Effects of NPK Fertilizer and Super Absorbent Polymer on Soil Moisture, Water Use Efficiency, Growth and Yield of Amaranthus (Amaranthus dubius) in Kilifi County

Abstract

Amaranth is an important leafy vegetable crop that provides nutrition inform of vitamins, minerals, anti-oxidants and other health benefits to humans. It does well in a variety of climatic conditions so long as the soils are of fertile, free draining and of good moisture availability. However, its production in Kilifi and much of the Coastal Kenya is constrained mainly by factors such as soil moisture stress and unbalanced nutrition. Therefore, to inform on conditions necessary for its sustainable production in the region, a study was set to evaluate the use of climate smart technologies, namely Super Absorbent Polymer (SAP), and NPK fertilizer. The study sought to determine the effects of NPK fertilizer and (SAP) rates on soil moisture, water-use efficiency, growth and yields of Amaranths in Kilifi county.  Thus, a3 by 3 factorial experiment laid in Randomized Complete Block Design (RCBD) with three replications was set at Pwani University Crop Science Research Farm between October and December 2022 and from January and March 2023.  Two factors were involved namely; SAP at 3 levels ((S0= 0 gm(0kg/ha), S1 = 2.5 gm (250 kg/ha) and S2 = 5 gm (500 kg/ha)) and NPK fertilizer at 3 levels: ((N0= 0 gm (kg/ha), N1 = 10 gm (200 kg/ ha) and N2 = 20 gm (400 kg/ha)). Data was collected on soil moisture content, water-use efficiency, plant height, leaf area, leaf chlorophyll content, stem diameter, number of leaves per plant, branch number, harvestable yield, fresh weight and dry matter. Soil analysis was conducted for pH, macro and micro nutrients before planting and after harvesting. The collected data for each variable was subjected to analysis of variance (ANOVA) using SAS software 14th edition and the means obtained subjected to Tukey’s Honestly Significant Difference Test for comparison at 5% level of significance. The results indicated that use of SAP and NPK enhanced soil moisture, WUE, growth and yield of Amaranths. However, significant interaction effects were notable when SAP and NPK fertilizer were combined; followed by NPK fertilizer without SAP; followed by SAP alone and lastly control.