底墒和施氮量对渭北旱塬冬小麦产量与水分利用的影响

通过西北典型旱地渭北旱塬5年定位试验，在施磷100 kg P2O5·hm-2的基础上，设0、80、160、240、320 kg N·hm-2 5个施氮水平，结合5年降水情况，研究了播前底墒与施用氮肥对旱地冬小麦产量及水分利用的影响.结果表明： 夏季7-9月的降水与播前底墒呈线性相关，每增加1 mm夏季降水，土壤贮水量增加0.6 mm；要保持小麦稳产或高产，底墒应保持在550 mm左右，夏季降水应有370～390 mm.夏季降水充足（>386 mm）的年份，前季小麦施氮量增加造成的下季小麦播前底墒下降不明显；降水偏少（<350 mm）的年份，前季小麦每增施氮肥100 kg·hm-2，可使下季小麦播前底墒减少9～17 mm.除底墒外，关键生育期的充足降水也是保证旱地小麦产量的重要因素，每毫米播前底墒和关键生育期降水分别能形成106～114和306～33.1 kg·hm-2小麦籽粒产量.变异分析表明，氮肥投入水平影响小麦对底墒的利用程度，底墒制约小麦植株干物质向籽粒转移的比例.

Effects of soil moisture before sowing and nitrogen fertilization on winter wheat yield and water use on Weibei Plain of Loess Plateau

A five-year site-specific experiment was carried out on the Weibei Plain of Loess Plateau in Shaanxi Province of northwestern China to study the effects of soil moisture regime before sowing (SMBS) and nitrogen fertilization on the grain yield and water use of winter wheat. On the basis of applying 100 kg x hm(-2) of P2O5, five nitrogen fertilization levels (0, 80, 160, 240, and 320 kg N x hm(-2)) were installed, and took the precipitation in the five years into consideration. In the study area, there was a linear correlation between the precipitation in summer (from July to September) and the SMBS, with an increment of 0.6 mm SMBS per 1 mm precipitation. For a stable or high wheat yield, the SMBS should be kept around 550 mm, and the precipitation in summer should be around 370-390 mm. In the years with adequate precipitation (> 386 mm) in summer, the SMBS in present winter wheat growth season less decreased by the increase of the nitrogen fertilization rate in previous growth season. However, in the years with less precipitation in summer (< 350 mm), the SMBS in present winter wheat growth season decreased significantly by 9-17 mm when the nitrogen fertilization rate in previous growth season was increased by each 100 kg N x hm(-2). In addition to SMBS, adequate precipitation in key growth stages was another important factor to ensure the wheat yield in dryland area because 1 mm SMBS could produce 10.6-11.4 kg x hm(-2) of wheat grain, and 1 mm precipitation occurred in the key growth stages could lead to more grain yield as high as 30.6-33.1 kg x hm(-2). Variation analysis showed that nitrogen fertilization rate affected the utilization degree of SMBS by winter wheat, while SMBS controlled the allocation and transportation of dry matter from vegetative parts to grain.