Seasonal Change of Photosynthetically Active Radiation Intercepted by a Spring Wheat Canopy and its Relation to Dry Matter Production

[摘要] Crop growth can be estimated by the amount of radiation intercepted by canopy and the efficiency of its conversion to dry matter. Diurnal and seasonal changes of photosynthetically active radiation (PAR), both intercepted and reflected by the canopy, were measured throughout a growing season for the spring wheat cultivars Haruyutaka and Selpek. The changes were correlated with total surface area including the leaves, culms, ears and senescent parts. The daily mean values of diurnal changes in penetration and reflection were the same when they were compared in a cloudy day and in a clear day. The penetration decreased with the growth of surface area. After flag leaf emergence, total surface area became 10 m2m-2 or more; After penetration rate decreased down to 10% and below, it did not change. There was a linear relationship between total surface area and the exponential value of the penetration, although the coefficient of light intercepted, Ks, changed with growth stages. On the other hand, reflection did not vary significantly (about 5%). The intercepted PAR was calculated by multiplying the incident solar radiation by the penetration and reflection. A linear relationship was observed between it and the crop growth rate (CGR). However, above 8 MJm-2d<-1> of intercepted PAR, Haruyutaka seemed to be saturated with light.

[学科分类] 农业科学（综合）

[关键词] Diurnal change;経時変化;Intercepted coefficient;光合成有効放射;Penetration;受光係数;Photosynthetically active radiation;透過率;Reflection;日変化;Seasonal change;春播コムギ;Spring Wheat;反射率