PJB-2001-47
FATE OF THE 15N-LABELLED UREA APPLIED TO IRRIGATED WHEAT GROWN AFTER COTTON HARVEST UNDER SEMIARID SUBTROPICAL CONDITIONS
TARIQ MAHMOOD, REHMAT ALI AND ZAHOOR ASLAM
Abstract
Fate of the fertilizer-N applied to irrigated wheat grown after cotton harvest was studied under field conditions using 15N-balance method. Of the total urea-N applied (100 kg ha-1), 47.7 kg N ha-1 was utilized by the wheat crop, the recovery being maximum in the grain component (30.0 kg N ha-1), followed by straw (16.9 kg N ha-1) and roots (0.9 kg N ha-1. Of the 24.3 kg N ha-1 of the fertilizer-N remaining in the soil at the crop harvest, most (22.2 kg N ha-1 was present in the organic form, whereas maximum (15.6 kg N ha-1 was recovered in the upper 10 cm soil layer. Total fertilizer-N loss during the wheat-growing season amounted to 28 kg N ha-1, which was 1.5 times the denitrification loss directly measured from the same field.
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