Optimisation of the seedball technology for sorghum production under nutrient limitations

The seedball technology is a simple and affordable seed-pelleting technique that uses locally available materials such as sand, loam, wood ash and seeds to enhance early crop establishment. It has been shown to be effective for pearl millet ( Pennisetum glaucum (L.) R.Br. ) subsistence production in Sahelian environments. The objective of this study was to optimise the seedball technology for sorghum ( Sorghum bicolor (L.) Moench) under greenhouse conditions. Series of pot experiments were conducted in order to identify optimal size, seed number as well as nutrient content under low- and normal-soil phosphorus availability. The identified optimal seedball formula for sorghum is: 80 g sand + 50 g loam + 25 ml water + about 20 seeds. As maximum 1.5 g NPK mineral fertiliser can be added as nutrient compound. Compared to the control treatment, seedballs significantly improved root and shoot biomass variables as well as nutrient uptake of sorghum seedlings grown for 19 days. The lower the substrate P level, the better the biomass enhancement effect of seedballs, i.e. likely caused by nutrient availability. The next step is on-farm field testing under Sahelian conditions.