Part 1. What farmers need to know.
Karl Czymmek, Senior Extension Associate, ProDairy, Cornell University and Dr. Quirine Ketterings, Professor of Crop & Soil Science, Cornell University
In the past 20 years, more than 600 dairy and livestock farms in NY have come under regulations and invested millions in best management practices. Annual fertilizer phosphorus purchases have been cut substantially and many dairies have made large reductions in phosphorus (P) fed to cows which reduces P in manure. Many other farms have made environmental improvements through state programs and their own initiative as well. Combined, these changes have resulted in millions of pounds less P applied to land annually and as a result, soil test P across NY is no longer increasing. Yet, in spite of the improvements, we have seen an increase in occurrences of Harmful Algal Blooms (HABs) in NY, a trend that is also being experienced across the US and around the world. No one is certain exactly what is going on. It is likely there are multiple causes. What we do know is that in the 60’s, 70’s and 80’s, phosphorus tended to accumulate in the environment resulting in “legacy phosphorus” in fields, stream banks and beds, and in lakes. We also know that annual rainfall is increasing, and storms have been getting more intense. More rain means more runoff and more runoff means more nutrient loss. It appears that some aspects of water quality have gotten worse, though many farmers have made significant improvements over the past decades. This tells us we have more work to do. The NY P Index (NY-PI) sits at the heart of this issue and is designed to help farmers implement practices related to manure and fertilizer phosphorus management that reduce the risk of phosphorus loss from fields and farms.
The first NY-PI was released in 2001 and like many things 18 years old, was in need of change. The updated version (NY-PI 2.0) incorporates new science and does a better job of addressing phosphorus loss risk while still giving farm managers options for recycling manure nutrients on crop fields. The process of updating the NY-PI was a broad partnership among faculty and staff in the Nutrient Management Spear Program (NMSP), PRO-DAIRY, and the Department of Biological and Environmental Engineering at Cornell University, along with NY Departments of Agriculture (NYSDAM) and Environmental Conservation (NYSDEC), and the Natural Resources Conservation Service (NRCS). Feedback from certified nutrient management planners and farmers was sought multiple times along the way.
The team tested the new NY-PI with field information from more than 300 NY farms across 40 counties, representing more than 33,000 fields. Some important facts: 90 percent of the fields had a Cornell Morgan soil test P (STP) below 40 pounds per acre, where additional P is recommended for crop growth. Fields with extremely high STP levels, represented by only a small fraction of the fields in the database, are a result of many years, in many cases, decades ago, where phosphorus loads to fields exceeded crop phosphorus removal. In a separate assessment of 18 dairy farms for which whole farm data were available, analysis showed that almost all fields on these farms were able to receive manure, though many fields needed some combination of risk reduction practices. Next month, we will explore how the P index works.
Part 2: How the P index works.
Karl Czymmek, Senior Extension Associate, ProDairy, Cornell University and Dr. Quirine Ketterings, Professor of Crop & Soil Science, Cornell University
In the December eLeader Newsletter, we introduced the new NY Phosphorus Index (NY-PI) and provided some background. Farms that are regulated as concentrated animal feeding operations (CAFOs) will need to start using the new NY-PI 2.0 when the CAFO Permit is updated (current permits are due to be renewed in 2022). Farms that are in state or federal cost share programs will need to use the tool based on NRCS determination. Agency discussions are in progress to make sure the roll-out is as smooth as possible.
Here is how it works: a farm field is rated based on an assessment of its runoff risk-related transport features, including those observed directly during a field visit and others from normal soil survey information (most of these factors are the same as those used in the old NY-PI). For example, being close to a stream or watercourse, poorly drained soil, or higher levels of soil erosion are some of the risk factors that can lead to a high transport score. For fields with a high transport score, manure and phosphorus fertilizer application practices can be selected to reduce the risk of phosphorus loss. These best/beneficial field management practices (BMPs) cover a combination of changes in application timing (close to planting) and method (placing phosphorus below the soil surface), and more vegetation on the soil surface when phosphorus is applied. Thus, implementation of BMPs will reduce the final NY-PI score. Field practices include manure and fertilizer spreading setbacks, ground cover (sod or cover crops), and placing manure below the soil surface (injection or incorporation). Combined with information about soil test phosphorus levels, the final NY-PI score results in a management implication: if risk is classified as low or medium, manure may be used at N-based rates; if classified as high, manure rate is limited to expected phosphorus uptake by the crop, and if very high, in most cases, no manure or phosphorus fertilizer may be applied. This transport × BMP approach is shown in Figure 1.
Coefficients were set for the new NY-PI using a database of more than 33,000 New York farm fields supplied by certified nutrient management planners and a second dataset that included data for PI assessment and whole farm nutrient mass balance assessments for 18 New York AFO and CAFO farms. While some farm fields had to have manure diverted, in almost all situations, the NY-PI 2.0 provided a pathway for farms with an adequate land base to both reduce risk and apply the manure generated from their herd. Stay tuned for documentation and software tools to help with implementation of the new NY-PI.