Effects of organic nitrogen fortifiers on some growth parameters of green amaranths (Amaranthus caudatus L.)

Chemical fertilizers for boosting crop production are becoming more expensive and scarce. Green amaranth (Amaranthus caudatus L.) is a fast growing and highly nutritious crop, but its common use in the diet of Nigerians is constrained by its high demand for nitrogen fertilizer. Thus, there is a need to find local fertilizer materials that are readily available to peasant farmers. A preliminary field study was conducted to evaluate urine and neem (Azadirachta indica L. juss) as alternative sources for mineral fertilizers in fortifying organic fertilizer (OF) made from cow dung and market waste compost, and OF fortified with urea and bone meal [organo-mineral fertilizer (OMF)], for yield and growth of green amaranth. Fifteen treatments, based on the percentages of N supplied, were NPK 15-15-15, OMF, OF, urine, neem and ten treatments of 50, 60, 70, 80 or 90% OF supplemented with a total of 50, 40, 30, 20 and 10% urine or neem, respectively, to provide a total application rate of 100 kg N ha(-1), with no fertilizer treatment as a control. Planting was done in two successions (main with fertilizer treatments and residual without further application). The fertilizer sources and levels had significant effects on plant height, number of leaves, stem girth, fresh weight and dry weight. The residual effects were also significant for plant height, number of leaves, total fresh and dry weights. Forty percent N urine amendment of the OF produced the highest total fresh amaranth biomass (269.3 g plot(-1) main effect and 110.8 g plot(-1) residual effect), which was significantly better than the values of (140 and 35.3 g plot(-1), respectively) obtained with respect to OMF during main planting and NPK during residual planting. Results of our study reveal that 40% N urine fortification of OF was a viable substitute for synthetic fertilizers in production of amaranth, and that urine and neem cake can be alternatives to mineral fertilizer for crop production.