Tillage and Tilth PDF

Agron-113 Tillage and Tilth Tillage: Tillage comes from an Anglo-Saxon word ‘tilian’ or ‘teolian’ meaning “to plough and prepare soil to sow, to cultivate & to raise crops”. Tillage is as old as Agriculture, Primitive man used to di...

Agron-113 Tillage and Tilth Tillage: Tillage comes from an Anglo-Saxon word ‘tilian’ or ‘teolian’ meaning “to plough and prepare soil to sow, to cultivate & to raise crops”. Tillage is as old as Agriculture, Primitive man used to disturb the soil for placing seed. Jethro Tull is known as ‘Father of Tillage’, Who had Written the book’ Horse hoeing Husbandry’. Definition: Tillage is the physical manipulation of soil with tools & implements for cultivation of crop plants Or Tillage is the manipulation of soil with tools & implements for loosening the surface crust & bringing about conditions favorable for the germination of seeds and the growth of crops. Soil Tilth: Soil Tilth is the term used to express soil condition resulting from tillage. Hence it is the resultant of the tillage. A soil is said to be in good Tilth when it is soft, friable & properly aerated. Definition: The Tilth is the physical condition of the soil brought out by tillage that influences crop emergence, establishment, growth and development. Tilth should be a loose, friable, airy, granular & crumbly structure of the soil with optimum moisture content suitable for working & germination or sprouting seeds or planting materials. Characteristics of good tilth Tilth indicates two properties of soil viz. the size distribution of aggregates and mellowness or friability of soil. Size distribution of soil aggregates: The relative proportion of different sized soil aggregates is known as size distribution of soil aggregates. However, it depends on soil type, soil moisture content (at which ploughing is done) & subsequent cultivation. Mellowness or friability: It is that property of soil by which the clods when dry become more crumbly. They do not crumble into dust but remain as stable aggregates of smaller size. A soil with good tilth is quite porous and has free drainage up to water table. Ideal soil tilth: An ideal soil tilth is not the same for all types of crops & all types of soils e.g. small seeded crops like Sesamum, mustard, bajra require a much finer tilth. Lentil, Black gram, Ahu rice, arhar require a moderately compact & firm tilth. Bold seeded crops like pea, maize germinate even in cloddy seedbed. A very fine, powdery condition of the surface soil is definitely bad for a heavy clay soil as it forms a cracked surface under rainy condition and all the rain water is then liable to be lost by run-off, taking away also with loamy & lighter soils. Objectives of Tillage To achieve adequate soil aeration for gaseous exchange in the soil and root zone. Getting adequate seed-soil contact to permit water flow to seed and root zone. To get a non-crusted soil to permit seedling emergence. To develop a low-density soil that permits root elongation and proliferation. To create an environment that provides adequate light to the seedling. To create a pest and pathogen free environment. Mixing the applied manures and fertilizers with the soil. Removing the hard pans, if any to increase the soil depth for water absorption. Effects of Tillage on soil & Plant growth A) Effect on soil: 1) loosens the soil which favors the germination & growth of crop, 2) Improves the soil structure due to alternate drying and cooling, 3) Improves soil permeability, soil aeration & soil inversion, 4) Facilitates the movement of water in soil, 5) Results in soil & water conservation through higher infiltration, reduce run-off & increase depth of soil for moisture storage, 1 Agron-113 6) Holds more water in the soil, 7) Increased soil aeration helps in multiplication of micro-organisms, 8) Organic matter decomposition is hastened resulting in higher nutrient availability, 9) Increase aeration helps in degradation of herbicide and pesticide residues. Tillage operations also influence the physical properties of soil like: 1) Pore space: Tillage increase the pore spaces i.e. space between the soil particles, due to equal amount of capillary & non- capillary (Macro & microspores) pores. These facilities free movement of air & moisture in the soil & increases infiltration. 2) Soil structure: Soil with crumble & granular clods are considered as soil with good structure which can be achieved by proper tillage operations at optimum moisture. This reduces the soil loss due to erosion. 3) Bulk density: when soil is loosened, the soil volume increases without any effect on weight. Therefore, bulk density of tilled soil is less than untilled soil which is favorable in many ways for crop, microorganisms, etc. 4) Soil colour: Tillage increases oxidation and decomposition resulting in fading of colour. The organic matter is mainly responsible for the dark brown to dark grey colour of soil. 5) Soil water: Tillage improves soil water in different ways which depends on soil porosity, soil depth & roughness. Also increases rate of infiltration, water holding capacity (WHC) & hydraulic conductivity. 