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Title: TILLAGE AND NITROGEN FERTILIZATION INFLUENCE GRAIN AND SOIL NITROGEN IN AN ANNUAL CROPPING SYSTEM.

Author
item Halvorson, Ardell
item Wienhold, Brian
item BLACK, A - USDA-ARS/RETIRED

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2001
Publication Date: 8/1/2001
Citation: Halvorson, A.D., Wienhold, B.J., Black, A.L. 2001. Tillage and nitrogen fertilization influence grain and soil nitrogen in an annual cropping system.. Agronomy Journal. 93:836-841.

Interpretive Summary: A long-term study evaluating the influence of tillage and N fertilization on spring wheat, winter wheat, and sunflower grain yields within a spring wheat-winter wheat-sunflower cropping system was recently competed. This study evaluated the influence of tillage system and N fertilizer rate on N removal in the grain and residual spring soil NO3-N within this spring wheat-winter wheat-sunflower rotation over 12 years. Grain N removal from the system and soil NO3-N levels varied with tillage, N rate, year, and cropping sequence. Nitrogen removal in the grain increased with increasing N rate most years. Total N removed in the grain tended to be lowest with no-till (NT) at the lowest N rate and highest with NT at the highest N rate. Total grain N removal with 12 crops as a fraction of total fertilizer applied was 144, 84, and 61% for the 34, 67, and 101 kg N ha-1 fertilizer rates, respectively. Soil NO3-N levels were not affected by N rate or tillage system during the initial years (1985-1989), but increased significantly following two consecutive drought years (1988 and 1989). Soil NO3-N levels varied with year and cropping sequence, increased with increasing N rates after the drought years and tended to be higher with CT (conventional-till) and MT (minimum-till) than with NT. Soil NO3-N movement below the crop root-zone appears to have occurred in only 1 or 2 years following above average precipitation periods. The results indicate NT, with annual cropping, may reduce NO3-N leaching potential compared with CT systems in the northern Great Plains.

Technical Abstract: Increasing the frequency of cropping in dryland systems in the northern Great Plains requires the application of N fertilizer to maintain optimum crop yields. A 12-yr dryland annual cropping rotation [spring wheat (Triticum aestivum L.)-winter wheat (Triticum aestivum L.)-sunflower (Helianthus annuus L.)] was monitored to determine the influence of tillage esystem [conventional-till (CT), minimum-till (MT), and no-till (NT)] and N fertilizer rate (34, 67, and 101 kg N ha-1) on N removed in grain and changes in spring soil NO3-N levels each year. Grain N removal from the system and soil N levels varied with tillage, N rate, year, and crop sequence during and following drought years. Tillage x year, N rate x year, and tillage x N interactions were significant for both factors. Nitrogen removal in the grain increased with increasing N rate most years. Total N removed in the grain tended to be lowest with NT at the lowest N rate and highest with NT at the highest N rate when evaluated over all plots in the study. Total grain N removal with 12 crops as a fraction of total fertilizer applied was 144, 84, and 61% for the 34, 67, and 101 kg N ha-1 fertilizer rates, respectively. Soil NO3-N levels were not affected by N rate or tillage system during the initial years, but increased significantly following two consecutive drought years. Soil NO3-N levels varied with year and cropping sequence, increased with increasing N rates after the drought years and tended to be higher with CT and MT than with NT. Soil NO3-N movement below the crop root zone appears to have occurred in only 1 or 2 years following above average precipitation. The results indicate NT, with annual cropping, may reduce NO3-N leaching potential compared with CT systems in the northern Great Plains.