Effects of Amendment of Agricultural Bye Products with Animal Manures on Soil Chemical Properties and Yield of Amaranthus in South Western Nigeria

The high cost and other problems associated with the use of chemical fertilizer in the humid tropics necessitated research into the effectiveness of locally available agricultural by-products as source of nutrient. A study was conducted in Akure, South West Nigeria, on the effect of wood ash, saw dust, ground cocoa husk spent grain (sorghum based brewery waste) and rice bran amended with or not with goat, pig and poultry manures on soil fertility and leaf yield of amaranthus (Amaranthus Viridus L.). Twenty organic fertilizer treatments were compared to control (no fertilizer and manure) and 400 kgha(-1) NPK fertilizer, replicated three times and arranged in a randomized complete block design. Application of spent grain, wood ash, cocoa husk saw dust and rice bran at 10t/ha increased soil organic matter, N,PK,Ca,Mg, pH,and amaranthus leaf yield. For instance, wood ash amended with poultry manure increased the soil O.M. (2.51%), N(0.31%) P(50.74mg/kg), K(0.89mmol/kg), Ca(0.77mmol/kg), Mg(0.094mmol/kg) and Na (0.459mmol/kg) compared to the sole form of wood ash which had soil O.M.(2.15%), N(0.212%), P(25.13mg/kg), K(0.77), Ca(0.47mmol/kg), Mg(0.065mmol/kg), and Na(0.176mmol/kg), respectively. The agricultural by-products (sole and amended forms) produced higher values of soil pH, Ca, Mg and O.M compared to NPK fertilizer. The soil O.M, pH, Ca and Mg contents in NPK fertilizer treatment decreased with the number of cropping. Spent grain + poultry manure increased soil O.M (2.46%), Ca (0.57mmol/kg), Mg(0.11 mmol/kg) and pH (7.20) compared to the NPK fertilizer which had soil O.M (0.4%), Ca(0.015 mmol/kg), Mg(0.005 mmol/kg) and pH(5.60). Agricultural by-products applied sole or amended with animal manure gave higher values of leaf Ca, Mg, P and K than the NPK fertilizer. Spent grain + poultry manure had the amaranthus leaf P(0.22%), K(0.99%), Ca(0.14%) and Mg (0.05) compared to that of NPK fertilizer leaf P(0.14%), K(0.81%), Ca (0.005%) and Mg(0.005%) respectively. NPK fertilizer increased; plant height and leaf yield of amaranthus better than other agricultural by-products amended with manures except in spent grain amended with pig and poultry manures. Spent grain amended with poultry manure had the amaranthus leaf yield values of 7.53, 11.63, 11.90 and 12.60t/ha in crop 1, 2, 3 and 4 compared to 7.50, 10.10, 11.63 and 12.40t/ha in NPK fertilizer treatment, respectively. Saw dust and rice bran with the highest C/N ratio were least effective in improving soil fertility and amaranthus leaf yield. It is recommended that application of agricultural by-products such as wood ash, cocoa husk, spent grain, rice bran and saw dust to soil at 10t/ha(-1) improved soil fertility and amaranthus leaf yield. The amendment of the agricultural by-products with goat, pig and poultry manures at 5t/ha(-1)each improved their effectiveness.