6) Soil temperature: Tillage creates up soil temperature for seed germination & seed establishment. Tillage loosens the soil surface resulting in decrease of thermal conductivity (rate of heat transfer at which the heat penetrates) and heat capacity (heat storage / unit area). B) Effects on crop growth: Tillage loosens the soil thereby favors the germination & establishment of seeding. Tillage helps in maintaining the optimum plant stand Increases depth of root penetration Roots proliferate profusely in loose soil & increase the growth of seminal & lateral roots. Reduce the competition within crop & weeds for light, water, nutrients & space thereby helps in better growth of crop Tillage reduces the pest attack on succeeding crop Tillage helps in availability of nutrients to crop in proper amount. Types of Tillage Operations Tillage includes use of different kinds of implements at different times are classified on the basis of their timing into- 3 types 1 Preparatory tillage: Tillage operations that are carried out from the time of harvest of a crop to the sowing of the next crop are known as preparatory cultivation/ Tillage. OR Operations carried out in any cultivated land to prepare seedbed for sowing crops are preparatory tillage. These are time consuming & costly but are to be performed at right stage of soil moisture & with right implements, otherwise it will not help in good growth of crop. These includes in sequence, ploughing, clod crushing, leveling, discing, harrowing, manure mixing & compacting the soil and implements to be used are ploughs, clod crushers, disc ploughs or harrow, bladed harrow etc. It includes primary & secondary tillage: a) Primary tillage: It mainly includes the ploughing operation which is opening of the compacted soil with the help of different ploughs. Ploughing is done to: i) Open the hard soil ii) Separate the top soil from lower layers iii) Invert the soil whenever necessary and iv) Uproot the weeds & stubbles. The cutting & inverting of the soil that is done after the harvest of the crop or untitled fallow or to bring virgin or new land under cultivation is called primary tillage. It may be done once or twice a year in normal or settled agriculture or once in four to five years in dry land agriculture. Primary tillage implements are - Wooden plough Soil turning plough 2 Agron-113 Mould board plough Disc plough Sub soil plough Chisel plough Rotary plough b) Secondary tillage: The tillage operations that are performed on the soil after primary tillage to bring a good soil tilth are known as secondary tillage. Lighter or finer operation performed on the soil after primary tillage are known as secondary tillage which includes the operations performed after ploughing, leveling, discing, harrowing etc. Secondary tillage implements are – Cultivator, disc harrow, spike tooth harrow etc. 2. Seedbed preparation: When the soil is brought to a condition suitable for germination of seeds & growth of crops, called as SEEDBED. After preparatory tillage the land is to be laid out properly for irrigating crops, if irrigation is available for sowing or planting seeding which are known as seedbed preparation. It includes harrowing, leveling, compacting the soil, preparing irrigation layouts such as basins, borders, ridges & furrows etc. and carried out by using hand tools or implements like harrow, rollers plank, rider etc. After field preparation, sowing is done with seed drills. Seeds are covered & planking is done so as to level & impart necessary compaction. 3. Inter tillage/ Inter cultivation/ Interculture / after care operation: The tillage operations that are carried out in the standing crop are called inter tillage operations. The tillage operation done in the field after sowing or planting and prior to the harvesting of crop plants known as inter cultivation. It includes gap filling, thinning, weeding, mulching, top dressing of fertilizers, hoeing, earthling up etc. unless these are carried out at right time, with suitable implements mainly hoes & hand tools the crop will not attain a vigorous growth. These operations are carried out in between the crop rows. Factors Influencing Tillage Operations: The preparatory cultivation of the lands done in various ways which is influenced by several factors but more important ones are: 1. The crop: The crop to be grown decides the type & preparatory tillage given to the land. Hardy crops like sorghum & other millets are not sensitive about tilth. Production of fine tilth will increase the cost of cultivation which is not economic. Small seeded or delicate crops like tobacco, chilli, coriander, Sesamum, mustard etc. require a fine seedbed for which land is repeatedly cultivated to get required fine tilth. Sugarcane & other root crops require deep cultivation of land to lose the soil to the required depth. 2. Type of soil: A clayey soil is amenable to cultivation only within a narrow range of moisture. Outside this range, the soil can’t be worked satisfactorily & increases the draft required. Too wet or to dry soils are difficult to cultivate. The lighter soils can be worked under a wide range of moisture & the draught required for their manipulation is much less. Loamy soils are easily brought to good tilt with little cultivation & expenditure of energy. 3. Climate: It influences the moisture in the soil, the draught required for cultivation and depth & types of cultivation done, For example, in scarcity areas the rainfall is low & the moisture in the soil prior to sowing does not ordinarily permit deep cultivation which tends to dry up soil to a greater depth & reduce moisture available to the crops eventually (finally) Sowings cannot be done till depth of cultivated soil is properly moistened. This results in delayed sowing & consequently the effect on growth & yield of crop Deep cultivation is beneficial in regions having better rainfall, particularly temperate regions for promoting aeration, summer showers are received in South India which favors moist condition & ultimately beneficial for preparing the land for next season crops. 