Ed Lentz, Extension District Specialist, Agronomy
To evaluate the effects that spring nitrogen application time may have on wheat yields.
| Cooperator: | OARDC Northwestern | Soil test: | pH 6.3, P 45 ppm, |
| Branch | K 177 ppm | ||
| County: | Wood | Fertilizer: | 0-0-60 = 100 lb/A |
| Nearest Town: | Hoytville | 0-46-0 = 50 lb/A | |
| Drainage: | Tiled | Planting Date: | October 1, 2001 |
| Soil type: | Hoytville clay | Planting Rate: | 160 lb/A |
| Tillage: | No till | Row Width: | 7.5-inch |
| Previous Crop: | Soybeans | Herbicides: | 4 oz. Stinger |
| Variety: | Hopewell | Harvest Date: | July 8, 2002 |
Experimental design was a randomized complete block with four treatments replicated four times. Treatments were four nitrogen application times — late February, first greenup, initial stem elongation, and late stem elongation. A Great Plains No-Till Drill was used for seeding. In the fall, 30 pounds of nitrogen was surface applied as urea-ammonium nitrate (28%). Seventy pounds of nitrogen (urea) was surfaced applied by a Gandy spreader in the spring for each treatment. Plots were 10 feet wide and 70 feet long. The center 11 rows were harvested for grain yield. A combine scale estimated grain weight. Grain moisture was approximately 11%. At flowering, measurements from 30 flag leaves were averaged for each plot by a Minolta Spad meter to estimate nitrogen uptake. Head number was estimated by counting spikes in three-foot sections from three areas in each plot.
Table 1. Wheat Grain Yield, Spad Meter Readings, and Head Number Response to Application Time of Spring Nitrogen.a
| Spring Nitrogen | Grain | Spad Meter | |
| Application | Yield | At Flowering | Heads |
| (bu/A) | (spikes/ft2) | ||
| Early stem elongation | 82.8 a | 44.8 b | 66 a |
| Late February | 73.3 b | 41.0 c | 66 a |
| Greenup | 68.1 c | 39.8 c | 61 b |
| Late stem elongation | 62.6 d | 48.0 a | 57 b |
| LSD (0.05) | 3.6 | 3.0 | 4.3 |
| F-test | 58.7 | 15.9 | 10.3 |
| a Means followed by the same letter within a column are not significantly different. | |||
Time of spring nitrogen had a significant effect on grain yield. Yields were the largest for applications at initial stem elongation and the smallest for late stem elongation. Spad meter values were higher for initial stem elongation than late February and greenup, suggesting nitrogen loss from these earlier applications. Even though the late stem elongation time had the highest meter values, it was too late to be utilized by the crop as evident by the fewer number of heads. Yields for greenup treatment would not have been expected to be lower than the late February application. The lower meter value and fewer heads than the late February application would suggest possible nitrogen loss, but the type of loss is beyond the scope of this experiment.
April weather conditions were conducive for nitrogen loss in 2002 (wetter and warmer than normal). Late February and greenup applications may have been early enough that ammonium-nitrogen had converted to nitrate-nitrogen and was lost during the wet and warm April. In other years, yields probably would not be as different among these application times. Late February may be as good as greenup for nitrogen applications. Nitrogen applications after initial stem elongation may be too late for adequate utilization by the crop.
The author of this report is grateful for the support provided by the OARDC staff at the Northwestern Branch.
For more information, contact:
Ed Lentz
Ohio State University Extension, Northwest District
1219 W Main Cross St., Suite 202
Findlay, OH 4 5840
419-422-6106
lentz.38@osu.edu