A minute P application contributes to a better establishment of pearl millet (Pennisetum glaucum (L.) R. Br.) seedling in P deficient soils

Many soils of the semi-arid tropics are deficient in P, and under such adverse conditions, the establishment of pearl millet seedlings is a critical step to achieve satisfactory crop stands. Phosphorus fertilizer is expensive for small holder farmers and is only applied at low rates, insufficient to give satisfactory crop stands. Methods are needed to enhance productivity at low rates of application. Here, we tested the hypothesis that a minute application of P at early seedling stage, equivalent to 125-500 g P/ha, would enhance the plant establishment under P-limiting conditions. We measured the minimum application of P needed to elicit a response of different genotypes. Pot experiments were conducted with pearl millet (Pennisetum glaucum (L.) R. Br.) hybrids to measure the response to P placed close to the root system, 5 days after sowing (DAS), compared with a non-limiting P control (DAP). The placement treatments were 0, 0.25, 0.50, and 1.0 mg soluble P per seedling, applied as KH2PO4 solution. The localized placement of P increased biomass in all three soils tested. In one soil, plant biomass at 1000 mu L (1 mg P) reached about 50% of the non limited control. If applied later than 19 DAS the placement had no effect on the plant biomass. Hybrid ICMP 451-P8 was more responsive than hybrid 81B-P6. Placement to 20 inbred lines of pearl millet increased biomass by an average of 105% compared with no placement with large genotypic variation. Although this work was not intended to be a way of applying P fertilizer to pearl millet under field conditions, it showed that applying minute amount of P to pearl millet seedling (equivalent to 125-500 g P/ha) enhanced their establishment and led to improved growth for at least 5-6 weeks after sowing. Further work is in progress to develop a feasible technology for field crops based on the results of this study.