It is easy to lose sight of the final goal when being involved in the processes of achieving that goal. Field sizes and locations, soil sampler, soil analysis, crop selection, and recommendations all easily overpower decisions about objectives. One such major objective is that the energy outputs per energy input from agriculture or any major activity within the rural environment be as high as possible. This may be expressed as a ratio of output to input or as net returns. The energy yield from corn fields in 1970 was 8.164.800 kilocalories per acre (Pimentel 1973:445).

Using this as a standard or base for comparison, since crops to be planted in the area have not been selected, it is useful to compute fertilizer costs (in energy) per acre. This shows the relative values and allows more rational decisions to be made in general. In particular, it can show the costs of soil movement and nutrient loss in terms of energy. To retain nutrients on the land means the same as not to have to replace them to grow a crop. Another consequence is to quantify, fairly precisely, the long term worth of land. "Poor land" can be re-thought as land that requires high energy investments to collect and produce any energy for people. The poorer the land, the more the energy costs. Some land is naturally poor. Some, with investment, can release its potentials for collecting energy. Some is rich, but its richnesss is being lost. Land management is, to a large extent, managing the energetics of the land. Taking an analysis that requires 500 pounds of 2-12-12 fertilizer per acre the analysis proceeds as follows:

	Rating	Kcal/lb Production Cost	Product
Nitrogen (N)	2	8,400	16,800
Phosphate (P)	12	1,520	18,240
Potassium (K)	12	1050	12,600
Lime (Ca)	74	1000	74,000
	100		121,640

The production costs for N, P, and K are from Pimentele (1973:445) and the lime is an estimate. The processing energy costs vary widely due to the type of lime selected.

Assume another soil type required 5-10-10 fertilizer.

	Rating	Kcal/lb Production Cost	Product
N	5	8,400	42,000
P	10	1,520	15,200
K	10	1,050	10,500
Ca+	75	1,000	75,000
			142,700

The difference, 1.17 times the first type, is substantial.

Broadcasting costs per acre are about 11,600 kcal.

The results suggest that land owners can either attempt to keep the nutrients where they are, cycling them in place, or hauling them in and broadcasting them. As long as fossil energy is relatively inexpensive and in good supply, the latter seems reasonable. However, the former is the more reasonable both as a means of reducing energy costs and preparing for uncertain energy availability and costs in the future. The Trevey provides a preliminary energy analysis based on inputs to a form showing the optimum crop selected by computer, then a cost effective, low-pollution fertilizer schedule will be prescribed. Using the fertilizer recommended, application rate, and pounds per acre, computations (as above) are made with the results being the total annual fertilizer energy needs for the area.