Losses of nitrogen and other soil constituents from two soils in filled-in lysimeters

Abstract

The results of an eight year lysimeter study conducted at Muresk, Western Australia, are presented. The lysimeters contained two soils, a lateritic sandplain and a noncalcic brown soil, upon which various agronomic treatments were imposed. Mean annual leaching losses of nitrate-nitrogen from the sandplain soil were 4 to 7 lb N per acre under fallow and 6 lb N per acre from subterranean clover pasture. Losses of nitrate-nitrogen from wheat, either with added urea or clover residues (equivalent to 60 lb N per acre) were much higher, viz, 14 to 21 lb N per acre. From the noncalcic brown soil, losses under fallow were 3 to 6 lb N per acre, under clover pasture 2 lb N per acre, and under wheat, either with urea or clover residue added, 4 to 19 lb N per acre. For the sandplain soil, mean annual losses per acre of constituents other than nitrogen were 6 lb K ; 13 lb Ca ; 5 lb Mg ; less than 0.2 lb P ; and 2 to 7 lb S. For the noncalcic brown soil the losses were much lower, viz., 1 lIb K ; 7 lb Ca ; 3 lb Mg; less than 0.2 lb P ; and 0 to 7 lb S. The leaching losses of K, Ca and Mg were related to plant cover, being higher under wheat than under fallow, particularly with the sandplain soil. A n attempt was made to relate changes in nitrogen content of the surface soil at the end of the experiment to the net gain (input minus output) of nitrogen over the same period. This approach was unsatisfactory due largely to the statistical errors associated with soil sampling.