Effect of P Placement on Yield of Tomatoes in Southwestern Nigeria

Research information developed under a temperate climate indicates that soil type, soil temperature, and soil moisture influence the response of arable crops to P placement methods. At a temperature of 10 C, banding was superior to broadcast while at 27 C (warm temperature) there was no difference between the two methods. Banding of P as opposed to broadcast was also suggested on tropical soils which have high phosphate-fixing capacity to reduce P fixation. There is no research information in Nigeria on the best P placement method on tomatoes (Lycopersicon esculentum), which require a high rate of P for maximum fruit yield. Five common methods of fertilizer placement techniques in Nigeria were therefore evaluated on fruit yield response to P by this crop in a field experiment on two soil types varying widely in their P sorption capacity (PSC). The two soils were lju, a gleyic luvisol (FAO classification), and Alagba, a eutric nitosol, both derived from sedimentary materials in the rain forest zone of Nigeria. The methods were ring, band, broadcast, hole, and hill. The results of the study for five seasons mostly on rainfed tomatoes show that on a soil with a relatively high PSC, P banded was superior to broadcast in fruit yield production of tomatoes in a wet year though banding was not significantly better than ring and hill placement which are more laborious than the band method. In a dry year however, the broadcast method was sometimes better than the band method. Phosphorus placed 15 cm deep and 7.5 cm in a planting hole below the seedling was inferior to all the other methods under various soil water regimes. On a soil with a low P sorption capacity, the differences among the methods were not significant except hole placement which gave the lowest phosphate response. A combination of band and broadcast placement of P is therefore recommended in P fertilization of tomatoes in Nigeria.