Andy Kleinschmidt, Extension Agriculture and Natural Resources Agent
Ed Lentz, Extension Northwest District Agronomist
Gary Prill, Farm Focus/Research Coordinator
Evaluate the yield response of soybeans to supplemental nitrogen applied at the R4 (full pod) stage.
| Cooperator: | Vantage Career Center/ | Herbicide: | PRE - Roundup Ultra (1.5 pt./A) |
| Farm Focus | + AMS (3.4 lb./A) | ||
| County: | Van Wert | POST - Roundup Ultra | |
| Nearest Town: | Van Wert | (1.5 qt./A) + AMS (3.4 lb./A) | |
| Soil Type: | Hoytville | Variety: | Wellman W3127RR (treated) |
| Drainage: | Tile | Planting Rate: | 200,000 seeds/A |
| Previous Crop: | Corn | Row Width: | 7.5 inch |
| Tillage: | No-till drilled | Planting Date: | May 17, 2000 |
| Soil Test: | pH 5.4, P 41 ppm, K 156 ppm |
Harvest Date: | October 2, 2000 |
The experimental design was a randomized complete block with four replications of three treatments. Treatments included: (1) 83 lb. per acre actual nitrogen from urea plus Agrotain® (5 qt. per ton of urea), (2) one pass of application equipment without fertilizer, and (3) no fertilizer or equipment traffic. Nitrogen was applied during the R4 growth stage (full pod development prior to seed formation) on August 4, 2000, using a broadcast spreader on a tractor in a 15-foot swath. One pass was made for each treatment to produce a 15-foot-wide by 712-feet-long treatment area, with a 10-foot-wide border between treatments. All plots were planted using a John Deere 750 no-till drill.
Harvest populations were evaluated by counting the number of plants on each side of a tape for a distance of 17.5 feet at three different locations in the treatment plot. The average of the number of plants counted per 17.5 feet was converted to plants per acre. The center 14.5 feet of each plot were harvested and then weighed by a calibrated weigh wagon, and grain yield was determined at 13% moisture.
Yield and harvest population means for each treatment are given in the table on the following page.
| Treatment | Harvest Population – plants/A – |
Yield – bushels/A –- |
| Nitrogen | 123,200 | 56.2 a |
| Equipment traffic | 128,100 | 58.9 a |
| No traffic | 119,000 | 65.2 b |
| LSD (P =0.05) | NS | 5.0 |
| CV (< 15%=credible) | 10.9% | 3.7% |
| Results with the same letter are not significantly different at P = 0.05.
NS = not significant. |
||
Supplemental nitrogen applied to soybeans during the R4 stage did not increase yields. This study complements work done at Farm Focus in 1999, whereby nitrogen applied to soybeans at the R2 reproductive stage did not increase yields. Urea requires at least 0.5 inch of rainfall for incorporation, otherwise nitrogen may be lost from volatilization. Agrotain® can delay these losses 1014 days after application. In 2000, total rainfall accumulation after 14 days was 1.37 inches, with 0.98 inches of rainfall occurring within two days of the application. Thus, it is safe to assume there was adequate incorporation of the urea.
In this study, the results showed a significant decrease in yield for the two treatments that received equipment traffic during the R4 reproductive stage. This can be expected when a plant is run over during a critical stage of growth. Fertilizer equipment used in this study left two tire tracks in the 14.5-foot-wide strip that was harvested from each plot. This indicates that when an application is made to soybeans during this late stage, it probably should be done by aircraft, or the producer should be willing to accept yield loss.
The authors wish to express their appreciation to Royster Clark for donating material used in this study.
For additional information, contact:
| Andy Kleinschmidt | Gary Prill | Ed Lentz |
| Agric. & Natural Res. Agent | Farm Focus/Research Coordinator | District Agronomist |
| OSU Extension, | OSU Extension, | OSU Extension, |
| Van Wert County | Van Wert County | Northwest District |
| 1055 South Washington Street | 1055 South Washington Street | 952 Lima Ave., Box C |
| Van Wert, OH 45891 | Van Wert, OH 45891 | Findlay, OH 45840 |
| 419-238-1214 | 419-238-1214 | 419-422-6106 |
| kleinschmidt.5@osu.edu | prill.1@osu.edu | lentz.38@osu.edu |