tillage

tillage

1. TILLAGE Tillage operation are carried out to prepare a fine seed bed for sowing crops. Tillage is the physical manipulation of soil with tools and implements to result in good tilth for better germination and subsequent growth of crops. Tilth is the physical condition of soil resulting from tillage. CHARACTERISTIC OF GOOD TILTH: Tilth indicates two physical properties of soil i.e. the size distribution of aggregates and mellowness or friability of soil. Friability is that property of soil by which when the clods become dry they are more crumbly. A soil with good tilth is quite porous and has free drainage up to water table. The capillary and non-capillary pores should be in equal proportion so that sufficient amount of water is retained in the soil as well as free air.

2. OBJECTIVES OF TILLAGE Suitable seed bed preparation Weed control Soil and water conservation Improvement of soil structure Soil permeability Soil aeration Root penetration Destruction of pests. Good seed bed is necessary for early seed germination and initial good stand of the crop. The seed bed should be fine for small seeded crops and moderate for bold seeded crops. Intimate contact between the soil particles are necessary to facilitate moment of water for quick germination.

3. Weed control is an important objective of tillage. Proper tillage results in soil and moisture conservation through higher infiltration, reduced run- off and increased depth of soil for moisture storage. When the compact soil is ploughed it becomes fluffy and can hold more amount of water. Removal of hard pans increases the soil depth for water absorption. Surface roughness and furrow slow down the velocity of run-off water and provide enough time for infiltration of water . Soil permeability is increased by breaking the compact layers. Tillage improves soil aeration which helps in multiplication of micro-organisms. Organic matter decomposition is hastened resulting in higher nutrient availability. Increased aeration also helps in degradation of herbicide, pesticide residues and harmful allelopathic effect exuded by roots of previous crops or weeds.

4. Tillage has limited impact on root growth as its roots occupy only a tenth of the soil mass. However, breaking of hard pans and compact layers increase depth of penetration of roots. The stubbles of previous crop are removed following tillage resulting in reduced pest attack on the succeeding crop. Crop residues and farmyard manure are incorporated into the soil. Herbicides and fertilizers are also mixed and incorporated into the soil to reduce the volatilization losses.

5. INFLUENCE OF TILLAGE ON SOIL PHYSICAL PROPERTIES: Tillage has considerable influence on soil physical properties like pore space, structure, bulk density, water content and colour . These effects of tillage last for about a month. Tillage practices have therefore greatest effect on seed germination, seedling emergence and stand establishment . TYPES OF TILLAGE Primary tillage Secondary tillage Tillage operations are carried out from the time of harvest of a crop to the sowing of the next crop and is known as preparatory cultivation. It consists of three distinct operations like primary tillage, secondary tillage and layout of seed bed.

6. Primary tillage or Ploughing It is the opening of compacted soil with the help of different ploughs. Ploughing ensures inversion of soil, uprooting of weeds and stubbles. The optimum time of ploughing depends upon soil moisture. The depth of ploughing mainly depends on the effective root- zone depth of the crops. Crops with tap root system require greater depth of ploughing than the fibrous roots. The number of ploughings necessary to obtain a good tilth depends upon soil type, weed problem and crop residues in the soil. Depending on the purpose, soil condition and nature of weed problem different ploughs are used, hence selection of plough is important. Mould board plough is used for deep ploughing and inversion. Disc plough is used for cutting of creeping or spreading grass and inversion.

7. TYPES OF PRIMARY TILLAGE Depending upon the purpose or necessity, different type of tillage are carried out. They are deep ploughing , sub-soiling and year round tillage. Deep tillage: One cm of surface soil over one ha of land weight about of 150 tonnes . Therefore, to plough deeper, enormous amount of energy is required. CRIDA (Central Research Institute for Dryland Agriculture) Hyderabad has classified of 5-6 cm depth as shallow, 15-20 cm depth as medium and 23-30 cm depth as deep ploughing . Deep ploughing when done in summer turns out large sized clods, baked by the hot sun. These clods crumble due its alternate heating and cooling due to occasional summer showers. This process of gradual disintegration of clods improves soil structure. The rhizomes and tubers of problematic weeds like cynodon dactylon , Cyprus rotundus die due to exposure to the sun. It also kills insect and pests.

8. A deep tillage of 25- 30 cm depth is necessary for deep rooted crop like pigeon pea, moderate tillage of 15- 20 cm is required for maize. Deep tillage also improves soil moisture content. However , the advantage of deep tillage in dry farming condition depends on rainfall pattern and crop. It is advisable to go for deep ploughing only for long duration and deep rooted crops. SUB-SOILING Hard pans may be present in the soil which restricts root growth of crops. There may be silt pans, iron or aluminum pans, clay pans or man- made pans. Man-made pans are tillage pans induced by repeated tillage at the same depth. These are present in most of the Indian soils. Root growth of crops is confined to top few centimeters of soil where deep penetration of roots is inhibited by hard pans. Sub- soiling is breaking the hard pans without inversion and with less disturbance of top soil. Chisel ploughs are used for breaking hard pans even at 60-70 cm depth. The effect of sub- soiling does not last` very long.

