Results from soybean nutrient management trials
Starter N application is commonly practiced in the northern U.S. and High Plains soybean production areas and is of particular interest in high residue situations.
Two sets of field trials were conducted to evaluate soybean response to nutrient management and other practices. The “starter/foliar” and “high yield” trials were conducted on-farm at the four 2011 Soybean Management Field Day sites near Bancroft, Elba, Clay Center (SCAL), and Cortland (Table 1). All sites were in corn in 2010 and rotated to soybean in 2011. Crop residue cover of soil was 95% at Bancroft and 45-65% elsewhere. All trials were planted in early May, but cool weather delayed seedling establishment.
Starter N application is commonly practiced in the northern U.S. and High Plains soybean production areas and may be of particular interest in high residue situations. Injection of 15 lb/ac N two inches to the side of the row resulted in a 6% yield increase in Brookings, S.D.
Foliar nutrient application is much promoted but previous research showed a low probability of profitable response from its use compared to traditional, well-managed soil fertility. New products such as those with slow release N may be effective and needed to be evaluated.
In addition, growth promoters and other practices used alone or in combination with other practices may be effective in increasing yield in already high-yield situations.
1) control with no starter N, foliar application, or row cleaning
2) row cleaning only
3 & 4) 5 or 10 lb/ac N in-furrow
5 & 6) 10 lb/ac N injected two inches to the side of the seed furrow or applied over the row
7, 8 & 9) foliar N application at V4, R2 (full bloom), or both at V4 and R2
10) starter plus foliar N application at V4 and R2
Planting was in 30-inch rows at about 150,000 seeds per acre, and without row cleaning, except for treatment 2. Starter N was applied as UAN diluted with water to reduce risk of seedling damage. The foliar treatment was a combination of Nachurs N-Rage (N-P-K 23-4-2 with 0.05% Mn; the N is 67% triazone; rate = 2 gal/ac) and Nachurs SoyGrow (0.36% Fe, 0.5% Mg, 2.6% Mn, and 1.5% Zn; rate = 1 pt/ac).
Early plant growth was not affected by starter N application except at the high-residue Bancroft site where early growth was increased with 10 lb/ac N injected in-furrow or 2-inch to the side of the row. However, this did not result in increased yield. Mean yield was two bu/ac more with foliar application at R2 compared with the control, but other treatments had no effect on yield at all locations (Table 2).
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