Effect of nitrogen fertilization and rice stubble management techniques on soil moisture content, soil nitrogen status, and nitrogen uptake by wheat

Abstract

The effects of nitrogen fertilization and stubble treatment on soil mineral-N content, moisture status and subsequent crop N uptake were studied in a series of wheat ( Triticum aestivum L.) crops planted soon after rice ( Oryza sativa L.) harvest. The experiments were part of a programme to define optimum management systems for intensive rice/upland cereal rotations. Stubble management, N application time and rate all influenced amount of soil mineral-N, accounting for up to 52, 67 and 75%, respectively, of the mineral-N variation. In turn, variation in soil mineral-N explained up to 70% of the variation in N accumulation by wheat. N accumulation was highly correlated with crop yield ( r 2 up to 0.95). Incorporating large quantities of rice stubble at wheat sowing reduced soil NO- 3-N concentration by 36% at stem elongation. Both N uptake and yield were reduced by 38% on these plots. Increasing quantities of rice stubble retained on the soil surface increased soil NO 3-N concentration by 46%, and wheat on these plots had a 29% increase in N uptake and a 37% increase in yield. Stubble burning rather than retention on the surface resulted in lower soil NO 3-N concentration, and this was ascribed to ammonia volatilization resulting from fertilizer contact with ash, and to reduced mineralisation in the drier soil. Application of N at wheat sowing significantly increased mineral-N status at least until stem elongation, while fertilization at tillering or stem elongation significantly increased soil mineral-N content at least until anthesis. It was concluded that stubble and fertilization management techniques can be manipulated in order to regulate soil mineral-N status, which in turn determined plant N uptake. Plant N uptake determined yield.