Month: June 2022

Farmers Produce More Milk with Less Phosphorus and Nitrogen!

Olivia Godber1, Mart Ros1, Agustin Olivo1, Kristan Reed2, Mike van Amburgh2, Kirsten Workman1,3, and Quirine Ketterings1

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

The Cornell whole farm nutrient mass balance (NMB) is an assessment tool that farms can use to calculate their nitrogen (N), phosphorus (P) and potassium (K) use efficiency at the farm level. By calculating the difference in the amount of nutrients imported into and exported out of the farm in a given calendar year, the amount of nutrients remaining on the farm or lost to the environment can be estimated (Figure 1).

Figure 1: A whole farm nutrient mass balance is derived by subtracting exports of nutrients in milk, animals leaving the farm, crops sold, and manure exported from nutrients imported with feed, fertilizer, animals, and bedding/manure/food waste, and dividing this difference by the total acreage of the farm (balance per acre) and by the total amount of milk produced (balance per cwt).

The balance per acre indicates how well the farm is putting nutrients to use on the farm, and the risk of losing nutrients to the environment. The balance per cwt milk indicates how efficiently the farm is using nutrients to produce milk. A positive P and K balance indicates soil buildup and potential losses for those nutrients over time. Nitrogen is more difficult to retain from one year to the next so a large portion of the N balance will be lost to the environment. Negative balances are undesirable as that can lead to yield losses and soil mining of P and K. Feasible balances were set for New York, Table 1: Feasible balances for New York dairy farms. Whole Farm Nutrient Mass Balances (lb/acre) (lb/cwt) Nitrogen 0-105 0-0.88 Phosphorus 0-12 0-0.11 Potassium 0-37 0-0.30based on data from 102 dairy farms (Table 1). Feasible limits are positive (>0) to account for unavoidable losses, inevitable in all biological systems.

The ideal situation is for a farm to fall within the optimal operational zone (or “Green Box”; Figure 2). A farm falls within the Green Box when both the balance per acre, and the balance per cwt of milk are within the feasible limits. When this is the case, there is a lower risk of losing nutrients to the environment, greater nutrient use efficiency, and being within the Green Box can have both economic and environmental gains for the farm.

Key drivers of excessive balances include animal density, the proportion of feed produced on the farm, feed use efficiency, and fertilizer use. Fine-tuning fertilizer use and the amount of crude protein (CP) and P in animal feed, as well as increasing the production of homegrown feed, can help to improve balances. When animal density increases above one animal unit (AU) per acre (where 1 AU = 1000 lb; a cow and her replacement is roughly two animal units), manure exports become increasingly important to meet the feasible balances, especially for P.

scatter plot of results
Figure 2: The “Green Box” signals farms that meet the feasible balances per acre (blue zone) and per cwt (yellow zone). Grey dots represent farms across New York that participated in the whole farm nutrient mass balance (NMB) assessment (2003-2021).

The Good News!

There has been great progress in the reduction of P balances of New York dairy farms. Farmers who conducted the NMB assessment in 2017-2019 had balances of 0.07 lb P/cwt (Table 2). Farms in the assessment in 2005-2007, had balances of 0.11 lb P/cwt. This shows tremendous improvement in P use efficiency while the P balance per acre only slightly increased (0.1 lb P/acre) and still below the feasible balance of 12 lb P/acre established for New York.

Dairy farms participating in whole-farm nutrient mass balance assessments in recent years: • Produced over 50% more milk per acre than farms participating in earlier years; • Produced this milk with a 36% improvement in phosphorus use efficiency; • Fed diets with a lower crude protein content, improving nitrogen efficiency; • Are actively engaged in identifying more opportunities for improvement in nitrogen efficiency.Did farmers give up milk? No! The average milk production per acre was 9,500 lb/acre in 2005-2007 (0.81 AU/acre), compared to 14,900 lb/acre in 2017-2019 (1.10 AU/acre). Overall, farms participating in 2017-2019 produced more milk, on less land, with no major change in the environmental impact (in terms of P) compared to farms participating in 2005-2007.

For N, the balance per cwt decreased from 0.89 to 0.82 lb N/cwt (CP of the diet went from 16.1% to 15.5%). The footprint per acre increased by 26 lb N/acre, reflecting both the higher animal density, and increased N fertilizer use of the farms in the 2017-2019 dataset. However, if no progress had been made in N management, particularly the lower CP content of the diets and increased milk yields, the increase in animal density of the more recent summary would have placed the farms even further outside of the Green Box for lb N/acre (closer to 128 lb N/acre, based on the performance of the farms in 2005-2007). Thus, for N this is also a good news story, but continued effort in management of N imports, exports and efficiency of use is needed for the N balance to be within the Green Box.

Next Steps?

