The Waste Products of Agriculture: Their Utilization as Humus
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PREFACE One of the main features of crop production at the present day is waste. Except in the Far East, where the large indigenous population has to be fed from the produce of the country-side, little is being done to utilize completely the by-products of the farm in maintaining the fertility of the soil. The ever-growing supplies of agricultural produce, needed by industry and trade, have been provided either by taking up new land or by the purchase of artificial manures. Both these methods are uneconomic. The exploitation of virgin soil is a form of plunder. Any expenditure on fertilizers which can be avoided raises the cost of production, and therefore reduces the margin of profit. It needs no argument to urge that, in maintaining the fertility of the soil, the most careful attention should be paid to the utilization of the waste products of agriculture itself before any demands are made on capital natural or acquired. For the last twenty-six years, the senior author has been engaged in the study of crop production in India and in devising means by which the produce of the soil could be increased by methods within the resources of the small holder. These investigations fell into two divisions 1 the improvement of the variety and 2 the intensive cultivation of the new types. In the work of replacing the indigenous crops of India by higher yielding varieties, it was soon realized that the full possibilities in plant breeding could only be achieved when the soil in which the improved types are grown is provided with an adequate supply of organic matter in the right condition. Improved varieties by themselves could be relied on to give an increased yield in the neighbourhood of ten per cent. Improved varieties plus better soil conditions were found to produce an increment up to a hundred per cent or even more.
Steps were therefore taken 1 to study the conversion of all forms of vegetable and animal wastes into organic matter humus suitable or the needs of the growing crop and 2 to work out a simple process by which the Indian cultivator could prepare an adequate supply of this material from the by-products of his holding. In other words he has been shown how to become a chemical manufacturer. This task involved a careful study of the various systems of agriculture which so far have been evolved and particularly of the methods by which they replenish the soil organic matter. The line of advance in raising crop production in India to a much higher level then became clear. Very marked progress could be made by welding the various fragments of this subject the care of the manure heap, green-manuring and the preparation of artificial farmyard manure into a single process, which could be worked continuously throughout the year and which could be relied upon the yield a supply of humus, uniform in chemical composition and ready for incorporation into the soil. This has been accomplished at the Institute of Plant Industry at Indore. The work is now being taken up in Sind and at various centres in Central India and Rajputana. The Indore process for the manufacture of humus is described in detail in the following pages. It can be adopted as it stands throughout the tropics and sub-tropics, and also on the small holdings and allotments of the temperate zone. How rapidly the method can be incorporated into the