Seasonal changes in denitrification potential of an irrigated sandy-clay loam under a wheat-maize cropping system receiving different fertilizer treatments
1999
Mahmood, T. | Bhatti, A.S. | Malik, K.A. (Nuclear Inst. for Agriculture and Biology, Faisalabad (Pakistan))
Study was conducted to follow seasonal changes in the denitrification potential (DNP) of an irrigated sandy-clay loam under a wheat-maize cropping system receiving different fertilizer treatments for the past ten years. Fertilizer treatments included: N-100 (urea at 100 kg N ha-1 a-1), N-200 (urea at 200 kg N ha-1 a-1), FYM-16 (farmyard manure at 16 t ha-1 a -1), FYM-32 (farmyard manure at 32 t ha-1 a-1) and the control (unfertilized). Urea-N was applied in four equal splits, two to each crop, whereas all farmyard manure was applied at the time of sowing wheat. Averaged across treatments during the growing period of wheat, DNP increased with crop growth, reached maximum at flowering, and declined at grain formation. Under maize, however, the DNP increased till flowering and remained unchanged at dough stage when the fodder was harvested. Average DNP during the wheat season was almost 1.6 times higher than that under maize. Averaged across sampling dates during the wheat season, N-200 showed 13 per cent higher DNP than the control, whereas N-100 had no effect. Under maize, DNP was 37 per cent higher with N-100 treatment than the control while N-200 had no effect. During the wheat season, DNP showed an increase of 66 and 114 per cent due to FYM-16 and FYM-32 treatments, respectively. However, the residual effect of FYM on DNP during the maize growing season was observed only with FYM-32 treatment which showed 34 per cent higher values relative to control. Denitrification potential was significantly correlated with aerobically mineralizable carbon and microbial biomass carrying capacity but not with microbial biomass carbon, total organic carbon and actual denitrification rates in the field.
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