Soil regeneration increases crop nutrients, antioxidants and adaptive responses

Abstract

Since 1981, the Rodale Farming Systems Trial (RFST) differentiated organic (org) from conventional (con) farming systems showing that org systems can have a transformative potential to increase soil quality. On the other hand, throughout the RFST history, con system never increased soil organic carbon (SOC) nor soil nitrogen, (SON). During the first 5 years, org systems were increased significantly (p = 0.05) for SOC and SON. Organic farming systems do not employ org restricted inputs i.e. synthetic fertilizers and pesticides instead they relied on biologically based inputs such as cover crops, extended legume rotation and organic amendment. Conventional system used recommended fertilizer and herbicide without biological based inputs. Both Org systems, significantly increased both SOC and SON but were not statistically different from each other. Increased SOC and SON opened a research venue supporting testing hypotheses of how soil improvement can affect i) crop nutrition ii) disease reactions and iii) adaptability. Unique org and con system legacies allowed effective SOC/SON differentiations and comparison. Different soil levels were compared under the same location and same genotypes eliminated confounding factors to better evaluate the effect of the differentiated soil condition. Over 22 plus years of systematic trial conventional maize and soybean farming failed to yield any statistical increase in either soil carbon or nitrogen from their original values SOC 1.8 to 2.0% SON 0.28 (p=0.05 ns); on the other hand, the organic farming legacies showed statistically significant with both SOC and SON increased (p=0.05) (soil carbon 2.3 to 2.6% and soil nitrogen 0.33 to 0.35%). Oats Avena sativa L. Ogle, 2003, maize Zea mays L. 2005, jalapeno peppers Capsicum annum L. Campell, tomato Solanum lycopersicum and carrots Daucus sativa form sp carota 2004 and 2005 were used as soil improvement bioindicators. In addition to SOC and SON improvement, crop mineral foliar nutrients were found highly significantly improved (p=0.01) under the organic agricultural system legacy. Organic system mineral increase varied from 8% for potassium to 74% for boron with a mean of 32.3% organic advantage over conventional soil legacy control from foliar analysis in oats 2003 significant differences were also found in oat grain composition for mineral contents. Crop mineral contents from org differentiated soils were significantly elevated (p=0.01) compared to the conventional soil legacy baseline. In addition to improved SOC/SON, crop mineral nutrients in oats, the antioxidant levels of tomato fruit, carrot roots and jalapeno pepper fruits were all significantly higher in organic legacy 18% (in jalapeno pepper) to 36% organic advantage (p=0.05) compared to conventional system legacy. Disease assessments were tested for how soil improvement would affect crop health/adaptability. Disease were not constraining in all environment/year combinations. Nevertheless, when present and constraining, disease reactions were consistently superior under org compared to a con soil legacy. In the org legacy significant reductions in disease were found for jalapeno pepper virus complex incidence, carrot splitting percent and carrot leaf blight and tomato late blight severities. Results confirm of a positive association between soil improvement, crop nutrient content, antioxidant, plant adaptability, and negative association with disease incidence and severity. Soil organic matter appears to have wide pleiotrophic effects deserving additional study for their detailed modes of action.