TOPDRESSING NITROGEN AS UAN NEAR THE BOOT GROWTH STAGE PI: Dr. Joel Ransom

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1 TOPDRESSING NITROGEN AS UAN NEAR THE BOOT GROWTH STAGE PI: Dr. Joel Ransom INTRODUCTION Does it pay to add N in-season in wheat or do you stick with one application pre-plant? There is a stigma with growing wheat. It has sometimes been referred to as poverty grass. This is because you need the stars to align to get bushels and quality grain to make wheat cash flow. In order to have this delicate balance, you have to have the fertility available when the wheat plant needs it, especially during grain fill when the kernel is forming protein. Past small-plot research at North Dakota State University (NDSU) found that UAN applied at the boot stage, which is later than previously recommended for yield enhancement, might be a practice that would benefit both protein and yield. When should a grower make the decision to add additional nitrogen? This is not an easy question to answer but it is an important one. Relevant research conducted by growers and researchers within the OFRN might help find the answers. The objective of this research was to compare the application of 100% nitrogen at the pre-plant timing with 100% nitrogen at the pre-plant timing plus 30 lbs acre -1 of nitrogen as UAN with a urease inhibitor near the boot growth stage on spring wheat yield and protein content. MATERIALS AND METHODS In 201, there were 13 locations and in 2016, there were 11 locations of this trial throughout NW MN. The site descriptions are in Table 1. There were two treatments in this trial; 100% nitrogen rate at the pre-plant timing, and 100% nitrogen rate at the pre-plant timing plus an application of 30 lbs acre -1 of nitrogen in the form of urea ammonium nitrate (UAN) with the urease inhibitor Limus (BASF) at the recommended rate. All applications were made with 10 gal per acre of UAN using streamer nozzles to mitigate plant tissue phytotoxicity or burning from the nitrogen fertilizer. The pre-plant nitrogen application for each individual producer s optimum nitrogen rate was determine by them, with his or her preferred nitrogen form and application method(s). All sites were set up the same, with the topdress application applied in strips, alternating with strips without additional N across the trial. The application was made from two nodes detectable on the stem to prior to the head emerging (Feekes to Feekes 10). The range in application timing was due to many factors including, trying to make the application before a rain event, workload and field condition constraints. Rain data were collected with the services from Climate Fieldview. Producer machinery was used to harvest the trials and plot weights were taken mostly with a weigh wagon that was provided by MN Wheat staff. MN Wheat owns one weigh wagon and borrows three others. Yields were adjusted to 13.5% grain moisture. We collected sub-samples of the grain from each plot, with an attachment to the weigh wagon s auger as the grain is augured out of the weigh wagon and into a truck. The attachment takes a small stream of continuous grain. Sub- samples were immediately analyzed for harvest moisture and grain test weight with a Dickey John mini-gac plus. Sub-samples were analyzed for grain protein at the Northern Plains Grain Inspection Service. There were some instances that the grower preferred using the scale on their grain cart to get the weights. In those cases, we would hold a piece of PVC pipe into the stream of grain as it was being unloaded into a truck to get the sub-samples. RESULTS AND DISCUSSION Results from the 13 locations are presented in Table 2. When combined over 11 of the locations, topdressing nitrogen significantly impacted test weight and grain protein. Test weight was reduced 0.5lbs/bu in the treated areas, while protein was improved a 0.5% over the untreated check. The topdressing of nitrogen did not affect yield. There were three environments that when taken alone, had yield that was significantly impacted by the nitrogen application. Two of these locations had improved yield and the other had a negative effect from topdressing nitrogen. s 12 and 13 included additional treatments that included 10 more gallons of UAN:water (50:50) post anthesis (post flowering). They also had a treatment of just the post anthesis UAN:water. The additional N treatments averaged over two points better protein at location 12 and only a couple bushels difference in yield. At location 13, the additional N treatments averaged about 1.5% better protein and bushels more yield. Since these data are from just two locations with multiple treatments with few replications, they should be viewed cautiously. Our initial hypothesis was that a late application of nitrogen near the boot stage could perhaps increase yield and at the same time increase protein. However, this result was only seen in a few environments. The environment where additional nitrogen decreased yield can be in part explained by within field variability, as this application of UAN (using streamer bars) is not known to have phytotoxic effects on the wheat plant. An increase in protein resulting from the added N was the other expected result of this trial. This was seen at every location and it was a statistically significant increase in Page 8

