It’s always great when we see others out there sharing the importance of agriculture, and in this instance – helping to tell our Sustaining Innovation message that Nebraska farmers are growing more corn using less resources!
Recently the United States Department of Agriculture (USDA) released a report on fertilizer use and prices for corn across the US. This report is the result of the Agricultural Resource Management Survey (ARMS) jointly conducted in 2010 by the USDA Economic Research Service (ERS) and USDA National Agricultural Statistics Service (NASS). ARMS data used to be collected annually for corn, but has been collected less frequently since 2001.The last ARMS data for corn prior to 2010 was in 2005. This information, coupled with data on crop production in Nebraska from the Nebraska State Agricultural Statistic Service, provides an opportunity to explore how efficiently Nebraska farmers are using nitrogen (N) fertilizer for corn production.
Figure 1 illustrates the average N rate for corn in Nebraska as reported in ARMS data. This illustrates that the average rate of N fertilizer has remained basically unchanged for the past 40 years – around 140 lb N/acre. At the same time, corn production has seen a steady, linear increase in Nebraska over the same period (Figure 2).
When these two datasets are combined, the resulting trend in nitrogen use efficiency, expressed as pounds of N fertilizer applied to produce a bushel of corn, is illustrated in Figure 3.
In 2010, this value was 0.84 lb fertilizer N per bushel of corn. This compares to an average value of 1.5 to 1.6 lb fertilizer N per bushel of corn in the 1970s – about twice the N fertilizer currently used per bushel. This data does not indicate that a bushel of corn requires only 0.84 lb N. There are other sources of N besides fertilizer available to the crop – mineralized soil organic matter, residual nitrate from previous fertilization, legume and manure credits, for example – which contribute to the total N need for a corn crop of 1.1 – 1.2 lb N/bu. This data does indicate that Nebraska farmers are using nitrogen fertilizer much more efficiently now than they were 30-40 years ago.
They accomplish this using a wide range of practices – accounting for all sources of N available to the crop besides N fertilizer, as indicated above, as well as efficiency-boosting practices such as sidedressing, fertigation, use of nitrification and urease inhibitors, use of slow release formulations, setting realistic yield goals, and efficient irrigation management.
University of Nebraska-Lincoln (UNL) guidelines on fertilizer use are available in the publication Fertilizer Suggestions for Corn (EC 117). Specific recommendations for fields using soil test information and cropping history can be calculated using the web resource SoilTest Nebraska (soiltest.unl.edu). Since 2005, UNL has provided economic adjustments to N fertilizer recommendations based on the relationship of crop and fertilizer N prices.
Figure 4 illustrates trends in the ratio of corn to N price over the past 50 years. The peak in this relationship occurred in the 1970’s, when fertilizer was quite inexpensive compared to the price of corn. In 2010, even though fertilizer prices seemed high, the value of the crop – on average – was even higher, resulting in a price ratio of 17:1. To avoid either deficient or excessive rates of N application, the price ratio range in UNL N recommendations for corn is confined between 4:1 and 10:1. To optimize profit, producers will want to use economic factors specific to their own situation; in general 2011 N rates should have been slightly higher than in recent years.
References: Richard B. Ferguson, UNL Extension Soils Specialist and UNL CropWatch