Vegetable crop production in Ghana over the past years has been a challenge due to water scarcity. The unpredictable and insufficient rainfalls has been a drawback on improving crop production and yield. This study aimed at estimating crop water requirement (CWR) and yield of okra in biochar amended soil. The FAO 56 dual crop coefficient approach was used to estimate CWR of a local variety of the test crop, okra (Abelmoschus esculentus L.). Models were developed to predict crop coefficient (kc) and yield using ground based remote sensing technique.

The experiment was conducted at the University of Ghana (UG) Forest and Horticultural Crops Research Centre (FOHCREC) in Kade. Two irrigation treatments, namely full irrigation (FI) and deficit irrigation (DI) and four biochar amounts were applied in 32 plots. kc at the initial, crop development, mid-season and late season growth stages determined are 0.28, 0.67, 0.91 and 0.86 under FI treatment and 0.32, 0.54, 0.98 and 0.8 for DI treatment though only FI data was presented under results. Seasonal accumulated water use by okra (ETc) was 273 mm under FI treatment and 246 mm under DI treatment. There were no significant differences in total above ground dry biomass yield (YTBM) in the different biochar amounts under FI and DI treatments at (P ≤ 0.05). There were significant difference in okra fresh fruit yield (YFF) in three biochar amounts only under DI treatment but no significant difference in YFF in all four biochar amounts under FI treatments was recorded.

From the results, it was concluded that biochar had effect on YFF under stressed and or limited water situations, thus DI and hence DI should be practiced in water scarce situations and areas especially when biochar is used. Premixing biochar with phosphorous fertilizer before incorporating into the soil also gave a better result in terms of high okra YFF over the alternative method of applying phosphorous fertilizer separately after biochar incorporated into the soil.iii