COS 47-1 - Reduced tillage cropping systems enhance the nutritional quality of soybeans under both organic and conventional management

Abstract: Agricultural management practices which reduce soil tillage, colloquially known as no-till or reduced-till agriculture, have proven useful in limiting erosion, improving soil water storage, and enhancing soil organic matter content in many agroecosystems. However, the extent to which these environmental improvements translate to plant health and ultimately crop nutritional quality are unclear. Past research has shown that tillage disrupts fungal mycelial networks in soils which leads to reduced mycorrhizal plant colonization. As mycorrhizal fungi are an important conduit for plant nutrient and water access in most crops including soybeans, we hypothesized that tillage-induced decoupling of soybeans and mycorrhizal fungi would correlate with reductions in plant nutrient uptake and overall nutritional quality. To test this hypothesis, we measured soybean mycorrhizal root colonization via microscopy and qPCR, seed and leaf mineral nutrient concentration, and seed ergothioneine antioxidant concentration from soybeans grown within long-term crop rotation trials comparing different tillage practices at two sites (one organic site and one conventional site). We found that root mycorrhizal colonization level was inversely related to tillage intensity. Tillage-induced reductions in mycorrhizal colonization were reflected in reduced seed nutritional quality in both the organic and conventional trials. Specifically, seed phosphorus concentration was positively correlated with mycorrhizal colonization and was 15% higher under no-till practices compared to till. In the organic trial, seed nitrogen and calcium concentration were between 6 - 17% higher in no-till plots compared to till. Across both trials, seed ergothioneine concentration was up to 40% higher in no-till plots compared to till. Overall, these results suggest that in addition to the positive environmental outcomes of adopting reduced tillage practices, plant mineral nutrient acquisition and crop nutritional quality are also improved in both organic and conventionally managed systems. Further, these results show that these improvements are partly driven by limiting disturbance to mycorrhizal fungi.