A new system for sidedressing nitrogen may increase yield by 20-30% per unit of rescue nitrogen by placing the nitrogen closer to the roots. Combine this with later sidedressing (V14-18), closer to peak plant need, and you have a recent on-farm replicated strip trial conducted by The Iowa Soybean Association (ISA) On-Farm Network. The trial spanned the extreme 2012-2013 growing seasons, which triggered weather-related nitrogen losses for many farmers.
“Weather extremes call for new, innovative ways to manage nitrogen that could change an unprofitable year into a profitable one,” says Pat Reeg, On-Farm Network director, that tested the new concept.
“Historically, late-season nitrogen applications haven’t always worked because we lacked the rainfall to move it into the plant’s ‘availability zone.’” Reeg says. “The Y Drop applicator may be a promising tool to change this.”
The Y Drop applicator increases the odds that your applied nitrogen enters the root zone because it surface-applies nitrogen just 2-3 inches from corn roots on both sides. Consider the extreme 2013 growing season in eastern Iowa, where the 2012 drought left more residual nitrogen in the soil after harvest, and record heavy spring 2013 rains leached it out of the soil. Then the weather dried up, threatening potential take up of rescue nitrogen treatments.
“Split nitrogen application gives you a lot of options especially when weather is extreme,” Reeg says. “The risk of losing nitrogen increases when applying all of your nitrogen down before planting (whether spring or fall) in years such as 2013 where fields received leaching rainfall events. Sidedressing nitrogen also has risk if farmers are unable to apply because fields are too wet or we lack the moisture needed to deliver sidedressed nitrogen to the plant roots. The Y Drop system is a new option that may help farmers with these weather extremes. Because every farm and circumstance is different, there is no one-size-fits-all nitrogen answer.”
Insure N availability in extreme weather
The On-Farm Network evaluated a 2013 sidedress trial on one Eastern Iowa farm combining the Y Drop application of 70 pounds of UAN, close to the corn roots, on July 8, 2013 at the V18 crop stage. The four replications with the additional nitrogen responded consistently with an average yield increase of 39 bushels per acre compared to the grower’s normal nitrogen program with a base rate of 156 pounds of spring-applied nitrogen The field received above average rainfall with18.8 inches in April-June. That base nitrogen rate represents what you might get using an Iowa State University Maximum Return to Nitrogen calculator for this situation to maximize corn yield in a normal year.
“In such a wet spring (the wettest on record in 146 years of tracking rainfall), nitrogen loss and availability can be unpredictable,” Reeg says. “The flash drought of 2013 increased the complexity of nitrogen management. If it becomes overly dry later in the season, we worry about nitrogen availability of sidedressing nitrogen. That translates to nitrogen in place, but unavailable to the corn—that’s where the Y Drop system may prove its worth.” Ongoing replicated On-Farm Network trials in 2014 will test the approach further.
Summer rainfall following the 2013 On Farm Network sidedress application was 3.1 inches rain in July and 1.1 inches in August.
Conventional wisdom says fertilizer dribbled on the surface needs moisture to transport it to the root zone and the potential exists for nitrogen loss by volatilization. However, with this close placement, early results suggest that dew may provide sufficient moisture to move nitrogen the 2-3 inches from application site to roots, according to Y Drop research, and further third-party tests will vet that. But so far, moisture has not been an issue, says Dennis Holland, Pioneer product agronomist, who laid out the trials.
“Anyone who’s been soaked walking in a corn field on a July or August morning knows that dew amounts to quite a bit of moisture (that could move the nitrogen to the root zone),” Reeg adds. “When sidedressing is followed by limited or below-average rainfall, initial research suggests that the Y Drop system may provide some advantages over nitrogen applied with a coulter-injection system.”
Two studies reveal the promise of nitrogen-placement tool and later timing
Dupont Pioneer tested Y Drop sidedress placement and late-season sidedress timing in Eastern Iowa in 2012 and 2013.
Both the DuPont Pioneer and the On Farm Network trials appear to confirm early “cautious optimism” about this new way to manage in-season nitrogen rates, using new tools and timing.
The DuPont Pioneer 2012 and 2013 trials on the same farm had 7-10-bushel yield gains from the Y Drop application versus the conventional coulter applicator. They were sidedressed later in the season (stageV14), when corn needs nitrogen the most (see chart).
New sidedress approach increases yields by 7-10 bu.
2012, Carson Farms, Linn County, Iowa
All received base nitrogen of 140 units UAN banded preplant; then 40 units of UAN were broadcast with a sprayer preplant with an herbicide.
