Many of our current strategies for nutrient management on farms focus on how to manage nutrients only once they are a part of the farm. These strategies include running risk assessments for phosphorus (P) and nitrogen (N) loss in drainage [phosphorus index (NY-PI 2.0); nitrogen leaching index (NLI)], and erosion with RUSLE2, the Revised Universal Soil Loss Equation, ver. 2. These risk assessments are complemented by in-field nutrient management strategies such as cover/double cropping and manure injection/incorporation.
All of these practices play a critical role in mitigating nutrient loss from cropland, but what they all have in common is that they are reactionary – they’re only intended to manage nutrients once they are already on the farm. Unlike these more common nutrient management practices, a whole farm nutrient mass balance (NMB) is a tool that can account for all nutrient [P, N, and potassium (K)] imports and exports from the farm gate. Other states have developed their own tools, but the Nutrient Management Spear Program (NMSP) of Cornell University began collecting data in the early 2000s to develop a model specific to New York’s dairy farms. While the tool was developed with NY farm data, it should still be helpful and applicable to farms outside of NY. As with many nutrient management practices, adhering to the recommendations should result in both economic and environmental benefits.
The concept of the tool is relatively simple and works on an annual basis. Although there is some data to track down, the accounting is relatively simple: we just add up all of the nutrient imports (feed, fertilizer, etc.), followed by all the nutrient exports (milk, crops, etc.), then find the difference, or net balance, by subtracting the imports from the exports (see figure). This balance can then be expressed per tillable acre or per hundredweight (cwt) of milk to reflect the efficiency of nutrient usage in crop production and milk production, respectively. Not only will the results show what types of balances your farm currently has, but you can also see how your balance compares to anonymized data from dairy farms across New York state. Although one year’s balance won’t provide enough information to begin making major decisions, it can provide a snapshot of your current status, and continuing to accumulate balances each year will provide valuable insights into the stability and sustainability of your farm’s current nutrient management strategies.
If you’re interested in developing a whole farm NMB, Cornell University has a number of resources to get you started. The easiest places to start would be at the main webpage for the NMSP team’s nutrient mass balance research, which has plenty of background material and testimonials from farmers who have participated in the program. Detailed information on the steps for developing a NMB and links to the software can also be found in Cornell’s Agronomy Fact Sheet series (Fact Sheet #25: http://nmsp.cals.cornell.edu/NYOnFarmResearchPartnership/MassBalances.html). Check back in next month when I’ll delve deeper into the tool and the types of results and insights the tool can provide.
— Laura Klaiber