Assessment of cassava peel and locust bean pod as soil organic amendments and their effects on the growth and yield of amaranthus hybridus (linn.)
This study evaluatedthe effect of locust bean pod and cassava peel on the growth performance of Amaranthus hybridus, determined the response of the plant to the application of the two wastes and assessed the effect of the wastes on soil physical and chemical properties. This was with a view to determining the most efficient agrowaste types for improved crop productivity. The experiment consisted of four and eight weeks of soil incubation of agro-wastes amendment (locust bean pod and cassava peel wastes) which was conducted at the Laboratory of the Institute of Ecology and Environmental Studies and in a greenhouse at the Faculty of Agriculture, Obafemi Awolowo University (O.A.U.), Ile-Ife. The seeds of Amaranthus hybridus were purchased from National Horticultural Research Institute, Ibadan. Bulked top soil of 0-15 cm were collected randomly from a site that had been cropped continuously for five years with a history of poor nutrient status within the University Research farm. The agro-wastes were obtained from a cassava milling industry in Ile-Ife while the locust bean pod were collected from a nearby farm in Saki town of Oyo State and were milled into powder with a cassava grinding machine at the workshop of Agricultural Engineering Department of O.A.U., Ile-Ife. The milled cassava peel waste and locust bean pod were analysed to determine their constituent elements. There were three treatments (100% Cassava peel waste, 100% Locust bean pod and 50% Cassava peel + 50% Locust bean pod) and each treatment was applied at 0, 3, 6, 9 and 12 t/ha and replicated three times. For soil incubation study, each air-dried and sieved 3 kg soil were mixed manually with each treatment level into planting pots. Forty-five pots each were left to incubate for either four weeks oreight weeks. Pre-soil analysis were carried out on the degraded soil using standard methods to determine soil pH, N, P, Na+, K,+ Ca2+ Mg2+and percentage organic carbon. Four seeds of Amaranthus hybridus were sown into the amended soils after incubation. The crop was irrigated twice in a week and weeds controlled manually. After germination, it was thinned to two stands per pot. Parameters such as plant height, number of leaves, and stem girth were determined at the tenth week after planting. Plant tissue and soil analysis were also carried to determine N, P, Mg2+, Ca2+, K+ and Na+ content using standard methods. The data were subjected to appropriate descriptive and inferential statistics. The results showed that application of eight weeks incubated cassava peel and locust bean pod mixture at 12 ton/ha gave the highest plant height (52.8 cm) of A. hybridus. Eight weeks incubated locust bean pod mixed with cassava peel at 12 t/ha improved the stem girth and number of leaves by 6 % and 27 % of A. hybridus. Pots with four weeks incubated locust bean pod only and its mixture with cassava peel at 12 t/ha applications increased both the fresh and dry weights of A. hbridusby 14 % and 36 % respectively. Potassium, magnesium, phosphorus and Ca of A hybriduswere all increased across the rates of application of amendments. Application of four weeks incubated locust bean pod at 6, 9 and 12 t/ha enhanced the total N, K, Mg, P and Ca contents of the soil. Available P was higher in pots with four and eight weeks incubated locust bean pod applied at 6 t/ha. The study concluded that the response of A. hybridus to organic wastes application was dependent on the duration of incubation of the waste and the rate of application for improved plant growth and yield.