Ed Lentz, Extension District Specialist, Agronomy
To evaluate the relationship between nitrogen rate and wheat yields.
| Cooperator: | OARDC Vegetable Farm | Fertilizer: | broadcast prior to planting |
| County: | Sandusky | 0-0-60 = 150 lb/A; | |
| Nearest Town: | Fremont | 18-46-0 = 150 lb/A | |
| Drainage: | Systematically tiled | Planting Date: | October 3, 2001 |
| Soil type: | Hoytville silty clay loam | Planting Rate: | 130 lb/A |
| Tillage: | No-till | Row Width: | 7.5-inch |
| Previous Crop: | Soybeans | Herbicides: | None |
| Variety: | Hopewell | Harvest Date: | July 15, 2002 |
| Soil test: | pH 6.3, P 50 ppm, | ||
| K = 143 ppm |
Experimental design was a randomized complete block with seven treatments replicated four times. Treatments were seven nitrogen rates — 0, 20, 40, 60, 80, 100, and 120 pounds of nitrogen/A. Urea was surface applied from a Gandy spreader for all treatments. All plots received 20 pounds of nitrogen from diammonium phosphate in fall 2001. A John Deere 1550 Drill was used at planting. Plots were 10 feet wide and 70 feet long. The center five feet was harvested for grain yield. A combine scale and a Dickey John tester estimated grain weight and moisture, respectively. Yield was adjusted to 14% moisture. Minolta Spad meter readings from 30 flag leaves were averaged at -flowering for each plot to estimate nitrogen uptake. Head number was estimated by counting heads in a single row for three feet from three areas in each plot.
Table 1. Wheat Grain Yield, Spad Meter Readings, and Head Counts.a
| Spring | Grain | Harvest | Spad Meter | |
| N Rate | Yield | Moisture | Reading | Heads |
| (lbs/A) | (bu/A) | (%) | (heads/ft2) | |
| 0 | 48.8 a | 11.3 | 34.9 a | 55 a |
| 20 | 54.2 a | 11.7 | 36.9 ab | 50 a |
| 40 | 64.4 b | 11.2 | 38.7 bc | 56 a |
| 60 | 67.7 bc | 11.4 | 39.8 cd | 57 a |
| 80 | 73.3 c | 11.5 | 42.0 de | 66 b |
| 100 | 80.5 d | 11.5 | 43.1 e | 69 b |
| 120 | 83.5 d | 11.4 | 43.6 e | 66 b |
| LSD (0.05) | 7.0 | NS | 2.4 | 8.0 |
| F-test | 29.6 | <1 | 15.7 | 7.0 |
| a Means followed by the same letter in the same column are not significantly different. | ||||
Yields increased with increasing nitrogen rate until the 100-lb treatment. Spad meter values showed that nitrogen uptake increased with greater nitrogen rates until the 80 to 100 lb treatments. Treatments receiving less than 80 lb of nitrogen/A had fewer heads, which may partially explain some of the lower grain yields with lower rates of nitrogen. Harvest moisture was not affected by nitrogen rate.
These results show that nitrogen rate may affect yields, nitrogen uptake, and head numbers. In general, yields increased until the 100-lb treatment. Nitrogen utilization is highly dependent upon the year. This study may explain what happened in 2002 but may not be a good predictor for future years. Nitrogen rate studies over many years and locations would be required before a general recommendation could be made.
The author of this report is grateful for the support provided by the OARDC staff at the Vegetable Branch.
For more information, contact:
Ed Lentz
Ohio State University Extension, Northwest District
1219 W. Main Cross St., Suite 202
Findlay, OH 45840
419-422-6106
lentz.38@osu.edu