Author: mmh262

The Power of Manure: Boosting Yields for Multiple Years

Aidan Villanueva1, Juan Carlos Ramos Tanchez1, Kirsten Workman1,2, and Quirine M. Ketterings1

1Cornell University Nutrient Management Spear Program (NMSP) and 2PRO-DAIRY

Introduction

Manure contains all seventeen essential nutrients and, when properly managed, can contribute to a circular economy by offsetting fertilizer needs and building soil resiliency. Of all nutrients contained in manure, the most difficult one to manage is nitrogen (N). Manure contains N in different forms, some of which is released within the growing season following the application, while portions of the organic N can be mineralized and converted to plant-available N over multiple years. 

Over the past three years, New York Farm Viability Institute (NYFVI), Northern New York Agricultural Development Program (NNYADP), USDA National Institute of Food and Agriculture, and New York State Department of Agriculture and Markets (NYSAGM) Department of Environmental Conservation (NYSDEC) co-sponsored the “Value of Manure” project, an initiative of the New York On-Farm Research Partnership of the Nutrient Management Spear Program (NMSP). The Value of Manure project now contains data for nineteen on-farm research trials collected over three seasons, and the results have been summarized each year: 2024, 2023, 2022. Here we report on the yield responses and fertilizer offsets for two trials at two different farms (Farm A and Farm B) where we collected two years of data, in the year of application, and in the year after manure application.

Trial Design

Each Value of Manure trial had three strips that received manure in 2023 and three that did not, for a total of six strips and three replications per treatment. At sidedress time, each strip was subdivided into 6 subplots and assigned varying rates of sidedress from 0 up to 200 lbs N/acre. No manure was applied in 2024 so that we could evaluate 2023 manure’s carry-over N contribution to yield in 2024 (2nd year benefits). For each trial and each year, we calculated the Most Economical Rate of Nitrogen (MERN), the point at which adding extra fertilizer stops paying for the extra yield increase. The MERN calculation assumed a fertilizer price of $0.73/lb of N, a $55 per ton silage value (at 35% DM), and a $4.2 per bushel grain value (at 85.5% DM). Farm A is in central New York and the trial field was a Lima silt loam soil (SMG2). Farm B is in northern NY and the trial field had a Grenville loam soil (SMG 4). See Table 1 for information about manure composition and application. 


Findings 2023-2024

For farm A (Figure 1): 

Without sidedress N, manure-treated plots yielded 101 bu/acre in 2023, compared to 69 bu/acre for plots without manure, a 32 bu/acre advantage from manure application. In 2024, without sidedress N, manure plots produced 64 bu/acre versus 57 bu/acre in non-manured plots, reflecting a 7 bu/acre benefit in the second year after application.

At the MERN (Figure 1), manured strips yielded 176 bu/acre in 2023 compared to 155 bu/acre in non-manured strips, a 21 bu/acre gain from manure application beyond what was gained from N fertilizer application. In 2024, the manured strips produced 200 bu/acre, while non-manured plots yielded 187 bu/acre, reflecting an additional 13 bu/acre benefit from manure in the second year after application.

At the MERN, manure plots required 13 lbs/acre more sidedress nitrogen than no manure plots to reach their economic optimum in 2023. In 2024, manure offset 36 lbs/acre of inorganic nitrogen, demonstrating its continued contribution in the second year after application.

Over the two years of the study, manure positively impacted yields and reduced fertilizer needs. Without sidedress nitrogen, manure provided a cumulative yield benefit of 39 bu/acre. At the MERN across both years, manure reduced fertilizer N requirements by 23 lbs N/acre and increased yields by 34 bu/acre, resulting in an economic gain of $159/acre, excluding costs of manure and sidedress application.

A series of graphs.
Figure 1. The most economic rate of N (MERN) without manure (dashed gray line) and with manure (dashed brown line) in 2023 (left) and 2024 (right) for farms A (corn grain, top) and B (corn silage, bottom).

For farm B (Figure 1):

On Farm B in 2023 (Year 1), without sidedress nitrogen, manure-treated plots yielded 24.8 tons/acre compared to 20.6 tons/acre for non-manured plots, a 4.2 ton/acre gain from manure. In 2024, without sidedressing, manure plots yielded 14.2 tons/acre versus 12.5 tons/acre in plots without manure, reflecting a 1.7 ton/acre benefit in the second year after application.

