Indian Creek Demonstrations: Practical Ways to Monitor and Promote Efficient N Management On the Farm.

As farmers and their advisers adjust nutrient management practices in order to reduce the loss of nutrients from crop production fields, it is critical to have some means of measuring the change that results.  Sampling the drainage water flowing from the fields is one approach, but it is expensive, and it is often impossible to know where the water being monitored is actually coming from.  For a series of demonstration projects for the Conservation Technology Information Center’s Indian Creek Watershed Project in Livingston County, Illinois, we have developed an alternative method to estimate effects of practice changes on nutrient use efficiency (NUE), which can guide N management to reduce losses. The first step is to establish a set of nutrient rate trials within the “old” and “new” management practices.  Each trial should have N rates from 0 to some level above the recommend N rate for the field.  A range such as 0 to 240 lb N per acre will work for most Midwest corn fields.  It is important to include the 0 rate (no N applied) for the NUE calculations.  In addition to traditional small plot trials, we have also developed a system that allows farmers to implement the NUE plots using their normal field equipment for application and harvest, without interfering with normal field operations. The plots are set up on a data card in a variable-rate controller system on the fertilizer applicator. The plots are laid out automatically without interfering with the normal field operations, and requiring no physical measuring or staking of plots.  The plots are harvested with a combine equipped with a yield monitor, without any interference with normal harvest, and the plot yield data can be extracted later for analysis. The data can be analyzed using the Crop Nutrient Response Tool developed by the International Plant Nutrition Institute (IPNI).  This Excel spreadsheet calculates various nutrient use efficiency parameters to help determine the agronomic, economic, and environmental comparison of the practices being evaluated. The NUE Plots and NUE Analysis do not measure the impact on water quality directly, but the most efficient rate of nutrient (MERN) value that is computed gives a direct measure of the proper nutrient rate for the field.  Based upon this information, future application rates can be adjusted up or down as indicated to improve NUE and reduce the potential for nutrient loss in the future.  The calculation also provides an economic analysis to guide the farmer and his advisers in nutrient management decisions.  To carry the concept to the watershed impact potential requires some assumptions regarding the current practices of all farmers in the watershed, and their ability to implement changes on the larger scale.  Using GIS analysis to extrapolate the results for the respective NUE plots to the whole farm, or even the entire watershed, would result in an estimate of the impact of applying the improved BMP system to that area, and the potential savings to farmers based upon real data from their farms, plus we can estimate the potential reduction in nutrient loss to the environment.