摘要
The fate of urea-and ammonium bicarbonate(ABC)-nitrogen (N) applied by prevailing traditional techniques to winter wheat (Triticum aestivum L.)or maize (Zea mays L.)grown in the fields of Fluvo-aquic soil was investigated using ^15N tracer-micro-plot technique.Results show that:(1) at maturity of wheat,N recovery in plants and N losses of urea and ABC applied at seeding in autumn were 31-39%,and 34-46%,respextively,while the corresponding figures for side-banding at 10 cm depth in early spring were 51-57%,and 5-12%;surface-broadcast of urea followed by irrigation at early spring was as efficient as the side-banding in improving N recovery in plants and reducing N loss,however,such techuique was found less satisfactory with ABC.(2)At the maturity of maize,N recovery in the plants and N loss of urea and ABC sidebanded at seedling stage or prior to tasseling ranged from 23% to 57%,and 9% to 26%,respectively.(3) Either in Wheat or in maize experiment,the majority of residual fertilizer N in soil profile (0-60cm) was in the form of biologically immobilized organic N,however,the contribution of ammonium fixation by clay minerals increased markedly nwith depth in soil profile.(4) Though the proportion of residual fertilizer N was generally highest in the top 20 cm soil layer,considerable reaidual N (nostly 6-11% of the N applied)was found in 60-100 cm soil layers.
The fate of urea-and ammonium bicarbonate (ABC)-nitrogen (N) applied by prevailing traditional techniques to winter wheat (Triticum aestivum L.) or maize (Zea mays L.) grown in the fields of Fluvo-aquic soil was investigated using 15N tracer-micro-plot technique. Results show that:(1) at maturity of wheat, N recovery in plants and N losses of urea and ABC applied at seeding in autumn were 31-39%, and 34-46%, respectively, while the corresponding figures for side-banding at 10 cm depth in early spring were 51-57%, and 5-12%; surface-broadcast of urea followed by irrigation at early spring was as efficient as the side-banding in improving N recovery in plants and reducing N loss, however, such technique was found less satisfactory with ABC. (2) At the maturity of maize, N recovery in the plants and N loss of urea and ABC sidebanded at seedling stage or prior to tasseling ranged from 23% to 57%, and 9% to 26%, respectively. (3) Either in Wheat or in maize experiment, the majority of residual fertilizer N in soil profile (0-60 cm) was in the form of biologically immobilized organic N, however, the contribution of ammonium fixation by clay minerals increased markedly with depth in soil profile. (4) Though the proportion of residual fertilizer N was generally highest in the top 20 cm soil layer, considerable reaidual N (mostly 6-11 % of the N applied) was found in 60-100 cm soil layers.
