The effect of increasing foliage and soil reflectivity on yield and water use efficiency of grain Sorghum crops (Sorghum bicolor (L.) Moench.) grown under arid conditions with stored soil water only, was studied during 3 years of randomized block field experiments. Suspensions of kaolin were sprayed on the soil and/or foliage at different growth stages to select the most effective placement and timing for the treatment. Soil-only applications were ineffective in increasing yields but canopy sprays resulted in an additional yield of 446 kg/ha, or 11% over the unsprayed controls, averaged over the 3 years of experimentation. The most effective period for foliage sprays started seven weeks after seedling emergence and ended 10 days later, immediately before the panicles emerged. During this period, known to be critical for Sorghum grain yield response to water status, the yield response averaged 2 kg grain/1 kg kaolin applied. Neither the total seasonal water use nor the rate of soil water depletion was affected by the foliage reflectance treatment.

It is concluded that under arid conditions, kaolin suspensions sprayed twice on the foliage of unirrigated grain Sorghum crops during the prepanicle-emergence stage shows promise as an effective method of increasing grain yield.