16340 % of that given to fully irrigated plots, from anthesis to harvest. The amount of
water supplied to an irrigated plot ( L) was calculated using
(^) (8.1)
(^) (8.2)
where Kc is the crop coefficient with a value of 0.8 for groundnut (Doorenbos and
Pruitt 1992 ) crop during the reproductive development period. The evaporation data
were obtained from the weather station at ICRISAT, which is given as:
(^) (8.3)
Open-pan evaporation was obtained from United States Department of Agriculture
(USDA) class A type pan and Kpan with a value of 0.7 as the pan coefficient. Wa-
ter use efficiency (WUE) was calculated as the ratio of above-ground biomass dry
weight (including pod weight) to the amount of water supplied.
8.2.4.2 Temperature Treatments
Plants were exposed to high temperatures by covering them with plastic tunnels
supported by an iron frame, referred to from now on as ‘heat tunnel’. Plants in the
high-temperature treatment were covered with heat tunnel from flowering to 20
days after flowering (DAF), the most sensitive period for temperature stress (Prasad
et al. 1999a). Temperature inside the heat tunnel was controlled so as not to exceed
42–43 °C by opening and closing the flaps of the heat tunnel. This also ensured that
humidity did not build up in the heat tunnel. The polythene sheet (400 μ thick) used
allowed 80 % transmittance of light for plants in the heat tunnel, and the surface was
cleaned regularly for any settled dust to maintain transmittance levels.
8.2.5 Crop Development
The time of the key reproductive stages (R1, R2, R3 and R8; Boote 1982 ) were re-
corded in each plot. Observations were made daily on ten plants per plot. The crop
was considered to have reached a particular reproductive stage when 50 % or more
of the plants were at that stage of development.
8.2.6 Growth Analysis
Sampling of plants was done once in the vegetative stage, before flowering, and
at weekly intervals after imposition of water and temperature stress treatments.
An area of 0.6 m^2 (0.5 × 1.2 m) from each plot was sampled at each harvest. A
L=×Plot area ETCETCc=×Evaporation K,Evaporation=−×Open pan evaporation Kpan8 Effect of High Temperature and Water Stress on Groundnuts ...