A LONG-TERM FIELD EXPERIMENT WITH COMMERCIAL FERTILIZERS AND MANURE: I. Fertility levels and crop yields in a rotation of swedes, oats and hay

Abstract

In a field experiment, conducted from 1936 to 1957, a rotation of swedes, oats and hay was followed and treatments included commercial fertilizers and manure.Changes in the chemical composition of the soil during the experiment included significant decreases in soil organic matter, total nitrogen and cation exchange capacity. In no case was the initial content of exchangeable potassium maintained and although changes in adsorbed and easily acid-soluble phosphorus were negligible with a number of treatments only one resulted in a significant increase.The treatments were applied in the swede year and yield differences with this crop were greater than for either the oats or hay. Data for the latter two crops indicated that with most of the treatments there was a tendency for yields to decline as the experiment progressed. This was not the case with swedes where variation in yields with rotation cycles was greater than it was in the case of oats or hay. There was a considerable residual effect from manure, and phosphorus had a greater effect on yields than either nitrogen or potassium.