Tilth and Tillage – Objects of Tillage
Objects of Tillage: These can be summarized in brief as below.
1. To make the soil loose & porous: It enables rain water or irrigation water to enter the soil easily & the danger of loss of soil & water by erosion and run-off, respectively, is reduced. Due to adequate proportion of microspores (capillary), the water will be retained in the soil & not lost by drainage.
2. To aerate the soil: Aeration enables the metabolic processes of the living plants & micro organisms, etc. to continue properly. Due to adequate moisture and air, the desirable chemical & biological activities would go on at a greater speed & result in rapid decomposition of the organic matter and consequently release of plants nutrients to be used by crops. Similarly, the evolution of CO2 gas in this process will result in forming weak carbonic acid in the soil which will make more nutrients available to crops.
3. To have repeated exchange of air / gases: There should be an exchange of air during the growing period of crops. As the supply of O2 from the air that is being constantly utilized in several biological reactions taking place in the soil; should be continuously renewed. At the same time CO2 that is released should be removed & not allowed to accumulate excessively decomposition of org. residues by micro- organisms where O2 is utilized & CO2 released. Deficiency or excess of O2 may reduce the rate of reactions.
O2 in soil air & atm. Air is more or less same i.e. 20 to 21% CO2 in atmospheric air is about 0.03% & in soil air 0.2 to o.3% which is 8to 10 times more than atmospheric air. It is, therefore, very necessary to often introduce atmospheric air in the soil to keep the concentration of CO2 under by suitable tillage operations.
4. To increase the soil temperature: This can be achieved by controlling the air- water content of soil & also by exposing more of the soil to the heat of sun. This helps in acceleration of activities of soil bacteria & other micro organisms.
5. To control weeds: It is the major function of tillage; Weeds rob food & water required by crop & competition results in lowering of crop yield.
6. To remove stubbiest: Tillage helps in removing stubbles of previous crop and other sprouting materials like bulbs, solons etc in making a clean field/seedbed.
7. To destroy insect pests: Insects are either exposed to the sun’s heat or to birds that would pick them up. Many of the insect-pests remain in dormant condition in the form of pupae in the top soil during off season & when the host crop is again planted, they reappear on the crop. Some may harbor on stubbiest or other eminent of the crop. Grubs & cutworms can be destroyed by tillage.
8. To destroy hard pan: Specially designed implements (Chisel plough) are helpful to break hard pan formed just below the ploughing depth which act as barrier for root growth & drainage of soil.
9. To incorporate organic & other bulky manures: Organic manures should not only be spread but properly incorporated into the soil. Sometimes bacterial cultures or certain soil applied insecticides require to be drilled into the soil for control of pests like white grub. White ants, termites, cut worms e.g. Aldrin.
10. To Invert soil to improve fertility: By occasional deep tillage the upper soil layer rich in org. matter goes down thus plant roots get benefit of rich layer and lower layer which is less fertile comes to top.