Strip-tilled corn yielded 3.7% less, had the highest grain-moisture content and the lowest test weight in a 2009 University of Nebraska fertilizer-placement research trial, according to university scientists Glen P. Slater and Richard B. Ferguson.

Sustained high fertilizer costs make it important to explore innovative options to manage nitrogen and phosphorus fertilizers more efficiently and effectively. The 2009 demonstration evaluated various nitrogen fertilizer application methods and their impact on crop health and yield for irrigated corn production.

Study Site and Treatments

An 18-acre demonstration site was used at the UNL South Central Agricultural Laboratory (SCAL) research farm in Clay County, Neb. The predominant soil type present was Hastings silt loam.

Agronomic activities included pre-plant and sidedress fertilizer application, ridge-till planting and furrow irrigation. Other than fertilizer application, management practices (hybrid, pesticides, irrigation, etc.) remained uniform across the entire study to optimize yield potential.

The soils of this location and the production system used are typical of irrigated corn production in the south-central region of Nebraska. The previous crop at this location was soybeans (65 bushels per acre yield in 2008).

Spring soil sampling took place February 25. Pre-plant fertilizer treatment application took place March 19 in conjunction with a SCAL Crop Clinic. The corn — Pioneer Hi-Bred 33D47-RR — was planted April 20.

The field-length treatment strip dimensions were 8 rows (20 feet) wide by 1,230 feet long. The study was a randomized, complete-block design with nine treatments and three replications. 

Fertilizer Formulation: Phosphorus and Nitrogen Applied (pounds per acre)

1. Anhydrous ammonia sidedress + Foliar CoRoN 32.5 (band) 98 
2. Anhydrous ammonia sidedress 32.5 (band) 133 
3. UAN/APP mix pre-plant 32.5 (band) 151 
4. Dual-placed anhydrous ammonia + APP pre-plant 32.5 (band 151 
5. Surface broadcast urea + MAP pre-plant 65 (broadcast) 151 
6. Anhydrous ammonia pre-plant, starter APP in-row + MAP 32.5 (band + broadcast) 151 
7. Anhydrous ammonia pre-plant, high rate starter APP in-row 32.5 (band) 151 
8. Strip-till anhydrous ammonia + MAP pre-plant 65 (broadcast) 151 
9. Surface broadcast ESN + MAP pre-plant 65 (broadcast) 151 
 
Fertilizers used

• Monammonium phosphate (MAP, 11-52-0) 
•Urea (46-0-0) 
• ESN (44-0-0) 
•Anhydrous ammonia (82-0-0) 5.15 pounds per gallon
•Ammonium polyphosphate (APP 10-34-0) 11.4 pounds per gallon
•UAN (28-0-0) 10.67 pounds per gallon
•CoRoN (25-0-0) 10.0 pounds per gallon — controlled-release fertilizer 

Nitrogen Recommendation

For 230 bushel yield goal: 196 pounds of nitrogen per acre, minus 45 pounds of nitrogen per acre credit for soybeans equals 151 pounds of nitrogen per acre.

Phosphorus Recommendation

64.8 pounds acre broadcast or 32.4 pounds per-acre-row.

Noteworthy Effect Of Treatments

Field conditions were good for pre-plant fertilizer application on March 19 with dry surface conditions in the soybean stubble and abundant subsurface moisture. The corn emerged by May 1 with excellent stands (29,363 plants per acre, on average). Anhydrous ammonia burn became evident in the strip-till treatments by mid-May (plants at V3 to V4), related to dry conditions after fertilizer application that were made more severe by the strip-till operation.

At V3, growth of the seedling root system had essentially ceased and secondary (nodal) roots began elongating, forming root hairs, and becoming the major part of the root system. In the strip-tilled corn, stands were reduced by 5.4%, the corn was significantly stunted, and the crop remained uneven for several weeks.

By later vegetative stages, the stunted corn appeared recovered, except for the loss in stand. Strip-till was the only fertilizer technique that caused this burn to occur. All other treatments had a healthy, uniform green appearance throughout vegetative stages.

Soil electrical conductivity (EC) was measured in the row on two separate dates for two treatments — Treatment 3, band-applied UAN between rows, and Treatment 8, strip-till applied anhydrous ammonia beneath rows.

On June 4, soil EC was significantly higher for Treatment 8 to a depth of 6 inches. A couple of weeks later, soil EC was still elevated for Treatment 8 to a depth of 9 inches, but trends for higher EC with the strip-till treatment were noted at all depths. The conclusion from observations and data collected was that strip-till injection of anhydrous ammonia beneath the row in the spring reduced soil moisture and bulk density beneath the row location, allowing ammonia to diffuse upward too close to the seed.

Sidedress nitrogen was applied with the John Deere 2510 research NH3 applicator May 27. Corn was cultivated June 5 to clean up emerged weeds. CoRoN nitrogen fertilizer was foliar-applied June 12 to Treatment 1, and the field was ridged June 12 for furrow irrigation. Four irrigation events took place from July 6 to Aug. 26 with 14.75 inches pumped (70% efficiency equals 10.3 inches available for crop). During the growing season there was 14.9 total inches rain, which was 78% of normal.

Yields

The study was harvested Nov. 10, 2009 with a John Deere 9600 combine with yield-mapping capabilities. Each treatment strip was weighed individually using a grain cart equipped with a scale. Grain samples were collected to determine moisture content and test weight. Except for Treatment 8, treatments that received the full 151 pounds of nitrogen yielded similarly. They averaged 236 bushels per acre. The strip-tilled treatment yielded 3.7% less, had the highest grain moisture content, and the lowest grain test weight. 
 
Yield Results

Bushels per acre; moisture; pounds per bushel
1. Anhydrous ammonia sidedress + Foliar CoRoN 228.3 cd 19.3 59.0 
2. Anhydrous ammonia sidedress   233.8 abc 19.2 59.1 
3. UAN/APP mix preplant  233.6 abc 18.8 59.7 
4. Dual placed NH3 + APP preplant 232.5 bcd 19.3 59.1 
5. Surface broadcast urea + MAP preplant 236.5 ab 18.9 60.1 
6. Anhydrous ammonia pre-plant, starter APP in-row + MAP 235.4 ab 18.9 59.7 
7. Anhydrous ammonia pre-plant, high rate starter APP in-row 238.6 a 18.9 60.2 
8. Strip-till Anhydrous ammonia + MAP pre-plant  227.2 d 19.8 58.4 
9. Surface broadcast ESN + MAP pre-plant 238.8 a 18.8 60.0 
(Yields with the same letter are not significantly different.)

Summary

Grain yields were excellent from this demonstration in 2009, a year with outstanding growing conditions. Yields were generally similar for most treatments, with two exceptions. They were the strip-till applied nitrogen (treatment 8) which was influenced by anhydrous ammonia damage early in the season, and treatment 1 (anhydrous ammonia sidedress + CoRoN), which had less total nitrogen than other treatments.

There was little evidence that foliar-applied CoRoN was able to replace nitrogen which was not supplied by anhydrous ammonia at V6. Treatment 2 also inadvertently received a somewhat lower total nitrogen rate than other treatments, but yield was not reduced significantly.