4. Type of farming: There are two types, irrigated & rained farming. Under irrigated farming intensive farming is followed which includes cultivation of more than two crops in a year continuously without much interval between 3 Agron-113 them. During this narrow period of interval, the land is to be cultivated repeatedly to bring required tilth without subjecting the soil for natural weathering for a long period. Dry land faming depends entirely on rains & in such areas only one crop is taken in a year. The interval between crops & successive cultivation operations is long. Weathering plays an important role than cultivation. Hence, they are limited with wide intervals between them. The cost of cultivation is kept down & the low productivity of land does not warrant a higher investment Modern Concepts of Tillage ❑ In conventional tillage, combined primary and secondary tillage operations are performed in preparing seed bed by using animal or tractor, which cause hard pan in sub soils resulting in poor infiltration of rain water, thus it is more susceptible to run off and soil erosion. ❑ Farmers usually prepare fine seed bed by repeated ploughing, when the animal of the farm is having less work. Research has shown that frequent tillage is rarely beneficial and often detrimental. ❑ Repeated use of heavy machinery destroys soil structures, causes soil pans and leads to soil erosion. Moreover, energy is often wasted during tillage processes. ❑ All these reasons led to the development of modern concepts namely the practices like minimum tillage, zero tillage, stubble mulch farming and conservation tillage, etc. Tillage is time consuming, laborious & costly, owing to this new concept like minimum tillage & zero tillage are introduced. 1. Minimum Tillage: It is aimed at reducing tillage operations to the minimum necessary for ensuring a good seedbed, rapid germination, a satisfactory stand & favorable growing conditions. It keeps 30 -50% crop residues on the soil surface. Tillage can be reduced by: i) Omitting operations which do not give much benefit when compared to the cost and ii) Combining agricultural operations like seeding & fertilizer application. The concept of minimum tillage was started in U.S.A. The immediate cause for introducing minimum tillage was high cost of tillage due to steep rise in oil prices in 1974. Advantages: i) Improve soil condition due to decomposition of plant residues in situ, ii) Higher infiltration caused by decomposition of vegetation present on soils & channels formed by decomposition of dead roots. iii) Less resistance to root growth due to improved structure. iv) Less soil compaction by reduced movement of heavy tillage vehicles. v) Less soil erosion compared to conventional tillage. Disadvantages: i) Less seed germination, ii) More ‘N’ has to be added as rate of decomposition of organic matter is slow. iii) Nodulation may affect in some legumes. iv) It promotes growth of volunteer crops and weeds. V) Poor crop growth when not managed carefully. 2. Zero tillage: It is an extreme form of minimum tillage. Primary tillage is completely avoided & secondary tillage is restricted to seedbed preparation in the row zone only. It keeps 50 - 75% crop residues on the soil surface. It is followed where: 1) Soils are subjected to wind & water erosion, 4 Agron-113 2) Timing of tillage operations are too difficult & 3) Requirements of energy & labour for tillage are too high. Two types of zero tillage – (a) Till Planting is one method of practicing zero tillage (b) Sod planting or sod culture: Sod refers to top few centimeters of soil permeated by and held together with grass roots or grass-legume roots. Advantages: 1) Soils are homogenous in structure with more no. of earth worms. 2) Organic matter content increased due to less mineralization. 3) Surface runoff is reduced due to presence of mulch. Several operations are performed by using only one implement. In this situation, weeds are controlled by spraying of herbicides. Disadvantages: 1) Higher ‘N’ is applied due to slower mineralization of org. matter. 2) Large population of perennial weeds appears. 3) Build up of pests is more. 3. Stubble mulch tillage: The soil is protected at all times either by growing a crop or by crop residues left on the surface during fallow periods. It is year-round system of managing plant residue with implements that undercut residue, loosen the soil and kill weeds. Soil is tilled as often as necessary to control weeds during the interval between two crops. However, it presents the practical problem as the residues left on the surface interfere with seedbed preparation & sowing operations. The traditional tillage & sowing equipment is not suitable under these conditions. 4. Conservation tillage: It is disturbing the soil to the minimum extent & leaving crop residues on the soil. It includes minimum & zero tillage which can reduce soil loss up to 99% over conventional tillage. In most cases, it reduces soil loss by 50% over conventional tillage. Conventional tillage includes ploughing twice or thrice followed by harrowing & planking. It leaves no land un-ploughed & leaves no residues on the soil. Modern methods of tillage are not practiced in Indian condition because: a) Left over residue is a valuable fodder & fuel. b) Limited use of heavy machinery & therefore problem of soil compaction is rare. Wet tillage or Puddling ❑ Under wetland system the land is prepared by puddling for planting wet rice. ❑ Puddling means mechanical manipulation of saturated soils with standing water in the field. ❑ Actually, the structure of the soil is destroyed under puddling. The optimum depth of puddling is about 10 cm in the clay and clay loam types of soils. ❑ Good puddling or neatly ploughed means the soil should be soft, uniformly levelled without weeds or stubbles and with minimum percolation. Why puddling? Puddling is done - ❑ To obtain a soft seedbed for the seedling to establish faster ❑ To minimize percolation of water so that water can stagnate in the field ❑ To minimize leaching loss of nutrients and thereby increase the availability of plant nutrients ❑ To facilitate better availability of nutrient by achieving reduced soil condition, ❑ To incorporate the weeds and stubbles into the soils, and ❑ To minimize the weed problems 5