Renewable is not a synonym for sustainable

One of my dad’s maxims was “never buy or sell hay.” Buying hay might bring in the seeds of weeds we had spent years trying to control; selling hay removed tons of nutrients without replacing it with commensurate manure.Thousands of years of unharvested prairie had built the rich silt loam. The first 75 years of diversified, value-added farming saw mainly livestock and livestock products leave a nearly-level farm, using no commercial fertilizer, yet with ever-increasing yields.

We began raising soybeans during World War II, rotating and covering about one-fifth of the acreage each year. By 1954, soil tests showed a need for phosphate fertilizer. (The southwest Iowa soils were high in potassium and we inoculated the beans for nitrogen fixation.)



A farmer may be able to sell some switchgrass grown from the nutrients in the soil, but over time will have to replace a lot of nitrogen, phosphorus and potassium and eventually some micro-nutrients.

Maintenance rates would cost around $30, at 2007 prices, per ton of dried switchgrass sold. For biofuels to be sustainable, fertilizer sources would have to be limitless and economical.

Des Moines Register