DISTRIBUTION OF NITROGEN FROM SOIL AND FROM FERTILIZER INTO THE WINTER WHEAT (Triticum aestivum L.) PLANT AT GRAIN MATURITY

In this experiment, the distribution within the plant of nitrogen originating from fertilizer and from soil was followed at six periods between anthesis and grain maturity. Fertilizer rate of 180 kg N.ha -1 was applied following two splitting schedules T2 (1/3-1/3-1/3) and T5 (0-1/3-2/3) at GS25, GS30 and GS37 resp. and compared to unfertilized control T1. Aerial parts of the plant were divided into several compartments i.e. S1 (organs under the fore-last node), S2 (fore-last node and stem portion), S3 (last node and stem), L2 (fore-last leaf), L3 (flag leaf), EC (ear chaff) and EG (grain). 15 N labelled NH4N03 was used to determine the recovery of nitrogen applications, and the part of fertilizer and soil nitrogen in each plant compartment. At maturity, fertilizer N recovery varied significantly in the whole plant and ranged from 68.14 to 78.62 % and in grain from 55.91 (r 5.28) % to 69.11 (r 5.07) % for T2 and T5 respectively. Total amounts of N in the whole plant (11.3; 26.4 and 26.4 g N.m - ² for T1, T2 and T5 respectively) were distributed in S1 (1.1; 1.9 and 1.0 g N.m - ²), in S2 (0.2; 0.3 and 0.2 g N.m - ²), in S3 (0.23; 0.52 and 0.41 g N.m - ²), in L2 (0.18; 0.47 and 0.38 g N.m - ²), in L3 (0.26; 0.67 and 0.61g N.m - ²), in EC (0.57; 1.34 and 1.17 g N.m - ²), and in EG (8.8; 21.2 and 22.6 g N.m - ²). Split nitrogen application affected the recovery of fertilizer nitrogen (FNR). By suppressing the first split application (GS25) and increasing the latest (GS37), the splitting schedule T5 (0-1/3-2/3) exhibited the highest total and grain recoveries of fertilizer nitrogen.