THE POTENTIAL OF SEAGRASS LITTER AS ORGANIC FERTILIZER IN KILIFI KENYA
KIMARU, ANGELA WAIRIMU
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ABSTRACT Beach-cast seagrass litter deposits are common in many coastal areas with extended seagrass meadows. Seagrass litter abundance on the shoreline is a contentious issue on the aesthetics of the beaches and as an environmental hazard to beach revelers. To change this perception and view the seagrass litter as a potential asset, this study assessed the seagrass litter accumulation patterns at Mombasa, Kilifi and Malindi shorelines. Further, the efficacy of composted seagrass fertilizer products was evaluated using amaranth (Amaranthus albus) as a test vegetable. Beach-cast seagrass was collected, weighed and returned insitu at Kenyatta beach in Mombasa, Bofa beach in Kilifi and marine park area in Malindi. The weights were translated to T/ha. Two samples of seagrass, each weighing 500kg, were composted in separate chambers, one with saline composite while the other, with desalinated composite. The litter was composted for 4 months, sifted and packaged as organic fertilizer for field trials. The performance of the seagrass organic fertilizer was compared to farmyard manure and inorganic fertilizer (DAP) in the field trial. New leaf development, leaf size, height, dry matter and leaf yield of Amaranthus plant were used as growth parameters to assess the efficacy of seagrass organic fertilizer. Highest accumulation of seagrass litter was noticed in Kilifi at 72.4T/ha which was significantly different (P<0.005) from Malindi at 26.5T/ha and Mombasa at 24.75T/ha. There was no significant difference in litter accumulation between Malindi and Mombasa. After four (4) months of composting seagrass, the saline setup achieved 85% decomposition, while the desalinated setup decomposed at 75%. However, fertilizer from the saline setup performed better than the desalinated, farm yard manure and the control. Half rate application of the saline product produced better results compared to all the applied rates of the seagrass products. Three weeks after transplanting, it achieved an average of 25.3cm plant v height compared to control at 22.7cm, while commercial fertilizer recorded 29.6cm as a positive control. New leaf development recorded an average of 12.8, 12.3, 12.1 and 13.2 leaves for seagrass products, farm yard manure, control treatment and commercial fertilizer, respectively. Half rate application of the saline product achieved 16.9T/ha leaf yield which was higher than all applied rates of the seagrass products and farm yard manure. However, commercial fertilizer recorded 30T/ha which was significantly different from all the treatments. Half rate application at 30g/hill saline seagrass product performed better than full rate 60g/hill of the same, and all application rates of the desalinated product. These findings indicate that seagrass fertilizer products are a potential alternative source of plant nutrients that can complement the available inorganic fertilizers.