Enhancing Sorghum bicolor (L.) grain yield with the use of field edge rainwater harvesting and NPK fertiliser in a dry region of Zimbabwe

Background: Farmers in marginalised areas across Africa are mainly resource poor and have limited capacity to procure enough inorganic fertilisers. This contributed immensely towards declining crop productivity causing food insecurity. Soil moisture stress is another key factor which has led to a decline in crop yields across semi-arid areas. This experiment determines the effects of field edge rainwater harvesting and NPK fertiliser microdosing on sorghum grain yields and agronomic nutrient use efficiency of two sorghum varieties (Macia and SV1). Rainwater harvesting techniques was the main plot factor with three levels (tied contour, infiltration pits and standard contour), sorghum variety was used as subplot factor with two levels (Macia and SV1) and NPK fertiliser as sub-sub plot factor with five levels (0, 25, 50, 100 and 150 kg ha(-1)) with all treatments replicated three times. A randomised complete block design arranged in split-plot was used. Results: Phosphorous was significantly increased from 3.32 to 3.52 mg kg(-1) with no significant (p > 0.05) increase in total nitrogen and soil organic carbon. Sorghum grain yields were statistically (p < 0.05) influenced by main treatment factors. Tied contour had considerably higher grain yield (861 kg ha(-1)) than infiltration pits and standard contours. Highest grain yield of 909 kg ha(-1) was observed from plots applied 150 kg ha(-1) NPK fertiliser. Macia variety performed significantly (p < 0.05) higher than SV1. Grain yields show significant (p < 0.05) increase with increasing fertiliser levels. Interaction of tied contour + Macia+ 150 kg ha(-1) NPK fertiliser had significant grain yields (1150 kg ha(-1)) compared to other treatments. Treatments applied NPK fertiliser show significant differences (p < 0.05) than unfertilised plots. Agronomic nutrient use efficiencies were significantly higher (p < 0.05) from all treatments applied 25 kg ha(-1) NPK fertiliser. Sorghum variety Macia had better nutrient use efficiency than SV1 in 2017/18 and 2018/19 seasons except during 2019/20 where results show insignificant differences. Conclusion: It can be concluded that farmers adopt the use of tied contour and Macia variety using 150 kg ha(-1 )to achieved higher yields. Combining rainwater harvesting method of tied contour and mineral fertiliser can increase sorghum grain yields in dry regions.