New York state, regional and county level nitrogen and phosphorus balances for harvested cropland

Olivia Godber¹, Kirsten Workman^1,2, Kristan Reed³, and Quirine Ketterings¹

¹Nutrient Management Spear Program, ²PRODAIRY, ³Department of Animal Science, Cornell University, Ithaca, NY 14853

Introduction

New York (NY) state is one of five states that collectively produce more than 50% of the annual milk supply within the United States. The local environment allows farmers to integrate crop and livestock systems, facilitating cycling of manure nutrients back to cropland. Thus, dairy farming provides NY with benefits, opportunities, and challenges in terms of environmental sustainability and climate resiliency. Improved balancing of crop needs for nitrogen (N) and phosphorus (P) with supply from manure is key for a circular agricultural economy. The objectives of this study were to calculate and evaluate (1) regional and county level N and P balances of harvested cropland; and (2) the contribution of manure to a circular agricultural economy for NY.

Nutrient balances were calculated for 2017 (most recent USDA Census of Agriculture year at the time) as the difference in nutrient inputs through purchased fertilizer and recoverable manure, and nutrients removed in harvested crops. Atmospheric N deposition, legume N fixation, and manure nutrient losses during collection, transfer, storage, and treatment were also estimated.

Key Findings!

The 2017 NY State P balance was 9 lbs P/acre. The N balance was between 35 and 85 lbs N/acre, depending on the proportion of legume cropland assumed to have received manure (Figure 1).

2 bar graphs with a key. — **Figure 1:** Breakdown of the inputs and crop removal of (A) phosphorus (P), and (B) nitrogen (N) at the New York state level in 2017. Estimated N losses of manure N during storage through volatilization and denitrification are identified.

For P balances at the regional level, a small range of 5 to 10 lbs P/acre was seen (Figure 2). Chemung County was the only county with a negative balance (-3 lbs P/acre).

Image of New York State sectioned off by region. Each region has a corresponding small bar graph indicating phosphorus input and crop phosphorus uptake. A few counties in gray are excluded. — **Figure 2:** Breakdown of phosphorus (P) inputs and crop P uptake at the regional level, and P balance at county and regional level for New York in 2017; counties in gray were excluded.

For N balances at the regional level, a small range of N balances from 17 to 41 lbs N/acre was seen (Figure 3A) when balances were calculated assuming that manure and purchased fertilizer N were applied to all cropland, and no N fixation occurred. Under the assumption that no manure or purchased N fertilizer was applied to legume cropland, and additional N inputs were included as a result of N fixation on legume cropland, a higher but still small range in N balances from 60 to 94 lbs N/acre was seen (Figure 3B). Under both assumptions the balances were calculated before storage and application losses of N.

Redistribution and application of manure to meet P-removal on only the non-legume cropland left a surplus of 3 lbs P/acre at the NY state level. Applying surplus manure to legume and non-legume cropland resulted in a slight, state-level, P deficit. In both scenarios, the large N deficit that cannot be met through legume N fixation alone indicates N fertilizer is required to meet crop needs under the reported yield and manure supply conditions. These results show NY’s ability to capitalize on the value of manure.

Two maps of the state of New York, sectioned off by region, with excluded counties colored in gray. Each map has small bar graphs corresponding with each region indicating the nitrogen input and crop uptake of nitrogen of the region. The map on top includes manure and purchased nitrogen being applied to all cropland, whereas the one on the bottom refers to non-legume cropland only. The maps are each purple. — **Figure 3:** Breakdown of nitrogen (N) inputs and crop N uptake at the regional level, and N balance at county and regional level for New York in 2017, assuming manure and purchased N was applied to **(A)** all cropland (assumes no legume N fixation) versus **(B)** non-legume cropland only (assumes legumes received N through fixation). Counties in gray were excluded.

Manure has value to cropland beyond N and P and consideration of these factors at the field level, in combination with field management history and soil test results, could help to prioritize where manure should be applied, and where purchased N and P inputs are required. Development and adoption of advanced manure treatment, storage, and application practices, with consideration of how livestock feeding practices can influence manure characteristics, could all help to further improve the value of manure, improve balances, and increase circularity and sustainability of the agricultural sector in NY.

Next Steps?

As updated manure excretion rates and the amount of nutrients lost during storage and application of manure become available, combined with an expected continuation in the upward trend of both cow numbers and milk production for NY, it will be important to continue assessments of nutrient balances and animal densities, and explore manure treatment options to allow for transport of manure nutrient throughout NY to avoid creating nutrient “hotspots” within the state. With the recent release of the 2022 USDA Census of Agriculture data, we aim to evaluate these scenarios in more detail for the 2022 state balances.

Full Citation

This article is summarized from our peer-reviewed publication: Godber O.F., Workman K., Reed K., and Ketterings Q.M. (2024) New York state, regional and county level nitrogen and phosphorus balances for harvested cropland. Frontiers in Sustainability 5:1352296. https://www.frontiersin.org/journals/sustainability/articles/10.3389/frsus.2024.1352296/full.

Acknowledgements

This research is funded primarily by a gift from Chobani, in addition to Federal Formula Funds and grants from the New York State Department of Agriculture and Markets (NYSAGM) and New York State Department of Environmental Conservation (NYDEC). For questions about these results, contact Quirine M. Ketterings at qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.