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Fluid Journal : Fluid Journal 1996-1998
Fall 1997 Summary: Corn yield increases of from 9 to 30 bu/A were obtained from treat- ments that increased the amount of available N in the NH4+ form to approx- imately 50 percent by applying a nitrifi- cation inhibitor (nitrapyrin or N-Serve) with ammonium forms of N fertilizer. These irrigated field experiments were conducted from 1983-86 in a calcareous soil low in organic matter (1.6%). _________________________________ The effectiveness with which N is used by corn is important because of the increasing costs of manufacture and distribution of N fertilizer. In the past 30 years the increase in corn yield has not been proportional in increased N use. A real need exists, therefore, to increase N fertilizer use efficiency by crops and to determine what soil and plant factors related to available N can limit crop productivity in given environments. Two forms of available N (ammonium, NH4+ and nitrate, NO3-) can be supplied to a crop by choosing N fertilizer forms and nitrification inhibitors. When used with ammonium sources of N, nitrification inhibitors result in NH4+ availability for an extended period of time, making it possible for corn to increase NH4+ uptake and possibly realize benefits of an enhanced NH4+ supply. In a normal sequence of events, N fertilizer is applied to the soil and NH4-N forms are rapidly nitrified to NO3-N, which is then the form of N mainly used by plants. This NO3- form also leaches readily and may be displaced from the root zone. Studies with nitrification inhibitors have been mainly designed to keep more N fertilizer in the slowly leachable NH4+ form, and thus conserve N for the crop. Corn and other crops can use both NH4-N and NO3-N. Studies have indicated that corn can grow better when supplied a mixture of NO3- and NH4+ than with NO3- alone. The result is more kernels per corn plant. Our objective in this study was to measure whether the supply of available N in various combinations of NH4+ and NO3- forms can affect corn yields. Our hypothesis was that a combined N supply of NH4+ and NO3- forms for corn would increase N use efficiency by the plant and increase corn yield compared with equal amounts of available N in either form alone. Response favorable As shown in Figure 1, irrigated corn yields increased when N-Serve was added to UAN. As can be seen, split applications of UAN were made in April, July, and August. Prior to this, preplant applications of P (100 lbs/A P2 O5) and K (200 lbs/A K2O) had been broadcast and disked in. Methodology Site. Field experiments were conducted in 1983, 1984, and 1986 in Fruita, Colorado. Soil. Soil at this site is a calcareous Youngston (formerly Ravola) fine sandy loam low in organic matter, and is a Typic Torrifluvents. Soil properties are shown in Table 1. Irrigation. At one site, level basins were established and irrigations produced no runoff. One experiment was conducted in 1986 outside the level basins. Usual farmer practices were followed with furrow irrigations. Runoff occurred. Water was applied as needed by ET measurements. Total water applied was 24 to 26 inches during the growing season in the level basins. Fertilizer. As already noted, P and K were broadcast preplant and incorporated by disking. Subsequent split applications of N were applied in the irrigation water in the level basins and within the furrows for a given treatment. The nitrification inhibitor, nitrapyrin or N-Serve, was Dr. Sterling Olsen, D.F. Champion, Dr. Calvin Pearson, Harold Golus Nitrification Inhibitor Boosts Corn Yields Colorado researchers combine UAN with nitrapyrin to increase amount of N available to plant in the NH4+ and NO3- forms.
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