productivity: Effects of application rates

The utilization of chicken manure as an organic fertilizer is essential in improving soil productivity and crop production. We carried out the study to assess the effects of chicken manure on soil chemical properties and the response of application rate on the yield of spinach (Spinacia oleracea) as well as the uptake of nitrogen and phosphorus nutrients. To quantify these effects, we added chicken manure to samples of Calcisols, Arenosols and Luvisols at application rates: 5, 10, 20 and 40 % chicken manure. The addition of chicken manure irrespective of application rate did not change the acidity or pH of Calcisol, suggesting its hypo-buffering capacity. While the results reveal increases of EC with increasing rate, at rate above 40%, the ECs were above the critical salinity level of 4 mS/cm indicating potential threat to soil productivity. The exchangeable bases increased with application rate, suggesting the positive effects of chicken manure in enhancing soil fertility. Similarly significant increase of nitrogen and phosphorus were observed following the addition of chicken manure. Initially the spinach yield increases up to optimum rate of 0.06, 0.07 and 0.16 g/plant for Luvisol, Arenosol and Calcisol, respectively and subsequently drops after critical threshold values; 15, 5 and 1 % for Calcisol, Arenosol and Luvisol, respectively. Interestingly above the rate of 40%, the yield was almost zero for all soils, suggesting the ineffectiveness of chicken manure in enhancing soil productivity