Differential Biomass Accumulation among African Leafy Vegetables as Affected by Wastewater Irrigation in Kitui County, Kenya

Water scarcity of fresh water in Sub-Saharan has led to utilization of the wastewater in home gardening and also in commercial production of vegetables. Wastewater is associated with various substances including nutrients and heavy metals hence it is pertinent to evaluate its effects on growth and yield of vegetables. An experiment was conducted to evaluate the effect of waste water released from the municipal council on the biomass accumulation in African leafy vegetables. Field experiments were carried out in two seasons and one greenhouse experiment. The field trial was laid out in a Randomized Complete Block Design (RCBD) and in the greenhouse the treatments were arranged in Complete Randomized Design (RCD) replicated three times. Four leafy vegetables were the treatments replicated three times. The vegetables were irrigated with waste water. Plant samples were collected at 6 WAP and 12 WAP, partitioned and dried in an oven and later weighed using electronic weighing balance. The findings revealed differences in biomass accumulation into various organs. Black nightshade depicted the highest leaf dry matter in the greenhouse at both 6 weeks after plant (WAP) and 12 WAP (24.62 g and 81.12 g respectively). Cowpea showed the highest increment (7 folds) in leaf weight between 6 to 12 WAP as compared to was paltry 3.6 folds. The highest stem dry weight was obtained in the amaranth species at 6 WAP and 12 WAP both in the greenhouse; recording 32.59 g and 90.12 g respectively. A similar trend was noted in root dry weight and root: shoot ratio. Cowpea had the least biomass accumulation potential across all the parameters in both seasons and in the greenhouse. The increased biomass growth is an indication sufficient availability of nutrient that promoted vibrant plant growth and also less toxicity from the heavy metals. Therefore, waste water can be put into use to enhance improved productivity of African leafy vegetables.