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Published June 03, 2008, 12:00 AM

Low-risk conservation tillage reduces soil erosion

ST. PAUL — Many things affect the impact of agriculture on soil and water quality in Minnesota. Annual rowcrops like corn and soybeans don’t protect the soil from direct raindrop impact until the leaf canopy closes, which is usually mid- to late June.

By: JODI DEJONG-HUGHES, U OF M EXTENSION, Worthington Daily Globe

ST. PAUL — Many things affect the impact of agriculture on soil and water quality in Minnesota. Annual rowcrops like corn and soybeans don’t protect the soil from direct raindrop impact until the leaf canopy closes, which is usually mid- to late June.

April through June has the greatest potential for water runoff in Minnesota. It’s wet, and soil moisture conditions are at or near field capacity while transpiration rates from row crops are low.

When the impact of raindrops detaches soil particles, they can be carried in runoff to surface tile inlets and streams. Excessive soil erosion results in the loss of yield potential over time. It also degrades streams and lakes with phosphorusinduced algal growth and sediment, reducing light penetration and depleting oxygen necessary for fish.

Maintaining crop residue cover until canopy closure reduces the impact of raindrops that dislodge soil particles, and can reduce the power of runoff water to move soil to streams. Residue is effective if left standing, anchored by roots.

Conservation tillage is defined as tillage systems that leave at least 30 percent residue cover on the soil surface after planting. Conservation tillage can greatly reduce soil erosion, with minimal effect on crop yields and often at lower production costs than conventional tillage. With adjustments to crop management, conservation tillage offers a low-risk way to reduce sediment and phosphorus losses from cropland to streams, rivers and lakes.

Tillage systems that leave more than 30 percent residue after planting corn work for many producers. However, adjustments to management may be required throughout the whole cropping system, in addition to a change in tillage implements.

Producers suggest:

• Well-drained soil, either natural or artificial, is beneficial for enhanced yield performance in a reduced tillage system.

• Chaff spreaders or choppers should be used to evenly distribute chaff leaving the combine, to avoid planting or tilling through piles of residue.

• Residue managers on the planter enhance early growth and promote uniform germination of seed.

• A heavy-duty, reduced tillage planter that is capable of proper depth control and firm seed-to-soil contact for good germination should be used.

• Band application of a starter fertilizer next to the corn row is good insurance against restricted root growth in cold, wet, fine-textured soils.

• Band or inject nitrogen fertilizer, if possible, rather than broadcasting it.

More detailed information is available in the U of M Extension publication “On-Farm Comparison of Conservation Tillage Systems for Corn Following Soybeans.”

It’s available at www.extension.umn.edu. Select “agriculture,” then “conservation tillage” in the crops section.

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