In 2023, at the MERN, manured plots yielded 24.3 tons/acre compared to 22.9 tons/acre for strips that did not receive manure, a 1.4 ton/acre increase due to manure beyond what was gained from N fertilizer application. In the second year (2024), yields were 17.3 tons/acre for manured strips versus 16.5 tons/acre without manure, resulting in a 0.8 ton/acre yield advantage due to the previous year’s manure application.

At the MERN, the plots that did not receive manure in 2023 required an additional 109 lbs N/acre of sidedress fertilizer to reach the MERN (Figure 1) compared to plots where manure had been applied. In the second year (2024), manure did not offset inorganic N fertilizer needs, as MERNs were similar for both manured and non-manured plots.

Looking at the two-year benefits from manure (Table 2), without sidedress N, the yield benefit from the manure amounted to 5.9 tons/acre. At the MERN across both years, manure reduced fertilizer nitrogen requirements by 109 lbs N/acre and increased yields by 2.2 tons/acre, resulting in an economic gain of $206/acre, excluding the costs of manure and sidedress application.

In Summary

Manure application increased yields in both 2023 and 2024, demonstrating both immediate and carryover effects at both study sites. Over the two years, when no N was sidedressed manure provided cumulative yield benefits of 39 bu/acre at Farm A and 5.9 tons/acre at Farm B. At the MERN (the point when N was optimally applied through sidedressing), total yield gains due to manure were 34 bu/acre at Farm A and 2.2 tons/acre at Farm B. Additionally, manure reduced fertilizer N needs by 23 lbs N/acre at Farm A and 106 lbs N/acre at Farm B over the two years. The combined benefits of N replacement and yield increases over both years resulted in overall economic gains of $159/acre at Farm A and $206/acre at Farm B, excluding fertilizer and manure application costs. These results highlight the significant agronomic and economic value of manure. Both trials will continue into 2025 to assess the three-year impacts on yield and fertilizer savings. Would you like to see similar data for your farm? Join the Power of Manure project! 

Relevant References

Value of Manure annual summaries:

Acknowledgments

We thank the New York Farm Viability Institute (NYFVI), Northern New York Agricultural Development Program (NNYADP), USDA National Institute of Food and Agriculture, New York State Department of Agriculture and Markets (NYSAGM) and Environmental Conservation (NYSDEC), participating farmers, consultants. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy. For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.

To Grid or Not to Grid: Precision Soil Sampling for Lime, P, and K Management of Corn Fields

Manuel Marcaida III1, Kirsten Workman1,2, and Quirine M. Ketterings1

1Cornell University Nutrient Management Spear Program (NMSP) and 2PRO-DAIRY

Introduction

Soil fertility often varies within a single field, impacting crop yield and efficiency of crop inputs. Grid soil sampling offers more detailed fertility information than whole-field sampling, enabling more targeted lime and nutrient applications. But is this added precision worth the investment and what grid size should be used? In collaboration with farmers and crop consulting firms, we analyzed the results of 20 New York corn silage fields (1149 total acres) with grid sample data at 0.5-, 1.0- and 2.5-acre resolution, to assess within-field variability in soil pH, phosphorus (P), and potassium (K) levels. Recommendations based on grid sampling were compared to those derived from conventional, whole-field, composite samples.

Key Findings

Grid sampling revealed substantial variability in soil nutrient levels

Although most fields had 2-8 (average 4) different soil series represented, soil series within a field all belonged to the same soil management group. However, each field showed a considerable range in pH, soil test P and soil test K (Figure 1). For some fields, grid sampling revealed low pH, P or K areas while for other fields, hot spots were identified (Figure 2).

Figure 1. Measured pH (A, B), phosphorus (C), and potassium (D) levels across fields, based on New York guidelines. Bar length shows total field area, and color changes indicate varying nutrient levels. The percentages at the end of each bar show the area needing lime or P or K fertilizer.
Figure 2. Field maps from two sample fields (A3, A1) showing the changes in lime (A), phosphorus (B), and potassium (C) recommendations based on the size of the soil sampling grid. This suggests that grid sampling helped identify areas that were suboptimal in pH and/or phosphorus-deficient, which would have been overlooked using whole-field averages. Management classifications were based on New York’s nutrient management guidelines (http://nmsp.cals.cornell.edu/guidelines/nutrientguide.html).

