Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 1999
Publication Date: N/A
Interpretive Summary: Land productivity along with improvement or maintenance of soil health must jointly be evaluated for sustainable agricultural practices. Winter wheat fallow has been the prevalent cropping system in the central Great Plains for 60 years. Alternative cropping systems evaluated for yield show that producers can crop more frequently if management practices include residue management and minimum tillage. A recent discovery of a soil glue, glomalin, produced by beneficial root-colonizing fungi provides a way to quantify the impact of cropping on soil stability. Almost all crops are hosts for these fungi, and recent work strongly suggests that soil stability is directly related to the activity of these fungi. Cropping systems were evaluated for impact on both soil aggregate stability and the amount of glomalin in aggregates in cropping system research plots in Akron, CO. Aggregate stability and glomalin were correlated across all cropping systems and controls examined. Wheat-corn-proso millet and wheat-corn-fallow had significantly higher aggregate stability than wheat-sunflower-fallow. More frequent cropping did not lead to lower soil stability except for the rotation that included sunflower. A perennial grass growing in an area around the research plots had the highest aggregate stability and glomalin values. Extensively plowed soil in buffer areas around plots had significantly lower aggregate stability and glomalin values than all of the crop rotations samples. Selected crops and cropping systems should be studied in greater detail to determine ways to manage the fungi that produce glomalin. The impact of this work will be preservation of agricultural soils for current and future generations.
Technical Abstract: Land productivity along with improvement or maintenance of soil health must jointly be evaluated for sustainable agricultural practices. Winter wheat fallow (W-F) has been the prevalent cropping system in the central Great Plains for 60 years. Alternative cropping systems show that producers can crop more frequently if management practices include residue management and dminimum tillage. The impact of different crops, crop rotations and tillag management practices on soil quality was assessed by measuring aggregate stability and the glue-like glycoprotein, glomalin, produced by arbuscular mycorrhizal (AM) fungi in soil from cropping trials established in 1990. Crops were wheat, corn (C), proso millet (M), and sunflower (S). Rotations sampled were W-F, W-C-M, W-C-M-F, W-C-F, and W-S-F. In the same area as the cropping trials, a perennial grass (crested wheatgrass) and a buffer area that had been planted to Triticale for the past two years (but prior to that had been extensively plowed) were sampled to indicate maximum and minimum values, respectively, of aggregate stability and glomalin. Results showed that aggregate stability and glomalin were correlated (r=0.73) across all treatments sampled. W-C-M and W-C-F had significantly higher aggregate stability than W-S-F. Soil from under the perennial grass had the highest aggregate stability and glomalin values. Triticale soil had significantly lower aggregate stability and glomalin values than all of the crop rotations sampled. Differences in cropping systems, and between the cropping trials and the perennial grass indicate that selected comparisons should be studied in greater detail to determine ways to manage AM fungi to increase glomalin and aggregate stability in these soils.