EFFECTS OF BLACK SHADE NET ON SOIL PROPERTIES, WATER USE EFFICIENCY, GROWTH AND YIELD OF Brassica rapa AND Brassica oleracea CABBAGES IN KILIFI COUNTY

Abstract

Cabbages are crucial vegetables in supplying fiber, minerals, and vitamins to humans. They also have properties that manage cancer and prevent type 2 diabetes, cardiovascular diseases, and inflammation of the digestive systems. Its production in the tropics is constrained by climatic and edaphic factors including soil moisture stress, high soil and air temperatures, high evapotranspiration, and unbalanced nutrition. Owing to the above challenges, sustainable production requires the adoption of technologies that can modify the growth environment with minimal environmental effects. Two field studies were conducted at Pwani University Agricultural farm, Kilifi County, to evaluate the effects of black shade net on soil properties, water use efficiency, growth, and yield of Brassica rapa and Brassica oleracea. The experimental layout was a randomized complete block design, with three replications. Treatments included; open field, 50% and 70% shading, using black shade net. Data collected included; soil chemical characteristics, soil moisture content, water use efficiency, air temperature, plant height, stem girth, crown circumference, leaf chlorophyll content, number of open leaves, number of quality heads, fresh head weight, and dry matter weight. Data obtained was subjected to analysis of variance using General Linear Model (GLM) SAS Computer package version 9.1. Based on the findings of this study, use of black shade net of 50% and 70% shading intensity significantly improved soil moisture content, with 70% and 50% shading recording 5.1% and 2.6% higher soil water content than open field, respectively. The soil chemical nutrients availability however, was not significantly influenced. Growing cabbages under black shade net of 50% and 70% shading intensity significantly improved water use efficiency. Brassica rapa under 70% shading recorded 49% higher water use efficiency than open field while, 50% shading recorded 50% more WUE than open field. Brassica oleracea under 70% shading recorded 41% higher water use efficiency than open field, vii while 50% shading recorded 25%. Maximum air temperature under black shade net was found to be lower than open field by 11.5% and 7.5% under 70% and 50% shading, respectively, while minimum air temperature was higher under black shade nets than open field by 11.6% and 5.7% under 70% and 50% shading, respectively. Brassica rapa under 70% shading significantly had higher plant height than those under open field by 85%, while those under 50% shading had 61% higher plant height than open field. Brassica oleracea under 70% shading significantly had higher plant height than open field by 81%, while under 50% shading plant height was 69% higher than open field. The number of quality heads for Brassica rapa was 55% and 47.5% more under 70% shading and 50% shading respectively than open field, while in Brassica oleracea, 70% shading and 50% had 60% and 52% more quality heads than open field respectively. From the study, areas that experienced relatively higher temperatures of around 30oC can use black shade net of 50% to70% shading intensity for cabbages production. Further investigation is recommended to evaluate chemical composition of cabbages under black shade nets to establish the difference between open grown cabbages and shaded cabbages