[Note to online version: The report for this project includes tables and figures that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact Northeast SARE at (802)-656-0471 or email@example.com.]
Nutrient balances were completed for 1992 through 1995. Nutrient efficiency in 1992 and 1993, prior to the initiation of this project, was considerably less than for the typical NY dairy farm. Beginning in 1994, dairy feed and mineral programs were adjusted to reduce unnecessary nutrient inputs. Purchased nutrient inputs in 1994 were greater because of increased animal numbers, but outputs (sales) increased by a greater relative amount, and the nutrient balance improved considerably. Nutrient efficiency declined slightly in 1995 vs 1994, but total tons of N and K remaining on the farm declined for the second consecutive year. P efficiency did not change significantly from 1992 to 1995. Though we decreased fertilizer P purchases considerably, this was overcome by decreased crop and livestock sales.
Three models were investigated for their ability to predict nutrient flow on dairy farms. DAFOSYM and the Penn State Farm Balance model were found inadequate for this purpose, but the Net Carbohydrate Protein System model was found to have the potential to predict nutrient output for dairy animals.
High soil clay content prevents spring application of manure to corn fields at Miner Institute and many other farms in the Champlain Valley. Beginning in 1994 we increased the use of topdressed dairy manure on alfalfa fields. For the seven years prior to 1994 an average of 18% of Miner Institute dairy manure was applied to alfalfa. In 1994, over 40% of dairy manure was topdressed on alfalfa, permitting a reduction in commercial fertilizer purchases. In 1995, 65% of the manure was applied to alfalfa, either as a topdress or just prior to seeding, permitting further reductions in fertilizer purchases. For the first 7 months of 1996, 75% of manure applied was to established alfalfa or land to be seeded to alfalfa. The 1996 total is expected to be within the 1994-1995 range.
Presidedress nitrate tests (PSNT) were done for the first time at Miner Institute in 1994 and have been done each year since then. Soil nitrate levels have been low enough that the application of supplemental N was required, so no reduction in nitrogen fertilizer use was achieved through this practice. However, we have publicized the value of this test in our monthly Farm Report with readership of 11,000, and its use in the region is increasing. On farms with heavy manure use PSNT has the potential to greatly reduce nitrogen fertilizer inputs.
a. Conduct a detailed evaluation of the nutrient balance on the 100-cow Miner Institute dairy farm, comparing it to the average New York dairy farm.
b. Improve existing models to predict the flow of N, P, and K through the cow, manure storage, and to the field.
c. Evaluate the effects of the farm nutrient balance of P by the substitution of manure for commercial fertilizer on established alfalfa.
d. Evaluate the effects on the farm nutrient balance of N by the use of pre-sidedress nitrate tests.
Miner Institute is located east of the Adirondack Mountains in the Champlain Valley. The soils are diverse, ranging from coarse gravel to lake-laid clay. Topography is generally flat, with poor drainage the most limiting soil-related factor. The climate is favorable for its Northern latitude, with a 130-day frost-free season and mean precipitation of 32”. The Institute dairy farm is typical of many in the region, with herd size of 120 cows (an increase from 100 cows in 1993 when the project began), and forages including corn, alfalfa, and grass. Most manure is handled as a slurry with 6-10% solids, with the rest composted and spread at 25% dry matter content.
Nutrient balance–Miner Institute has been involved in nutrient balance investigations since 1983. The 1992-93 balances found that we had improved P and K efficiency since 1983, but were less efficient for N. We were also less efficient in nutrient utilization than the typical NY dairy farm. Adjustments were then made in dairy rations, the crop rotation adjusted to better utilize dairy manure, and forage was sold to bring inventories more in line with existing herd size. Nutrient inputs were greater in 1994, but outputs were considerably greater, resulting in an improvement in nutrient efficiency. A comparison between a typical 100 cow dairy farm and the 4-yr. Miner Institute mean is in Table 1.
Compared to the typical NY dairy farm, the average (1992-95) mass balance for N, P, and K on the Miner Institute farm was 13%, 11%, and 23% higher, respectively. The typical farm uses 63% less fertilizer N, 75% less fertilizer P, and has 75% less N from nitrogen fixation than does Miner Institute. However, during 1992-93 Miner Institute was pursuing an aggressive fertilization program to correct low soil potassium levels on a number of fields. Miner Institute also has a higher proportion of cropland in alfalfa, as can be seen from the considerable difference in N fixation.
