Influence of Composted Phyto-residues and Harvesting Frequency on Growth and Forage Potentials of Grain Amaranth (Amaranthus cruentus) Under Oxic Paleutult Soil Conditions

Earlier research activities on Amaranthus cruentus were majorly focused on the suitability of its small edible grains for human and livestock consumptions, but other certain beneficial attributes of the crop-plant, such as relatively long succulent stem, high foliage production and rapid re-growth which make the shoot a potential forage crop (particularly under improved soil nutrition), had been enshrouded and therefore suffered adequate studies. Field studies were carried out in the year 2010, at the Teaching and Research Farms, Ladoke Akintola University of Technology, Ogbomoso, Nigeria, to evaluate the forage potentials of Amaranthus cruentus, under suitable agronomic practice and improved soil nutrition. The trial treatments were: four application rates (0.0, 1.5, 3.0 and 6.0 t ha-1) of composted-Tithonia biomass and four harvesting frequencies (i.e. zero or no-harvesting, mono-weekly, mono-fortnightly and mono-monthly harvestings). The trials were laid out in a Randomized Complete Block Design (RCBD) and were replicated three times. At the fourth week after sowing, some growth parameters were measured prior to 1st cutting or harvesting. At every harvest, the harvested shoot dry weight and nutrient uptake of N, P and K were determined. After the final harvest, the cumulative dry weights of the above-ground biomass (followed by the below-ground biomass), were determined. Compost rate of 3.0 t ha-1 under mono-fortnightly cutting or harvesting gave the best values of all the growth parameters measured i.e. plant height, stem circumference, number of leaves and leaf area. Biomass yields obtained from both the no-harvesting / zero-harvesting and the mono-fortnight harvesting (cumulative), which received 3.0 tons of composted materials were statistically similar and the best, compared to the other treatment combinations. Therefore, mono- fortnight harvesting or cutting of grain amaranth with 3.0 t ha-1 application of composted Tithonia-residues may be beneficial to its accelerated shoot re-growth. This makes it dually suitable for human consumption as a leaf vegetable and a desirable forage / soilage for livestock management. Also, this approach may encourage maximum utilization of available soil nutrients and equally promote crop and animal production efficiency. Keywords: Grain amaranth, Forage potentials, Composted phyto-residues, Harvesting frequency, Oxic paleutult soil