hard soil pan for storing rainwater into the soil. Also, the practice of strip cropping with legume crop between rows of main crop (e.g. maize) can be taken; and a good crop cover or residues without soil disturbance by tillage can be established.
The residues form a kind of protective cover over the top soil surface, also provides a means for adding organic contents in the soil. The residues get decompose and mixed in the soil; and thus adds organic contents. In the process, the worms and other soil mesofauna burrow within the soil in seeking of food, and forms channels and bio-pores in the soil, through which air and water move easily.
In United States the zero tillage has been in practice from last several decades; and coverage area is increasing at accelerated rate. In Brazil and Paraguay the lands suffer with severe erosion problems due to rainstorms of very high intensities during southern summer.
The heavy disk ploughing followed by disk harrowing is very common practice there, resulted many problems, such as:
i. Loss of organic cover of the forest area.
ii. Pulverization of surface soil along with compaction of sub-soil layer.
iii. Loss of organic matter from the upper soil layers due to rapid oxidation.
iv. Loss of runoff generated from the rainstorm.
v. Reduction in soil depth due to erosion of topsoil.
vi. Reduction in surface water flow and drying-up of streams and rivers during dry seasons.
The conservation agriculture has also been proved very promising in control of soil erosion/loss in many countries. In Paraguay, the zero tillage was firstly used in the late 1970s but was not widely adopted on mechanized medium and large farms. By the year 1993 about 20000 ha area was engaged under conservation tillage which was further extended to 250000 ha by 1995-1996 (FAO, 1997) and to 480000 ha by the year 1997, which was 51% of the total cultivated area of Paraguay.
Like conservation tillage, this technique also includes several farming practices. In general, all those farming practices, which improve the crop growth, yield and land husbandry, and decrease the amount of labour or fertilizer inputs, are included under conservation farming.
Few important practices of conservation farming followed in different countries, are described as under:
Farming on Ridge:
In India this system is followed at wide scale. In this technique the planting is done on gentle gradient ridges. Sometimes, it is also followed in the combination of graded channel terrace for making more effective.
In this farming system, the infiltration rate gets increase; and the surplus rainwater flows (overland flow) over the land surface at very slow velocity, as result the soil erosion gets reduce, significantly. Also, sometimes this practice is used with vegetative mulches (crop residues) to encourage infiltration rate, and reducing the formation of overland flow; and the soil erosion, thereby.
The practice of strip cropping is most useful on gentle slopes, to reduce the soil erosion by appreciable level without aid of any bunds or drains in the land segment.
The Crop rotation is another well-established and simple practice of conservation farming. The main objective of this system is to improve the soil fertility by growing legumes; to control pest or disease; and to check the soil erosion. Under this kind of practice in semi-arid parts of Australia, the cereal crop in alternate array with self-regenerating annual forage legume have resulted very significant effect on fertility enhancement along with appreciable control of soil erosion.
Fallowing or keeping the land fallow is done to conserve moisture contents in the soil profile for rain fed farming. In drier wheat lands of Australia, this is done in summer to enrich soil moisture before sowing the winter wheat. This practice has also been reported very effective in cracking clay soils, where there is risk of soil erosion during summer season, when high-intensity summer thunderstorms fall on the bare soil. However, this practice is not suitable, in general, because of several reasons.
The mixed cropping and inter-planting are widely used as traditional farming techniques. In this practice, the combination of crops of different planting dates and of different length of growth periods is used.
This practice involves relatively large amount of labour requirement for planting of different crops and their harvesting, separately; and also there is possibility of mid-season change in cropping plan depending on the rainfall pattern in the early of season. On the other hand, if legumes are taken under mixed cropping, then there is enrichment of nitrogen level in the soil for cereal crop.
The mulching offers advantage regarding providing of protective cover to the soil, especially when crop cover is not practical to develop. Mulching improves soil infiltration, and also increases the soil temperature.
Also, there are few disadvantages of this practice, given as under:
i. Huge amount of crop residue requirement.
ii. Problems of pest, disease, or nitrogen lock-up.
iii. Lack of implements, which can plant, or drill through the mulched layer.
iv. Rapid oxidization of organic mulches at high temperatures.
Effects of Conservation Agriculture:
1. Crop Yield:
The effect of conservation agriculture on crop yield is very conducive. As compared to conventional cultivation the conservation tillage operations such as minimum tillage, zero tillage etc., increase the crop yield, better. On this aspects the impact of conservation tillage on wheat and soybean yield based on several years harvested data, over traditional method is presented in Table 11.5.
2. Soil Moisture:
The soil moisture conservation due to practices of conservation agriculture is very promising. However, as compared to zero tillage the practice of creating big size pore spaces in the soil, and leaving a rough surface is found more effective for moisture conservation in the soil. Also, the practices such as mulch tillage, residue management and development of soil cover cause very conducive effect on moisture conservation. Especially, for better soil moisture conservation from the rainwater, the tillage operations should be performed before start of rainy season.
On ploughing the topsoil layer becomes rough and porous, as result when rainfall takes place then a large percentage of rainwater gets absorbed by the soil because of surface roughness. The rainwater stored in the soil can be utilized for rain fed farming in better way by selecting suitable cropping system, based on the level of soil moisture. Derpsch et al. (1991) noticed that on use of residues the percentage of rainfall infiltrating into the soil was quite high as compared to without residues.
3. Soil Health:
The impacts of zero tillage and conventional tillage on soil health are presented by comparing few soil indicators, such as:
i. Size and stability of soil aggregates.
ii. Enrichment of soil organic matter.
iii. Increase in number of earthworms.
