A pot experiment was conducted to study the N availability to wheat and the loss of15N-labelled fertilizer N as affected by the rate of rice-straw applied. The availability of soil N was also studied. The straw was incorporated in the soil 2 or 4 weeks before a sowing of wheat and allowed to decompose at a moisture content of 60 or 200 of the water-holding capacity. The wheat plants were harvested at maturity and the roots, straw, and grains were analysed for total N and15N. The soil was analysed for total N and15N after the harvest to determine the recovery of fertilizer N in the soil-plant system and assess its loss. The dry matter and N yields of wheat were significantly retarded in the soil amended with rice straw. The availability of soil N to wheat was significantly reduced due to the straw application, particularly at high moisture levels during pre-incubation, and was assumed to cause a reduction in the dry matter and N yields of wheat. A significant correlation (r=0.89) was observed between the uptake of soil N and the dry matter yield of wheat with different treatments. In unamended soil 31.44 of the fertilizer N was taken up by the wheat plants while 41.08 of fertilizer N was lost. The plant recovery of fertilizer N from the amended soil averaged 30.78 and the losses averaged 45.55
展开▼