2 all but four of the locations. The increases ranged from 0.1% to 0.8% greater protein. When taken as a whole, the combined 13 locations did not produce enough extra protein with the topdress to make the extra nitrogen application economical in today s wheat market. However, the locations that had the greater increases in protein, approached the response needed to pay for the application in years when there would be a sizeable protein premium/discount in the market. See Table 3 for economic analysis. The results from the topdress N trials this year contrast with what was found in prior small plot research in North Dakota (ND) and MN. Just like in 2016, the 201 growing season had a warm April. Farmers were able to get into the fields early and the nice weather likely increased the amount of nitrogen generated through mineralization, so these plots were likely not short on nitrogen. The exceptions to this were the areas that were dry which would have decreased the amount of mineralization occurring in the soil. Table 1. Agronomic details for all 13 locations of the topdress nitrogen trial in St. Hilaire St. Hilaire Roseau Roseau Red Glyndon Olso Perley Mavie Audubon Danube Mentor Mentor Lake Falls Planting 4/22 4/22 5/5 5/5 4/1 4/11 5/11 4/13 5/ 4/21&2 4/8 5/5 5/4 Date Harvest Date 8/28 8/28 8/20 8/29 8/19 8/8 8/29 8/21 8/20 8/23 8/8 8/19 8/23 Rainfall Total (in) Rainfall Days from Topdress App. 1 (in) Previous Soybean Soybean Soybean Soybean Soybean N/A Edible Soybean Soybean Soybean Wheat Soybean Soybean Crop Beans Corn Soybean Fine Hegne- Fargo Silty Silty Silt Silt Cobbly Fine Soil Type Bolles Linkert Linkert SY Ingmar SY Ingmar Linkert Shelly Linkert Croplan 3530 Mayville SY Soren Croplan 3419 Variety Prosper Albany Croplan 3419 N Topdress 6/23 6/23 6/13 6/13 6/5 6/10 6/2 6/8 6/12 6/21 6/ 6/6 6/6 Date Feekes Growth Boot Boot 2 Nodes 2 Nodes Boot Boot 4 Nodes Boot 2 Nodes Boot 3 Nodes 2 Nodes 2 Nodes Stage 1 Days post-application of topdress UAN. Page 9

3 Table 2. Effect of topdressing nitrogen near the boot stage compared with no topdressing of nitrogen on test weight, grain protein, and yield, at 13 diverse environments throughout NW MN and combined over 11 environments. Treatment Combined Test Weight (lb bu -1 ) No Topdress N With Topdress N LSD (0.05) 0.4 NS NS NS NS NS NS NS NS NS NS 0.50 NS NS LSD (0.10) 0.2 NS NS NS NS NS NS NS NS NS NS 0.41 NS NS Grain Protein Content (%) No Topdress N With Topdress N LSD (0.05) NS NS NS NS 0.1 NS NS NS NS NS LSD (0.10) NS NS NS NS NS Yield (bu ac -1 ) No Topdress N With Topdress N LSD (0.05) NS NS NS NS NS NS NS NS NS NS -- NS LSD (0.10) NS NS NS NS NS NS NS 1.49 NS NS -- NS NS non-significant NS non-significant difference at difference the 95% at confidence the 95% confidence level. level. LSD least significant difference, if the means differ by more than the LSD number the numbers are statistically different. LSD least significant difference, if the means differ by more than the LSD number the numbers are statistically different. Page 10

4 Table 3. Economic analysis of the topdress nitrogen application of all locations individually and the combined analysis, NW MN, Combined (1-11) % No Topdress N Protein With Topdress N Protein Protein gain/loss $ Protein gain/bu 1 $0.36 $0.2 $0.16 $0.12 $0.2 $0.36 $0.25 $0.01 $0.24 $0.16 $0.10 $0.20 $0.88 $0.81 Topdress Yield Total $ Gain topdress for protein/acre ($) $28.80 $1.46 $1.38 $12.28 $18.58 $29.81 $18.8 $0.85 $19.34 $12.45 $6.51 $16.84 $64.94 $56.94 Application Costs 1bu/ac ($) 2 $26.25 $26.25 $26.25 $26.25 $26.25 $26.25 $26.25 $26.25 $26.25 $26.25 $26.25 $26.25 $51.25 $51.25 Financial outcome ($) $2.55 ($8.9) ($8.8) ($13.9) ($.6) $3.56 ($.48) ($25.40) ($6.91) ($13.80) ($19.4) ($9.41) $13.69 $ Protein premium of +$0.10 per fifth above 14% up to 15%, +0.2 per fifth above 15% and a protein discount of -$0.08 per fifth below 14%. 2 December wheat price of $6.00/bu. Considering 1 bu/ac lost due to tire tracks from the application. $8.00/ac application cost for machinery and time. $11.00/ ac for 10 gallons of $1.25/ac for the Limus N stabilizer Page 11

5 CONCLUSIONS The additional 30lbs per acre of nitrogen as UAN in combination with a urease inhibitor did not improve yield beyond the control. However, it did increase protein by 0.5% combined over 11 locations. If we continue to get these results from this timing and rate of N, it may make more sense to do the post-anthesis (flowering) growth stage application, where between % protein increases are routinely gained. s 12 and 13 showed this. Though these results need to be viewed with caution since they are from only two locations and two replications at each location. Nevertheless, the 60lbs of additional nitrogen, 30lbs N streamed on at the boot stage and 30lbs N applied with flat fan nozzles post-anthesis, did achieve a 2.0% increase in protein. For the 2018 season, the OFRN plans to continue this trial but add more predictive tools to sense nitrogen deficiencies in season. Predictive tools such as imagery from a UAV, tissue testing and chlorophyll meter readings. We likely will not have as many locations with the added work, but the goal is to improve the nitrogen use efficiency and grower financials. Page 12