Abstract:
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 thisii
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.
