Figure 1. Planter surface dribbling nitrogen in a dual band, on either side of the seed furrowVolatilization risk increases when surface dribbling nitrogen, although subsurface banding and dribbling yielded similarly in these trials.
Dual banding nitrogen did increase yield in these trials as compared to single banding.
Planter applied N can reduce risk of nutrient loss, but applications could be impacted by weather.
Introduction
Nitrogen (N) is an essential nutrient in corn production. Corn needs a high amount of nitrogen to support plant growth and development. Nitrogen is a component of amino acids and enzymes that support a variety of plant essential functions. Insufficient nitrogen can severely impact crop yields. A well-designed nitrogen plan will supply enough nitrogen to support crop growth demand without applying excess that could potentially be lost. Splitting up application timings can help ensure enough nitrogen is available at times of rapid crop growth and help prevent excess nitrogen from being lost to leaching. One way to accomplish this is by applying a portion of the total nitrogen with the planter.
At Planting Nitrogen Placement Trial
Agronomy in Action Research trials were established at nine Midwest locations to determine if at-planting nitrogen applications increase yield potential, and if so, does the response vary based on placement. Fifty pounds per acre of urea ammonium nitrate (UAN) nitrogen was applied 2-inches to one or both sides of the seed furrow as a surface dribbled (Figure 1) or sub-surface band (1-2-inch depth) application with the planter. Individual treatments of incremental nitrogen applications were compared against the base pre-plant nitrogen rates applied across the entire trial, which varied by local farmer.
Leaf chlorophyl measurements were taken at R1 from the ear leaf of the dual-banded subsurface treatment and check plots to identify trial locations that were deficient in nitrogen. Chlorophyll measurements were taken using an at LEAF® CHL PLUS chlorophyll meter which allows noninvasive quantification of plant chlorophyll content.
Trial Results
Chlorophyll readings were higher in plots receiving incremental nitrogen than plots with base nitrogen rate at eight of nine trial locations, indicating most of the locations had the potential to respond to nitrogen. Of the eight sites, chlorophyll readings were significantly higher than check plots at the Malta, IL location, indicating it had the highest likelihood of increased yield with incremental nitrogen (Graph 1). Yield data from individual locations was used to identify sites more responsive to nitrogen to understand if N placement differences exist. Statistical yield increases from one or more nitrogen treatments was observed at Clinton, IL, Malta, IL, Janesville, WI, Grundy Center, IA, and Bridgewater, SD. Results were averaged across these locations to look for differences amongst treatments (Graph 2). When averaging across N responsive sites, significant yield increases were observed with all nitrogen treatments compared to the no extra nitrogen treatment. In general, dual banded nitrogen applications increased yields more than single banded applications but the response was
Graph 2. Yield effect of placement at nitrogen responsive sites.
Graph 3. Yield effect of placement at sites less responsive to nitrogen.more significant (7.3 bu/ac) within surface dribbled treatments. When averaged across locations that did not have a significant response to incremental nitrogen, N placement had no effect on yield (Graph 3).
Summary and Conclusion
Banding fertilizer has been found to greatly increase the amount of nitrogen taken up by the plant in comparison to broadcast applications.1 Surface applied nitrogen fertilizer is much more dependent on rainfall to move it into the rooting zone and more vulnerable to volatilization than soil incorporated nitrogen. Due to this, previous trials have found that nitrogen uptake is greater with subsurface banding than when dribbling on the surface.1 Cooler temperatures and timely rainfall which incorporated surface dribbled nitrogen into the soil at these locations resulted in minimal volatilization even though surface dribbling would normally have a higher risk of loss. Previous research has not shown significant differences in plant nitrogen uptake when applying as a single or dual band on both sides of the row.1 Yield advantages from dual banding in our trial was likely not related to volatilization since dual banded surface dribble and subsurface banded nitrogen treatments were similar. Potentially, the response to dual banding was a result of how nitrogen dispersed more evenly throughout the soil rooting zone resulting in more efficient uptake. Additional trials would need to be done to know how repeatable this dual banding response is.
Nitrogen applied at planting requires additional planter setups and can slow down planting to refill tanks. Nitrogen placement is important as high salt concentration in proximity of the seed may affect germination. Moving the applied band of nitrogen two or more inches away from the furrow can resolve this issue. Soil type should also be taken into consideration as nitrogen can more easily move into proximity of the seed in sandy soils. Shifting nitrogen applications away from fall or spring preplant timings to planting and in-season side dress timings can reduce some of the risk of loss of N to the environment, but weather conditions can limit in season applications. Wet weather could delay applications beyond optimal timing or prevent application entirely in severe instances. Risks of in-season application should be weighed against the total number of acres to cover to determine feasibility of split nitrogen application programs.
Reference:
1Griesheim, K., R., Mulvaney, T. Smith and A. Hertzberger. 2023. Nitrogen-15 evaluation of fertilizer placement at planting for corn production. Soil Science Society of America Journal, vol. 87, issue 2, pp. 309-323
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