Lime and fertilizer recommendations vary depending on soil nutrient variability

For lime and P, grid sampling increased the recommended amount of lime for corn in alfalfa rotations (rotation target pH of 7.0) for many of the fields (Figure 3). This suggests that grid sampling helped identify areas that were suboptimal in pH and/or P-deficient that would be overlooked with use of whole-field averages. In contrast, for several fields, grid sampling revealed areas with sufficient K, which could result in K fertilizer savings (Figure 3).

Figure 3. Comparing the total cost or potential savings when using grid-based sampling at various grid sizes versus traditional whole-field recommendations for corn in rotation with alfalfa. All prices for lime and fertilizers were based on current rates from the USDA Agricultural Marketing Service at the time of our analysis.

Grid sampling increased total fertilizer or lime recommendations for 12 out of 20 fields, discovering low-pH or soil test P and/or K deficiencies that would have been missed using whole-field averages. On the flip side, seven fields had lower lime and nutrient input costs with grid sampling because there was no need to apply lime and fertilizer in already optimally limed or fertilized areas within the fields.

Half-acre grid size provides more detailed fertility insights, but it is also more costly (both in sampling costs and analytical costs). A cost-effective long-term strategy is to start with high-resolution (0.5-acre) sampling to characterize soil fertility and establish fertility-based zones (such as low, medium, optimum, high, very high). In subsequent years, sampling can then be done per fertility zone at a lower grid resolution of 2.5 acre within each zone, significantly reducing costs while still maintaining the benefits of precision nutrient management. This approach aims to homogenize the field over time through targeted applications, potentially leading to more uniform soil conditions.

Conclusions

Grid soil sampling enables more precise fertilizer and lime application by identifying within-field nutrient variability. Although results of this study suggested that for many of the 20 fields, grid-based sampling added to the cost of production and crop input needs, it should be recognized that detection of deficient areas allows a farmer to address yield barriers. Whether grid sampling leads to higher costs or significant savings, the long-term value is in applying fertilizer and lime only where needed. A cost-effective approach could be to begin with high-resolution (0.5-acre) sampling to define zones of low, medium, optimum, high or very high fertility, followed by lower-resolution (e.g., 2.5-acre) sampling within each fertility zone in future years.

Full citation

This article is summarized from our peer-reviewed publication: Marcaida, M., K. Workman, and Q.M. Ketterings (2025). Implication of Soil Grid Sampling on Lime, Phosphorus, and Potassium Management of Corn. Agronomy Journal 117: e70074. https://doi.org/10.1002/agj2.70074.

Acknowledgments

The authors would like to thank the staff of Champlain Valley Agronomics, Western New York Crop Management Association, and participating farmers for field selection and sampling. Funding came from the Northern New York Agricultural Development Program, the New York Corn and Soybean Growers Association via the New York Farm Viability Institute, the New York State Department of Environmental Conservation and the New York State Department of Agriculture. This research was also supported, in part, by the intramural research program of the U.S. Department of Agriculture, National Institute of Food and Agriculture, Hatch 2021-22-210. The findings and conclusions in this publication have not been formally disseminated by the U.S. Department of Agriculture and should not be construed to represent agency determination or policy.

For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.

Stalk Nitrate Test Results for New York Corn Fields from 2010 through 2024

Sanjay Gami¹, Juan Carlos Ramos Tanchez¹, Mike Reuter², and Quirine M. Ketterings¹

¹Cornell University Nutrient Management Spear Program (NMSP) and ²Dairy One

Introduction

            The corn stalk nitrate test (CSNT) is an end-of-season evaluation tool for N management for corn fields in the 2nd or more years after a sod. It allows for identification of situations where more N was available during the growing season than the crop needed (CSNT>2000 ppm). Results can vary from year to year but where CSNT values exceed 3000 ppm for two or more years, it is highly likely that N management changes can be made without impacting yield. 

