Entire read here, and it’s interesting stuff. I don’t even agree with everything he says, but it is still a very informative read:
Norman Borlaug, founder of the green revolution, estimates that the amount of nitrogen available naturally would only support a worldwide population of 4 billion souls or so. He further remarks that we would need another 5 billion cows to produce enough manure to fertilize our present crops with “natural” fertilizer. That would play havoc with global warming. And cows do not produce nitrogen from the air, but only from the forages they eat, so to produce more manure we will have to plant more forages. Most of the critics of industrial farming maintain the contradictory positions that we should increase the use of manure as a fertilizer, and decrease our consumption of meat. Pollan would solve the problem with cover crops, planted after the corn crop is harvested, and with mandatory composting. Pollan should talk to some actual farmers before he presumes to advise a president.
Pollan tells of flying over the upper Midwest in the winter, and seeing the black, fallow soil. I suppose one sees what one wants to see, but we have not had the kind of tillage implement on our farm that would produce black soil in nearly 20 years. Pollan would provide our nitrogen by planting those black fields to nitrogen-producing cover crops after the cash crops are harvested. This is a fine plan, one that farmers have known about for generations. And sometimes it would even work. But not last year, as we finished harvest in November in a freezing rain. It is hard to think of a legume that would have done its thing between then and corn planting time. Plants do not grow very well in freezing weather, a fact that would evidently surprise Pollan.
And even if we could have gotten a legume established last fall, it would not have fixed any nitrogen before planting time. We used to plant corn in late May, plowing down our green manure and killing the first flush of weeds. But that meant the corn would enter its crucial growing period during the hottest, driest parts of the summer, and that soil erosion would be increased because the land was bare during drenching spring rains. Now we plant in early April, best utilizing our spring rains, and ensuring that pollination occurs before the dog days of August.
A few other problems come to mind. The last time I planted a cover crop, the clover provided a perfect habitat in early spring for bugs, bugs that I had to kill with an insecticide. We do not normally apply insecticides, but we did that year. Of course, you can provide nitrogen with legumes by using a longer crop rotation, growing clover one year and corn the next. But that uses twice as much water to produce a corn crop, and takes twice as much land to produce the same number of bushels. We are producing twice the food we did in 1960 on less land, and commercial nitrogen is one of the main reasons why. It may be that we decide we would rather spend land and water than energy, but Pollan never mentions that we are faced with that choice.