In the minds of the public, organic food production is associated with efforts to save the planet, but Warren Morgan, an apple grower and packer in Quincy, Washington, questions whether cultivation—one of the few options that organic growers have for managing weeds—is really a greener practice than using herbicides.
Speaking at the Washington State Horticultural Association’s annual meeting in Wenatchee last December, Morgan said pioneers of the organic movement wanted to minimize their impact on the land and its inhabitants by avoiding the use of toxic crop protection materials. So, most growers were forced to use mechanical methods or burning because no organically certified herbicides were available. Cultivation came to be considered a green growing practice, because it was used in organic production.
When Morgan, who operates Double Diamond Fruit, decided to pursue a more sustainable form of fruit growing, he bought a cultivator because that’s what organic growers were using.
"We ran it this spring, and it did a great job of killing the weeds that were present and gave us a nice, clean, tilled look that had a certain aesthetic appeal," he said. "When we had finished, we started discussing what we had really accomplished environmentally. It wasn’t long before we had a very active debate about whether tillage or chemicals were really the path to a greener apple-growing world."
Morgan believes improving soil health is an important part of becoming more sustainable and that cultivation is a contradiction of organic farming because it has negative impacts on the soil.
Cultivation has the advantages of integrating compost into the soil, speeding the decomposition and mineralization of organic matter, and destroying rodent habitat, but it also has a number of negative effects. It discourages growth of soil-borne organisms, destroys the soil’s capillary structure, kills tree roots, requires large quantities of fossil fuels, and is not a natural practice.
Cultivation requires more tractor horsepower than weed spraying and usually must be done three times per season, and sometimes as many as four, on each side of the tree row. Another problem with cultivation is that it improves the odds of successful reseeding of weeds by preparing a seedbed for better germination. In some respects, cultivation breeds cultivation, Morgan said.
Chemical herbicides, on the other hand, have the advantage of not requiring as much fossil fuel because of fewer passes through the orchard. They don’t have a detrimental effect on tree roots, water infiltration, or organic matter. Morgan said only one or two applications are generally needed per season, and it may be possible to spot spray from a Honda four-wheeler (which is more fuel efficient than a tractor) rather than do a complete application. Also, by avoiding cultivation and allowing mulches to develop (through side-discharge mowing and additional composting), weed growth is spotty and diminished.
Drawbacks of chemicals are that they may result in resistant weed species, and they are not natural.
Neither cultivation nor use of herbicides is ideal, Morgan said. However, growers need to control weeds because they consume large amounts of water and nutrients, and once these are tied up in fresh plant material, it takes a long time to get them back into a form where they are available to the trees, he said.
"You can’t just let the weeds grow, reseed, and spread. Keeping weeds from reproducing and gradually reducing the number of viable weeds in your tree row is very important."
By using sustainable growing practices, rather than organic, Morgan feels he has the flexibility to pursue practices that make sense both economically and environmentally and has developed his own set of best management practices with the top priority being to build soil organic matter and biodiversity. He’ll:
• Produce orchard-grown mulches at low cost;
• Supplement mulches with conventional fertilizers for the next five to seven years and avoid cultivation.
• Reduce irrigation applications and the amount of water applied, because the mulch helps keep the moisture in the soil.
• Use herbicides with the smallest environmental footprint and use as few as possible. With continued use of the mulch, weed pressure may be lower in the future.
• Rotate herbicides to avoid creating resistant weed species.