Ed Lentz, Extension District Specialist, Agronomy
Producers sometimes broadcast urea-ammonium nitrate (28% N solution) with herbicides to reduce application costs (weed ‘n’ feed program). This practice may lead to unacceptable N losses from volatilization and denitrification. Sidedress N programs may reduce this loss potential and provide more N to the crop, but require another trip. The objective of this study was to compare grain yields between broadcast and sidedress applications of urea-ammonium nitrate.
| Cooperator: | OARDC, | Planting Date: | May 29, 2002 |
| Northwestern Branch | Seeding Rate: | 30,000 seeds/A | |
| County: | Wood | Row Width: | 30-inch |
| Nearest Town: | Hoytville | Herbicides: | |
| Drainage: | Tiled | PRE: | 2.4 qt/A Harness Xtra |
| Soil type: | Hoytville clay | 1 pt/A Atrazine | |
| Tillage: | Conventional till | 26 oz./A Roundup | |
| Previous Crop: | Soybeans | Ultramax + AMS | |
| Variety: | Pioneer 34B24 | POST: | 2 pt/A Basagran |
| Fertilizer: | N = 160 lb/A | Harvest Date: | October 28, 2002 |
| Soil test: | pH = 6.5, P = 104 ppm | ||
| K = 208 ppm |
Experimental design was a randomized complete block with three treatments replicated four times. Treatments were as follows:
Plots were 10 feet wide and 70 feet long and consisted of four rows. The center two rows were harvested for grain. A combine scale and sensor estimated grain weight and moisture, respectively. Yield was adjusted to 15% moisture. At silking, 10 ear leaves were collected and sent to Spectrum Analytical Lab for nitrogen content. Harvest population was estimated by counting plants per 17.4 feet of row from each harvest row.
Table 1. Average Corn Grain Yield and Other Agronomic Traits in Response to UAN Management Systems.a
| Application | Grain | Harvest | Harvest | Tissue |
| Method | Yield | Moisture | Population | Nitrogen |
| (bu/A) | (%) | (plants/A) | (%) | |
| Broadcast | 111.1 a | 22.4 | 25,750 | 2.6 |
| Injected | 106.5 a | 21.4 | 26,000 | 2.5 |
| Zero N check | 87.8 b | 20.5 | 26,875 | 2.3 |
| LSD (0.05) | 14.7 | NS | NS | NS |
| F-test | 8.46 | <1 | <1 | 2.81 |
| a Means followed by the same letter within a column are not significantly different. | ||||
Grain yields were similar between a broadcast application of urea-ammonium nitrate at planting and a sidedress application at growth stage V6. Differences may have not been detected because of an abnormally hot and very dry summer, which greatly reduced yields at this site. Normally, yields would be expected between 175 to 200 bu/A.
Tissue nitrogen was below the nitrogen suffiency range (2.9 - 3.5%) for all treatments. Possible restricted root growth and/or lack of soil water movement may have prevented nitrogen uptake by the plants. The lack of differences between the zero check and other treatments for nitrogen uptake would be further evidence of limited nitrogen availability. Root development may have been restricted from early cool, wet conditions followed by hot, dry conditions, which would have reduced nitrogen uptake.
No conclusion from this study should be made about nitrogen application methods for urea-ammonium nitrate. Other factors were more limiting than nitrogen, and masked any differences that may have occurred between application methods.
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 45840
419-422-6106
lentz.38@osu.edu