Evaluation of locally and commercially available organic materials on Nakati yield

Abstract

Soils in Uganda are of inherent poor soil fertility and among the problems inherent to tropical soils include low pH, nutrient deficiency and low organic matter. The loss of soil fertility has been manifested through loss of organic matter, and in turn leading to decline in soil organic carbon (SOC). Soil organic carbon depletion has subsequently led to low yields of crops and this has affected productivity. There has been a rise in the number of commercially available organic materials on the market, whose effect on crop yields is not known. A study was conducted to evaluate the effect of locally and commercially available organic materials on Nakati yield in MUARIK, Wakiso District. The pot experiment was set up in a greenhouse in a Completely Randomized Design (CRD) with seven treatments and four replications. The treatments included the control, cattle manure, ferti-plus, bio-king, humate, G5 and biochar. The application rate for all organic materials was 7.6t/ha of organic carbon, hence having different amounts of each organic material applied. This was aimed at obtaining the critical levels of soil organic carbon (1.74%). Data was collected 8 weeks after planting and the parameters included plant height, number of leaves, stem girth, leaf width, leaf area, fresh weight, and dry matter weight. The data was subjected to analysis of variance (ANOVA) to assess the effect of the organic materials on yield of Nakati. The results showed that the organic materials increased the yields significantly (p<0.05) in comparison with the control. Ferti-plus and cattle manure had significantly higher yields than other organic materials, with the highest number of leaves, fresh weight, leaf area, stem girth and dry matter weight while the control had the lowest mean of all the parameters. The increase in yields is attributed to the mineral content of the different organic materials N, P and K. The low yield observed under the control is due to the nature of the soil being ferralsols since it was acidic (pH 5.18), low organic carbon (1.36%), and low N content (0.063%). There was no relationship between the organic carbon content of organic materials and the yields of Nakati that were obtained, and this is an indicator that other factors, not included in the study have a stronger influence on yield. This was observed through a regression analysis of the carbon stocks and the different yield parameters. Therefore, the use of ferti-plus, cattle manure, biochar and humate is cost effective, profitable and is important in improving the yields of Nakati in a sustainable manner. Cattle manure provides the cheapest source of organic carbon, and is the most profitable organic material that should be used by the farmers.