Findings 2010-2024

            In 2024, 47% of all tested fields had CSNT-N greater than 2000 ppm, while 37% were over 3000 ppm and 28% exceeded 5000 ppm (Table 1). In contrast, 20% of the 2024 samples were low in CSNT-N. Two years of CSNT monitoring is recommended before making management changes unless CSNT’s exceed 5000 ppm, in which case one year of data is sufficient.
            Some of the variability in CSNT distribution over the years may be reflect differences in growing season (Figure 1). The percentage of samples testing excessive in CSNT-N across 2010-2024 was most correlated with the total precipitation in May-June with droughts in those months translating to a greater percentage of fields testing excessive. The year 2024 was classified as normal based on these criteria although some areas experienced drought conditions for parts of the season, possibly contributing to a higher percentage of stalks testing excessive in CSNT.

            Within-field spatial variability can be considerable in New York, requiring (1) high density sampling (equivalent of 1 stalk per acre at a minimum) for accurate assessment of whole fields, or (2) targeted sampling based on yield zones, elevations, or soil management units. The Adaptive Nitrogen Management for Field Crops in New York lists targeted within-field CSNT sampling as one of five end-of-season evaluation tools. Samples received in more recent years may also reflect more targeted field sampling. 

A bar graph.
Figure 1: In drought years more samples test excessive in CSNT-N while fewer test low or marginal. The last 15 years included six drought years (2012, 2016, 2018, and 2020 through 2023), three wet years (2011, 2013, and 2017), and five years labelled normal (2010, 2014, 2015, 2019, and 2024) determined by May-June rainfall (less than 7.5 inches in drought years, 10 or more inches in wet years). Weather data are state averages; local conditions may have varied from state averages.

            Because crop and manure management history, soil type and growing conditions all impact CSNT results, conclusions about future N management should consider the events of the growing season. This includes weed and disease pressure, lack of moisture in the root zone in drought years, lack of oxygen in the root zone in wet years, and any other stress factor that can impact crop growth and N status. 

Relevant References

•   Instructions for CSNT Sampling: http://nmsp.cals.cornell.edu/publications/StalkNtest2016.pdf.
•.  Agronomy Factsheets #31: Corn Stalk Nitrate Test (CSNT); #63: Fine-Tuning Nitrogen Management for Corn; and #72: Taking a Corn Stalk Nitrate Test Sample after Corn Silage Harvest. http://nmsp.cals.cornell.edu/guidelines/factsheets.html.
•.  Adaptive Nitrogen Management for Field Crops in New York (2025): http://nmsp.cals.cornell.edu/publications/extension/AdaptiveNitrogenManagement2025.pdf. 

Acknowledgments

We thank the farmers and farm consultants that sampled their fields for CSNT over the years.

For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/. 

New York Dairies Show the Way to Reduce Greenhouse Gas Emissions

Olivia F. Godber¹, Karl J. Czymmek², Michael E. van Amburgh³ and Quirine M. Ketterings¹

¹Nutrient Management Spear Program, ²PRO-DAIRY, and ³Dairy Nutrition, Department of Animal Science, Cornell University, Ithaca, NY 14853

Introduction

              In a recent study, 36 medium to large dairy farms (>300 cows) located across New York state were assessed for greenhouse gas (GHG) emissions for the 2022 calendar year using The Cool Farm Tool. Cows were predominantly Holstein. Dairies ranged in animal density from 0.71 to 1.96 animal units per acre (one animal unit is 1000 pounds of live weight). Herds produced an average fat and protein corrected milk (FPCM) yield of 29 000 lbs per cow per year using 64% homegrown feed. Total FPCM production was 1.92 billion lbs, sold to four dairy cooperatives. This milk production represented approximately 12% of total NY milk production in 2022. 

Findings

              The GHG emission intensity ranged from 0.63 to 1.06 lb CO₂eq per lb of FPCM (mean GHG emission intensity = 0.86 lb CO₂eq per lb FPCM). Methane was the biggest contributor, accounting for 60% of total GHG emissions on average, with enteric methane as the largest contributor (45% of total farm emissions). With several studies suggesting the US average GHG intensity of around 1lb CO₂eq per lb FPCM, this study shows these New York dairies to be leaders in sustainability.  

