Marketable yield and nutritional composition of amaranths in response to fertiliser

Field experiments were conducted at the University of Limpopo, Syferkuil and Lwamondo Experimental Farms during the 2006/2007 and 2007/2008 growing seasons to determine the effect of nutrient input dynamics on marketable yield and nutritional compositions of two Amaranthus species. A. hybridus and A. hypochondriacus were planted in a 2×6 factorial split-plot experiment using a randomised complete block design replicated three times. Organic fertilizer (poultry manure) and inorganic fertilizer (LAN/urea) were applied at rates equivalent to 0, 50, 75, 100, 125 and 150 kg N ha^-1. Application of fertilzer increased marketable yield of amaranth, irrespective of location, source of nitrogen and the species of the amaranth. Interactions between amaranth species and nitrogen fertilizer application were significant (P≤0.05) for fresh marketable mass of amaranth. Both Amaranthus species also differed significantly in fresh marketable yield. The highest fresh leaf mass of 91 g plant^-1 was obtained for A. hybridus compared to 82 g plant^-1 obtained for A. hypochondriacus with with 150 kg ha^-1 N treatment at 12 WAT. For inorganic N source, A. hybridus had higher average dry matter value of 91.2% and protein content of 5.1% compared to 90.8 and 3.2% of dry matter and protein contents, respectively, in A. hypochondriacus. Amaranths grown in inorganic fertiliser treated soils had higher dry matter and protein contents fibre contents than that grown in organic fertilizer treated soils.