Nutrient modeling–Three models were investigated: DAFOSYM, Penn State Farm Balance Model, and the Cornell Net Carbohydrate Protein Model, UPenn version (NCPS). DAFOSYM and the Penn State model are whole farm models, while NCPS is a single cow model. DAFOSYM integrates all aspects of the farm into one model. In exploring DAFOSYM’s capabilities it was found to be too restrictive to use in this project. Although considerable time was spent attempting to refine the inputs to approximate farm conditions (including discussions with the developer of the model), constraints within the model would not allow accomplishment of this goal. The Penn State model is an accounting model with little predictive capability. Since the objective is to improve the predictive ability of existing models, the Penn State model was found to be unsuitable for this purpose. As an accounting tool, however, this model is user-friendly and easy to interpret.
Efforts therefore concentrated on the NCPS model. Elements within the model were extracted to form a report based on predicted nutrient output. The model is partially mechanistic and predicts the potential based on inputs, so it is easy to compile nutrients not used for production or maintenance into a predicted output report. For parameters not predicted in the model, the literature was reviewed and predictive equations were used which are generally accepted by the scientific community.
Once the report page was compiled, we conducted a study to determine the quantity of manure excreted from four classes and two breeds of dairy cattle, comparing observed outputs with those predicted by the model. The model adequately predicted the excretion of dry matter, N, and P for all groups. However, as the milk production of the animals increased, the predictive ability of the model was reduced.
Substitution of manure for fertilizer–A 1992 research trial at Miner Institute found that topdressing 3000 gallons/acre of slurry dairy manure had no adverse effect on alfalfa or groundwater quality. This was confirmed by a 1994 research trial in Massachusetts. In 1994 applications of manure to established alfalfa at Miner Institute increased from less than 20% of total manure (average of 1987-93) to over 40%. At the same time the amount of commercial fertilizer applied to alfalfa decreased by 40%.
Applications of dairy manure at rates which meet the K needs of the crop result in considerably more P than needed by alfalfa. Analyses of the dairy manure at Miner Institute shows a P2O5:K2O of 1:2, while alfalfa removes these nutrients from the soil at a ratio of 1:4. In 1994 a soil P stratification study on four fields characterized the fate of the P applied as manure. The fields had widely varying histories of manure application, ranging from 0 to 175 tons/acre since 1981. Samples were taken from six depths in the top 24” of soil. Soil analysis determined that essentially all P remained in the plow layer. Plant available P was medium and high in the two fields which had received heavy applications of manure, but P levels on all fields were low at depths below 8”. Water-soluble P was high in the top 1” of soil in one heavily manured field, indicating the importance of practices which prevent soil erosion and limit water runoff.
Presidedress nitrate tests (PSNT)–Five Miner Institute corn fields were sampled in 1994, four in 1995, and five in 1996. Nitrate levels over 21-25 ppm (the range of sufficiency levels recommended by universities in the Northeast), indicate a need for supplemental N. In 1994 nitrate levels on the Miner Institute fields ranged from 3-13 ppm, in 1995 from 7-23 ppm, and in 1996 from 3-11 ppm. Since soil nitrate levels were generally low, supplemental N was applied to all fields tested, and this test therefore did not result in a decrease in fertilizer N use. However, evaluation of soil nitrate levels soon after corn harvest in these fields found low to medium levels of nitrate, indicating that most of the supplemental N had been used by the crop.
One of the problems with PSNT is the necessity for the test to be done very soon before nitrogen application. It can take a week or more to send the sample to the laboratory and get the results back. For this reason, in 1996 we evaluated the N-Check test which is intended for on-farm use. We used the N-Check on the same five sample which were submitted to the University of Vermont Agricultural Testing Laboratory. The results are in Table 2.
Since any reading below 21-25 ppm indicates a need for supplemental N, the N-Check performed acceptably for these samples. One problem is that the test is designed for nitrate levels in water samples, so it’s calibrated for very low nitrate levels and lacks the refinement between 20 and 30 ppm, where the greatest accuracy is needed. It may be possible to dilute samples, although the efffect of this on accuracy isn’t known. The test kit costs about $50 for 25 samples, and would take someone not familiar with laboratory procedure about 1 1/2 hours to run five tests.
The results of this project have been presented at the following meetings: Northeast Production Medicine Symposium in Syracuse, NY; Vermont Veterinary Society annual meeting in Vergennes, VT; NY Forage and Grassland Conference in Auburn, NY; Orleans Farm Management seminar in Newport, VT; St. Lawrence/Champlain Valley Seminar in Chazy, NY; Dairy Day in Chazy, NY;
National Alfalfa Symposium in Syracuse, NY; Sullivan County, NY Dairy Day; Orange County, NY Dairy Day; Jefferson County Grass Management Meeting in Watertown, NY; Central NY Forage Symposium; and the California Animal Nutrition Conference in Fresno, CA.
A number of articles involving various phases of this project have appeared in the Miner Institute Farm Report which has monthly readership of 11,000. Our readership consists of approximately 60% farmers and 40% agricultural professionals in both the public and private sectors. Miner Institute also published a 1992-1994 Research Report which included summaries of this research.
