Fertilizer nitrogen balance study on sandy loam with winter wheat

The uptake of labelled nitrate was studied under field conditions using a sandy loam soil and winter wheat as the crop. Thirty per cent of the added labelled nitrate was found in the grain, 13% in the straw plus chaff and only 2% in the harvested roots. The labelled nitrogen in the plant comprised about 6% of labelled fertilizer origin, and about 94% from the soil. By analysing the soil after harvest, it was shown that 16% of the fertilizer nitrogen was in the 0–6 cm layer, 19% in the 6–12 cm layer, 6% in the 12–25 cm layer and 5% in the 25–50 cm layer. This means a total residual fertilizer nitrogen of 46%. A study was made of the border effect by analysing the plants of the first and second row around the fertilized plot. The results show that the plants of the first row took up 1.4% of the added fertilizer and those of the second row only 0.4%. The total recovery of the added fertilizer in soil and plant was 93.1%, indicating that 6.9% was lost under conventional cultivation practice.