Changes in aggregate stability and concentration of glomalin during tillage management transition

Improvement in structure of degraded soils or prevention of degradation of structure in healthy soils requires an understanding of processes contributing to aggregate stability. The impact of cropping systems on a specific molecule that contributes to aggregate stability is part of the process that has not been elucidated. The relationship between aggregate stability and glomalin, a glycoprotein produced by arbuscular mycorrhizal (AM) fungi, was studied during the first 3 yr in transition from plow tillage (PT) to no tillage (NT) maize (Zea mays L). Results showed a high linear correlation (r(2) = 0.78, n = 32) between glomalin concentration in aggregates and aggregate stability. Increases in both aggregate stability and glomalin were measurable from gear to year in NT plots, but NT was significantly higher than PT after 2 or 3 Sr (P < 0.05). Comparison of NT plots after 3 yr with nearby soil in grass cover indicated that there was 20% greater stability and 45% higher concentration of glomalin in the grass-covered soil. Comparison of PT and NT (3 yr) interrow samples with intrarow samples indicated that plant roots and NT management may have a synergistic effect on aggregate stabilization, These results show that cropping systems should be evaluated for the impact on production of glomalin by AM fungi.