Alan Rotz, USDA/ARS, Pasture Systems and Watershed Management Research Unit, University Park, PA.


Producers continue to look for management changes that can improve their efficiency and thus increase or at least maintain the profitability of their farms. They must also consider the efficiency of nutrient use and the reduction of nutrient losses to the environment. Environmental and profitability issues often conflict since the farm value of the nutrients saved is normally less than the cost incurred in reducing their loss.

When making management decisions, producers and those advising producers must consider the impacts occurring throughout the farm. This requires the integration of considerable information, which is often difficult without the assistance of computers. Whole-farm simulation provides a comprehensive assessment of production systems by considering all the major components, the most important interactions among these components, and their impacts on farm performance, profitability, and the environment.


To determine the long-term farm impacts of management changes including different cropping systems and various strategies and technologies that either reduced or improved forage quality.


Simulations were performed to evaluate forage management options on a typical farm in the mid Atlantic and northeast regions. The simulated farm included 100 cows and 200 acres of cropland. The soil was a Hagerstown silt loam. Simulations were done over 25 years of State College, Pennsylvania weather. The base farm produced 100 acres each of alfalfa and corn with the alfalfa harvested as silage using a four cutting strategy and most of the corn harvested as silage. These crops supplied all of the forage and a portion of the grain needed to meet the nutrient requirements of the herd.

Alternative cropping systems included:

  1. half of this alfalfa replaced with grass with the same 50% from corn silage.
  2. a shift toward more corn with 70% of the forage from corn silage and 30% from alfalfa.
  3. inclusion of rye double cropped with corn where 18% of the forage came from rye silage with a little over 50 and 30% from corn and alfalfa silages.

To illustrate the effects of reduced alfalfa quality, a three cutting harvest strategy was simulated with about one more week between each harvest. For improved alfalfa quality, an adjustment was made to represent a 10% genetic improvement in fiber digestibility. Finally, two strategies were used to improve corn silage quality: increasing the cutting height by 12 inches, and using a mechanical processor on the chopper to breakdown forage particles.


Simulation results illustrated that the production and use of more corn silage, particularly when double cropped with rye silage, reduced nutrient losses from the farm with relatively small effects on farm profitability. Use of a three cutting strategy for alfalfa production with longer regrowth periods between harvests reduced farm profit by $80/cow. Genetic improvement of alfalfa for a 10% increase in fiber digestibility provided up to a $76/cow increase in farm profit. Increasing the cutting height in corn silage harvest improved forage quality, but provided a net loss in profit of $12/cow. Mechanical processing provided a more economical means of improving corn silage quality where an assumed 2% increase in milk production increased profit by $42/cow per year.