Conservation Tillage : Type, Advantage and Limitation

Conservation tillage is any method of soil cultivation that leaves the previous year's crop residue (such as corn stalks or wheat stubble) on fields before and after planting the next crop, to reduce soil erosion and runoff. To provide these conservation benefits, at least 30% of the soil surface must be covered with residue after planting the next crop. Some conservation tillage methods forego traditional tillage entirely and leave 70% residue or more.

The main principle of conservation tillage includes three main points:

1. Retention of crop residue: It helps in checking the evaporation of soil moisture by covering the soil capillary. It also prevents the soil erosion. The residue also serves as a rich source of humus and helps to increase the fertility of the soil.
2. Soil tilling with at least 30% surface covered with residue
3. Crop rotation: it helps to increase the soil fertility. It also eradicates the weed and pest problem.

         Conservation tillage has two basic advantages for the grower: conservation of soil, water, and soil organic matter; and reduction of costly inputs while maintaining or improv­ing crop yields and profits. The types of conservation tillage are as follow:

1. Minimum tillage/ reduced tillage

Minimum tillage is aimed at reducing tillage to the minimum necessary for ensuring a good seedbed, rapid germination, a satisfactory stand and favorable growing conditions. Tillage can be reduced in two ways

1. By omitting operations that do not give much benefit when compared to the cost
2. By combining agricultural operations like seeding and fertilizer application.

Minimum tillage has certain advantages:

1. Improved soil conditions due to decomposition of plant residues in situ
2. Higher infiltration caused by the roots
3. Less resistance to root growth due to improved structure
4. Less soil compaction by the reduced movement of heavy tillage vehicles
5. Less soil erosion compared to conventional tillage

Minimum tillage also has some disadvantages as

1. Seed germination is lower with minimum tillage
2. More nitrogen has to be added as rate of decomposition of organic matter is slow
3. Nodulation is affected in some leguminous crops like peas and broad beans
4. Sowing operation is difficult with ordinary equipment
5. Continuous use of herbicides causes pollution problems and the dominance of perennial problematic weeds.

Minimum tillage can be practiced in different methods as

1. Row zone tillage
2. Plough plant tillage
3. Wheel track planting

2. Zero tillage

Zero tillage is an extreme form of minimum tillage. Primary tillage is completely avoided and secondary tillage is restricted to seedbed preparation in the row zone only. It is also known as no-till and is resorted to where soils are subjected to wind and water erosion, timing of tillage operation is too difficult and requirements of energy and labour for tilling is too high. Zero tilled soils are homogeneous in structure with more number of earthworm, the organic matter content increases due to less mineralisation. Surface runoff is reduced due to the presence of mulch. Till planting is one of the methods of practicing zero tillage. In zero tillage, herbicide functions are extended.before sowing, the vegetation present has to be destructed for which broad spectrum , non selective herbicides with relatively short residual effect (paraquat, glyphosate) are used. During the subsequent stages, selective and persistent herbicides are needed.

3. Mulch tillage Mulch tillage system varies , but the common objective is to leave crop residue on the surface of soil to serve as mulch. A variety of implements are used to incorporate a part of the crop residue into the soil, the remainder left on the top. One type of mulch is stubble mulch tillage, in which the goals are to conserve  moisture and to protect the soil from wind and water erosion. Implements such as sweep plow, chisel plow, and stubble mulch plow are use in various mulch tillage systems.

Two methods are adopted for sowing crops in stubble mulch farming

1. Similar to zero tillage, a wide sweep and trash bars are used o clear a strip and a narrow planter shoe opens a narrow furrow into which seeds are placed.
2. A narrow chisel of 5 to 10 cm widh is worked throug the soil  at a depth of 15 to 30 cm leaving all plan residues on the surface. The chisel shatters the tillage pans and surface crusts. Planting is done through resiues with special planters.

