Nitrate Leaching through Lysimeters in a Corn‐Soybean Rotation

Abstract

AbstractLeaching of NO3‐N can be excessive under continuous corn (Zea mays L.) production. To reduce NO3‐N losses, corn might be rotated with soybean [Glycine max (L.) Merr.], which does not require fertilizer N. Six large, undisturbed monolith lysimeters (8.1‐m2 surface area, 2.4 m deep) were used to investigate NO3‐N leaching in a 6‐yr cornsoybean rotation study in eastern Ohio. Four lysimeters (Y103 A, B, C, and D) contained a moderately well‐drained Keene silt loam (fine‐silty, mixed, mesic Aquic Hapludalf) on a 6% slope, and two lysimeters (Y102 A and C) contained a well‐drained Rayne silt loam on a 13% slope (fine‐loamy, mixed, mesic Typic Hapludult). In the spring of each year, 224 kg N/ha as NH4NO3 was surface applied, and a rye (Secale cereale L.) winter cover crop was used following soybean. Nitrate‐N levels in lysimeter percolate varied seasonally from 1 to 20 mg/L and on a 2‐yr cycle, showing the influence of the crop rotation. The highest NO3‐N levels usually occurred during the dormant season following corn. During the 6 yr of the study, the flow‐weighted average NO3‐N concentration in the percolate was 10.5 and 14.3 mg/L from the Y103 and Y102 lysimeters, respectively. Mean annual NO3‐N losses in the percolate were 31.6 and 47.1 kg/ha, respectively. These NO3‐N losses are smaller than losses from continuous corn production previously measured with the same lysimeters. Thus, a corn‐soybean rotation may be one strategy for reducing NO3‐N loading to groundwater.