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Fluid Journal : Winter 2011
lost to the air or water. Synchronizing the amount and timing of N availability with N requirements of the crop will reduce environmental losses of N while optimizing crop productivity. Therefore, N efficiency should be improved if N supply is closely matched with crop demand, both in terms of amount and timing of supply. One method of supplying N at a gradual rate is the use of controlled- release fertilizer products. Polymer- coated urea products are available that release N at a rate controlled by soil temperature. Efficiency of urea N use may also be improved by slowing the conversion of urea to ammonium and ammonium to nitrate. Urease inhibitors slow the conversion of urea to ammonium, while nitrification inhibitors slow the conversion of ammonium to nitrate. Producers may also choose the use of split applications of N to reduce the initial investment in N fertilizers in Summary: Field studies evaluated the effects of various enhanced efficiency nitrogen (N) fertilizers on spring wheat emergence, yield, and protein content as affected by soil type, slope position, and seeding date. Emergence of hard red spring wheat was not affected by fertilizer management, indicating no damage or benefit from the various fertilizer sources. Late seeding stand was higher than at early seeding at both the Phillips and Brandon locations and was higher on the upper slope than on the lower slope positions at the Brandon site. There was no consistent effect of slope position on biomass yield at either site. Cool conditions delayed emergence and early June frost may have reduced biomass production with the early seeding date. At the Phillips site, biomass yield tended to be higher at the upper slope position with early seeding but not with late seeding. The upper slope would be better- drained with somewhat warmer soil temperatures than the lower slope, therefore would perform better with early seeding than would the lower slope. Biomass yield at heading increased with N applications at both locations, but there were generally no benefits from use of enhanced efficiency fertilizers as compared to spring banding of the untreated urea. Split applications tended to produce lower yields than application of all N as an in-soil band at the time of seeding. Grain yield was higher with late seeding than early, which is in contrast to the normal pattern for this region and to the results observed in the first two years of the study. Grain yield with fall-banded control release urea (CRU) was similar to that of spring-banded urea, while fall-banded urea frequently produced lower yield than spring-banded urea, indicating that CRU could improve performance of fall-applied N. In addition to highest possible crop return per dollar, study also considered evaluation of environmental beneﬁts. A Look at the Economic Beneﬁts of Enhanced Efﬁciency Nitrogen Fertilizers The Fluid Journal • Ofﬁcial Journal of the Fluid Fertilizer Foundation • Winter 2011 • Vol. 19, No. 1, Issue #71 Drs. C. Grant, A. Moulin, and N. Tremblay It is essential that producers use N efficiently in order to attain the highest possible crop return per dollar invested in fertilizer. Excess N in agricultural systems can also have a major negative impact on environmental quality. During microbial conversion in the soil, N can release nitrous oxide, a gas with a greenhouse effect approximately 300 times that of carbon dioxide. Groundwater may also be polluted by nitrate leaching. In order to increase nitrogen use efficiency (NUE), one must reduce the amount of N lost to the air and water and increase the proportion used by the crop. Nitrogen is lost from the plant/soil system through four major pathways: volatilization, immobilization, denitrification, and leaching. Ammonia or ammonium-producing sources of N can be lost via volatilization. The longer N is present in the soil solution before the crop takes it up, the more risk there is of the N being environments where crop yield is highly variable. With this strategy, use of in-crop assessment of crop N status would be valuable to determine if the additional N was needed by the crop. A number of different systems are available for assessing in-crop N status. These include tissue N analysis and estimation of plant chlorophyll content using the SPAD meter or the GreenseekerTM. Benefits of CRU, urease or nitrification inhibitors, or split applications vary with environment. If soils are dry, N losses from denitrification and leaching will be low, reducing the potential benefit from split applications or CRU. However, split applications to reduce initial N investment could still reduce economic risk. If soils are wet, losses can be higher and potential benefit greater. Objectives of this study were to determine: • Economic benefits of using split N applications, CRU, or urease and nitrification inhibitors Winter 2011 The Fluid Journal 08
Early Spring 2011