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The Integrator

County Agent News
Dan Folske
July 16, 2018 

The Integrator

            “The Integrator” is a monthly newsletter from the USDA Northern Great Plains Research Laboratory at Mandan. It features articles about ongoing and completed research at the facility which is well known for its research in no-till, soil health and the effects of tillage.

            The following article about perennial forages as part of a crop rotation system is this month’s lead article. You can subscribe to receive this newsletter via email by contacting Cal Thorson at cal.thorson@ars.usda.gov or 701-667-3018

Perennial Forages Important for Improving Soil Health

Dr. Mark Liebig 

Adding perennial forages in annual cropping systems can offer significant benefits to agricultural landscapes. In addition to providing feed for livestock, perennial forages improve nutrient and water cycling, increase wildlife habitat, and provide novel educational and recreational opportunities for people of all ages.

Some landscape-scale benefits associated with perennial forages are due to changes in soil properties. Under perennials, limited soil disturbance and increased organic matter inputs from roots lead to changes in soil properties which can improve soil health.

Despite this logical connection, management guidance for producers regarding use of perennial forages in annual cropping systems is lacking. Specifically, the length of time needed for soil health improvements to occur under perennial forages is unclear. In part, this is due to differences in forage types and productivity across regions.

To address this need, NGPRL scientists conducted a multi-year study to measure changes in soil properties under perennial grasses, legumes, and grass-legume mixtures at an experimental site near Mandan, North Dakota. Soil measurements were made over a five-year period, and included continuous spring wheat as an annual crop control.

Relative to continuous spring wheat, perennial forages reduced soil acidification and soil bulk density, and increased aggregate stability (Fig. 1) and a moderately-degradable pool of soil organic matter.

Results suggested that soil responses to perennial forages occurred as soon as two years after forage establishment, but peaked four years after establishment.

Among perennial forages, intermediate wheatgrass alone or mixed with alfalfa reduced soil bulk density and increased moderately degradable organic matter compared to alfalfa, but such differences took four to five years to be detected.

Outcomes from the study suggested perennial forages maintained or improved near-surface soil health, but effects were subtle and were generally slow to occur. Results also showed the importance of strategic management (e.g., no-till, cover crops, increased residue retention) to ensure improvements in soil heath are preserved between perennial-annual transitions.

Adapted from Liebig, M.A., J.R. Hendrickson, J. Franco, D.W. Archer, K. Nichols, and D.L. Tanaka. 2018. Near-surface soil property responses to forage production in a semiarid region. Soil Sci. Soc. Am. J. 82:223-230. Mark Liebig, 701-667-3079, mark.liebig@ars.usda.gov

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