干旱与灌溉处理对冬小麦冠层内光分布的影响

为探讨北方冬麦区节水灌溉的关键时期,借助干旱和灌溉对冬小麦冠层光分布,获取本地化参数,为华北农业干旱预报模型的修正提供依据。采用美国CID公司生产的CI-110型植物冠层分析仪,对干旱和灌溉条件下冬小麦冠层内光分布进行直接测定。结果表明,干旱和灌溉条件下,无论是高氮还是低氮、中氮,平均叶面倾角(MLA)都随生育期的延长呈现出先下降再上升的趋势。高氮和低氮时,随着生育期的延长,干旱处理和灌溉处理的冬小麦散射辐射透过系数(TCDP)都呈现先下降再上升的变化趋势;中氮时,干旱处理和灌溉处理的冬小麦TCDP在开花期和灌浆期都呈现一直上升的趋势。无论高氮还是中氮、低氮,冬小麦直接辐射透过系数(TCRP)的值都随着天顶角角度的增大而减小,冬小麦TCRP的值随着冬小麦生育期的推进,都呈现出先下降、后上升的变化趋势。高、中、低氮3种情况下,干旱和灌溉处理的冬小麦每个生育期均呈现随着天顶角角度的增加,消光系数K也增大;高氮时,多数情况下,冬小麦冠层的消光系数K干旱的大于灌溉的;中氮、低氮时,多数情况下,冬小麦冠层的消光系数K干旱的小于灌溉的。干旱和灌溉对冬小麦冠层光分布的影响:灌溉增加了冬小麦的平均叶面倾角(MLA);干旱和灌溉处理条件下冬小麦的TCDP差异较小,TCDP与MLA变化趋势相似,也都呈现出先下降、再上升的变化规律;干旱和灌溉处理冬小麦TCRP,无论高氮还是中氮、低氮,都随着天顶角角度的增大而减小,在7.5°、22.5°时干旱和灌溉对冬小麦TCRP的影响较大,而在37.5°、52.5°、67.5°时对冬小麦TCRP的值影响很小;每个生育期消光系数K均随着天顶角角度的增加而增大。

Influence of Drought and Irrigation Treatment on the Distribution of Light in Winter Wheat Canopy

In order to study the key period of water-saving irrigation in northern winter wheat areas, with the help of influence of drought and irrigation on winter wheat canopy light distribution, we obtain the localization parameter, and provide the correction basis for agricultural drought prediction model in North China. The CI-110 type plant canopy analyzer produced by CID company in the United States is used for direct measurement of drought and irrigated winter wheat canopy light distribution. The results show that: under drought and irrigated conditions, whether in high nitrogen, low nitrogen, or medium nitrogen situations, the mean leaf angle (MLA)first decreases and then increases with growing time. In high nitrogen and low nitrogen situations, with the extension of growing period, after the drought and irrigation treatment winter wheat transmission coefficient for diffuse penetration(TCDP) first decreases and then increases. In medium nitrogen, after the drought and irrigation treatment winter wheat TCDP increases at flowering period and filling stage. Whether in high nitrogen, low nitrogen or medium nitrogen, the value of winter wheat transmission coefficient for radiation penetration(TCRP) decreases with the increasing of zenith angle, and first decreases and then increases with growing period. Under 3 conditions of high, medium and low nitrogen, after drought and irrigation treatment winter wheatextinction coefficient (K) increases with the increasing of zenith angle in every growing period. In high nitrogen, the extinction coefficient K of drought winter wheat canopy is larger than that of irrigation in most conditions. In medium and low nitrogen, the extinction coefficient K of drought winter wheat canopy is smaller than that of irrigation in most conditions. The influences of drought and irrigation on winter wheat canopy light distribution are as followed. Irrigation increases the MLA of winter wheat. Winter wheat TCDP under drought and irrigated conditions have little differences. The TCDP and MLA have similar change trend, all first decreases and then increases. Drought and irrigated winter wheat TCRP, whether in high nitrogen, medium nitrogen or low nitrogen, decreases with the increasing of zenith angle. Drought and irrigation have greater influence on the winter wheat TCRP at 7.5°, 22.5°, and have little impact at 37.5°, 52.5°, 67.5°. The extinction coefficient K increases with the increasing of angle at each growth period.