4. Strip-Till- The seedbed is divided into a seedling zone and a soil management zone. the seedling zone (5 to 10 cm wide) is mechanically tilled to optimize the soil and micro-climate environment for germination and seedling establishment. The interrow zone is left undisturbed and protected by mulch. Strip tillage can also be achieved by chiselling in the row zone to assist water infiltration and root proliferation

5. Rotational Tillage – Tills the soil at a specific interval.(every crop, every other year)

6. Ridge-Till Ridge-till involves planting row crops on permanent ridges about 4-6 inches high. The previous crop's residue is cleared off ridge-tops into adjacent furrows to make way for the new crop being planted on ridges. Maintaining the ridges is essential and requires modified or specialized equipment

PURPOSES OF DOING CONSERVATION  TILLAGE :

• Reduce erosion and transport of adsorbed particulate phosphorus (P)
• Reduce runoff and transport of soluble P
• Conserve soil moisture for crop use and increased yield
• Reduce particulate emission to the atmosphere
• Crop residue provides food and cover for wildlife
• Improves soil and water quality by adding organic matter as crop residue decomposes; this creates an open soil structure that lets water in more easily, reducing runoff.

EFFECTIVENESS:

Conservation tillage and crop residue management are very effective at reducing soil erosion. Crop, climate and soil conditions impact the efficiency and effectiveness of this set of management practices, and can reduce soil erosion from 30 to 90 percent. No tillage/direct seeding is entirely successful for controlling erosion. The use of current erosion prediction models (RUSLE2 for water and WEQ for wind) will provide an estimate of soil erosion losses or reductions. Absence of soil disturbance and build up of soil organic matter will improve water and nutrient infiltration with time. Up to a 100 percent reduction in runoff has been reported using both conservation tillage and crop residue management. Residue mulch and reduced soil surface disturbance can conserve up to 30 percent more soil water for crop uptake, and, therefore, increase crop nutrient utilization during critical periods of crop production.

COST OF ESTABLISHING AND PUTTING THE PRACTICE IN PLACE:

Conservation tillage and crop residue management will reduce the number of unnecessary tillage passes. Each tillage pass would bury additional crop residue. Tillage operations require operator time, fuel and depreciation of equipment, all of which have a cost to the producer. The initial cost of equipment changeover and increased management required by the producer/operator will be offset by eventual savings in time, fuel and equipment depreciation. Every ton of soil saved by controlling erosion will reduce P transport by a minimum of 0. 1 pound.

OPERATION AND MAINTENANCE:

Long-term tillage reduction and increased crop residue management provide the greatest benefit to the soil over time. Up to seven years of continuous management may be required before full benefits of these practices can be realized. Less tillage and greater amounts of crop residue on the soil surface provide the greatest protection from both soil erosion and nutrient runoff. Existing soil compaction, as well as perennial weed control, must be addressed early in the tillage modification. Perennial weeds can be controlled with crop rotations and mode of herbicide action.

HOW DOES THIS PRACTICE WORK?

Leaving crop residue o the soil surface year around, before and after plantin, provides soil surface protection at critical times to protect the soil against wind and water erosion. Reducing tillage operations improves soil surface properties, including improved soil aggregation accounting for increased infiltration and percolation; less compaction due to less usage of field implements; and more biological activity due to an increase in organic matter. Adding soil surface cover increases water infiltration, reducing soil drying and maintains more moisture for crop utilization.

WHERE THIS PRACTICE APPLIES AND ITS LIMITATIONS:

This set of management practices applies to all cropland where tillage is commonly performed to loosen soil, prepare a seedbed, seed crops and control pests. Both are a most effective control measures where soil erosion processes are carrying particulate phosphorus and where runoff can desorbs phosphorus and carry soluble phosphorus from the soil surface. Although the premises that conservation tillage and crop residue management enhance soil surface properties and prevent soluble nutrient runoff and soil erosion are valid, the use of reduced tillage limits fertilizer and manure (organic) application to surface positions. This builds a stratified layer of crop nutrients (including phosphorus) on or near the soil surface. The P concentrated at the soil surface is vulnerable to extreme rainfall, runoff and wind events that can remove this highly concentrated material from the soil surface.

While reduced tillage and soil organic buildup contribute to stable soil structure deep into the soil profile, this undisturbed structure produces macro pores and preferential flow channels that can direct nutrients (including phosphorus) downward into deeper parts of the soil profile.

