Economic Analysis of Nitrogen Sources and Placement Methods in No-Tillage Corn

No-tillage production reduces the effects of declining soil productivity and water quality where severe erosion is a concern. Proposed federal environmental regulations may restrict N fertilizer applications, thereby reducing no-tillage yields. Soil injected N is more effective than broadcast N, although costs of labor, equipment, and energy are higher for injection than for broadcasting. This study compares the levels of N required to achieve specified no-tillage corn (Zea mays L.) yields from injection vs. broadcast applications. The costs of achieving the specified yields also are compared. Data from field experiments conducted at the Milan, TN, Experiment Station in 1983, 1984, and 1985 are used to estimate corn yield response functions for injected and surface applied N. Results suggest that injecting requires 31% to 59% less N per acre than broadcasting to achieve average field experiment yields for 1983, 1984, and 1985. Even though machinery and labor costs are higher, costs of achieving 1983, 1984, and 1985 average experimental yields are $12, $8.76, and $9.63/acre lower for injecting urea-ammonium nitrate (UAN) than for the least costly broadcastalternative. Similar reductions in cost for injected anhydrous ammonia (AA) compared with the least costly broadcastalternative are $16.99, $15.50, and$16.16/acre for 1983, 1984, and 1985, respectively. Results suggest that achieving average experimental yields through injection rather than broadcasting can reduce N use by at least 30% while reducing costs of fertilizer N and its application by as much as 50%. Research QuestionProposed federal regulations may restrict the application of N to reduce detrimental environmental effects. Soil injection of N sources has improved the effectiveness of N relative to broadcasting. Machinery, labor, and energy costs of injection are higher than broadcast costs because of increased application time and more expensive equipment. An evaluation of the economic tradeoffs between the costs of injection and broadcasting to achieve specific no-tillage corn yields is important in determining whether the higher machinery, labor, and energy costs of injection are offset by the reduced cost of fertilizer N. Literature SummaryBroadcast fertilizers remain on the soil surface for no-tillage systems reducing the effectiveness of certain N sources. Soil injection applications have improved the effectiveness of urea-containing materials relative to surface broadcasting. Injection of N sources is a potential method of reducing the use of N by increasing the efficiency of fertilizer N, while maintaining or even increasing economic returns. Information is limited on the economic tradeoffs of injection vs. surface application methods on no-tillage corn. Study DescriptionThis study evaluates injection of fertilizer N, as opposed to broadcasting, as a method of reducing N use to achieve specific yields. The costs of injection and broadcasting are also compared to see if the higher machinery, labor, and energy costs of injection are offset by the reduced cost of fertilizer N relative to broadcasting. Data were obtained from a 3-yr field experiment that began in 1983 and ended in 1985 at Milan, TN, on a Memphis silt loam soil. The experimental design allowed the evaluation of N sources, N rates, and application methods for notillage corn production. Zero, 50, 100, 150, and 200 lb N/acre were applied after planting. Sources of N were ammonium nitrate (AN), urea-ammonium nitrate (UAN), urea, urea-urea phosphate (UUP), and anhydrous ammonia (AA). AN, urea, UAN, and UUP were broadcast; urea, UAN, and UUP were surface banded; and urea, UAN, and AA were injected. A wheat cover crop preceded no-tillage corn production each year. Weather conditions at the Milan Experiment Station in 1983 were poor, while in 1984 precipitation was excellent. In 1985, precipitation was about average. Average yields across all treatments were 55 bu/acre, 116 bu/acre, and 95 bu/acre for 1983, 1984, and 1985, respectively. Because Tennessee corn yields have not changed appreciably since 1984 and the same application methods are used, these data are still applicable in defining cost-efficient N sources and application methods. A yield response function was estimated by regression. That response function was used to calculate the levels of N required to achieve 15% less than average, average, and 15% greater than average no-tillage corn yields across all experimental treatments for 1983, 1984, and 1985. Those specific yields were chosen because they are consistent with the data used to estimate the yield response functions. No presumption was made that farmers actually target those yields. Costs of applying the amounts of N required to achieve those yields were also calculated. Applied QuestionsHow much less N is required for injection than for broadcasting to achieve specific yields? Table 1 contains the estimated amounts of N required to achieve 1983, 1984, and 1985 average experimental no-tillage corn yields with various N sources and application methods. Results indicate that N rates can be reduced within the range of 43% to 59% by injecting urea, UAN, or AA rather than surface applying urea, UAN, or UUP. Estimated reductions in N rates are lower when comparing surface application of AN with injection of urea, UAN, or AA, ranging from 31% to 43%. Thus, substantial reductions in N rates can be achieved from injection compared with broadcasting N, without reducing yields. Do the higher machinery, labor, and energy costs of injection relative to surface application offset the reduced cost of fertilizer N? The major cost of applying any of the N sources is the cost of fertilizer N. Machinery, labor, and energy costs are small in comparison. For example, the total cost of achieving the 1983 average yield of 55 bdacre by broadcasting urea is estimated to be $32.83. The cost of urea ($31.52) constitutes 96% of the total cost of broadcasting urea. In contrast, the cost of AA constitutes only 63% of the total cost of injecting AA because machinery and labor costs are higher than for broadcasting urea, the price of AA is lower than the price of urea, and 59% less N is required to achieve a yield of 55 bdacre. Results indicate a reduction in the total cost of applying N between $9/acre (29% reduction for 1984) and $12/acre (41% reduction for 1983) by injecting UAN rather than applying the least costly broadcast alternative (AN for the 1983 finction and urea for the 1984 and 1985 functions). When comparing injected AA with the least costly broadcast alternative, differences in total cost are even more pronounced. Total costs are reduced by about $16/acre giving percentage reductions in total costs of 58%, 51%, and 53% for 1983, 1984, and 1985, respectively. These findings suggest profits can be substantially increased or economic losses reduced by injecting rather than broadcasting N to achieve these specified yields. However, higher costs related to timeliness and safety should be weighed against the potential benefits of injection before deciding on the source and method of N application. Table 1Estimated N rates required to achieve 1983,1984, and 1985 average experimental netillage corn yields, Milan, TN, Experiment Station. 198355 bulacre19841116 bulacre198595 bulacreAuulication method and N sourceN rateDiff†% DiffN rateDifft% DiffNrateDifft% Diff----------lb/acre---------------------lb/acre---------------------lb/acre-----------Surface applied urea, UAN, or UUP153−90−59140−60−43142−64−45Surface applied AN111−48−43116−36−31116−38−33Iniected urea, UAN, or AA63----80----78----†Reduction in the N rate to achieve the respective yield by injection rather than surface application.