Assessment of plant-extractable soil water in castor beans (Ricinus communis L.) using infrared thermometry

Assessment of plant-extractable soil water from experimental plots using in frared thermometer was carried out through a field experiment on rainfed ca stor beans (Ricinus communis L.) conducted for 2 years (1992-1993) at Hyder abad, India. The castor beans (cultivar: Aruna) were planted on three diffe rent dates in both years. Attempts were made to normalize canopy temperatur e and stress degree days (SDD) for environmental variability to accurately assess the plant-extractable soil water (PESW) using an Infrared thermomete r. Normalization of SDD for variability of temperature and saturation defic it (division of SDD by air temperature and saturation deficit), greatly imp roved the predictability of the soil water status (PESW), than that based o n SDD. The coefficients of determination (R-2 values) of the relationship b etween PESW and SDD after normalization were 0.65 and 0.61 in the years 199 2 and 1993, compared to 0.19 and 0.08 before normalization, in respective y ears. This simple method of normalization of SDD (the division of SDD with weather parameters), which seems to be a promising technique for assessing the soil water status through remote sensing techniques in semi-arid tropic s (SAT) needs to be further tested in other environmental conditions and al so in other crops, for realising the long-felt objective of assessing soil moisture status with the help of infrared thermometry. (C) 1999 Elsevier Sc ience B.V. All rights reserved.