Impacts of Results/Outcomes
A detailed analysis of the nutrient balance on the Miner Institute farm has been useful in discussions with farmers and agricultural professionals. At the beginning of this project the Institute’s nutrient balance was worse than for a typical NY dairy farm, and caused us to take a critical look at the various nutrient inputs. We were surprised at the amount of nutrients entering the farm as straw for bedding, and made changes in cropping practices to reduce this purchased input. Since then we have counseled many farmers about the economic and environmental impact of large nutrient imbalances.
Our nutrient cycling results also show the impact that feed minerals can have on the nutrient balance. Often one or more nutrient can be reduced with no effect on animal performance. Most dairy ration balancing programs predict production based on feed inputs, or vice versa. There is little accounting for excess nutrients, and it is common practice to overfeed some nutrients or to feed them in forms which are not efficiently utilized by the animal. The value of the Net Carbohydrate Protein System (NCPS) as a nutrient management tool is its ability to predict not only production but nutrient output. Managers can then assess changes in quantity and form of nutrient outputs as different feed ingredients are used to balance the ration. The NCPS will allow farmers to asses the impact that a particular feeding regime will have, not only on the cow but on the environment.
The direct impact of substituting dairy manure for fertilizer on alfalfa has been a savings of $24 per acre per year. This practice represented a savings of $1800 in 1994, $1400 in 1995, and an estimated $1400 in 1996. We have also changed our crop rotation to permit the application of manure prior to seeding alfalfa in late July. By using relatively high rates of composted manure we can supply the nutrients required for the alfalfa seeding as well as for the first production year. Since we begin to topdress manure in the second production year, it is possible that we will be able to completely replace fertilizer with manure in our alfalfa production system. We seed an average of 40 acres of alfalfa per year, at our normal fertilization rate representing an annual savings of about $1000.
The impact on our total fertilizer purchases has been dramatic. In 1988 through 1993 we purchased an average of 54,698 pounds of fertilizer nutrients each year. From 1994 though 1996, we purchased an average of 33,652 pounds of fertilizer nutrients, or 38.5% less. Soil fertility levels continue to be maintained at medium to high levels, indicating that reduction of fertilizer purchases should not adversely affect crop yields.
The initial nutrient balance caused us to take a close look at the mineral program for the dairy operation, and we eliminated unnecessary K (and therefore unnecessary expense) from the mineral mix.
Changes in practice–The amount of manure topdressed on alfalfa fields in the US continues to increase. This is supported by recent recommendations that little or no manure be applied to grass fields which will be used for dry cow forage. The proportion of dairy manure stored as a liquid or slurry continues to increase, and farmers with these systems are better able to topdress manure on alfalfa. Most farmers are pleased with the results: Topdressing manure decreases fertilizer purchases, maintains yields, and supplies nutrients to a growing crop when there is less chance of leaching and runoff.
Operational recommendations–After many years of nutrient balances on the Miner Institute farm, we know that while almost all dairy farms have large nutrient imbalances, there are practical steps which can be taken to reduce inputs and save money while maintaining high levels of production. Farmers can substantially reduce fertilizer purchases by applying manure to growing alfalfa and just prior to forage seeding. In some cases fertilizer purchases for alfalfa can be eliminated entirely, but fertilizer may need to be purchased for land which is next to non-farm neighbors who may object to the strong odors of liquid manure.
In two of the three years in which PSNT were done at Miner Institute, soil nitrate levels were unusually low throughout the Northeastern US. This may contribute to why the tests at the Institute indicated a need for supplemental N. Nonetheless, PSNT should continue to be stressed as an important analytical tool for dairy farmers.
Research results were presented a number of meetings where producers and other agricultural professional were present. These included 600 farmers and 110 veterinarians at meetings throughout the Northeastern US, and over 700 in attendance at the California Animal Nutrition Conference. In addition, Institute staff frequently counsels individual farmers concerning nutrient management, drawing on what has been learned in this project.
Areas needing additional study
a. A nutrient balance provides a snapshot view of what is occurring on a particular farm. It does not improve our understanding of the effects of the farm ecosystem. We need to understand the effects of changes in manure handling system on nutrient loading and pollution potential, and the influence of dairy farm type (pasture-based vs confinement, for instance) on nutrient efficiency.
b. We need to better understand the relationship between the nutrient balance on a particular dairy farm and changes in soil fertility. In spite of annual surpluses of 200% or more of P and K on the Miner Institute dairy farm, soil fertility levels as measured by Cornell University soil analyses have changed very little in the past ten years.
c. How much phosphorus is too much? We need to know at what soil test level this nutrient will be susceptible to leaching losses. This is important since topdressing manure at a rate which will meet the K needs of alfalfa will result in a considerable surplus of P.