              The relatively low GHG emission intensity achieved by the farms in this study reflect high quality and quantity of home-grown feed, careful nutrient management, quality nutrition and high animal productivity, and for several of the farms also the installation of more advanced manure management systems such as solid-liquid separation with cover and flare, and anerobic digesters. These characteristics allow optimization of milk production through high feed efficiency, demonstrate the recognition of the value of manure offsetting synthetic fertilizer use, and the farm’s ability to take advantage of the dilution of maintenance concept through high milk yields and components. 

              Another important finding of the study is that many of the key drivers of GHG emission intensity for these farms were related to homegrown feed production and manure management, two main areas of management that also impact whole farm nutrient use efficiency. Reducing fertilizer and feed purchases not only benefits the GHG emission intensity of the farm but also contribute to improvements in whole farm nitrogen and phosphorus balances and improves farm economics. 

Highlights

•  Medium to large New York dairy farms in a recent study averaged a GHG intensity of 0.86 lb CO₂eq per lb of fat and protein corrected milk, much lower than the national average.  

•  Manure management system (implementation of solid-liquid separation with cover and flare, and anaerobic digesters), was a major driver of lower GHG emissions on the farms.

•  Homegrown feed (both total amount and quality), heifer/cow ratio, and feed efficiency all impacted emissions with reduced emissions for integrated farms that grow a large portion of the forages fed to the cows on the farm itself, have lower heifer/cow ratios, and for farms that implemented precision feed management. 

Invitation

              The farms in this study represent a considerable proportion of New York’s milk production but expansion of the database will be needed to develop additional understanding of drivers of emissions and opportunities for improvements over time. Many of the farms that participated with 2022 data are continuing to participate now with 2023 and 2024 data. We welcome additional farms to join and would particularly also invite more farms with under 300 cows to participate to better represent the diverse New York dairy industry.  

Full Citation

              This article is summarized from our peer-reviewed publication: Godber, O.F., K.J. Czymmek, M.E. van Amburgh, and Q.M. Ketterings (2025). Farm-gate greenhouse gas emission intensity for medium to large New York dairy farms.  Journal of Dairy Science.  https://www.journalofdairyscience.org/article/S0022-0302(25)00124-9/fulltext.

Acknowledgments

              We thank the farmers and farm advisors and coops that participated in the assessment. For questions about these results or inquiries about participating, contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/. 

Logos of associated partners, from left to right, NMSP, Cornell University, Cornell CALS and PRO-DAIRY.

Manure Continues to Offset Nitrogen Fertilizer Needs and Increase Corn Silage and Grain Yields: Value of Manure Project 2024 Update

Juan Carlos Ramos Tanchez¹, Carlos Irias¹, Allen Wilder², Janice Degni³, Paul Cerosaletti³, Dale Dewing³, Kirsten Workman¹𝄒⁴, and Quirine M. Ketterings¹ 

¹Cornell University Nutrient Management Spear Program, ²Miner Agricultural Research Institute, ³Cornell Cooperative Extension, and ⁴PRO-DAIRY

Introduction

              Manure contains all seventeen nutrients a plant needs, making it a tremendously valuable nutrient source. In addition, manure can help build soil organic matter, enhance nutrient cycling, and improve soil health and climate resilience when managed appropriately. Previous research in New York State indicates that these manure benefits contribute to crop yield beyond just the fertilizer value of manure.  The Value of Manure Project, part of the New York On-Farm Research Partnership, is funded by the New York Farm Viability Institute (NYFVI) and the Northern New York Agricultural Development Program (NNYADP), with additional support from the New York State Departments of Agriculture and Markets and Environmental Conservation, and the US Department of Agriculture’s National Institute for Food and Agriculture. This statewide project evaluates nitrogen (N) and yield benefits of various manure sources and application methods to corn silage and corn grain. Eight trials were conducted in 2024, adding to eleven trials conducted in 2022 and 2023. Here we summarize the findings of the 2024 trials.

What we did in 2024

              Trials were implemented within commercially farmed corn fields in western (1 trial), northern (2 trials), central (4 trials), and southeastern (1 trial) New York. Each trial had three strips that received manure and three that did not, for six strips per trial (Figure 1a).

