Canopy temperature and water stress quantificaiton in rainfed pigeonpea (Cajanus cajan (L.) Millsp.)

Field studies were conducted at Anand (22°35′N, 72°55′E), India, to investigate utility of remotely sensed canopy temperature to assess crop water status and to quantify terminal water stress in rainfed pigeonpea (Cajanus cajan (L.) Millsp.) during the southwest monsoon seasons of 1993–1994 and 1994–1995, using different planting dates. Canopy–air temperature differential were measured by thermal IR thermometer. Differences in temporal variation in canopy–air temperature differential clearly described the differential response of pigeonpea to soil water availability. The canopy–air temperature differential (Tc−Ta) was significantly (P≤0.05) related to soil moisture, soil water content in the root zone and evapotranspiration. Significantly negative relationship was also noticed for yield attributes with both Tc−Ta and stress degree days (SDD) during reproductive ontogeny. Total water use during reproductive phase in pigeonpea decreased with increasing SDD. A close relationship between seed yield per plant and SDD in flowering stage clearly showed the potential utility of canopy temperature to describe water stress effects in rainfed pigeonpea.