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Residual Soil Nitrogen as Affected by Continuous, Two‐Year, and Four‐Year Crop Rotation Systems
Author(s) -
Varvel G. E.,
Peterson Todd Andrews
Publication year - 1990
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1990.00021962008200050024x
Subject(s) - sorghum , agronomy , crop rotation , fertilizer , cropping system , loam , leaching (pedology) , red clover , crop , mathematics , biology , environmental science , soil water , soil science
Crop rotation systems may reduce inorganic N fertilizer needs because of increased N mineralization, but if that N is mineralized either too early or too late with respect to crop needs, it can also be susceptible to leaching. These concerns prompted an investigation of a long‐term field study at Mead, NE on a Sharpsburg silty clay loam (fine, montmorillinitic, mesic, Typic Argiudoll) to determine effects of crop rotation and N fertilizer application on residual inorganic N levels to a depth of 150 cm after 4 yr. The study included continuous corn ( Zea mays L.), continuous soybean [ Glycine max (L.) Merr.], continuous grain sorghum [ Sorghum bicolor (L.) Moench.], corn/soybean and grain sorghum/soybean 2‐yr rotations, and corn/oat [ Avena sativa (L.)] + clover [80% yellow sweetclover [ Melilotus officinalis (L.) Lam.] + 20% red clover [ trifolium pratense ]}/grain sorghum/soybean and corn/soybean/grain sorghum/oat + clover 4‐yr rotations with three rates of N fertilizer application. High N application resulted in greater residual NO 3 –N concentrations for the continuous corn and grain sorghum systems than in any of the other cropping systems to a depth of 150 cm. Residual NO 3 –N concentrations were low (<4 mg kg −1 at depths below 30 cm) at all N application rates in continuous soybean and 2‐ and 4‐yr cropping systems. Nitrogen removal by grain accounted for 50% of the applied N in continuous corn and grain sorghum systems at the low N application rate, but only 20 to 30% of the applied N at the high rate. Likewise, only 20 to 30% of the applied N was accounted for by N removal in the rotation systems at either N aplplication rate. Indirect results from our study suggest immobilization by crop residues and soil organic matter, not leaching, is probably most responsible for apparent N losses in these cropping systems. Although the mechanisms were not specifically identified, our results do show that crop rotations can reduce inorganic N fertilizer needs and at the same time reduce the amount of N available for leaching, both of which are important to farmers in the western Corn Belt.