Soil moisture, dryland sorghum (Sorghum bicolor L.) growth and grain yield responses to in-field rain water harvesting tillage methods

Dryland Sorghum, which is the fifth most important cereal crop in the world, is grown in Zimbabwe typically as a rain-fed crop in areas receiving low, erratic and highly variable rainfall. A two-season field trial was carried out at Save Experiment Station (20°24′S; 28°29′E) in Zimbabwe to establish soil water storage, selected biometric parameters of dryland grain sorghum responses to in-field rainwater harvesting tillage methods. Deep basin tillage method significantly increased the soil moisture content by 14.6% (62.5 mm); 6.2 % (26.5 mm) above that on the ridges and in furrows of open and closed end tied ridges, respectively. Soil moisture storage in deep basins, on ridges and in furrows of open and closed end tied ridges exceeded that in conventional tillage plots by 98.0 mm (29.8%); 35.5 mm (10.8%) and 69.5 mm (21.1%), respectively. Consequently, sorghum plant biometric growth parameters in deep basin tillage treatments were significantly higher than those in conventional, open- and close-ended tied ridges tillage plots. However, the use of conservation tillage methods where tied end ridges are opened introduces homogeneous soil water build-ups in furrows and ridges as those observed in tied end ridges with closed ends. As a consequence, biometric growth parameters of sorghum are not altered by substituting open with closed end tied ridges.