Figure 1. Layout of a 2024 Value of Manure study plot. Three strips received manure before planting corn (1a). At the V4-V6 stage each of the six strips received six different inorganic N sidedress rates (1b).

              Four trials (D, E, F, G) received manure in spring 2023 but not in 2024. For these trials, we tested yield and fertilizer offset carryover benefits of 2023 manure into the 2nd year (2024) after manure application. For all other trials, manure was applied in spring 2024 before planting corn. Dairy manure treatment and application methods varied across trials (Table 1).

*Note: manure was applied in the spring of 2023 in trials D, E, F, and G so we tested its carryover value for 2024. For all other trials, manure was applied in the spring of 2024. SMG = soil management group (http://nmsp.cals.cornell.edu/publications/factsheets/factsheet19.pdf).

              Strips were 1200-1800 ft long and 35-120 ft wide for all but one trial where strips were 300 ft long. When corn was at the V4-V6 stage, each strip was divided into six sub-strips (Figure 1b) and subplots were sidedressed at a rate ranging from 0 to 200 pounds N per acre. Sidedress rates were trial-specific, based on the expected N needs for that field stemming from its specific characteristics and history. For each trial, manure was analyzed, and samples were taken for general soil fertility, Pre-Sidedress Nitrate Test (PSNT), Corn Stalk Nitrate Test (CSNT), yield, and forage quality. Soil test phosphorus (P) levels in the trials were in the medium to very high category (Table 2). Soil test potassium (K) was optimum or very high for five of the trials, while trials D, F, and G tested medium in K. Magnesium soil test values were high or very high for all trials. Soil test zinc (Zn) was medium for trials C, D, and G and high for all other trials. Manganese (Mn) and iron (Fe) were in the normal category.

What we have found so far

              As we also found in 2022 and 2023, trials differed in their responses to manure and sidedress inorganic N (Figure 2). Common among all trials in 2024 was that yield responded to N sidedress application in all eight trials. In seven of the eight trials (A to G), manure increased yield to levels not achievable with fertilizer alone by 0.3 to 2.7 tons/acre and 13 bushels/acre (Table 3). Out of these seven trials, in one of the trials with medium levels of K (F), manure applications increased yield to such elevated levels (2.3 tons/acre) that it also increased the crop’s need for fertilizer N, similar to what was observed for two trials in 2023. Yield in trial H only responded to manure in the lower N rates, likely reflecting the low application rate of this trial and low manure N contribution (3,840 gallons/acre, surface applied without incorporation). In trials A, C, and E manure did not replace inorganic N fertilizer, but still resulted in a yield increase.

Figure 2. Most Economic Rate of Nitrogen (MERN) in eight Value of Manure trials conducted in 2024. Orange text boxes are the MERN and yield at MERN for manured plots; gray text boxes are MERN and yield at the MERN for no-manure plots. Corn silage yields are in tons/acre at 35% dry matter (DM). Corn grain yields are in bushels/acre at 84.5% DM.
*Note: manure was applied in the spring of 2023 in trials D, E, F, and G so we tested its carryover value for 2024. For all other trials, manure was applied in spring 2024.

              The PSNT levels where liquid or digested manure was applied in 2024, were higher than their no-manure counterparts for all but one trial, showing that manure supplied crop available N to the soil (Table 4). The exception was trial C, where the application rate was relatively low (5,200 gallons/acre), which may have contributed to a lack of a response in PSNT. The PSNT results in the no-manure plots incorrectly identified trials B, C, and E as not needing additional N. In the manure plots, PSNTs also incorrectly suggested trials A, C, E, and H did not need sidedress N. For the manure carry-over trials (D, E, F, and G), PSNT levels were similar in manure and no-manure strips (Table 4), suggesting limited to no carryover into the second year, although each of these trials had a yield increase where manure was applied the previous year. 

              In all eight trials, CSNT levels of the plots that did not receive manure or sidedress fertilizer N were low, consistent with the yield response to N. In the plots that received manure but no N fertilizer, only trial B was in the excess category, consistent with the lack of a sidedress-induced yield response in trial B manured strips (trial B manure MERN = 0 pounds N/acre, Table 3). In the other trials (A, C, D, E, F, G, H) the manure strips without N fertilizer addition were in the low CSNT category, accurately reflecting the need for additional N.

