Issue link: https://read.dmtmag.com/i/50987
"It's not going to meet your whole nitrogen need, but it's going to be a nice "It's not going to meet your whole nitrogen need, but it's going to be a nice contribution," he said. Morgan calculates the cost of applying the herbicide contribution." —David Granatstein and planting the crop at $84 per acre. Based on those costs, Granatstein figures that a four-foot-wide swath of alfalfa supplies available nitrogen at a cost of around 65 cents per pound, versus 70 cents for a commercial fertilizer. A wide swath of cover crop that is mowed and blown onto the tree row in midseason might provide the trees with too much nitrogen, affecting fruit quality and delay- ing maturity, Granatstein warned. To avoid that, the clip- pings can be dropped into the alley at certain times in the season. Although there was no statistical difference between the amount of biomass in the areas that were sprayed or unsprayed before planting, the nitrogen level in the sprayed areas is greater. This is because the unsprayed cover crop contains a greater proportion of grass and other species, he reported. Young orchard In 2010, Morgan planted another cover crop trial in a young, grafted Fuji block that had greater light penetra- tion. Alfalfa and white clover were seeded in May into existing vegetation, doing a double pass with the same drill to create a seven-foot-wide swath. Kukes said that as well as blowing the cover crop clip- pings under the trees, he rakes prunings into the tree row after flailing. He has tried growing white clover in mature orchards, and, although it grew well at first, it was gradually outcompeted by the grass. "In older orchards, there's so much shade from the trees, it's hard to establish the cover crops without taking out the grass," he said. "From now on, when we have a new orchard, we'll establish cover crops when the ground's bare and the trees are in," he said. Red clover Neighboring orchardist Jack Toevs has planted red clover as a cover crop in a block of organic Piñata apples. The clover was planted in the fall of 2009, along with grass, into a bare alley using a grass drill with an attachment for small seeds. He got the seed from Montana. Red clover is a biennial plant that can be perpetuated by letting it go to seed, Granatstein said. It can be mowed close after harvest to remove hiding places for voles. Toevs said he does not control voles, but he's seen a barn owl, hawks, and even an osprey around his orchard that he thinks are preying on mice. Junell Wentz, a cherry grower at Wenatchee Heights, said she uses a mixture of oats and plaster of Paris to kill voles. She attaches short sections of pipe to a PVC T-joint, and places a mixture made of three parts oats and one part dry plaster of Paris in the middle pipe with a cap on. Voles enter the open pipes and eat the mixture. The plas- ter of Paris moistens and hardens in their gut, killing them. Wentz said birds will not enter the pipe to eat the mixture, and birds of prey that eat the dead voles are unaffected because the mixture is nontoxic. • www.goodfruit.com GOOD FRUIT GROWER DECEMBER 2011 55