Influence of Management and Temporal Crop Bio-diversification on Soil Organic Carbon and Soil Structural Stability in Long-Term Integrated Nutrient Management System

Placid Mike Mpeketula and Sieglinde Snapp
W.K Kellogg Biological Station; Department of Plant, Soil and Microbial Sciences, Michigan State University

Presented at the All Scientists Meeting (2015-04-15 to 2015-04-16 )

Understanding processes that ameliorate cropping system productivity and sustainability is particularly important in intensively managed row crop systems. Soil organic carbon accumulation is known to be linked to cropping system productivity. However soil organic carbon accrual and soil structural stabilization have rarely been determined along temporal crop diversity gradients in integrated nutrient management systems. We investigated the role of temporal crop bio-diversification through the manipulation of crop diversity in a 20 year study located at Kellogg Biological Station, southwest Michigan. The treatments included continuous monoculture corn ©, Corn-soy biculture (CS), Corn-soy-wheat triculture (CSW), and a polyculture of corn-soy-wheat with a cover crop (CSWco). We quantified Soil Organic Carbon (SOC), labile soil organic carbon (Permanganate Oxidizable Carbon –POXC) and water stable aggregation at 3 different depths (0-5, 5-20 and 20-25 cm) to i) determine the long term response of the measures to crop bio-diversification in integrated compost and integrated fertilizer management systems, and ii) examine the relationship between various soil measures to structural stability of fine loamy mixed, semi active, mesic Typic Hapludalf soils of the long term trial. Results indicated that POXC and water stable aggregate size fractions responded to long-term treatment differences. Over the 20 year period, management had stronger influence compared to diversity for most the measures examined with integrated compost management showing improved soil structural stability as evidenced by an increase (19%) in water stable macroagregates for 0-5 cm depth. Of all measures and across all depths, POXC and intra-aggregate carbon were moderate predictors of water stable aggregation (r2 = 0.62, 0.42 respectively). Furthermore biodiverse rotational systems had better aggregate stability compared to monoculture treatments across the two nutrient management systems (p<0.001). The results indicate that improvements in soil structural stability are attainable under integrated compost management in the long term, and that crop bio-diversification is an additional means of ameliorating soil structural stability.

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