Comparative Effect of Sunn Hemp with Farmyard Manure and Inorganic Fertilizer Levels on Growth of Cotton in Titanium-mined Reconstituted Soils in Kwale County, Kenya

Abstract

Cotton growth performance in Kenya have declined over the years, with Kwale County being one of the areas that were once suitable for cotton farming experiencing serious setbacks with soil loss and reduced arable land due to enhanced mining activities. The aim of this study was to assess the potential of combining sunn hemp with farm yard manure and inorganic fertilizers to enhance cotton growth in titanium-mined and reconstituted soils of Kwale County. Field trials were conducted in May–August 2022 and September–December 2023 at Base Titanium Mining company, Kwale County, on a randomized complete block design with three replications.  Ten treatments with variation in mixtures of sunn hemp, farmyard manure (7.5 or 15.0 tons/ha) and NPK fertilizer (100 or 200 kg/ha), were applied in four site conditions: undisturbed soil, topsoil-covered mined land, reconstituted soil without topsoil and reconstituted soil with topsoil. Data collected included: Soil analysis and cotton growth parameters such as plant height, leaf number, leaf length, leaf width, number of fruiting branches, length of the longest fruiting branches, number of nodes on the longest fruiting branch, internodal length, leaf chlorophyll content and canopy temperature. Data collected was subjected to analysis of variance (ANOVA) using the SAS statistical package (SAS, Version 10). Significant means at the F-test were ranked using Turkey's test at a 5% significance level. Results indicated that cotton with 200 kg NPK with sunn hemp significantly enhanced cotton chlorophyll content by (32.7%), leaf numbers (78.6%) and plant height (41.5%) compared to control. These findings indicate the possibility of utilizing organic-inorganic input mixtures in reclaiming mined land and improving cotton development, though additional long-term studies are recommended for large-scale application and validation.