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Effect of urea and ammonium sulphate applied before sowing on sudangrass seedlings
Published online by Cambridge University Press: 27 March 2009
Summary
Studies were conducted to determine possible leaching or fixation problems in growing sudangrass (Sorghum Sudanese Stapf.) when urea, ammonium sulphate plus triple superphosphate, and ammonium polyphosphate fertilizer were applied as a seed-bed application to the very sandy soils of the Libyan Sahara near the Kufra Oasis. The effectiveness of the nitrogen source was measured by plant colour, leaf analysis, and seedling height.
The urea nitrogen plus single superphosphate when applied and watered-in did not supply enough nitrogen to obtain a vigorous green seedling compared with ammonium polyphosphate (21% N, 53% P 2O6), which produced excellent vigorous green seedlings. The ammonia source supplied more nitrogen than the urea imder the conditions of these trials.
The application of urea 1, 2, 4, and 8 days before sowing was inadequate in supplying nitrogen to meet the early demand of the sudangrass seedlings. Sudangrass seedlings after 26 days were only 5–6·3 cm tall. With a seed-bed application of 36–72 kg N/ha as ammonium sulphate under comparable circumstances, sudangrass seedling height was 21·7 cm. The plants receiving no nitrogen applied before sowing were 6·7 cm high, similar to those which received urea.
Under these virgin sandy soil conditions, the ammonium sulphate and ammonium polyphosphate (21% N, 53% P2O5) fertilizers applied to the seed bed were retained within the root zone in sufficient amounts to give a vigorous, non-deficient sudangrass seedling. Nitrogen from urea was deficientand presumed leached beyond reach of the seedling root when applied to the seed bed. Applied post-emergence, however, urea was a very satisfactory source of nitrogen.
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- Copyright © Cambridge University Press 1976
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