Abstract

The different size fractions of the experimental plots of the Old Permanent Manu- rial Experiments at Coimbatore were determined during 1922, 1929 and 1976. The data revealed that during 55 years of experimentation, the coarse sand fraction significantly reduced and clay fractions increased. Of the major nutrients N. P and K. nitrogen app- lication increased the clay content whereas others did not. The influence of nitrogen. might be mainly due to its content in the organic residues added to the soil. Coarse fraction was not influenced by the different treatments. Cattle manure application (5) tons/acre) was as good as NPK fertilization in maintaining the proportion of mechanical fractions.

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