Study the fate of chlorine in paddy soil and the effect of residual chlorine on succeeding crops by using 36 Cl

This paper comprises the results of two experiments to evaluate the fate of chlorine radical of ammonium chloride in the field condition. Rice was used as the first test plant, followed by soybean as a succeeding crop. Ammonium sulphate and urea at rates of 8 and 16 kg N/rai were used as standard fertilizers, both being effective sources of nitrogen for paddy. The yields obtained from ammonium chloride was somewhat similar to those of the commonly used nitrogen fertilizer. Higher rate of applied nitrogen fertilizers gave higher grain yields. The labelled ammonium chloride 36 Cl made it possible to trace chlorine radical in the plant top and its residual in the soil. The results indicated that chlorine content in the plant material consistently increased with increasing rate of ammonium chloride application when compared to the plant receiving ammonium sulphate and urea. The percentages utilization of chlorine by plant was in a range of 3.8-4.6 at primordial initiation growth stage. This values were greater and in the range of 6.6-9.2% at harvesting time. Amount of ch lorine left in soil depth was measured after the above plants were removed. The data showed that there was more accumulation of chlorine activity in the soil depth at 0-30 cm. Soybean was seeded on the crown of the rice plant in the field to further evaluate the fate of the residual chlorine to a succeeding crop. In this experiment, two levels of phosphorus, at rates of 6 and 12 kg P205/rai were applied. Nitrogen fertilizer as urea and potassium as potassium sulphate were added to maintain normal growth of the plant. The results showed that the yields of soybean were not significantly different in the treatments being studied. The chlorine content in parts of soybean plant grown on ammonium chloride plot was not different, in particular, when compared to that of ammonium sulphate and urea. Percentages utilization of chlorine by soybean was in the range of 0.001-0.002%. The experiment suggests practical means in supporting the use of ammonium chloride as a nitrogen source in paddy and in other crops. Further research may be concentrated on the efficient use of this fertilizer.