COS 54-8
Legacy effects of agronomic management at the Kellogg Biological Station LTER
Arbuscular mycorrhizal fungi (AMF) have been shown to be important contributors in agro-ecosystem sustainability, particularly through transfer of soil nutrients such as P and N to plants. Conventional agricultural systems typically include disturbances such as tillage and fertilization, shown to both directly and indirectly alter AMF ecological function. Climate change has been predicted to alter rainfall patterns and increase the occurrence of both long and short term drought conditions, potentially contributing to legacy effects of cropping system management on AMF and other soil microbial ecological function. To examine the effects of reduced rainfall and different agricultural management regimes on crop growth, we performed a full factorial greenhouse experiment utilizing soil inocula from the Kellogg Biological Station-LTER Main Cropping System Experiment. We compared Triticum aestivum var “Glenn” growth in soils from the T1 (conventional), T2 (no-till), T4 (organic), and T7 (early succession) agricultural management treatments under both drought and ambient conditions. We separated AMF and bacterial community effects on crop growth using live soil, sterile soil, and microbial wash inocula from each agronomic treatment.
Results/Conclusions
Under ambient conditions, wheat aboveground biomass responded positively to the live soil inoculum and negatively to the microbial wash treatments (F=41.81, p<0.0001), indicating that AMF provides benefits while the bacterial community is mostly detrimental to the crop. Agronomic treatment was also significant (F =15.38, p<0.0001), with inocula from the conventional and no-till fields providing less aboveground growth benefit than inocula from organic or successional fields. Root biomass followed similar patterns. Under drought conditions, the benefits of AMF disappeared. These results are evidence of an agricultural legacy effect on the AMF community where application of inorganic fertilizer in T1 and T2 has selected for less beneficial and potentially more parasitic AMF species. In a changing climate, benefits of AMF may be further reduced.