Treatment Field 1 ave Field 2 ave Details
Untreated 164 bu/ac 125 bu/ac 2 reps/location No sidedress (control)
SuperU 166 bu/ac 128 bu/ac 2 reps/location Broadcast at V8
Sidedress 167 bu/ac 132 bu/ac 3 reps/location Coulter sidedress at V4
Y Drop 177 bu/ac 139 bu/ac 3 reps/location Sidedressed with Y Drop at V14
Credit: Pioneer Product Agronomist Dennis Holland
Four different in-season nitrogen treatments focused on application timing, placement and nitrogen source. One pass of vertical tillage incorporated the preplant nitrogen before planting. This study was conducted in two long-term continuous-corn fields with conventional tillage.
Each treatment replicate was 60 feet wide (24, 30-inch rows) and 2,200 feet long.
The two bold rows above (Sidedress and Y Drop) received 70 pounds UAN solution sidedressed. The conventional treatment (Sidedress) was applied at V4 with a 60-foot sidedress bar with 30-inch coulter spacing at 4 inches deep between two corn rows.
The Y Drop treatment was applied at the V14 stage. This dribbles a nitrogen stream on both sides of corn plants next to their base. Especially important in 2012, the drought year: The Y Drop sidedresser delivered the nitrogen 2-3 inches from the corn root zone. This meant less reliance on root growth or soil moisture to connect the plant to the nutrients. Delivering nutrients immediately before the corn plant’s largest nitrogen-uptake and growth stage (see graph) is more efficient.
9-bu. gain from sidedressing later and placed near roots
Field & rotation Sidedress yield Y-Drop yield; 2013, Carson Farms, Linn County, Iowa
Field 1 – corn on corn 179 bu/ac 197 bu/ac
Field 2 – corn on soy 206 bu/ac 218 bu/ac
Field 3 – corn on soy 241 bu/ac 241 bu/ac
Field 4 – corn on corn 201 bu/ac 202 bu/ac
Field 5 – corn on corn 179 bu/ac 190 bu/ac
201 bu/acre 210 bu/acre
Credit: Pioneer Product Agronomist Dennis Holland
These results come from similar DuPont Pioneer research a year later, comparing conventional sidedress and Y-Drop-applied sidedress. Both use the same rate of UAN solution, but with different application timing and placement. Each of the five fields had treatment strips approximately 2,200 feet long. 24 rows were treated with sidedress nitrogen beside 24 rows treated with the Y Drop.
These studies, all with the same Linn County Iowa grower, demonstrate the potential of how different nitrogen sources, timing and placement can make nitrogen more effective.
Consider more than just nitrogen rate
Nitrogen rate is just one of the four stewardship Rs best practices (the right rate, right form, right time and right placement).
Nitrogen rate is vitally important, along with tools like split application and nitrogen sensors to fine-tune your rate as conditions unfold. New technologies that tweak timing and placement may improve nitrogen use efficiency.
The situation resembles your car-insurance rate, says Pat Reeg, On Farm Network director: “Just as your car-insurance premium rate is based on probabilities hinging on many variables (your age, gender, driving record, vehicle, etc), the correct nitrogen-management program should also consider probabilities based on validation of nitrogen products and practices. The On-Farm Network promotes an adaptive management approach within and across growing seasons providing growers flexibility in adjusting nitrogen management accordingly as weather conditions unfold.”
“Historically, late-season nitrogen applications haven’t always worked out because we lacked the rainfall to move it into the availability zone. The Y Drop system may be a promising tool to change this.”
When will we know if this really works?
While these early results from simple tweaks to conventional practices are exciting, it is still too soon to attribute consistent gain to a new sidedress application placement and timing
“I never recommend a one-size-fits-all approach for any practice,” says Pat Reeg, director of the Iowa Soybean Association On Farm Network. “We’ll conduct replications within and across sites to better understand the probabilities of products and practices from varying weather conditions and spatial variability within fields.” (All On Farm Network trials are replicated at least three times.)
“I’m intrigued by the Y-Drop placement and potential for improved nitrogen-use efficiency, especially when we do not receive rainfall after late-season nitrogen applications,” Reeg adds. “Because nitrogen that is not available and utilized by the corn plant does not provide a return on investment and becomes a water quality concern if moved out of the soil.
“In a broader sense, I encourage every farmer to identify what works best on his or her farm instead of repeating same thing each year on every acre, especially with tighter margins. To me, nitrogen placement and timing are two big variables worth exploring.”
The On-Farm Network is testing the Y-Drop system and Ag Leader OptRX crop sensor this year.