On-Farm Soil Quality Testing in Organic and Conventional Peach Orchard Systems.

Soil quality problems such as erosion, depleted soil organic matter and nutrient reserves, salinity, and reduced water holding capacity are of increasing concern to farmers in the Intermountain West. Marginal soils require more amendments and fertilizers to meet crop needs. As input costs rise and water resources are increasingly limited, effective methods of evaluating soil quality and fertility is of growing importance. Standard commercial tests typically quantify soil nitrogen, phosphorus, potassium, pH and salinity. These factors alone are not sufficient to predict the long-term effects of management on soil quality. Comprehensive soil quality testing is not routine, hence is often cost prohibitive, unavailable or confusing to interpret. The goal of this study was to assess the effectiveness and use of simple chemical, biological, and physical soil quality indicator tests that can be completed on-site. The tests included modified slaking tests, litter bag tests, and the Solvita, LaMotte and Rapid soil test kits, selected to measure aggregate stability, decomposition rates, soil respiration, macronutrients, and pH respectively. Results were correlated to comparable lab analyses. Soil samples were collected from two experimental peach orchards located on the Utah State University Research farm in Kaysville, Utah, with documented differences in soil quality. On-site soil physical test correlated most closely to the biological and chemical lab results. The best correlation was found between Solvita and lab measured respiration (R = 0.88). Followed by the modified slake test which was also closely correlated to lab respiration  (R  = 0.83). The best correlation between the chemical tests was found using the Lamotte simple potassium test compared to laboratory measured potassium (R =0 .57). The weakest simple chemical test was the Rapidtest for phosphorus (R =0.02). Soil structural tests such as the modified slake test may be effective and cost effective tools for monitoring soil quality on site.