Farm Horizons, October 2014

Soil compaction and lack of nitrogen take toll on corn crop

By Dave Schwartz
Certified crop advisor, Gold Country Seed

The 2014 growing season was a challenge from the start. Most fields were tilled and planted this spring when soils were too wet. Some growers waited, with hope that field conditions would improve.

As it turns out, our earliest planted crops, even though soil conditions were not ideal, are looking like they will be our best crops.

Growers that delayed planting most likely planted in worse conditions and planted much too late for optimum yield. Research shows that corn yields begin to decrease when corn planting is delayed until after May 1. I talked to growers this past week that planted corn as late as June 25. In most cases, these were dairy farmers that needed feed for their livestock.

This was a challenging spring, with record-setting rainfall in May and June that created ideal conditions for soil compaction and severe nitrogen loss.

Soil compaction will reduce crop yields this year in most corn and soybean fields in Wright and neighboring counties.

One can learn much about the crop by scouting fields in late summer. I found unevenness in plant height of corn and soybeans in nearly every field I walked. Tall, healthy plants had much larger ear size than stunted plants only a few rows away.

One possible solution to reduce soil compaction yet this fall is to run tillage equipment deeper than normal, and, hopefully, break up some of the compaction.

Frost may help reduce soil compaction near the soil surface, but has little effect on soil compaction deeper in the soil profile.

Ward Voorhees, a nationally-recognized soil compaction expert, spoke at one of our extension service meetings years ago, and his advice was to do fall tillage down to a depth of 12 inches for best results. Tillage equipment has a shattering effect on soil compaction if soils are relatively dry. Deep tillage is much less effective if soil is wet.

The other common thread in most corn fields that I scouted late this summer was nitrogen deficiency. Low areas in fields where water stood, or sandy soils were affected most. Nitrogen deficiency symptoms to watch for are yellowing leaves at the base of the corn plant, beginning at the leaf tip and moving up the midrib.

Yield losses this year may be as much as 30 to 40 bushels per acre for growers who applied all of their nitrogen last fall.

In the future, it may be wise to avoid any fall application of nitrogen, and rely instead on two spring applications. Nitrogen is the key nutrient for optimum corn production. n

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