CONSERVATION OF HUMUS IN TROPICAL SOILS

Abstract

THE part played by humic manures in soil processes and in plant nutrition, both as a source of mineral elements and by improving the physical condition of the soil, is well known. The advantages of properly devised rotational systems of cropping in soil husbandry are also established by both practice and experience. It is therefore reasonable to expect results of great economic importance by a combination of rotational cropping with humic manuring. The permanent manurial small plots at the Institute of Plant Industry, Indore, afforded an opportunity of studying the relative importance of humic manures and crop rotation on the conservation of soil properties. These plots, sixteen in number, have, since 1933, been receiving annual surface dressings of farm compoat, farmyard manure and municipal compost, all at ten tons per acre, and have been under a four-year rotational cropping with (i) cotton, (ii) sann (Orotalaria juncea), ploughed in and followed by wheat, (iii) ground nut, and (iv) jowar (Andropogon sorghum) ; one set of four plots (including a control immanured plot) being under a particular crop during a season. The plots treated with the different humic manures, while yielding more or less alike from year to year with all the crops, had frequently given more than double the yields of the untreated plots.