This mechanical tool can be adopted for use in India to enable rainwater to percolate into the soil
Food security in India is getting more and more dependent on annual monsoons. In a year of low rainfall, a large section of the people, especially those below the poverty line, have to depend on subsidised government food rations. If this situation continues, the country will be stressed for resources to provide food for the people.
Coping with water shortage from failed monsoons is somewhat similar to coping with an economic crisis by a family where the breadwinners are laid off work. A family that practises saving money for a ‘rainy day’ can coast over the bad times better than one without any savings as a safety net.
India is blessed with better rainfall than many other countries. However, over 95 per cent of water received from rainfall is lost through run-off. The chief obstacle against harnessing rainwater from run-off and to recharge the depleting water table for future agriculture use is the sub-surface hardpan that prevents water percolation down the soil profile. This hardpan is formed due to ages of primitive farming practices involving shallow ploughing of land for farming. If this obstructive hardpan can be broken up mechanically, water will freely percolate down the soil profile to be stored for use during periods of water shortage.
Method used in breaking up hardpan
Because they are centuries old, the hardpans in India are stone hard and will require mechanical tools to break them up. In developed countries, a tool named ‘chisel’ was developed more than half a century ago. This tool can be easily adapted for use in India, and its effectiveness is already demonstrated in several regions of the country.
Chisels of various lengths from 18” to 48” are commonly used in the west to loosen ground to the various depths required for various crops. The chief advantages of chiselling are:
(a) It enables rainwater to percolate deep into the soil profile, recharging the water table, thus storing water underground for future use by humans and crops.
(b) It enables plant roots to penetrate deep into the soil profile to exploit both water and nutrients from a larger volume of soil, enhancing crop yields.
(c) It reduces the problem of siltation of lake and riverbeds.
(d) It protects soil fertility by retaining topsoil from erosion through run-off.
(e) It protects the environment by preventing pesticides used in farming operations from contaminating water bodies through surface run-off.
How and when to do chiselling?
Climatically, India has an advantage over western countries in the number of crops grown per year. With good planning a three-crop rotation can be adopted for most areas in India. The rotation may include a cereal crop followed by a pulse or edible oil crop and finally a vegetable crop. The cereal crop will provide the staple food, the pulse and oil crops the protein and oil component of a good balanced diet, and the vegetables vitamins, minerals and fibre, and also good cash flow for the farmer. Besides, this rotation can be used for improving soil fertility through atmospheric nitrogen fixation by the pulse (leguminous) crops.
In the economics of farming, the vegetable crop produces the maximum return for the farmer. Although adopting a three-crop rotation needs good planning, it has been proved very successful, especially when modern crop production technologies are adopted.
Chiselling is done most efficiently several weeks prior to the onset of the monsoon, when the soil conditions are still dry. Where a field is chiselled for the first time, it is found necessary to go for at least two trips across the field with gradual increments of shank depth. The second pass needs to be at a 45 degree angle to the first one.
Forming of bunds
Chiselling may be included as part of land preparation before planting a crop. Normally, 6 to 8 inch high bunds are formed around each field. It is possible to raise the height of these bunds by a few more inches to facilitate capture and for holding rainwater from run-off during heavy rains.
Prior to the chiselling operation, it is necessary to disc the field once and level the ground. After chiselling, it is desirable to level the ground once again. This is a good time for collecting soil samples for analysis.
Following application of recommended soil amendments and fertilizers based on soil test results, all materials need to be incorporated in the soil 5 to 6 inches deep by disking. Allow 10 to 15 days for equilibrating the materials with the soil for the best results.
During the monsoon season, when the first rains fall on the ground, the rainwater percolates deep into the soil profile due to breaking of the hardpan by chiselling.
During subsequent rains, instead of being lost as surface run-off, more and more water percolates deeper into the soil.
Special soil treatment
The higher bunds around the field will hold more water if a large amount of rainfall hits the ground and will slowly move down the soil profile to build up the water table. During times of excessive rainfall, there may be some overflow of water over the bunds. In order to prevent finer particles of soil being lost through this overflow, special soil treatments can be done before the onset of the monsoon. That will help aggregate the finer clay particles to heavier particles, which will settle to the bottom of the water, preventing loss of the fertile fraction of the soil. Thus only some clear water will flow over the dykes, preventing sedimentation of lake and riverbeds.
Thus if enough effort is made to do these operations right and on time, farmers can enjoy a ‘savings account’ of water that will come handy during times of drought.
(Dr. Lux Lakshmanan is Director, California Agriculture Consulting Service, Davis, California, U.S. He can be emailed at: firstname.lastname@example.org)