Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/2009
Publication Date: 2/1/2010
Citation: Adeli, A., Tewolde, H., Sistani, K.R. 2010. Comparison of broiler litter and commercial fertilizer at equivalent N rates on soil quality. Communications in Soil Science and Plant Analysis. 41:2432-2447. Interpretive Summary: The effects of broiler litter on soil nutrient dynamics and quality need to be determined so that farmers can improve manure management and our confidence in manure nutrient credits leading to minimizing offsite nutrient movement can be improved. Fertilizing crops with inorganic N sources is believed to benefit soil quality by increasing soil organic C through boosting crop growth and plant residue followed by improving soil chemical, physical, and biological properties. However, a recent study revealed that long-term N fertilization depleted soil organic carbon by promoting the decomposition of crop residues and soil organic matter following by deterioration of soil quality. In addition, as commercial fertilizer N prices rise, interest in using broiler litter N as an economical alternative source to commercial fertilizer for row crop production has been considered. Application of litter to cotton (Gossypium hirsutum L.) as a N source has been shown to be an agronomically viable alternative. The effects of broiler litter relative to inorganic fertilizer at equivalent N rate has been compared and reported that total N in litter was as effective as N from ammonium nitrate on cotton yield, but the effects on soil quality is lacking in the literature. With recent interest in using broiler litter for row crops in Mississippi and increasing concerns for possible negative effects of excessive application on soil nutrient imbalances and quality, the optimum rate that do not negatively affect soil quality must be achieved. The objective of this study was to compare broiler litter with inorganic fertilizer applied at equivalent N rates to cotton on the quality of an upland soil.
Technical Abstract: A 3-year study was conducted to determine the effects of variable rates of broiler litter relative to inorganic fertilizer at equivalent N rates on soil nutrient content and quality in an upland Granada silt loam (fine-silty, mixed, active, Thermic, Fraglossudalfs) soil. Treatments included annual broiler litter rates of 0, 2.2, 4.5, 6.7, 10.1 and 13.4 Mg ha-1 and commercial fertilizer at the rates of 34, 68, 112, 134 and 168 kg N ha-1 which are equivalent to estimated available N in broiler litter in the year of application. Commercial fertilizer N equivalency was calculated based on the general assumption that 50% of broiler litter N is available for plant use in the year of application. The results indicated that soil receiving poultry litter had higher organic matter, microbial biomass C and were more enriched in P, K and Ca in the surface soil than soil with commercial fertilizer. Application of broiler litter to the soil resulted in greater total N, pH and CEC and lower bulk density than soil fertilized with commercial fertilizer. Application of broiler litter or fertilizer at rate >112 kg N ha-1 did not benefit cotton yield and exceeded plant N utilization potential as evidenced by excessive end-of-season soil residual NO3-N level. Although broiler litter and commercial fertilizer were applied at equivalent N rates, at rates > 112 kg N ha-1, the magnitude of residual soil NO3-N was greater for inorganic fertilizer than broiler litter in each year, indicating the possible dependence of broiler litter on microbial activity for N mineralization or a greater potential of NH3 volatilization for broiler litter.