用冠气温差指导冬小麦灌溉的指标研究

Use of crop water stress index as indicators for scheduling irrigation in winter wheat.

对6个不同灌水处理的冬小麦测定其冠气温差,计算水分胁迫指数,并建立水分胁迫指数与冬小麦产量之间的关系结果表明,冠气温差与土壤含水量有良好的相关关系,冠气温差由正值变为负值相对应的1m土层土壤含水量为田间持水量的60％左右,可作为灌水的下限指标。对充分供水的冬小麦,中午时段随大气饱和水汽压差的增加,冠气温差的负值越大,具有良好的线性关系。据此建立了充分供水条件下冠气温差与饱和水汽压差的关系方程,作为基线方程,计算不同灌水处理的冬小麦旺盛生长期间水分胁迫指数(CWSI)。水分胁迫指数与最终作物经济产量的关系是一非线性关系,随水分胁迫指数的减少而产量增加,但当水分胁迫指数减少到一定程度时产量达到最大,这时水分胁迫指数若再减少,产量反而降低。结果显示平均水分胁迫指数在0.1～0.2左右,是冬小麦最优产量所允许的水分供应状态。

Canopy-ambient air temperature differences( Tc - Ta) for six irrigation treatments of winter wheat were monitored during booting to grain filling period at Luancheng Station from 2000 to 2001 season. The results showed that the midday Tc - Ta was closely related to soil moisture condition. Soil moisture at 60% of field capacity for the 1m soil profile of winter wheat corresponded with the changing of Tc - Ta from positive to negative. For a non-water-stressed treatment , Tc - Ta was negatively related to the atmospheric vapor pressure difference (VPD). A baseline equation of Tc -Ta with VPD was established to calculate the Tc - Ta under non-water-stressed condition for the purpose of calculation of crop water stress index(CWSI). The relation of average CWSI with grain yield was non-linear. With the decrease in CWSI, grain yield increased. When CWSI was at about 0.1 ~ 0.2, the grain yield of winter wheat reached the optimum. Thus, the average CWSI at 0.1 ~ 0.2 might be taken as the indicator for irrigation scheduling of winter wheat.