9. Year round tillage: T illage operations carried out throughout the years are known as year round tillage. In dry farming regions, field preparation is initiated with the help of summer showers. Repeated tillage operations are carried out until sowing of the crop. Even after the harvest of the crop the field is repeatedly ploughed or harrowed to avoid weed growth in the off season.

10. b. Secondary tillage: Lighter or finer operations, performed on the soil after primary tillage are known as secondary tillage. After ploughing , the fields are left with large clods with some weeds and stubbles partially uprooted. Harrowing is done to a shallow depth to crush the clods and to uproot the remaining weeds and stubbles. Disc harrows, blade harrows and cultivators are used for this purpose. Planking is done to crush the hard clods to smoothen the soil surface and to compact the soil lightly. Thus, the soil is ready for sowing after ploughing by harrowing and planking. Generally, sowing operations are also included in secondary tillage. Secondary tillage also includes layout of seed bed and sowing. The field has to be laid out for irrigation and planting. These operations are crop specific. Tillage operation carried out in the standing crop is called after tillage. It includes drilling or side dressing of fertilizers, earthing up and inter cultivation.

11. MINIMUM TILLAGE: Minimum tillage is aimed at reducing tillage to the minimum necessary for ensuring a good seed bed, rapid germination, satisfactory stand and favourable growing conditions. Tillage can be reduced in two ways. By omitting operations which do not give any benefit when compared to the cost. By combining agricultural operations like seeding and fertilizer application. THE ADVANTAGES OF MINIMUM TILLAGE ARE-- Improved soil conditions due to decomposition of plant residues in place. Higher infiltration caused by the vegetation present on the soil and channels formed by the decomposition of dead roots. Less resistance to growth due to improved structure. 4 less soil compaction by the reduced movement of heavy tillage vehicles and less soil erosion compared to conventional tillage.

12. However, these advantages are evident only on coarse and medium textured soils and is evident only after 2-3 years of practicing minimum tillage. THE DISADVANTAGES OF MINIMUM TILLAGE: Seed germination is lower. More nitrogen has to be added as rate of decomposition of organic matter is slow. Nodulation is affected in some leguminous crops like peas and cowpea. Sowing operations are difficult with ordinary equipment Continuous use of herbicides cause pollution and perennial weed problems.

13. MODERN CONCEPT OF TILLAGE In conventional tillage the soil is opened with a mould board plough for primary tillage. The soil mass is broken into a loose system of clods of mixed sizes. Subsequently a fine seed bed is prepared by secondary tillage in which operations like crushing of clods, repacking, incorporation of plant residues, fertilizers, smoothing of soil surface etc. is done . This process involves wastage of energy and destruction of soil structure. To cut down cost of tillage researches were done to know whether several tillage operation are needed or not. The concept of minimum tillage was conceived in USA as repeated use of machinery resulted is destroying soil structure, causing soil pans and also soil erosion. The important aspect of tillage is weed control and this can be achieved by using herbicides. The practice of inverting the top soil in order to bury the crop residues is less important object of tillage in modern field management. Crop residues can and in many cases be left over as stubble mulch to protect against soil erosion and evaporation loss. Researchers have shown that frequent tillage is often rarely beneficial and in fact detrimental. All these reasons led to the development and practice of minimum tillage, zero tillage and stubble mulch farming.  

14. The practice of inverting the top soil in order to bury the crop residues is less important object of tillage in modern field management. Crop residues can and in many cases be left over as stubble mulch to protect against soil erosion and evaporation loss. Researchers have shown that frequent tillage is often rarely beneficial and in fact detrimental. All these reasons led to the development and practice of minimum tillage, zero tillage and stubble mulch farming . Cont …

15. ZERO TILLAGE Zero tillage is an extreme form of minimum tillage. In this primary tillage is completely avoided and secondary tillage is restricted to seed bed preparation in the row zone only. It is also referred to as no - till and is resorted to where soils are subjected to wind and water erosion, timing of tillage operation is too difficult and the requirements of energy and labour for tillage is high. Zero tilled soils are homogenous in structure with more number of earthworms. The organic matter content increases due to less mineralization. Surface runoff is reduced due to presence of mulch. The favourable effect of zero tillage is evident after two years of its practices. Till planting is one of the method of practicing zero tillage. The machinery accomplishes four tasks in one operation . Clean a narrow strip over the crop row Open the soil for seed insertion and fertilizer application Place the seed Cover the seed properly

16. The seedling establishment in zero tillage is 20% less than in conventional methods. Higher dose of nitrogen has to be applied as mineralization of organic matters is slow. Large populations of perennial weeds appear. Build- up of pest is also a problem.   STUBBLE MULCH TILLAGE An approach to keep the soil protected at all times from erosion whether by growing a crop or by crop residues left on the surface during fallow periods is known as stubble mulching tillage or stubble mulch farming. It is a year round system of managing plant residue with implements that induce residue, loosen the soil and kill weeds. Soil is tilled as often as necessary to control weeds during interval between two crops. Good management of stubble mulch farming system begins with the harvest of the crop . Stubble mulch tillage, however, presents practical problems. The residue left on the surface interferes with seed bed preparation and sowing operations. The traditional tillage and sowing equipment is not suitable under these conditions.