Improving Dairy Farm Sustainability I: An Approach to Animal and Crop Nutrient Management Planning

Abstract

This two‐part article reports on a process for integrating knowledge to develop and evaluate nutrient management plans for dairy farms. The focus is on accounting for and managing N, P, and K on a commercial farm. The case study farm was a well managed, progressive dairy farm located in central New York with 320 lactating cows ( Bos taurus ), 290 heifers, and 600 acres of crop land. This farm had the resources and management skills that are a model for dairy fanning in the future. However, mass nutrient balances indicated that 60 to 72% of imported N, P, and K were in excess of nutrient exports from the farm; 60 to 80% of the imported nutrients were from purchased feeds. Evaluation and refinement of animal diets resulted in a reduction in crude protein content of the rations by 2 percentage points while supporting a 13% increase in milk production and a 34% decrease in total N excretion. Partial budgets projected that ration reformulation increased net farm income by $40 200. Implementation of a crop nutrient management plan was expected to decrease fertilizer purchases and application expenses by about $1350, but construction of a remote manure storage pond and custom spreading of manure resulted in a decrease of net farm income of $4000. The vast quantity of data required and the complexity of the analysis indicate that developing computerized decision aid tools will be necessary to apply the process to a large number of farms. Research Question Water quality concerns and proposed or enacted nutrient management regulation have created a heightened awareness of the need for improved nutrient management on dairy farms. Mass nutrient balances indicate about 67% of N, P, and K imported onto dairy farms as purchased feed, fertilizer, and N fixation are not accounted for as products sold. A process is needed that reduces nutrient loading on dairy farms. This process should incorporate (i) an assessment of nutrient imports and exports, (ii) a more accurate system for formulating animal diets, (iii) a system to protect water quality by predicting manure and soil nutrient status and determining agronomically appropriate manure and fertilizer application rates, and (iv) a method to evaluate the impact of proposed changes on farm profitability. Literature Summary Many studies have shown that more nutrients (N, P, and K) are imported onto dairy farms than are exported. There is a need for nutrient management on dairy farms to protect water from contamination from these excess nutrients. When environmental objectives are met by more efficient allocation of resources and better use of information, economic efficiencies may also be realized. Since nutrients constitute a scarce resource, practices designed for economically efficient nutrient use should also be environmentally sound. The need for a multi‐disciplinary approach in sustainable agriculture research has been well documented. The benefits of farmer involvement in sustainable agriculture research have also been noted. However, few studies that use a multidisciplinary approach have also attempted to use commercial farms to study sustainability. Study Description The purpose of this study was to develop and evaluate a process for integrating knowledge across agricultural disciplines to produce and evaluate nutrient management plans for dairy farms. In this two‐part article we report on a process to account for and manage N, P, and K on a case study dairy farm. Mass nutrient balances were constructed to evaluate the nutrient status of the farm. A dynamic model of cattle nutrition, the Cornel1 Net Carbohydrate and Protein System, was used to evaluate cattle nutrient use. The reformulated rations were developed with the objective of increasing nutrient efficiency and reducing feed costs while maintaining or increasing milk production. The crop nutrient management plan was used to replace as much commercial fertilizer as possible with manure nutrients. Partial budget analysis was used to project the impact of the alternatives on net farm income. Applied Questions On the case study dairy farm, to what degree do nutrient (N, P, and K) imports exceed exports? Mass balances of N, P, and K for the case study farm indicated that 59 to 72% of the nutrient imports from purchased feeds, fertilizers, and symbiotic N fixation were not accounted for in the nutrient exports of milk and animals. What steps can dairy producers take to limit excess nutrient loading? Partitioning of the various nutrient imports showed that purchased feeds accounted for 61% of the N, 81% of the P, and 63% of the K. Ration reformulation resulted in an increased use of farm‐produced alfalfa silage, a reduction in crude protein content of the rations by 2 percentage points, and a 25 to 40% reduction in excreted nutrients. This was accomplished while herd milk production increased by 13%. Reductions in ration crude protein were achieved by closely balancing the nutrient supply and requirements for both rumen bacteria and the whole animal. A step‐by‐step process of nutrient management planning for efficient use of manure nutrients resulted in manure being substituted for much of the fertilizer requirement. Soil testing, manure analysis, feed ingredient analysis, and monitoring of animal dry matter intake were critically important tools in the process. What effect do proposed animal and crop nutrient management plans have on farm profitability? Reformulating rations increased net farm income by $40 198. Of this total, $11 700 was due to increased milk production associated with a decrease in the energy required to excrete excess N, the remaining increase was due to reduced purchased feed costs. The projected benefit of the crop nutrient management plan was $1300. Constructing a remote manure storage pond would increase net profits by $2300 if existing labor were used for spreading but would be reduced by $4000 if manure was custom applied. The predicted effects of the proposed crop nutrient management plan were small compared with the farm's revenue and expenses because the farmer was already following recommended fertilizer application rates fairly closely. What process will integrate knowledge to predict dairy farm sustainability? The development of nutrient management plans is a process that integrates animal, crop, and farm management information. Computerized decision aid tools are needed to accurately match nutrient requirements of animals and plants to nutrients available on each unique farm, and to determine the fate of excess nutrients. These decision‐aid tools are needed to predict the economic and environmental impact of alternative practices in each unique production setting. What did the multidisciplinary group learn about knowledge integration? The interactions among project members forced us to think about our own disciplines from a new perspective. On the other hand, the process of integrating knowledge was not simple or obvious. For example, there was no mechanism to determine a crop rotation that would optimize both animal and crop production. Also, differences among disciplines in the collection of data and formulation of recommendations had to be resolved. The combination of on‐farm data collection and modeling was challenging, because some participants were uncomfortable with the assumption‐making inherent in using models. What are the benefits and challenges of case study research? Working with commercial farmers helped identify and focus on the most important problems and the development of practical solutions and increased the visibility of the project. However, because the farm was an active commercial farm, the farm manager did not routinely collect the type of data needed for research, and the farm was continually changing even as data were being collected. This made interpretation of results more difficult. In addition, because the scientific team did not control management practices on the farm, comparative experiments were impossible.