Kinetics of 15N -labelled nitrogen from co-compost made from cattle manure and chemical fertilizer in a paddy field

Abstract

In order to produce an effective organic fertilizer, cattle manure was cocomposted with chemical fertilizer. And the kinetics of nitrogen uptake by rice plants from the co-compost was investigated using the 15N labelled co-composts on either cattle manure or chemical fertilizer. As a control, nitrogen kinetics from the mixture of cattle manure and chemical fertilizer without co-composting was investigated. At the early stage, rice growth may have been promoted by co-composting, while, it may have been promoted by the larger N-content of cattle manure at the harvesting stage. The ratios of nitrogen uptake by rice plants and residual nitrogen in soil from the cattle manure and chemical fertilizer were determined by measuring 15N -atom%. The N -uptake ratios by rice plants from the cattle manure in the co-composted plot were about 2–4 times higher than those from the cattle manure without co-composting. However, the N -uptake ratios from the chemical fertilizer in the co-composted plot were lower than those from the chemical fertilizer without co-composting. The N -content of the rice plants derived from chemical fertilizer without co-composting decreased consistently after 28 d. The nitrogen from chemical fertilizer in the co-compost was absorbed again in the latter period of rice growth. The total nitrogen uptake by rice plants from cattle manure and chemical fertilizer was similar regardless of co-composting. However, co-composting would be advantageous at least· in terms of the following aspects: increase of the N -uptake by rice plants from cattle manure, slow-release ability of nitrogen from chemical fertilizer, decrease of nitrogen loss by denitrification.