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Poultry litter (PL) can supply N, P, K, and other plant nutrients; however, excessive application may cause environmental problems, depending on management and crop nutrient demand. Changes in soil test (ST) nutrient content in a Cecil soil (a fine, kaolinitic, thermic Typic Kanhapludult) during a 10-yr period of PL use was evaluated at the USDA-ARSJ. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA. During the cotton (Gossypium hirsutum L.) cropping phase (1995-2000), 4.4 Mg PL ha-1 yr-1 resulted in small changes in ST nutrient content in the surface 15 cm. Differences were observed between tillage treatments, with less accumulation of Ca, Mg, and Mn and greater accumulation of Zn for no-till (NT) than conventional tillage (CT). During the corn (Zea mays L.) cropping phase (2001-2005), average annual PL inputs (11.2 Mg hat) increased P and Zn contents, with changes being similar for CT and NT After 10 yr, ST nutrient contents in the surface 15 cm reflected 25, 4, 45, 26, 17, and 97% of the input from PL for P. K, Ca, Mg, Mn, and Zn, respectively. Changes in soil profile nutrient content (to a depth of 60 cm) from 1997 to 2005 were predominantly at 0 to 15 cm, where P and Zn increased >200%. Accumulation of Ca, K, P, and Zn at lower depths was also observed. Strategies for increasing nutrient removal following repeated long-term application of PL should be considered to avoid excessive levels of nutrients. [ABSTRACT FROM AUTHOR]

The use of urea fertilizers in grasslands is likely to increase in areas with concentrated animal feeding operations as restrictions on manure applications are implemented. Concerns have been raised about the economic and environmental impacts of NH3 loss from these urea fertilizers. This study evaluated NH3 losses from Nitamin (a urea polymer), urea-N H4N03 (UAN), and granular urea applied to tall fescue (Festuca arundinacea Schreb.) plots at 50 kg N ha1 in fall and spring for 2 yr. Fertilizers were applied to circular plots (30-rn diameter) and NH3 loss was measured by the modified passive flux method for 69 to 120 d after application. In a separate laboratory study, Nitamin, UAN, and urea were surfaced applied to fescue thatch at 100 kg N ha1 and treatments were incubated at 24°C and 90% relative humidity for 31 d. In fall applications, urea lost more NH3 (19% in 2004, 46% in 2005) than UAN or Nitamin, which were not different from each other (6% in 2004, 34% in 2005). In contrast, there were no differences among fertilizers in spring applications, with average losses of 13% in 2005 and 17% in 2006. In the laboratory study, urea lost significantly more NH3 (24%) than UAN or Nitamin, which were not different from each other (average 9% loss). These results indicate that Nitamin and UAN undergo similar NH3 losses, and that both fertilizers may lose less NH3 than urea under conditions favorable to volatilization. Abbreviations: CRH, critical relative humidity; RH, relative humidity; UAN, urea-ammonium nitrate. [ABSTRACT FROM AUTHOR]

A tool to estimate the amount of net N mineralized under field conditions would be useful to adjust N fertilizer rates. A simulation model of soil N may be useful to develop such estimates, but must first be evaluated under the conditions in which it will be used. In this work, we implemented the N subroutine of CERES-N in Stella 6.0 modeling software to simulate net N mineralized from soil organic matter and cotton residues at three locations in a Coastal Plain field of south Georgia. The model was first calibrated with laboratory data of net N mineralized from an incubation study of cotton leaves and stems, and then used to simulate net N mineralized at three field locations. The calibrated model underestimated net N mineralized at two of the field locations by 45% and 56%, respectively. This underestimation was apparently caused by an underestimation of N mineralized from soil organic matter. To explore possible reasons for the underestimation, we collected soil samples monthly for 1 year to measure potentially mineralizable N at the three field locations, and used the data to modify the rate of soil organic matter mineralization throughout the year according to a sinusoidal wave. Simulated values of net N mineralized with this modification were within the 95% confidence interval for field-measured values. These results suggest that further research should be conducted to study the dynamics of the microbial population and microfauna present in soil, which may be partially responsible for seasonal changes in N mineralization rates. [Copyright &y& Elsevier]

Cotton has become a dominant crop in the southeastern USA, but only about 12% of the 620,000 ha of cotton (Gossipium hirsutum L.) in Georgia, for example, is under conservation tillage. Georgia and bordering states produce about 42% of the poultry in the United States and in Georgia alone, this results in over 1.6 million Mg of poultry litter (PL) annually. The fertilizer value of PL is well-recognized but much of it is applied to pastures and only a small percentage is applied to crop land. Limited information is available on the response of cotton to PL as fertilizer in conservation tillage systems in the Southeast. The performance of cotton under two tillage and two fertilizer treatments was evaluated from 1996 to 1999 to highlight management options for increased adoption of conservation tillage and PL use. Cotton, followed by a rye (Secale cereale L.) cover crop, was grown under a factorial arrangement of tillage (no-till (NT) vs conventional tillage (CT)) and fertilizer (ammonium nitrate, as conventional fertilizer (CF) vs PL) on a Cecil sandy loam (clayey, kaolinitic thermic Typic Kanhapludult; Chromi-Alumic Acrisol) near Watkinsville, Georgia. Average lint yield from 1996 to 1999 was in the sequence no-till poultry litter (NTPL)>no-till conventional fertilizer (NTCF)>conventional tillage poultry litter (CTPL)>conventional tillage and fertilizer (CTCF). Differences were significant at P≤0.05 for NTPL vs CTPL, NTPL vs CTCF, and NTCF vs CTCF. Average yield differences were also significant between NT and CT but not PL and CF. PL yielded more than CF only in 1997. NT generally had a more favorable soil water regime than CT. Yield differences among treatments occurred during the first 3 years only. Drought in the fourth year reduced yield across all treatments and negated treatment effects. Lint yield would increase in the southeastern USA and an additional outlet for the PL would be created by adopting NT and fertilizing with PL in cotton production. [Copyright &y& Elsevier]

Spray irrigation of forested land can provide an effective system for nutrient removal and treatment of municipal wastewater. Evolution of N2 + N2O from denitrifying activity is an important renovation pathway for N applied to forested land treatment systems. Federal and state guidance documents for design of forested land treatment systems indicate the expected range for denitrification to be up to 25% of applied N, and most forest land treatment systems are designed using values from 15 to 20% of applied N. However, few measurements of denitrification following long‐term wastewater applications at forested land treatment sites exist. In this study, soil N2 + N2O–N evolution was directly measured at four different landscape positions (hilltop, midslope, toe‐slope, and riparian zone) in a forested land treatment facility in the Georgia Piedmont that has been operating for more than 13 yr. Denitrification rates within effluent‐irrigated areas were significantly greater than rates in adjacent nonirrigated buffer zones. Rates of N2 + N2O–N evolved from soil in irrigated forests ranged from 5 to 10 kg ha−1 yr−1 N on the three upland landscape positions and averaged 38 kg ha−1 yr−1 N within the riparian zone. The relationship between measured riparian zone denitrification rates and soil physical and chemical properties was poor. The best relationship was with soil temperature, with an r2 of 0.18. Overall, on a landscape position weighted basis, only 2.4% of the wastewater‐applied N was lost through denitrification. [ABSTRACT FROM AUTHOR]