Assessment of Soil Nutrient Status and Determination of Potassium Dosage for Maize Production in Kaaga, Meru County Kenya

Abstract

Food insecurity is a major global concern because many people suffer from malnutrition, under-nutrition, and starvation. In Sub Saharan Africa; it is estimated that about 239 million of people suffer from hunger and the number is likely to go up in the future. One of Kenya‘s big four agenda is improving food security by producing 2.76 million bags of maize annually. Food insecurity is mainly caused by inadequate food production due to inefficient agricultural practices. Maize farmers in Kaaga mainly use 23:23:0 NPK fertilizers which implies it contains no potassium partly because of the assumption that the soils are rich in potassium. Potassium, being a macronutrient, cannot be underestimated in crop production because it plays many critical roles. The use of these fertilizers in Kaaga has led to small or no increment in the yields. The reason for their ineffectiveness has not been investigated and reported. In light of this, the present study aimed at assessing the soil nutrient status and ultimately determine the optimum potassium dosage for maize production in Kaaga area, Meru County. Soil pH, electrical conductivity, Cation Exchange Capacity (CEC), Organic Content (OC), nutrient levels and bio-available levels of phosphorus and potassium were determined using reported literature methods. The study found most of the physical-chemical parameters to be sufficient except OC and CEC with average concentrations of 10.95±0.16 g/Kg and 141.40±0.03 meq/100g, respectively. The levels of Mg2+, Ca2+, and P were found to be sufficient with averages of 24.14±0.04mg/kg, 54.82±0.04mg/Kg and 55.85±0.32mg/Kg, respectively. However the soils were found to be deficient in nitrogen, exchangeable K and total K were with mean levels of 0.17±0.09 %, 0.85±0.11mg/Kg and 2.26±0.04mg/Kg respectively. Free energy of replacement was calculated from K concentration and found to be -3533 Calmol-. Adsorption studies found the soils to best fit into Freundlich isotherm model with R2 of 0.951. Subsequently, the Freundlich isotherm was used to estimate the K acreage dosage. The potassium dosage of 221.63Kg/ha was found to give the optimum maize yield of 3404 Kg/ha. This study has established the need to replenish the soils with K fertilizer in addition to other parameters which were deficient. Ultimately, this will improve maize yield, reduce extreme poverty and thus help in the realization of the government big four agenda and the millennium goals.