Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2010
Publication Date: 2/1/2011
Citation: Caesar, T., Sainju, U.M., Wright, S.E., Shelver, W.L., Kolberg, R.L., West, M.S. 2010. Long-term tillage and cropping effects on biological properties associated with soil aggregation in semi-arid eastern Montana, USA. Biology and Fertility of Soils. 47:157-165.
Interpretive Summary: To effectively reverse soil degradation and decrease soil quality due to conventional-tilled spring wheat-fallow system practiced in the semiarid Northern Great Plains, no-tilled continuous wheat cropping and lentil-wheat rotation have been proposed to replace fallow. Using a set of biological markers to study the long-term tillage and cropping effects, our results showed: 1) an improvement of aggregate stability over 12 years of no-till continuous spring-wheat system compared to fallow-wheat rotation, the values reach those of samples from a nearby perennial grass and 2) leaving a moderate lentil residue amount on the soil surface past seeding of the following spring wheat crop in no-tilled lentil-wheat system seems to be a better alternative than fallow systems or lentil-wheat systems under tillage to minimize N mineralization from the legume residue and still control erosion by increasing soil stability.
Technical Abstract: Long-term tillage and cropping may influence biological attributes responsible for semi-arid soil aggregation in Montana, USA. Aggregate stability, glomalin, basidiomycete fungi, uronic acids, total organic C (TOC) and total N (TN) at 0-5 cm soil depth from 1991 to 2003 were evaluated in different aggregate-size classes (4.75-2.00; 2.00-1.00; 1.00-0.50; and 0.50-0.25 mm) for the following treatments: 1) 12th year of fallow phase after 11 years of conventional- and no-tilled spring wheat-fallow (CTF and NTF), 2) 12th year of lentil phase after 11 years of conventional- and no-tilled spring wheat-lentil (CTL and NTL), 3) 12 years no-tilled continuous spring wheat (NTCW), and 4) 16 years undisturbed pasture (P). No-tilled continuous wheat may increase soil aggregation by increasing the biological attributes tested compared with conventional-tilled wheat-fallow. Similarly, grassland soils may increase soil aggregation by increasing these attributes compared to cropland soils. Aggregate stability was increased in conventional till compared with no-till and in grassland compared to cropland in middle aggregate size classes (2.00-1.00; 1.00-0.50 mm). In general, adding lentil in rotation with wheat did not influence aggregate stability compared to fallow-wheat after 12 years, however, leaving a moderate amount of lentil residue on the soil surface in no-tilled lentil-wheat (NTL) seems to be a better alternative than fallow (CTF and NTF) or lentil-wheat under tillage (CTL) to minimize N mineralization from the legume residue and still control erosion by increasing soil stability.