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United States Department of Agriculture

Agricultural Research Service

Title: Fertilizer Nitrogen Recovery and Yield Response to Nitrogen by Dryland Sunflowers in a No-Till Dryland Rotation

Authors
item Vigil, Merle
item Benjamin, Joseph
item Schepers, James

Submitted to: National Sunflower Research Forum 2001 Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 26, 2001
Publication Date: January 17, 2001

Interpretive Summary: Knowledge of sunflower response to fertilizer nitrogen (N) and fertilizer N recovery in the Central Great Plains region is limited. The objectives of this study are: (i) to measure grain yield response to added fertilizer in no-till managed sunflowers and (ii) to determine N fertilizer recovery of this crop in a no-till four year rotation as affected by placement. Fertilizer solutions labeled with a non-radioactive heavy isotope 15N wer used to determine the fate of the fertilizer in the cropping system. The use of the isotope enables researchers to determine how much of the added fertilizer actually makes into the crop and how much is left behind or unaccounted for and lost from the system. Scientist applied 3 atom % 15N to 4 leaf stage sunflower in the a wheat-millet or (corn)-sunflower-fallow rotation. Six fertilizer placement methods were tested in a two year study: surface broadcast, surface band(dribble), subsurface band; and three deep subsurface placements of: 60 cm (2 ft), 120 cm (4 ft) and 165 cm (5.5ft) deep. At mid bloom and at physiological maturity 3-4 Plants are harvested at the soil surface and separated into leaves, stems and heads. Each plant tissue analyzed for N isotope ratio. The highest fertilizer recovery was found in the subsurface banded treatment both years (60-70%). With the 60 cm placement we measured as much as 54% fertilizer recovery. The dribble treatment and the surface broadcast treatments were similar with average recoveries of 35 and 40% respectively. At the 120 and 165 cm depths we measured average recoveries of only 18 and 16% respectively.

Technical Abstract: Knowledge of sunflower response to fertilizer nitrogen (N) and fertilizer N recovery in the Central Great Plains region is limited.The objectives of this study are: (i) to measure sunflower response to fertilizer N under no- till management and (ii) to determine N fertilizer recovery of this crop in a no-till four year rotation as affected by placement. Fertilizer solutions labeled with 3 atom % 15N were applied to 4 leaf stage sunflower in the a wheat-millet or (corn)-sunflower-fallow rotation. Six fertilizer placement methods were tested in a two year study: surface broadcast, surface band(dribble), subsurface band; and three deep subsurface placements of: 60 cm (2 ft), 120 cm (4 ft) and 165 cm (5.5ft) deep. Labeled urea-N was applied at N rates of 30 and 60 lbs N/acre 4 inches away from the sunflower row in 4, (30 inch wide rows) row micro-plots 2 m long. At R-4 and at physiological maturity 3-4 Plants are harvested at the soil surface and separated into leaves, stems and heads. Each plant tissue analyzed for N isotope ratio. The highest fertilizer recovery was found in the subsurface banded treatment both years (60-70%). With the 60 cm placement we measured as much as 54% fertilizer recovery. The dribble treatment and the surface broadcast treatments were similar with average recoveries of 35 and 40% respectively. At the 120 and 165 cm depths we measured average recoveries of only 18 and 16% respectively.

Last Modified: 7/24/2014