Long-Term Effects of Poultry Litter Application On Soil Phosphorus and Micronutrients in No-till Cotton Production System.

A study was initiated at the Tennessee Valley Research and Extension Center, Belle Mina, AL in 1996 to evaluate cotton (Gossypium hirsutum L.) performance with long-term poultry litter (PL) application in different tillage systems. Eleven treatments were evaluated with different combinations of tillage, cropping system, and N source and rate. Treatments include incomplete factorial combinations of three tillage systems [conventional till (CT), mulch-till (MT), and no-till (NT)], two cropping systems [cotton- fallow and cotton-winter rye (Secale cereale L.)], and two nitrogen sources and rates [100 kg N ha^‑1 from ammonium nitrate (AN), and 100 and 200 kg N ha^‑1 from poultry litter (PL)]. Cotton was rotated with corn (Zea mays L.) every third year. In all tillages, application of PL at 100 kg N ha^-1 resulted in higher available soil P (0-15cm) compared to AN at the same rate. Conventional-till, mulch-till and no-till systems recorded approximately 3, 2 and 3 times, respectively higher available P with application of PL at 100 kg N ha^-1 compared to AN at the same rate. Application of PL at double rate (200 kg N ha^-1) in NT plots resulted in significant build up of P. Among micronutrients Mg, Zn, Cu, and B were significantly influenced by tillage and nutrient source interactions. In all tillages, application of PL at 100 kg N ha^‑1 resulted in significant increase in Mg and Zn concentrations in soil compared to AN at 100 kg N ha^‑1. Concentrations of Cu and B did not change significantly with application of PL at 100 kg N ha^‑1, but doubling the rate of PL (200 kg N ha^‑1) resulted in significant increase in their concentration compared to AN at 100 kg N ha^‑1. Winter cover crop did not influence P and micronutrient status in the soil.