Legume Alleyway Groundcovers Influence Tree-Row Soil Quality in An Organic Orchard.

Organic stone-fruit orchards rely on groundcovers and organic matter inputs to maintain or improve soil quality and fertility for prolonged tree growth and productivity. Nitrogen (N) fixing legume groundcovers have been associated with increased soil quality and soil N in orchard soils. A certified organic peach trial was initiated in 2008 at the Utah Agricultural Experimental Station, Kaysville, Utah to evaluate the impact of orchard floor management practices on soil quality. Four treatments with two factors, tree-row (living-much or straw-mulch) and alleyway (grass or legume) were compared with industry standards. Individual treatments were living-mulch (Lobularia maritima) with legume (Lotus corniculatus L.) (LL), living-mulch with grass (Festuca rubra and Lolium perenne L.) (LG),straw-mulch with legume (NL), and straw-mulch with grass (NG), tillage with grass (TG) and weed fabric with grass (WG). During tree establishment, steer manure compost provided 25, 25, and 48 grams total N per tree from 2008 to 2010 respectively. A combination of steer manure compost and feathermeal (13-0-0) applied from 2011 to 2013, supplied 96, 96, and 226 g N per tree. The biomass from alleyway mowing deposited into the tree-row of legume treatments, provided an additional 54 g N per tree per year. Higher soil organic carbon (SOC) (22.6 vs. 19.6 g C kg soil, p<0.05) and total N (2.4 vs. 2.0 g N kg soil, p<0.05) was observed in tree-rows with legume alleyways compared to grass treatments by 2012. The ratio of C to N was not significant between treatments. Dehydrogenase, β-glucosaminidase, urease, and cellulase potential activities were greater (p<0.001) in tree-row soils with a legume alleyway compared to grass. Increased SOC, N and potential biological activity in tree-row soils, suggests greater nutrient cycling potential and soil quality when incorporating legume groundcovers into orchard floor alleyways.