              In 2024 we documented “yield bumps” resulting from manure application beyond what could be obtained with fertilizer only in seven of the eight trials, consistent with observations for seven of the eleven trials in 2022 and 2023. These yield bumps were also present in all four “carry-over” trials, signaling that manure applied in 2023 continued to be beneficial to crop yield in 2024. Those yield increases in the trials with optimal or high fertility status show that manure has additional benefits beyond its nutrient contributions. The CSNT results consistently reflected where N was needed and allowed for documentation of the N contributions of manure. The PSNT results showed inconsistencies this year with five trials where corn yield still responded to sidedress N even though the PSNT values were high. 

Next steps in 2025

              To re-evaluate the current N crediting system and learn how to predict and take into account yield bumps, the Value of Manure project requires the addition of more trials beyond the nineteen trials completed so far. Thus, the Value of Manure Project will continue in 2025. We will be testing additional manure types and application methods in various soil types and weather conditions. Join us and obtain valuable insights about the use of manure on your farm! If you are interested in joining the project, contact Juan Carlos Ramos Tanchez at jr2343@cornell.edu.

Additional resources

Acknowledgments

              We thank the farms participating in the project and their collaborators for their help in establishing and maintaining each trial location, and for providing valuable feedback on the findings. For questions about this project, contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.

Greenhouse gas emissions and nutrient use efficiency assessment of six New York organic dairies

Agustin J. Olivo¹, Olivia F. Godber¹, Kristan F. Reed¹, Daryl V. Nydam², Michel A. Wattiaux³ and Quirine M. Ketterings¹

¹Department of Animal Science, Cornell University, Ithaca, NY United States ²Department of Public and Ecosystem Health, Cornell University, Ithaca, NY United States, ³Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States.

Introduction

Improving nutrient use efficiency and reducing greenhouse gas (GHG) emissions are important environmental priorities for organic-certified dairy operations. Regular assessment of key performance indicators (KPIs) via decision-support tools can help monitor farm performance and identify opportunities for improvement in these areas. Multiple decision-support tools have recently emerged to evaluate these indicators. However, these tools vary in complexity, required data inputs, scope and aggregation. A study was recently conducted at Cornell University to evaluate nutrient use efficiency and GHG emissions in six organic dairies, and to analyze the impact of alternative farm management practices on GHG emissions. Three decision support tools were used: Cornell nutrient mass balance (NMB) calculator, for whole-farm nutrient use efficiency, and Cool Farm Tool (CFT) and COMET, for GHG emissions. Farms had between 30 and 138 cows, 76 and 266 acres, and were certified organic (Farms 1-6) and grass-fed (Farms 3 and 4). Evaluations were done for two years.

Key findings

Farms showed high whole-farm nutrient use efficiency, primarily driven by low nutrient imports.

Farm-gate NMBs ranged from -5 to 17 lbs N/acre for nitrogen (N), and -2 to 7 lbs P/acre for phosphorus (P). Of the six farms, four met the feasible levels for N per hundredweight (cwt) of milk and per acre of cropland, versus two farms for P and five farms for K (Figure 1). Feasible levels are NMB performance ranges that previous research has shown farms in New York can operate within. Balances were generally low, explained by low animal densities and low nutrient imports. For N, inputs from legume fixation were equivalent to or larger than nutrients imported with feed and organic fertilizer purchases for all farms. Legume stands in sod and pasture fields played an important role in the sustainability of the farms when it comes to N management. For P, low inputs resulted in negative P balances in three of the six farms. Continuously operating under negative P balances may compromise the long-term sustainability of farms by reducing soil test P levels and ultimately crop yields. It is therefore relevant that farms continue tracking farm-gate NMBs, as well as changes in soil test P and plan fertility programs accordingly.

Fig. 1. Farm-gate N and P balances (lbs/acre) vs milk production (1000 lbs/acre) for six case-study farms. The green area indicates the optimal operational zone, where balances per acre (blue square) and per cwt (yellow triangle) are within feasible levels defined for dairies in NY. F=farm.

