Black Shade Net Effects on Soil Properties and Cabbage Water Use Efficiency in Humid Coastal Environment

Cabbage is a popular vegetable grown in Kenya for food and income generation. Despite the important role played by the crop within the country, current climate change effects and population pressure pose a need for increasing production through utilization of available resources. A study was therefore conducted to evaluate the effects of black shade net on soil properties and cabbage water use efficiency in humid coastal environment. Black shade nets of 0%, 50% and 70% shading intensity and two cabbage types (Brassica rapa and Brassica oleracea) were evaluated in Randomized complete block design with three replications. 0% represented open field. Data collected included: soil chemical characteristics, soil moisture content, air temperature, fresh head weight, dry matter weight, and water use efficiency. Data obtained were subjected to analysis of variance using general linear model SAS Computer package version 9.1 and means separated using Tukey’s test at 5%. From the findings obtained, the use of black shade net of 70% and 50% shading significantly increased soil moisture content by 5.1% and 2.6% than open field. Maximum air temperature in 70% and 50% shade nets was lower than open field by 4.6⁰C and 1.8⁰C respectively while minimum air temperature under 70% and 50% shade nets was higher than open field by 2.7⁰C and 1.6⁰C respectively. Brassica rapa from 70% shading had 35% more fresh weight per plant than open field while those from 50% had 30%. Brassica oleracea from both 70% and 50% shading had 44% and 29% more fresh weight per plant respectively than those from open field. Although shade nets did not have significant effect on availability of nutrients within soil solution, 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, while 50% shading recorded 25% increase than open field. Owing to the fact that shade nets did not have significant effect on available nutrients within the soils but significantly influenced WUE, there is need for further studies to understand the effects of shade nets on cabbage nutrient use efficiency under the same environment.