Application of the Cornell Nutrient
Management System on A Commercial Farm

Carl D. Bannon
Area Field Crop Specialist
Cornell Cooperative Extension

Tom P. Tylutki
Area Dairy Specialist
Cornell Cooperative Extension

Introduction

Nutrient management planning requires an integrated approach that monitors the nutrient inputs onto farms such as fertilizer, feed, and nitrogen fixation compared to the outputs in agricultural products such as grain, eggs, meat, and milk.

Surveys of mass nutrient balances of New York State dairy farms have indicated that greater than 2/3 of the N, P, and K entering the farm remain on the farm (Klausner, 1995a). The majority of the imported nutrients are from purchased feed. Nutrients that remain on dairy and livestock farms are primarily in manure and often exceed the nutrient requirement of the farm's cropping program. The relationship between the amount of nitrogen (N), phosphorous (P) and potassium (K) remaining on the farm is independent of herd size in the Northeast, because most of these farms have a similar animal unit to land ratio (animal density). Manure nutrients are available for crop production but can be lost to the environment from ammonia volatilization, leaching, denitrification, and/or runoff. Due to these high levels of nutrient accumulation on livestock farms, an integrated approach to nutrient management planning is needed.

Integrated nutrient management planning must ensure effective utilization of all imported nutrients as well as manure nutrients in an effort to minimize environmental risks. Nutrient inputs such as feed and fertilizer must be critically evaluated to meet, and not exceed, the demands of the herd and crop program. Soil testing and forage analyses are important components of dairy and livestock nutrient management planning programs. This requires all farm advisors (crop specialists, nutritionists, SWCD, NRCS, and veterinarians) to work collaboratively. These practices can have both economical and environmental advantages to farms and communities.

The Cornell Nutrient Management Planning System (CNMPS) is a suite of Microsoft ExcelÒ spreadsheets developed by faculty and staff in the Departments of Soils, Crops and Atmospheric Sciences, Animal Science, Agricultural and Biological Engineering, and Cornell Cooperative Extension. The goal of the software is to integrate soil fertility, crop management, crop rotations, animal nutrition, economic, and engineering considerations into a viable nutrient management plan. The software consists of four integrated components: 1) calculating a mass nutrient balance, 2) evaluating and improving the animal feeding program, 3) evaluating and modifying crop rotations, and 4) developing a crop nutrient management plan. This paper will demonstrate the use of the CNMPS on a commercial dairy farm in New York State by a team of Cornell Cooperative Extension Specialists (Bannon and Klausner, 1997; Tylutki and Fox, 1997; Kilcer, 1997).

McMahon's EZ-Acres is a 500 milking cow dairy farm located in Homer, NY. This farm has recently consolidated its herd to a modern freestall barn and has constructed new dry cow and heifer facilities. EZ-Acres farmland is composed of a mix of level well-drained soils and moderately well drained sloping soils. The well-drained soils are used for corn silage and alfalfa rotations. These fields lie over the Homer-Preble Aquifer, the sole source of drinking water for the city of Cortland. Many of these fields also border Factory Brook, a trout stream which travels through the farm. The sloping fields are composed of heavier textured soils that have a low water leaching potential but a high run-off potential. Run-off from these fields can enter tributaries to Factory Brook.

The mass nutrient balance was calculated for the farm for July 1, 1996 through June 30, 1997. This compares the amount of N, P, and K entering the farm from feed, fertilizers, purchased animals, and N fixation with farm exports of N, P, and K from milk and animal sales. The case study farm has 77.3%, 67.5%, and 65% of the imported N, P, and K remaining on the farm, respectively. The majority of these nutrients must be managed in manure. Klausner (1995a) has reported similar percentages of nutrients remaining within the farm boundary for herds of all sizes. Typically, two-thirds of imported nutrients come from imported feed with the remaining third coming from fertilizer. This herd, however; only imports 9.1%, 12.7%, and 0% of their N, P, and K, respectively from fertilizer. These low levels are accomplished by proper use of manure as a crop nutrient source. The farm has been working with Cornell Cooperative Extension for several years developing a crop nutrient management plan. As various phases of the nutrient management plan have been implemented, the farm dramatically reduced use of commercial fertilizer with no yield loss.

The land required for manure applications is a function of the nutrient requirement of the cropping program, the nutrient content of the manure, the number of animals and their manure production (Bannon and Klausner, 1996). Animal density guidelines are used in the nutrient management planning process to predict appropriate animal to land ratios. These ratios compare the number of 1000-pound animal units with the acreage in the farm's cropping program. Animal density guidelines have been developed for New York by Klausner (1995b). These guidelines are intended to prevent over applications of manure while increasing the quantity of on-farm forage produced. Proper use of the guidelines requires good management skills on the part of the farmer.

