Nutrient mass balances help weigh farm options

Authors: Young, Eric

Submitted to: Journal of Nutrient Management
Publication Type: Trade Journal
Publication Acceptance Date: 12/15/2020
Publication Date: 6/1/2021
Citation: Young, E.O. 2021. Nutrient mass balances help weigh farm options. Journal of Nutrient Management. May 1, 2021. Pg. 10-11.

Interpretive Summary:

Technical Abstract: Nutrient management decisions are important considerations on Upper Midwest dairy farms of all sizes given the expense and risk associated with applying fertilizer and manure in cold climates that have high seasonal loss potential. One of the more critical agri-environmental factors affecting dairy farms is the amount and distribution of their cropland base. More specifically, the fraction of total cropland that can viably receive livestock manure relative to the total number of animals fed from the same land is a useful measure of relative land sufficiency and environmental risk. Similarly, a farm nutrient mass balance (NMB) is a broad farm-scale estimate of the difference between nutrient imports (coming onto and off the farm in the form of purchased feeds/fertilizers) and exports (products sold off the farm as milk, meat, crops, manure/compost) and offers more detailed information on overall farm nutrient efficiency. Research at Cornell University has established farm level nutrient mass balance (NMB) guidelines for nitrogen (N), phosphorus (P), and potassium (K) based on animal and crop nutrient optima aimed at maximizing crop and animal nutrient use efficiency. Moderate, positive farm-level N-P-K balances are suggested since large values indicate nutrient enrichment (less efficient) and low to negative values indicate under-fertilization over time. Farm NMBs can also be expressed per hundred weight of milk (cwt), which helps to standardize any given farm’s economic/environmental performance compared to a range of other farms. While NMBs should not be used as an nutrient loss risk indicator, if done consistently, they can be another important precision nutrient management tool to identify farm nutrient inefficiencies.