Energy use (1999-2000) and Output/Input ratios for the Wisconsin Integrated Cropping Systems Trial

Johanna Oosterwyk and Joshua L. Posner [1]

Introduction

The consumption of non-renewable energy in agriculture is an issue that waxes and wanes in the public interest. The sudden rise in oil prices in the early 1970’s spawned a number of studies on the use of energy in agriculture (Pimentel, 1973; Heichel, 1973). Energy however, remained relatively cheap, and technologies requiring high-energy inputs continued to be popular. Then again, in 1990, farmers were concerned about the effect of the impending conflict in the Middle East on natural gas prices for drying corn during the wet fall of that year. The following winter, during Operation Desert Storm, fertilizer dealers were not quoting prices for anhydrous ammonia for delivery in the spring, but when prices didn’t rise, interest in low energy alternatives again waned. Most recently, as fuel prices climbed to record heights in the summer of 2000, farmers were again asking the same questions that they have many times about the economic returns from high input systems.

Methods

Predicted energy use in the six rotations of the Wisconsin Integrated Cropping Systems Trial has been estimated by using published tables that quantify the energy required to produce agricultural inputs (Pimentel, 1980; Stout, 1984) and the Minnesota Farm Machinery Economic Estimates (1992) for fuel use estimates. Software called ABCS (Agricultural Budget Calculation Software) estimates fuel usage for specific field operations. Energy conversions for all fertilizer products (anhydrous ammonia, urea ammonium nitrate, starter, etc.) are based on the total amount of product applied. Some of the key conversions used to calculate energy consumption are summarized in Table 1.

In order to compare energy use in six cropping systems and their output/input ratios, the team addressed three theoretical issues:

1. Only the fuel cost in spreading manure were counted as an input in systems 4, 5 and 6. The energy content of the manure and the equivalent energy value of the nutrients in the manure were not considered as external inputs to the cropping system on a dairy farm.
2. The energetic value of each cropping system’s output was calculated on a total energy basis, and not as metabolic energy for either cows or humans. In this way the numbers were standardized, regardless of end use of the agricultural product.
3. In order to simplify the calculations, human energy in terms of labor per system was not included as part of the inputs.

Results

Calculated energy use and output/input ratios for the past nine years are presented in Tables 2 and 3. Table 2 shows the variation in inputs between the specific phases of each cropping system, while Table 3 illustrates the differences in energy efficiency between whole systems.

Table 2 first compares the inputs and outputs of the corn phase of each cropping system. The first two cash grain systems (continuous corn and corn following soybean) are clearly higher in inputs than the other three systems, where the use of pesticides, fertilizers and, except in the case of CS3, drying costs are much higher. Due to the higher moisture of no-till corn at harvest, drying costs in CS2 account for a greater portion of the total inputs and decrease the efficiency of that system. Also, in CS4 and CS5, we harvest the corn as high moisture ear corn, avoiding drying costs, which can make up one-third to one-half of the total energy inputs in the years when corn is grown. Corn production also varied greatly by system so the energy represented by corn yields varied by the same measure. The forage-based systems consistently produce higher corn yields than the cash-grain systems, which increase the output/input ratio. The resulting output/input ratios vary from about 7 to 11 in the cash grain systems, while in the forage based systems, the corn phase is much more energy efficient and ratios range from 20 to 30.

The two soybean phases (CS2-drilled, no-till; CS3-row soybeans) have more similar input patterns. Though the no-till practices in CS2 kept fuel prices down and yields were also higher, increased herbicide use made the ratios fairly even between CS2 and CS3. However, compared to corn, growing a legume like soybeans with no nitrogen fertilizer requirement or energy for drying results in higher output/input ratios of around 13. In 1999, Lakeland added soybeans to the low-input forage rotation (CS15), which resulted in an output/input ratio near 20. This may be due to adding soybeans to a system that had not had soybeans and generating greater yields. Also, this system is organic unlike CS2.

In the forage systems (CS4, CS5, and CS6) the alfalfa phases are especially energy efficient. For instance, Hay I produces a ratio of around 40 since maximum production is usually achieved in this phase and the energy inputs of planting have been accounted for the previous year in the direct seeding phase. Rotational grazing (CS6) has the highest input/output ratio. Purchased inputs in this system are very low, and, unlike CS3, weed management and harvesting is done by the animals instead of machinery driven by diesel fuel.

While looking at the energy inputs and outputs by phase permits better understanding of the numbers, whole systems analyses are crucial if we want to understand the implications of energy use on Wisconsin farms. As can be seen in Table 3, the energy inputs in the cash grain systems were higher than the energy inputs in the forage rotations. By the same token, within enterprise types, increasing plant diversity resulted in decreasing energy inputs, and when we compare the energy value of the output to the inputs, we find again that increasing plant diversity resulted in increasing efficiency in energy use. In the cash grain crops, System 3, with its rotation of corn, soybean and wheat and red clover, consistently out-performed System 2 (corn-soybean), both of which proved to be more energy efficient than the continuous corn rotations in System 1. The same pattern was seen in the forage rotations. The pasture mix of timothy, brome grass, canary grass and red clover, was more energy efficient than the oats/alfalfa/corn rotations of System 5 and the alfalfa-corn rotation of System 4 (CS3>CS2>CS1; CS6>CS5>CS4).

References

Fuller, E. B. Lazarus, L. Carrigan, G. Green. 1992 Minnesota farm machinery economic cost estimates for 1992. Minnesota Extension Service. U. of Minn Agriculture.

Grain drying, handling and storage handbook. 1987. Midwest Plan Service. Ames, IA. 2nd ed.

Heichel, G. H. 1973. Comparative efficiency of energy use in crop production. Connecticut Agricultural Experiment Station Bulletin 739. New Haven, CT.

National Research Council. 1989. Nutrient requirements of dairy cattle. 6th ed. National Academy Press. Washington D.C.

Pimentel, D. L. Hurd, A. Bellotti, M. Forster, I. Oka, O. Sholes, and R. Whitman. 1973. Food production and the energy crisis. Science 182:443-449.

Pimentel, D. 1980. Handbook of energy utilization in agriculture. CRC Press, Inc. Boca Raton, Fla.

Stout, B. A. 1984. Energy use and management in agriculture. Wadsworth Inc. Belmont, CA.

1. Professor of Agronomy, University of Wisconsin-Madison. Email: jlposner@facstaff.wisc.edu

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