Effect of Organic and Inorganic Amendments/fertilizers, on Soil Chemical Properties in Solanum Aethiopicum (Nakati) Production, Mukono District, Central Uganda.

Abstract

This research as hypothesized was intended to increase the availability of major soil nutrients for increased yield of nakati in continuously cultivated agro-ecosystems. The objectives were 1) to assess the effect of selected organic and inorganic amendments on availability of major nutrients under nakati production system, 2) and to assess the effect of the different soil amendments on the yield of nakati. The experiments were conducted in a Completely Randomized Design of 5 treatments, each in three replications, for two growing seasons (2014 and 2015). The 15 experimental plots were each 1m x 2m in size. The treatments comprised: 4 t/ha of wood ash alone (T1); 2.5 t/ha of cow dung compost alone (T2); 2.5 t/ha of cow dung compost + 4 t/ha of wood ash admixture (T3); 300kg/ha of NPK (17:17:17) inorganic fertilizer alone (T4); and a treatment-free control group (T0). All treatment materials were applied at once, 3 weeks before the commencement of the first cropping season and incorporated into the top 20 cm of soil. At 3 WAP higher soil pH, OC, OM, total N, available P, K, Na, Ca, Mg, CEC and BS% were observed in the cow dung compost-wood ash admixture (T3) treated plots. Fresh Nakati biomass weight in the T3 treatments was the highest among all treatments and the control at the end of the first cropping season. At 3 WAP, the sole wood ash (T1) treated experimental plots showed higher increases in soil pH, K, Na, Ca, Mg, CEC, and BS% than the sole cow dung compost (T2) treated experimental plots but had less effect on OC, OM, total N, and available P. Low levels of fresh nakati biomass weight on the sole wood ash and sole cow dung compost treated experimental plots was recorded at end of first cropping season in 2014. However, with regard to the cow dung compost (T2) experimental plots, the initial low nakati growth and least fresh nakati biomass weight was probably due to microbial immobilization of nutrients. This scenario was reversed at the end of the second cropping season with both the sole wood ash (T1) and the sole cow dung compost (T2) treatment plots showing higher fresh nakati biomass weight than the other treatments. 3 WAP the pH, total N, cations, CEC and base saturation percentage were higher in the NPK fertilized plots. This was reflected in the observed higher first season fresh nakati biomass weight when compared to the other treatments except for the cow dung compost-wood ash admixture (T3). This situation was reversed at the end of the second season when lower levels of total N, Na, Ca, Mg, and the CEC were recorded in the NPK fertilized plots with the fresh nakati biomass weight being among the worst. At 52 WAP higher levels of pH, available P, K and CEC were observed in the cow dung compost-wood ash admixture (T3) treated plots. However, the fresh nakati biomass weight was not among the best at this point of time possibly due increased retention and slower release of nutrients. This suggests longer term soil chemical fertility maintenance with the cow dung compost-wood ash admixture treatment.

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