BY JOHN HOLLAND
Farmers have fertilized for much of the past century with nitrogen obtained from petroleum and phosphorous mined from rocks.
Experts meeting in Modesto this week suggested looking at something else right under our feet – the microbes that can enhance the soil if given a chance.
Healthy ground has lots of plant residues that the tiny creatures break down into nutrients for the next crop. They also help make the dirt porous enough for proper movement of water and air.
“Microbes are critical in creating soil structure,” said Kate Scow, professor of soil science and soil microbial ecology at the University of California, Davis.
She spoke at the 24th annual conference for the state Fertilizer Research and Education Program, held at the DoubleTree Hotel. It drew researchers, industry people and others interested in how to help plants grow without harming the air or water.
Synthetic fertilizers came about in the 1940s and have boosted crop yields for a growing population. But for the long term, speakers said, farmers need to foster the biodiversity underground.
Earthworms chew on plant material and excrete castings that enrich new growth. Insects have their own roles in the food cycle – including dying so they can be decomposed by other soil denizens.
Farmers can encourage all this by keeping tilling to a minimum and growing other vegetation between the crop rows. They can use compost, made from plant waste broken down by bacteria. They can apply livestock manure at a rate that assures that nitrogen goes up into the feed crops, not down into the groundwater.
Wind and rain can erode bare soil at a rate much greater than it formed over a few centuries, said Z. Kabir, regional soil health specialist for the federal Natural Resources Conservation Service. He also noted how excess nitrogen can cause algae buildups in waterways, and he showed a photo of Chinese children swimming in one of them.
The conference was co-sponsored by the Western Plant Health Association, an industry group that promotes safe use of fertilizers. It urges farmers to apply them only when the crops need them, and in a way that avoids pollution.
Scow said healthy soil retains water during a drought and captures some of the carbon that contributes to climate change. Beans and certain other crops rely on microbes that pull nitrogen from the air, reducing the need for synthetic fertilizer.
“Everything’s connected,” Scow said. “Everything’s complicated.”