Response of maize to phosphorus in sole maize and maize-pigeonpea cropping system in semi-arid areas of Tanzania
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Mkoma, A. 2015. Response of maize to phosphorus in sole maize and maize-pigeonpea cropping system in semi-arid areas of Tanzania. MSc thesis in Soil Science and Land Management. Morogoro, Tanzania: Sokoine University of Agriculture.
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Estimating crop response to fertilizer application and identification of effective fertilizer materials is important for plant nutrient management and in sustaining soil fertility. Unlike other agro-ecological zones, no fertilizer recommendations have been established for the semi-arid zones in Tanzania. This could be due to the fact that semi-arid areas are regarded as marginal land for agricultural production. To address this gap, field experiments were carried out to establish phosphorus (P) fertilizer rates and identify the effective P source for semi-arid areas of Kongwa and Kiteto districts in a sole maize and maize-pigeonpea cropping system. Assessment of soil fertility status on experimental sites was carried out. Triple Super Phosphate (TSP) fertilizer was used to test various application rates: 0, 7.5, 15, 30, 45 and 60 kg P ha-1. For P-source triall, Minjingu Mazao, Minjingu hyper phosphate and TSP were tested at 0 and 30 kg P ha-1 for each fertilizer material. Sole maize or intercropped with pigeonpea was used as the test crop in two fertilizer trials. The treatments were arranged in a Randomized Complete Block Design (RCBD) with three replications. Soils in the study sites were deficient of P, N and Ca; and had very low organic matter contents. Compared to the control, the fertilizer treatments had higher yield across sites and cropping system. The 15 kg P ha−1 fertilizer rate increased the grain yield by 38 to 49% in sole maize and 55 to 60% in maize-pigeonpea intercropping system at Njoro and 51 to 54% in sole maize and 44 to 46% in maize pigeonpea intercropping system in Moleti. Maize yield obtained with 15 kg P ha−1 was equivalent to the maximum yield obtained under 30 kg P ha−1 fertilizer rate. Maize yield obtained after 30 kg P ha-1 fertilizer rate declined slightly possibly reflecting sufficiency level of P. These results suggest that 15 kg P ha-1 P is the agronomic P fertilizer rate for maize production under sole maize and maize-pigeon pea intercropping system in semi-arid areas of Kongwa and Kiteto districts, Therefore, application of this particular rate in maize and maize-pigeon pea cropping system may be an option for the marginal farmers in the region as farmers may reduce the application rate by 50% without losing yield significantly. Maize grain yield obtained with Minjingu Mazao fertilizer treatment was similar to the yield obtained with TSP fertilizer in Moleti site (3.6 vs. 3.7 t ha-1) and Njoro site (3.9 vs. 4.2 t ha-1). High response of maize to Minjingu mazao is attributed to slightly acidic soil condition, starter N, calcium and fortified micronutrients in this fertilizer material. Thus farmer may use Minjingu mazao or TSP as they are equally suitable P sources in maize production in semi-arid areas of Kongwa and Kiteto districts.