Effect of Manures Composted with High Quality Organic Residues on Dry Matter Accumulation, Nitrogen Uptake and Maize Grain Yield

Nitrogen is a major limiting nutrient in the maize-growing areas of central Kenya highlands. Due to the high cost of inorganic fertilisers, the majority of the farmers use farmyard manure (FYM) to improve crop productivity. However, FYM produced in the area is often of low quality particularly in terms of N concentration. Studies previously carried out in the region showed that composting FYM with different proportions of Tithonia diversifolia (tithonia) or Lantana camara (lantana) improved the N content of the manure considerably. This study was conducted to test whether composted manure would improve growth and yield of maize. A field trial consisting of seven treatments: FYM composted with tithonia (1:1 and 3:1 ratios), or lantana (1:1 and 3:1 ratios), FYM composted alone, inorganic N fertiliser and an absolute control was laid out in low N site. Maize (Zea mays cv. Hybrid 513) was the test crop. The treatments were arranged in a RCBD replicated 3 times. The various compost types and the inorganic fertiliser were applied at an equivalent rate of 100 kg N/ha. Above ground maize biomass was taken at 2, 6, 10, 14 and 18 weeks after crop emergence, dried to a constant weight and the N content determined. The plant N uptake for each period was calculated as a product of dry matter and N content in the maize tissue. Grain yield was adjusted to 13% moisture content. It was observed that dry matter yield, N uptake and final grain yield of maize were significantly higher in FYM composted with tithonia or lantana than the control or FYM composted alone treatments. Amongst the composts, the highest dry matter accumulation and N uptake was observed in FYM composted with tithonia at 1:1 ratio. Inorganic fertiliser treatments gave the highest dry matter and N uptake. Based on the growth and N uptake in the fertiliser treatment it was concluded that the N release in all the compost was lower than the crop demand.