Father and son Joe and Nick Bavaro, who manage almond orchards in California’s Stanislaus and San Joaquin counties, say they want to be good stewards of the land. But for every environmentally friendly practice they implement, they say there’s a trade off, such as increased energy use and the accompanying carbon emissions.
Take the dilemma of how to get rid of brush that’s pruned from the trees every fall after harvest. In the past, many growers created large piles and burned them.
But under legislation, growers of nut trees will no longer be able to burn their brush prunings by June 1, 2010.
Senate Bill 705 is designed to reduce smoke and the accompanying particular matter emissions caused by open-field burning of agricultural waste.
Instead, growers have to figure out other ways to get rid of the annual piles of brush.
Many have gone to shredding or chipping the prunings. Large, diesel powered machines with upwards of 400 horsepower gobble up the branches and limbs, spitting out pieces that range in size from a toothpick to a 2-inch-diameter chip. The size typically varies with the brand of machine.
The chips are too large to leave in an orchard to decompose, so growers have had to find other disposal options.
If there’s a nearby co-generation plant, it can use them for fuel.
“The product with this product is the cost of transportation of getting it to Tracy [where a co-gen plant is] or these other facilities,” Nick says.
Hauling the chips out of the orchard and leaving them in piles is not wise, he says. They have been known to spontaneously combust.
Nick says they prefer to leave the toothpick-sized shreds in the orchards because they recycle nutrients to the soil, helping build its humus and organic content.
“We were doing it every year, and we were starting to build up a mat,” he says. “It takes nitrogen to break this down, and we don’t like to put it on the field if we don’t have to.”
The shreddings are typically spread in the tree middles during the fall, and growers hope for a wet winter to aid decomposition.
If they use micro-sprinklers or drip that only wets the tree rows, the middles receive little if any additional moisture.
The concern is if the shreddings aren’t fully broken down by the following August harvest, machines that pick up the nuts shaken on the ground also will pick up the small wooden pieces. Hullers and shellers then must remove the field trash at their plants.
Some growers have turned to lightly disking the shreddings into the soil. The more soil-to-wood contact there is, the better the soil microbes will be able to decompose the material.
Based on research conducted by University of California Cooperative Extension farm adviser Roger Duncan, the Bavaros say they’ve reduced the amount of brush they prune annually from their trees.
“You’re always going to have tree that fall over and the need for some light pruning,” Nick says.
“There’s not nearly as much brush coming out now than there has in the past,” Joe says. “We’ll maybe do two or three years light, let it go a couple of years, then come back and prune and use a bigger chipper and remove the chips.”