Permanganate Oxidizable Carbon and Nutrient Stratification in Long-Term No-till Systems.

The stratification of soil carbon and nutrients is a common phenomenon in soils under conservation tillage relative to more intensively tilled soils. Nutrient stratification impacts extractable soil test levels, fertilization recommendations and nutrient losses. Therefore, understanding organic matter and nutrient stratification in soils is critical for sound nutrient management in continuous no tilled cropping systems. The objective of this study was to document the effects of conservation tillage on soil nutrients and organic matter fractions through depth in a long-term tillage study in Ohio. Soils were sampled at 2.5 cm interval depths down to 30 cm across three tillage intensities (moldboard plow, chisel till, no till) and three crop rotations (continuous corn, corn-soybean, corn-alfalfa) at 3 sites. Soil pH, Mehlich-3 extractable nutrients, soil organic matter and permanganate oxidizable carbon (POXC) were measured on all soils. Results indicated that tillage regimes had a greater effect on soil properties than crop rotation and that stratification of soil nutrients and soil organic matter fractions was greatest in no till systems. Significant depth-by-tillage interactions were evident across many soil properties indicating that depth of soil interval strongly influences soil test levels. Overall the results indicate that depth of sampling has large implications for assessing nutrient and organic matter fractions in continuously no till soils and that these warrant consideration for effective nutrient management.