Soil Nutrient Cycling and Water Use in Response to Orchard Floor Management in Stone-Fruit Orchards in the Intermountain West

An organic peach orchard trial evaluated the effectiveness of different organic management approaches to enhance soil quality and conserve water without compromise to fruit tree growth and fertility. Two tree-row treatments: ‘straw mulch’ (Triticum aestivum L.) and ‘living mulch’ (Lobularia maritima (L.) Desv.) were tested in combination with two alleyway groundcovers: ‘grass’ (Festuca rubra L. with Lolium perenne L.) and a legume, ‘Birdsfoot trefoil’ (Lotus corniculatus L.). The novel treatments were compared with tillage and weed fabric tree-rows with grass alleyways. After mowing, cuttings from the trefoil alleyway were deposited into tree-rows, which provided additional N to fruit trees. The trefoil treatments resulted in higher levels of soil organic matter and available nitrogen, and microbial activity, as well as a higher density of larger tree roots and greater trunk growth. This suggests trefoil alleyways enhanced soil fertility and improved tree vigor to a greater extent than grass and tillage treatments. Few differences in water use were found among orchard treatments. Trends indicate slightly higher water use in trefoil than grass, but not enough to offset the observed soil quality and tree growth benefits. These findings suggest incorporating trefoil groundcovers into orchard alleyways may provide ecological benefits such as improved soil quality and prolonged fertility without substantial increases in water use