EZ-Acres farm has 550 adult dairy animals with an average weight of 1450 pounds and 430 youngstock with an average weight of 680 pounds. There are a total of 1075 crop acres with 43% in corn silage production and 57% in hay crop silage production. The hay acreage is approximately 50% alfalfa and 50% perennial forage grasses. The animal units per tillable acres are 1.01.

The Cornell Net Carbohydrate and Protein System (CNCPS) is an animal nutrition model designed to evaluate and predict animal nutrient requirements (Fox, 1992). The CNCPS was used to make an initial analysis of the current herd feeding programs. The cow ration is 46% forage and 54% purchased feed, well within acceptable guidelines. Predicted total milk production for the year is 12,340,570 lbs. This level of purchased feeds results in a large percentage of nutrients imported. As more feed is imported by a farm to meet protein requirements, P and K are almost always imported in quantities much higher than is required by the cows and crops. Management of this excess P and K is difficult given the limited land resources found on many farms. Potassium is not considered a water quality risk, however; K accumulations in soils is linked to high K concentrations in grass and legume crops which is a concern for dry cow health.

The goal of this analysis is to minimize purchased feeds to minimize nutrient imports. We concluded this farm has the potential to improve management of the hay crops to increase both yield and quality to allow for more home-grown forage to be fed while maintaining, or improving, milk production. The proposed feeding program was designed to utilize high quality orchardgrass hay-crop silage.

From a nutrient management point of view, this change has dramatic implications. Milk production remained constant, however; the percent of the ration that is home raised was increased to 78% from 46%. By decreasing the amount of feed purchased, the amounts of N, P, and K imported were also decreased dramatically. The average percent purchased N was decreased 55%, P was decreased 48%, and K was decreased 82%. Efficiencies of nutrient utilization were similar between the current and proposed feeding systems; the benefit is a higher degree of nutrient recycling within the farm boundary. Manure production was increased 10% due to the higher forage intake of the herd.

Crop available manure nutrients and crop nutrient requirements were predicted using the Cornell crop nutrient management planning software (Klausner and Barry, 1996). Manure N is not adequate to meet the entire nitrogen requirement of EZ-Acre's cropping program, so additional N fertilizer is purchased. Phosphorus and K in manure collected annually exceed the annual demand for P and K in the cropping system. Manure is composed of approximately 50% ammonium N and 50% organic N. Ammonia N is easily lost by volatilization if it is not incorporated into the soil within 24 hours. About 55% of the organic N is mineralized to a plant available form when the organic N during the year of application is added to the organic N mineralized from previous year's applications. Without ammonia conservation, there is not enough manure N to meet the crop requirements. A surplus of P and K is produced in manure compared to the annual crop nutrient requirement.

Manure applied to meet the crop's N requirement often results in excessive applications of P and K and excessive soil test levels of these nutrients. Fertilizer P and K application rates should be determined by soil testing with recommendations based on regional crop response research.

EZ-Acres fertilizer program consists of a corn starter fertilizer with 20 pounds per acre of N and P and no K.

Soil analyses from the Cornell Nutrient Analysis Laboratory showed high levels of both P and K. Because the soils in NY are often cold and wet in the early spring, a starter fertilizer containing N, P, and K is recommended unless the soil test levels are very high.

To verify the need for additional N for corn (beyond a starter fertilizer) the Pre-Sidedress Nitrogen Test (PSNT) is used (Klausner, 1996). The PSNT is taken when the corn is 6-12 inches tall to determine if sufficient N is present for maximum economic yields from organic N sources such as manure and crop residues. Utilization of the PSNT on EZ-Acres corn fields has resulted in a 75 to 96% reduction in purchased sidedress-N fertilizer over the past 4 years, without a reduction in yield.

EZ-Acres farm spreads manure year round. There is 10 days of storage in the milking barn and bedded manure is spread as needed from dry cow and youngstock housing facilities. Manure is applied to cornfields with low run-off potential during the winter. Manure is spread on grass hay and then legume hay fields during the growing season. In the spring of 1997, approximately 100,000 gallons were spread on neighboring crop farms. This was required because all corn fields had manure applied and were planted and grass hay fields were within a week of harvest.

EZ-Acres has made excellent progress in implementing their nutrient management plan. For dairy farms to sustain themselves, profitability needs be linked to environmental stewardship. Community and neighborhood relationships cannot be ignored. Implementing nutrient management plans often involve storing manure and applying it to fields that may have not received manure in the past. This often brings new odors to neighborhoods and associated complaints. Dairy farmers and other livestock producers need to be increasingly proactive in maintaining good community relations. These relationships need to be considered in the planning and implementation of nutrient management. Nutrient management planning is one strategy dairy and livestock producers can use to help position themselves for the future.

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