Whole-farm GHG emissions intensity showed variability and were directionally in agreement between CFT and COMET.

Estimations from CFT for GHG emissions intensity, a common way to report farm GHG emissions, ranged from 0.98 to 2.10 lbs of CO2-equivalent (CO2-eq, a common unit to aggregate all GHGs generated in the farm), per lbs of fat and protein corrected milk (FPCM). This value did not include carbon sequestration in soils (Figure 2). Baseline estimations from COMET (that consider different farm GHG sources to CFT) ranged from 0.69 to 2.48 lbs CO2-eq/lbs FPCM. Ranking of farms was similar between the two tools, suggesting that both tools can help identify, among multiple farms, those with the greatest emissions and need for implementing GHG mitigation measures. Enteric fermentation was the single largest source of GHG emissions, followed by energy and fuel use, and feed production or cropland emissions. Manure management emissions were larger for farms with liquid manure storages (Farms 4 & 5), compared to farms with solid manure handling (Figure 2).

A bar graph.
Fig. 2. Annual average GHG emissions intensity from Cool Farm Tool and COMET across six organic dairies. Numbers above each bar correspond to aggregation of all emission sources. FPCM: fat and protein corrected milk.

Cow milk productivity and manure management strategies showed opportunities to reduce farm GHG emissions.

A scatterplot.
Fig. 3. Average GHG emissions intensity calculated with Cool Farm Tool and COMET for farms 1-6, as related to average milk production per cow. F=farm.

Milk production per cow ranged from 4,400 (Farm 3) to 22,000 (Farm 5) lbs/cow per year and was negatively associated with GHG emissions intensity. The greater the milk production per cow, the lower the whole-farm GHG emissions intensity (Figure 3). Statistical analysis showed that, for farms with similar characteristics, increasing milk production from 4,000 lbs/cow/year to 11,000 lbs/cow/year could decrease GHG emissions intensity by almost 1 lbs CO2-eq/lbs FPCM. 

Analysis of alternative management strategies in the areas of crop management, manure management and farm energy use showed changes in GHG emissions intensity ranging from -8% to +8% compared to current management, when considered alone. For example, theoretical implementation of solid-liquid manure separation and/or anaerobic digestors in farms with liquid slurry storages resulted in an average reduction between 6 and 8% in whole-farm GHG emissions intensity (Figure 4). Implementing strategies such as composting or piling of manure resulted in an increase in GHG emissions intensity for most farms, given the starting practice of daily spread is associated with low GHG emissions (Figure 4). Other strategies such as replacing 50% of the farms’ grid energy use with a solar source and reducing 20% the farm fuel use resulted in a 2% decrease in whole-farm GHG emissions intensity.

A bar graph.
Fig. 4. Average change in GHG emissions intensity across farms and years compared to baseline estimations, with the implementation of alternative management strategies related to manure management. SLS: manure solid-liquid separator.

Conclusions

Farm-gate NMBs were low or negative, particularly for P. Additional nutrient imports, coupled with nutrient management planning, adequate legume stands, and diet balancing may help improve nutrient balances. GHG emissions varied largely across farms, with enteric fermentation, feed production, fuel and energy use, and manure management representing the largest sources. Management changes that resulted in the greatest GHG emissions intensity reductions included increasing milk production per cow and implementing manure treatment systems in farms with liquid slurry storages.

Full citation

This article is summarized from our peer-reviewed publication: Olivo, A.J., O.F. Godber, K. Reed, D.V. Nydam, M. Wattiaux, and Q.M. Ketterings (2024). Greenhouse gas emissions and nutrient use efficiency assessment of six New York organic dairies. Journal of Dairy Science https://doi.org/10.3168/jds.2024-25004. 

Acknowledgements

We thank the participating farmers, Cornell Cooperative Extension (CCE) Educators Janice Degni, April Lucas, Paul Cerosaletti, Dale Dewing, and CCE intern Mikala Anderson for sharing, collecting and processing data, and giving feedback on findings. We appreciate the support of the COMET outreach team at Colorado State University. This project was funded by The Sustainability Foundation at Cornell University, a gift from Chobani, and the Department of Animal Science at Cornell University. 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/.