Yield variability of soybean [Glycine max (L.) Merrill] as affected by foliar applied kaolin under irrigation in Sudan savanna of Nigeria

A field trial was conducted during the hot, dry season in 2020 to assess the effect of foliar-applied antitranspirant (Kaolin) on yield and yield components of irrigated soybean [Glycine max (L.) Merrill]. Treatments consisted of two varieties of soybean (TGX1835-10E and TGX1955-4F), three growth stages for the application of kaolin (node initiation, flower initiation, and pod initiation), and application rates (0%, 3%, 6%, and 9% w/v). The factors were factorially combined and laid out in a split-split-plot design and replicated three times. The result obtained after comparison between two varieties of soybean, three growth stages of foliar applied kaolin, and four kaolin rates indicated that variety, application at growth stage, and kaolin rates indicated higher significance, significance, and non-significance effects on measured; number of pods plant-1, seed pod-1, hundred seed weight (g), grain and fodder yield (kg ha-1) taken at harvest. The average yield of 2.3 t ha-1 was recorded in TGX1835-10E and 2.5 t ha-1 in TGX1955-4F. Kaolin applied at flower and pod initiation recorded a higher grain yield at BUK, and at Kadawa application at pod initiation recorded a higher grain yield. Kaolin rates applied at 3 and 6% averagely indicated grain yield of 2.8 t ha-1 and 2.7 t ha-1, respectively. Applying 3% kaolin rate is recommended for soybean production in area with low heat load (low temperature) on leaf surfaces within the growing cycle of the crop and 6% rate in area with higher heat load (higher temperature) on leaf surfaces.