Yield and Nutrient Dynamics in Conventional and Organic Sweet Corn Production Systems

Poultry litter is abundant in Georgia and is an inexpensive N source in an organic system. However, poultry litter characteristics are variable and nutrient availability for crops, along with potential accumulation of nutrients or metals in soils, depends on several litter and soil factors, necessitating site‐specific studies. Our objective was to determine if organic N management with poultry litter and cover crop yield comparably to synthetic fertilizers without accumulation of nutrients or metals. Sweet corn (Zea mays L. var. saccharata) was grown in plots receiving four treatments: Control (no N), ammonium sulfate at 112 (AS1) or 224 (AS2) kg N ha–1 and combined use of poultry litter, blood meal, and crimson clover (Trifolium incarnatum L.) at 112 kg available N ha–1 (PL). The average 3‐yr yield was greater in AS1, AS2, and PL than in Control, with no significant difference among AS1, AS2, and PL. However, yield was significantly lower in PL than AS1 and AS2 in 2013 when there was excess rain that might have affected N mineralization and availability. Mid‐season nitrate N concentrations were lower in 2013 than the other years in 0‐ to 15‐cm layer. End‐of‐season cornstalk nitrate N was within sufficient range for AS1, AS2, and PL in all years and failed to reflect low yield in 2013 in PL. There was statistically significant buildup of Zn in PL but it was not toxic and did not affect yield. Overall, the use of PL resulted in comparable yield as AS treatments except in 2013. Core Ideas Combining poultry litter with cover crop for N gave similar yield to (NH4)2SO4. Nitrogen credits from the cover crop reduced the quantity of poultry litter applied. Reduced poultry litter application minimized accumulation of metals and nutrients. The potential for post‐season nitrate loss was lower in poultry litter treatment than (NH4)2SO4 plots.