
%0 Journal Article
%A Wetselaar, R 
%A Norman, MJT 
%T Recovery of available soil nitrogen by annual fodder crops at Katherine, Northern Territory
%J Australian Journal of Agricultural Research
%D 1960/10/01
%V 11
%N 5
%P 693-704
%K 
%R https://doi.org/10.1071/AR9600693
%U https://www.publish.csiro.au/paper/AR9600693 
%X In 1958-59, a field trial was carried out at Katherine, N.T., to compare the recovery. of available soil nitrogen by fodder sorghum, Sudan grass, and bulrush millet when grown after an all-grass ley, a legume ley, and a long period of fallow. After 6 years of grass, available soil nitrogen remained low throughout the cropping season at all soil levels to a depth of 5 ft, and nitrogen yield from the fodder crops averaged only 17 lb/acre. After 7 years of Townsville lucerne, available soil nitrogen was low at the start of the season, but soil nitrogen was quickly mineralized and, in the absence of a crop, was leached to give a peak concentration of nitrate nitrogen at 2&ndash;3 ft. All three crops intercepted this mineral nitrogen efficiently to give an average aboveground nitrogen yield of 75 lb/acre, approximately half the nitrate nitrogen available in the 5 ft soil layer on uncropped land at the end of the season. After 5 years of clean fallow, soil nitrogen had been mineralized and leached to a considerable depth, 260 lb of nitrate nitrogen per acre being accumulated in the 0&ndash;5 ft layer. Fodder sorghum and Sudan grass depleted soil nitrogen appreciably in the 0&ndash;2 ft layer, and gave an average above-ground nitrogen yield of 62 lb/acre. Bulrush millet depleted soil nitrogen throughout the 0&ndash;5 ft profile to give a nitrogen yield of 154 lb/acre. Bulrush millet is therefore regarded at Katherine as an outstanding crop for the recovery of deep accumulations of soil nitrate nitrogen and their conversion to harvestable fodder protein. 