BENEFITS OF CONSERVATION TILLAGE

 Environmental Benefits:

v Reduces soil erosion from both water and wind (90% erosion reduction can be expected when using a no-till instead of intensive tillage system).

v Increases organic matter (each tillage trip oxidizes some organic matter; research shows continuous no-till can increase organic matter in the top 2 inches of soil about 0.1% each year).

v Improves water quality (when combined with irrigation water management, crop nutrient management, inte­grated pest management, conservation crop rotation, in integrated system, conservation tillage plays an impor­tant role in improving both runoff to streams, rivers, and lakes as well as water that finds its way into aquifers).

v Improves wildlife habitat (the crop’s residue provides food and shelter. In addition, if combined with other needed habitat, such as grassy cover and woody areas, wildlife may increase significantly).

v Other benefits include reduced soil compaction, utiliza­tion of marginal land, some harvesting advantages, and conservation compliance.

Economic Benefits:

o  Yields are good, if not better, than reduced or intensive tillage system when managed properly.

o  Optimizes soil moisture (improved infiltration and increased organic matter are especially important on droughty soils and may help the crop through a persis­tent dry period. Tillage reduces available moisture by about ½” per trip).

o  Saves time (On a 1000 acre farm, an additional 100 hours are needed for every pass (example based on 18’ disk, 160 hp FWD). Many growers take advantage of the time savings by exploring other “opportunities”).

o  Reduces fuel consumption (no-till can reduce fuel use by 3.5 gallons/acre compared to intensive tillage).

o  Reduces overall production costs (NMSU reports that irrigated wheat yields in Clovis are comparable between conventional and conservation tillage, but production costs for conservation tillage are lower by as much as $50 per acre).

o  Reduces machinery wear (less machinery means fewer pieces need to be replaced. Economists report this amounts to a $5/acre reduction in costs).

Practical benefits 

• Fewer trips across the fields saves time and money (lowers fuel, labor and machinery maintenance costs) and reduces soil compaction that can interfere with plant growth
• Optimizes soil moisture, enhancing crop growth in dry periods or on droughty soils

DISADVANTAGES OF CONSERVATION TILLAGE

• Dries the soil before seeding.
• The soil loses a lot of its nutrients likecarbon, nitrogen and its ability to store water. See No-till farming
• Erosion of soil.
• Higher rate of fertilizer and chemical runoff.
• Decreases the water infiltration rate of soil. (Results in more runoff and erosion since the soil absorbs water slower than before)
• Reduces organic matter in the soil (Microbes, carbon compounds, earthworms, ants, etc.)
• Destroys soil aggregates
• Compaction of the soil, also known as a tillage pan
• Eutrophication
• Can attract some harmful insects to the field.

CONCLUSION.

        Tillage operations are needed for seedbed preparation, weed control, management of crop resi-dues, mixing fertilizer in the soil, improving soil aeration, alleviating compaction and optimizing soil temperature and moisture regimes. The choice of tillage practice depends on soil, climatic, crop and socio-economic factors.

Conservation tillage, a crop production system involving the management of surface residues, prevents degradative processes and restores and improves soil productivity. The experimental data presented in this review show that conservation tillage has a wide application for sustainable crop production on a range of soils in the humid and sub-humid tropics. Major goals of conservation tillage are improved maintenance of surface residue for erosion control and efficient water conservation in the different agro-ecological regions. A limitation is its heavy dependence on herbicides and pesticides, which can lead to serious water pollution.

Conservation tillage procedures must be related to the particular site. Their successful application and use over a wide range of soil conditions depends on matching the procedure to soil type, crop cultivar, climatic factors and other aspects of the environment. Appropriate recommendations to farmers should be based on scientific data from well-designed and adequately equipped long-term experiments. The priorities for the development of conservation tillage systems include:

1. the development of cheap alternative methods of weed control, especially in tropical Africa for farmers with few resources;
2. the development of effective and specific herbicides to control weeds for countries where the farmers can afford them (such herbicides should not harm subsequent crops);

iii.      the development of suitable crop rotations including cover crops, and improved cropping sequences that result in more effective storage of rainfall and efficient utilization of soil available water,

1. provision of appropriate equipment for planting and fertilizer application, and

1. the breeding of crop cultivars that are adaptable to conservation tillage systems and also have characteristics that aid in erosion control as well as improve soil fertility