Tillage and Tilth

• Tillage refers to the mechanical manipulation of the soil with tools and implements so as to create favourable soil conditions for better seed germination and subsequent growth of crops.
• Tilth is a physical condition of the soil resulting from tillage.

Objective of Tillage; 

The objective of tillage are..

• To prepare ideal seed bed favourable for seed germination, growth and establishment.
• To loosen the soil for easy root penetration and proliferation.
• To remove other sprouting materials in the soil.
• To control weeds.
• To improve soil physical conditions of Soil.
• To ensure adequate aeration in the root zone which in turn favour for microbial and biochemical activities.
• To break hard soil pans and to improve drainage facility.
• To incorporate crop residues and organic matter left over.
• To conserve soil by minimizing the soil erosion.
• To conserve the soil moisture.
• To assure the through mixing of manures, fertilizers and pesticides in the soil.
• To facilitate water infiltration and thus increasing the water holding capacity of the soil.

Types of Tilth

• Fine Tilth refers to the powdery condition of the soil.
• Coarse Tilth refers to the rough cloddy condition of the soil.
• Fine seedbed is required for small seeded crops like ragi, onion, berseem, tobacco.
• Coarse seedbed is needed for bold seeded crops like sorghum, cotton, chickpea, lab-lab etc.

Types of Tillage..

• On Season Tillage: It is done during the cropping season (June–July or Sept.–Oct.).
• Off Season Tillage: It is done during fallow or non-cropped season (summer).
• Special Types of Tillage: It is done at any time with some special objective/purpose.

On Season Tillage; Tillage operations done for raising the crops in the same season or at the onset of the crop season are called as on season tillage. They are,

a) Preparatory Tillage

It refers to tillage operations that are done to prepare the field for raising crops. It is divided into three types viz.,

1. Primary tillage,
2. Secondary tillage,
3. Seed bed preparation.

1. Primary tillage 

• The first cutting and inverting of the soil that is done after the harvest of the crop or untilled fallow, is known as primary tillage.
• It is normally the deepest operation performed during the period between two crops.
• Depth may range from 10–30 cm.
• The main objective is to control weeds to incorporate crop stubbles and to restore soil structure.

2) Secondary Tillage

• It refers to shallow tillage operation that is done after primary tillage to bring a good soil tilth.
• Incorporation of manures and fertilizers, leveling, mulching, forming ridges and furrows are the main objectives.
• It includes cultivating, harrowing, pulverizing, raking, leveling and ridging operations.

3) Seed bed preparation

• It refers to a very shallow operation intended to prepare a seed bed or make the soil to suit for planting.
• The Objectives of Seed bed preparation are Weed control and structural development of the soil.

b) Inter Tillage/Inter Cultivation

• It refers to shallow tillage operation done in the filed after sowing or planting or prior to harvest of crop plants i.e., tillage during the crop stand in the field.
• It includes inter cultivating, harrowing, hoeing, weeding, earthing up, forming ridges and furrows etc.
• Inter tillage helps to incorporate top dressed manures and fertilizers, to earth up and to prune roots.

Off Season Tillage.

Tillage operation is done for conditioning the soil during uncropped season with the main objective of water conservation, leveling to the desirable grade, leaching to remove salts for soil reclamation reducing the population of pest and diseases in the soils. etc. They are:

1. Stubble or Post harvest tillage – Tillage operation carried out immediately after harvest of crop to clear off the weeds and crop residues and to restore the soil structure.
2. Summer tillage – Operation being done during summer season in tropics to destroy weeds and soil borne pest and diseases, checking the soil erosion and retaining the rain water through summer showers. It is called as Kodai uzavu in Tamil Nadu state.
3. Winter tillage – It is practiced in temperate regions where the winter is severe that makes the field unfit for raising crops. Ploughing or harrowing is done in places where soil condition is optimum to destroy weeds and to improve the physical condition of the soil and also to incorporate plant residues.
4. Fallow tillage – It refers to the leaving of arable land uncropped for a season or seasons for various reasons.

Modern Concept of Tillage: Main aim of modern concept of tillage is to minimize the cost of cultivation by reducing some tillage operations.

1. Minimum Tillage;

• Minimum tillage is aimed at reducing tillage to the minimum necessary for ensuring a
• good seedbed, rapid germination, a satisfactory stand and favourable growing conditions.
• Minimum tillage can be achieved by the following methods:

(a) Row zone tillage – Primary tillage is done with mould board plough in the entire area of the field, secondary tillage operations like discing and harrowing are reduced and done only in row zone.

(b) Plough-plant tillage – After the primary tillage a special planter is used for sowing. In one run over the field, the row zone is pulverized and seeds are sown by the planter.

(c) Wheel track planting – Primary ploughing is done as usual. Tractor is used for sowing, the wheels of the tractor pulverize the row zone in which planting is done.

Advantages (especially in coarse and medium textured soils)

• Improved soil conditions due to decomposition of plant residues in situ.
• Higher infiltration caused by the vegetation present on the soil and channels formed by the decomposition of dead roots.
• Less resistance to root growth due to improved structure.
• Less soil compaction by the reduced movement of heavy tillage vehicles.
• Less soil erosion compared to conventional tillage.

Disadvantages

• Seed germination is lower with minimum tillage.
• More nitrogen has to be added as the rate of decomposition of organic matter is slow.
• Minimum tillage recommended to conserve organic matter in the soil.
• Nodulation is affected in some leguminous crops like peas and broad beans.
• Sowing operations are difficult with ordinary equipment.

Zero Tillage/No Tillage/Chemical 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-tillage.Weeds are controlled using herbicides. Hence, it is also referred as chemical tillage.

Advantages

• Zero tilled soils are homogenous in structure with more number of earthworms.
• These soil physical properties are apparent after two years of zero tillage.
• The organic matter content increases due to less mineralization.
• Surface runoff is reduced due to the presence of mulch.

Disadvantages

• In tempereate countries highest dose of nitrogen has to be applied for mineralization of organic matter in zero tillage.
• Large population of perennial weeds appears in zero tilled plots.
• Higher number of volunteer plants and build up of pests are the other problems.

Stubble Mulch Tillage or Stubble Mulch Farming

In this tillage, soil is protected at all times either by growing a crop or by leaving the crop residues on the surface during fallow periods. Sweeps or blades are generally used to cut the soil up to 12 to 15 cm depth in the first operation after harvest and the depth of cut is reduced during subsequent operations.

Conservation Tillage  it is done to conserve soil and water by reducing their losses. Modern tillage methods are practiced in western countries especially in USA. In India, it is not suitable due to several reasons.

• In USA, straw and stubbles are left over in the field but in India, it is a valuable fodder for the cattle and fuel for the home.
• Use of heavy machinery in India is limited and therefore, problem of soil compaction is rare.
• The type of minimum tillage that can be practiced in India is to reduce the number of ploughings to the minimum necessary i.e., unnecessary repeated ploughings/harrowing can be avoided.