The conservation tillage develops a significant effect on soil stability and size of aggregates as well. In unstable soil, if tillage operation (ploughing) is done at high moisture content then there develop large size soil aggregates after drying. And in this condition, an unstable soil becomes stable to resists the wind erosion, significantly. The conservation tillage also plays very important role to enrich the organic matters in the soil, in which the green manuring is one of them.
The green manuring can be done by growing green manure crops in the field, and turning them in the soil by using soil turning implements. After lapse of few months, the turned green crop gets mixed in the soil; and thus enriching the level of organic content in the soil. Since, soil is in well-aerated condition on use of conservation tillage, and is well with organic contents, therefore, there is created a very good environment for nourishing the earthworm.
4. Runoff and Erosion:
The practices of conservation agriculture such zero tillage, minimum tillage, residue management, soil cover etc., are very effective to reduce the runoff and soil erosion, both. In zero tillage, there is very little soil disturbance, i.e. soil is not tilled to a greater depth, but there develops soil roughness. These two effects in combine form reduce the runoff/overland flow rate.
Similar effect is also found in minimum tillage case, but less in extent as compared to the zero tillage. The residue management and measures for development of soil covers also cause very influencing effect on runoff and soil erosion, both. In these two cases, the soil surface always remains in rough condition, as result the level of runoff or overland flow likely to get generate is reduced to a large extent, which also lowers the rate of soil erosion.
5. Farm Economics:
The conservation tillage plays very significant role to enhance the economic returns from the farm.
The possible reasons may be:
i. Conservation of soil, water and nutrients in the soil.
ii. Profile water management.
iii. No effect on levelness of top soil surface.
iv. Easy application of suitable farming techniques.
v. Timely accomplishment of all farm operations.
vi. Lesser requirement of crop inputs.
In general, the on-farm benefits are realized in following terms:
i. Rapid increase in organic matter content in the upper soil layers, causes increase in the biodiversity and activity of earthworms, fungi, bacteria etc., in the soil.
ii. Better soil structure & stability of soil aggregates, and thereby enhancement in infiltration rate.
iii. Reduction in soil loss by more than 80%; runoff by 50% or more and safe use of sloping areas.
iv. Increase in nutrients storage; or greater availability of P, K, Ca, Mg in the root zone, causing lesser fertilizer requirement.
v. Better seed germination and plant growth; better root development with greater depth; and good resilience of crops in rainless periods due to increased water holding capacity.
vi. Increase in crop yield.
vii. Reduction in variations of soil temperature during daytime, and thus to cause absorption of water and nutrients, significantly.
viii. Lesser investment on use of machineries and animal power for crop production.
ix. Reduction in cost of labours, fuel and machineries.
x. Greater flexibility in farm operations, especially regarding optimum date of planting.
xi. Increase in possibilities for diversification of livestock, high-valued crops, vertical integration into product processing and other activities, and improvement in quality of life.
And off-farm benefits are given as under:
i. Reduction in flood risk by 30-60% due to enhanced infiltration rate, and delay in overland flow.
ii. Increase in time of concentration; better ground water recharge and improvement in water-table position.
iii. Lesser use of herbicide, pesticide and more recycling of animal wastes.
iv. Reduction in pollution and eutrophication of surface water by agro-chemicals mixed in the surface runoff and eroded soils.
v. Lesser sedimentation and infrastructure damage, such as silting of waterways, large dams etc.
vi. Reduction in water treatment cost due to presence of lesser sediment, bacterial and chemical contaminations.
vii. Saving up to 50% of cost of erosion control measures’ use.
viii. Reduction in fuel consumption by 50-70% or more.
ix. Reduction in the pressure on agricultural frontier.
x. Reduction in deforestation.
xi. Enhancement in diversity and soil biota activities.
Constraints of Conservation Agriculture:
Although, the conservation agriculture is very successful for sub-humid and humid climates, but there are few important constraints for its application in semi-arid environments, which may cause hindrance.
The typical constraints of conservation agriculture are outlined as under:
i. Shortage of water limiting crops.
ii. Availability of insufficient residues.
iii. Sale or preferential use of crop residues for fodder, fuel and building materials.
iv. Inability to control livestock grazing, especially in the areas where communal grazing is prevalent.
v. Inability to control residue consumption by termites.
vi. Insufficient money or credit to purchase suitable equipments.
vii. Lack of knowledge on conservation agriculture amongst extension and research personnel.
Nowadays, a number of techniques have been developed and tested to overcome various constraints related to conservation agriculture. For example – in the areas where crop residues are preferentially used as fodder, there should be developed additional new sources of fodder production to overcome this type of constraint, but there must be provision for protection of such fodder lands against grazing. The hay or silage should be produced as additional dry-season fodders using improved pasture species, or from forage trees or crops of high biomass.
Similarly, few crop species are not very suitable to direct sowing into crop residues, because of likelihood of development of weed, pest or disease problems. The conservation agriculture technique is not immediately successful on seriously degraded soils with surface crusts, compacted soils, low fertility or severe weed infested lands, unless these problems are first removed using suitable remedial measures.
Similarly, the hardpan soils are also not immediately suitable for conservation agriculture, because of soil compaction and reduced soil porosity and improper subsoil environment to develop a good root system.
However, the problem of hardpan can be eliminated by using deep ploughing operation followed by establishment of cover crops prior to introduce conservation agriculture, and then growing of the crops producing large quantity of residues.
The conservation agriculture is less likely to get success in poorly drained soils, because the added residues can cause anaerobic condition in the soil, in which the toxic substances can harm the crop growth. The use of no-till planters and seed drills for direct sowing may be a major constraint because of their heavy cost. However, by designing and constructing low cost hand tools or animal drawn implements this constraint of conservation agriculture can be removed.