|KUCHENREUTHER, MARGARET - University Of Minnesota|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/12/2015
Publication Date: N/A
Technical Abstract: In the upper Midwest, economic and social interests in bioenergy and low-carbon fuels are stimulating the conversion of cropland into perennial biomass systems. Landowners are embracing the change by developing diverse whole-farm management systems that can balance economic and environmental risk of production by building on ecosystem services. We evaluated soil nutrient dynamics in a low-diversity perennial production system with and without fertilization and annual harvesting. An on-farm randomized split-plot block experiment (1.6 ha (4-acre)) was established to compare the whole plot effect of four fertilizer treatments (zero, composted cattle manure, half rate (30-10-30 NPK) and full rate (60-20-60 NPK)) and split-plot effect of harvest versus no-harvest. Harvesting occurred every fall, since 2010; fertilizers were applied in June of 2011 and 2013. Soil nutrients, including total and organic C, total N, ortho-P, and mineral N were evaluated to depths of 60 cm in fall-collected samples. Potentially mineralizable N (PMN) was measured at select spring and fall sample dates. Total soil C and N decreased with depth between 0-30 cm, but both increased substantially at the 30-60 cm depth, with no apparent effect of fertilization or harvest treatment. Ortho-P followed the C and N pattern with depth; however, over time it increased in non-harvested but fertilized treatments, suggesting P loss over time could occur with continued biomass removal. Fall mineral N declined over time, with no apparent impact due to harvesting or fertilization, suggesting increased immobilization rates from the conversion to perennials. PMN was stimulated within two weeks of fertilization with inorganic fertilizer but not with composted manure. Inorganic fertilization exhibits a priming effect, which might lead to C loss with long-term application. Coordinated with production and ecosystem service measurements, perennial systems appear to more sustainable if maintained with low inputs.