It is clear from the data collected by the farmers in these NMB assessments that there has been tremendous progress in lowering the amount of N and P used to produce milk by dairy farmers in New York. Future work should focus on further reducing the CP content of cow diets without compromising performance, and optimizing manure storage and land application systems (e.g. timing, injection or incorporation) to minimize N losses from manure and reduce the reliance on fertilizer imports. For higher density farms, exploring options for cost-effective manure export should also be a focus. Improving N management on the farm will not only have the potential to improve N balances and farm economics, but also reduce nitrous oxide (N­2O) emissions, a potent greenhouse gas.

Acknowledgements

We thank the farmers and farm advisors as well as many past and current NMSP team members who worked on the whole farm nutrient mass balance project with us over the past 15+ years. This research is funded primarily by a gift from Chobani, in addition to Federal Formula Funds, and grants from the Northern New York Agriculture Development Program (NNYADP), Northeast Region Sustainable Agriculture and Education (NESARE), 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/.

Homegrown Feed for Dairy Farms in New York

Olivia Godber1, Mart Ros1, Agustin Olivo1, Kristan Reed2, Mike van Amburgh2, Kirsten Workman1,3, and Quirine Ketterings1

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

Introduction

Between 2017 and 2019, 110 New York dairy farms completed their whole farm nutrient mass balance assessment. Of the feed fed to the animals on the farms, almost 70% was homegrown, which means it was produced on the land-base operated by the farm itself (Figure 1a). Almost all this homegrown feed was forages such as corn silage, alfalfa, and grass. The farms averaged 0.56 mature cows per acre (weighted by tillable acres). How does this compare to average values in the United States and why is this important?

Comparison with Dairies in New York and Nationally

The share of homegrown feed for the New York farms was considerably high than typically reported across the US. The number of mature cows per acre was higher across the US (Figure 1b), while farmers in the assessment spent considerably less on feed costs per unit of milk produced than reported for the US (Figure 1c).

graphical representation of study results
Figure 1: (a) The share of homegrown feed on New York dairy farms participating in the 2017-2019 nutrient mass balance assessment (histogram); (b) the average number of mature cows per acre of cropland on dairy farms in the US (boxplot) and on New York dairy farms (blue diamond) according to the 2017 USDA Census of Agriculture, and the average number of mature cows per tillable acre for New York dairy farms participating in the 2017-2019 nutrient mass balances (green diamond); (c) the average amount spent on purchased feed per ton of milk sold for US dairy farms (boxplot) and New York dairy farms (blue diamond) according to the 2017 USDA Census of Agriculture.

Importance of Optimizing Homegrown Forage Production

The more feed that is homegrown, the greater the opportunity for the farm to: • Reduce feed imports and fluctuation in associated costs; • Control and adjust for changes in forage quality; • Reduce the need for synthetic fertilizer by enhancing nutrient recycling on the farm through manure application to the land base; • Maintain/improve soil test phosphorus levels; • Improve soil health, crop production and climate resiliency with use of manure; • Enhance carbon sequestration; • Avoid costs associated with manure export off the farm; • Reduce greenhouse gas emissions associated with fertilizer production and transport of feed; • Implement practices that promote biodiversity on the farm-base through crop rotation and management.For most dairy farms, feed purchases are the largest annual expense, so growing forages on the farm’s land base reduces the costs of feed. However, there are also other reasons why optimizing homegrown feed is key.

    • Reducing the amount of feed that needs to be imported helps to avoid the carbon and energy footprint that imported feeds have (production elsewhere plus transport to the farm).
    • By minimizing feed imports, farms are also minimizing the risk of feed price fluctuations and economic uncertainty.
    • Farmers that grow feed have greater control over the quality of that feed. They can select what crops are needed and in which quantities to meet the needs of their animals.
    • Farmers can, to a certain extent, alter crop management practices as needed, and optimize nutrient use, thereby reducing nutrient losses to the environment.
    • By increasing nutrient recycling with the use of manure on the farm itself, farms are reducing their reliance on fertilizer use. This results in a smaller environmental footprint for feed production. Optimizing the use of manure over synthetic fertilizer can also help with managing volatile fertilizer prices and with the farm’s overall economic sustainability.
    • Farms with insufficient land base will need to export manure. By optimizing feed production and animal density, a farm can reap the benefits of using manure, thereby avoiding extra expenses incurred with manure export (if feasible at all) and avoiding carbon emissions associated with the transport of manure beyond the farm boundaries.

Acknowledgements

We thank the farmers, farm advisors and past and current NMSP team members who worked on the whole farm NMB project with us over the past 15+ years. This research is funded primarily by a gift from Chobani, in addition to Federal Formula Funds, and grants from the Northern New York Agriculture Development Program (NNYADP), Northeast Region Sustainable Agriculture and Education (NESARE), New York State Department of Environmental Conservation (NYDEC). For questions, contact Quirine M. Ketterings (qmk2@cornell.edu) or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.