Andy Kleinschmidt*, Extension Agriculture and Natural Resources Agent
Gary Prill, Extension Associate, Farm Focus/Research Coordinator
Ed Lentz, District Agronomy Specialist
Objective: Evaluate the yield response of soybeans to supplemental N at the R2 reproductive stage.
Background |
|
| Cooperator:
County: Nearest Town: Soil Types: Drainage: Previous Crop: Tillage: Soil Test: |
Marsh Foundation/Farm Focus
Van Wert Van Wert Hoytville silty clay loam Tile Corn Fall deep-tilled and land leveled CRP (10 years) pH, 6.1; P, 72 ppm; K, 155 ppm |
| Herbicide: | PRE - 1.5 pt/acre Roundup Ultra + 3 pt/acre Squadron
POST - 1 pt/acre Roundup Ultra |
| Variety:
Planting Rate: Planting Date: Harvest Date: |
Callahan 8297 RR (treated)
200,000 seeds/acre May 11, 1999 September 16, 1999 |
The experimental design was a randomized complete block with four replications of three treatments. Treatments included: (1) 83 lb/A N from urea plus Agrotain® (5 qt/ton of urea), (2) one pass of application equipment without fertilizer, and (3) no fertilizer or equipment traffic.
Nitrogen was applied during the R2 growth stage using a broadcast spreader on a tractor in 15-foot swaths. Two passes were made for each treatment to produce a 30-foot wide treatment area.
Plot length was 464.5 feet. The center 14 feet of each plot was harvested and weighed by a weigh wagon to determine grain yield at 13% moisture. Harvest populations were estimated by counting the number of plants in three-foot sections from two adjacent rows. Counts were made at three different locations in each plot.
| Treatment | Harvest Population | Yield |
| ----plants/A---- | ---- bu/A ---- | |
| N (83 lb/A) | 207,152 | 48.2 |
| Equipment traffic without N | 199,408 | 47.8 |
| No N or Equipment traffic | 198,440 | 51.7 |
| LSD (P = 0.05) | NS | NS |
| CV | 6.26% | 5.28% |
| NS = not significant | ||
Supplemental nitrogen applied to soybeans at the R2 reproductive stage did not significantly increase yields. Lack of rainfall may have diminished the potential benefit of additional N. Urea requires at least 0.5 inch of rainfall for incorporation, otherwise N may be lost from volatilization. Agrotain®, an urease inhibitor, can delay these losses 10-14 days after application. In this study, 0.25 inch of rain occurred within one day after N application. Total rainfall accumulation after 14 days was 0.92 inches. Yields were not significantly better on plots that received no fertilizer or equipment traffic.
In conclusion, this one-year study suggested no benefit from applying supplemental N to soybeans at the R2 reproductive stage. Driving across plots at flowering at the R2 stage did not significantly lower yields. Results may be different in a year with normal rainfall.
The authors express their appreciation to American Cyanamid, Callahan Seeds, Monsanto, and Royster Clark for donating material used in this study.
*For additional information, contact:
Ohio State University Extension, Van Wert County
1055 South Washington Street
Van Wert, OH 45891
419-238-1214
aklein@postoffice.ag.ohio-state.edu