Kinetics of 15N-labelled nitrogen from co-compost made from cattle manure and chemical fertilizer in a paddy field: Effect of mixing ratio of cattle feces and ammonium sulfate

Abstract

In order to produce an effective organic fertilizer for plant uptake and to examine the characteristics of a nitrogen fertilizer, cattle feces and (NH4)2SO4 were co-composted, and the kinetics of nitrogen uptake by rice plants from the co-compost was traced by the use of 15N. Cattle feces and (NH4)2SO4, either of which was labelled with 15N, were co-composted in a ratio of 1: 3 or 3: 1 for nitrogen, and the nitrogen kinetics from cattle feces or (NH4)2SO4 was investigated. In addition, four non-co-composted plots and a chemical fertilizer plot were set up as a control experiment. A 1 : 3 or 3 : 1 mixture of cattle manure and (NH4)2SO4, either of which was labelled with 15N, was applied in the nonco- composted plots. And only (NH4)2SO4 without manure was applied as a nitrogen fertilizer in a plot. In addition to the data on the 1 : 1 co-compost reported in our previous paper (Matsushita et al. 2000: Soil Sci. Plant Nutr., 46, 355–363), the characteristics of these co-composts as nitrogen fertilizer were estimated. The 1 : 3 co-compost was an efficient nitrogen fertilizer for rice plant uptake. The effect was conspicuous, especially in the early period of rice growth. However, inorganic nitrogen was in short supply in the middle period, and became mineralized again in the latter period of rice growth. The cocompost may not be suitable as a slow-acting fertilizer but could be efficient as a quick-acting fertilizer, in terms of organic matter content. When cattle feces and (NH4)2SO4 were co-composted in a ratio of 3 : 1, the dry weight of the rice plants in the co-composted plots was significantly lower than that in the non-co-composted plots on August 12 and afterwards. The least active growth was associated with a shortage of inorganic nitrogen. Especially, the N-uptake ratio by rice plants from (NH4)2SO4 in the 3 : 1 co-compost decreased by about 40% of the value in the non-co-composted plot. The results suggested that (NH4)2SO4 was actively assimilated during the co-composting period in the 3 : 1 co-compost. The co-compost may not satisfy the plant requirement for nitrogen. In contrast, this co-compost could be efficient as an amendment material for soil with a low nutrient content, because the N -residual ratios in soil from (NH4)2SO4 were about 80%. On the other hand, the N-uptake ratio from (NH4)2SO4 with cattle manure in the non-co-composted plot was lower than that without cattle manure in the early period, compared with that in the latter period of rice growth. The results indicated that the slow acting ability of nitrogen from (NH4)2SO4 increased by the addition of cattle manure. Considering the nitrogen loss through the composting process, the N -uptake ratios from cattle feces and (NH4)2SO4 were in the order of 1 : 3 non-co-composted plot > 1 : 3 co-composted plot>3 : 1 non-co-composted plot>(NH4)2SO4 only plot>3 : 1 co-composted plot. In summary, the 1 : 3 co-compost made of cattle manure and (NH4)2SO4 may display a Quick acting ability, the 3 : 1 co-compost could increase the soil nitrogen content, and the mixture of cattle manure and (NH4)2SO4 may exhibit a slow acting ability for nitrogen. In taking account of nitrogen utilization, the simultaneous application of cattle manure and (NH4)2SO4 without co-composting appears to be an efficient method compared with the co-composting method.