PJB-2007-196
SEASONAL CHANGES IN SOIL MICROBIAL BIOMASS NITROGEN UNDER AN IRRIGATED WHEAT-MAIZE CROPPING SYSTEM
TARIQ MAHMOOD*, REHMAT ALI, FAQIR HUSSAIN, KAUSER ABDULLA MALIK AND GHULAM RASUL TAHIR
Abstract
Seasonal changes in soil microbial biomass nitrogen (Nmic) were followed under an irrigated wheat-maize cropping system receiving urea and/or farmyard manure (FYM) at 0–200 kg N ha–1 year–1 for the past ten years. The Nmic was maximum (109–218 kg N ha–1) at the wheat stem elongation stage and minimum (80–148 kg N ha–1) at the wheat tillering stage. Fertilizer application significantly increased the Nmic, indicating that the belowground processes were limited by N availability. Averaged across sampling dates, the Nmic ranged from 93 kg N ha−1 (in unfertilized) to 176 kg N ha–1 (in FYM applied at 32 t ha–1 year–1), whereas the annual Nmic flux ranged from 57 kg N ha–1 (in unfertilized) to 118 kg N ha–1 (in FYM applied at 16 t ha–1 year–1). Crop dry matter and N yields increased due to fertilizer application. At an equivalent N application rate, urea applied alone produced maximum yields, followed by urea combined with FYM, whereas FYM applied alone yielded minimum. The size and flux of Nmic were poor indicators of the crop N availability, whereas the soil mineralizable N determined by alkaline permanganate method at the crop sowing stage was significantly correlated with the soil mineral N, and with the crop dry-matter and N yields.
To Cite this article:
Download
