Lime, Manure And Inorganic Fertilizer Effects On Soil Chemical Properties, Maize Yield And Profitability In Tharaka-Nithi County, Kenya

ABSTRACT

In Sub-Saharan Africa, acidic soils occupy 29% of the total area, while about 13% of the Kenyan total land area has acidic soils, widely distributed in croplands of the central regions. The high soil acidity coupled with soil nutrient depletion negatively affect performance and yields of maize in the region. This study was therefore carried out at Kirege in Tharaka Nithi County for two cropping seasons; short rains (SR) in 2016 and long rains (LR) in 2017 to determine the effects of manure, lime and inorganic fertilizer on (i) soil chemical properties (ii) maize yield and (iii) profitability. The treatments included manure (0, 5 and 10 t ha-1), lime (0 and 2 t ha-1), and P fertilizer (0, 30 and 60 kg P2O5 ha-1). Maize (H516) was used as the test crop. The experiment was laid out in a randomized complete block design with eight treatments replicated ten times in farmer’s fields. Key variables measured were soil chemical properties, plant growth parameters; height, chlorophyll content, grain yield and economic data. Data generated was subjected to analysis of variance and means using least significant differences of means (LSD at p≤0.05). The results showed that sole lime (2 t ha-1) significantly (p=0.0001) increased soil pH by 17.7%. Reduction in soil exchangeable acidity was clearly seen in treatments lime and manure; Lime and fertilizer had the highest change of 27.8% and 30.6% in 2016 short rains and 2017 long rains respectively. Application of combined lime, manure and P fertilizer had the highest increase in soil available P (+22.5) and plant height (296.13 cm). The study observed high maize yield of 5 t ha-1 with application of combined lime, manure and P fertilizer obtained at the end of the second season. Lime and fertilizer had the highest net benefit of 128.75 USD/ha in the 2017LR followed by sole fertilizer with 105.94 USD/ha. Treatments that had high grain yields did not have high net benefit. There is need to consider economic returns when selecting agricultural production technologies. Use of lime plus fertilizer could therefore, be recommended to smallholder farmers of Tharaka Nithi County, Kenya.