Northwest Iowa Crop Update Newsletter by Todd Vagts ISU Extension Crops Specialist Counties Served:  Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.
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Volume 2, Number 27

Northwest IA Crop Update, September 30, 2002
(Word Document)

Introduction
With harvest well underway, we need to begin thinking about residue management and prevention of soil compaction.  Crop residue may not appear to have much value, but in reality the residue is extremely important for soil protection, improvement of soil characteristics and may also be a used for livestock feed.  The increased rainfall the area had in August will translate into soils more vulnerable to soil compaction during harvest.  Pay close attention to tire pressure on harvest equipment and attempt to minimize traffic in the field.  A few adjustments this fall may pay off next year in greater yield potential.

Hidden Soybean Yield Loss
When soybeans are harvested below 13% moisture, you are loosing yield.  An example is as follows: 50 bushel per acre soybean yield at 9 % moisture equals 2.4 bushel per acre hidden soybean yield loss (13% moisture minus 9% moisture equals 4 points of moisture times 0.6 bu/point/acre hidden yield loss, or 2.4 bushel per acre).    

Corn stalks have feed value
Cornstalks can be a great source of winter feed for cattle.  Cornstalks that are supplemented with protein, vitamins and minerals can supply the nutritional needs of cows that are in moderately good body condition.   Cornstalks are generally considered to have about 80 to 90 percent of the energy of mixed grass and legume hay per pound of dry matter, but only 20 to 30 percent as much protein.  Adding soybean meal can be a good way to increase protein content.  More information on the value of cornstalks can be obtained from the ISU Extension publication FM 1867

Manage Crop Residue and Protect Your Soil Resource
As you make tillage plans for this fall, keep in mind the important role that crop residues play in your overall conservation plan.  The amount of soil lost to erosion each year is directly proportional to the amount of crop residue remaining on the surface. You may already have made substantial changes in your farming operation to reduce erosion, but at the heart of your conservation plan should be some provision for conservation tillage. Conservation tillage is defined as tillage that leaves at least 30 percent of the field surface covered with crop residue after planting.

All crop residues (stalks, straw, chaff, and even the finest materials) stop rain splash, slow and trap runoff, and allow water infiltration. Plant residue also improves soil organic matter, which enhances soil physical and chemical properties such as soil tilth, aggregate stability, and cation exchange capacity.  Plan your tillage management systems to provide crop residue coverage, such as Mulch-tillage, No-till or Strip-tillage.   An even distribution of crop residue while harvesting is critical. Concentrated crop residues can insulate the soil's surface from the sun, reduce seed to soil contact, and make it tougher to plant in the spring. Doing a good job of spreading chaff and stalks can minimize the amount of tillage needed to plant the crop next year.

Soil erosion leaves others dealing with the problems of unwanted sediments, negatively effects aquatic habitat, and contributes to water pollution and excess nutrient runoff. It is also carelessly washing away your most important and irreplaceable resources. Using crop residue is a simple, powerful strategy for saving that resource.

Top 10 Ways to Leave More Residue 

1. Follow a crop rotation sequence with high-residue-producing crops (e.g., soybeans do not provide the same protection as corn)

2. Wait until spring for tillage operations

3. Reduce the number of tillage passes

4. Plant rye or wheat as a winter cover crop, especially when growing low-residue crops, such as soybeans

5. Set chisels and disks to work shallower

6. Stop using the moldboard plow

7. Drive slower on tillage operations; driving faster throws more soil and covers residue

8. Use straight shanks and sweeps on chisel plows; twisted shanks may bury 20 percent more residue

9. No-till drill soybeans instead of planting them conventionally; no-till drilling keeps more residue on the soil surface and generally produces a quicker canopy

10. Convert to a no-till system

Source:  Use crop residues for soil conservation ICM Newsletter 5/3/1999.  Michael J. Tidman and Gerald Miller.  And Plan for 2002 residue before harvest, ICM Newsletter 9/17/2001.  Mahdi Al-Kaisi, Assistant Professor, Department of Agronomy, and Mark Hanna, Extension Agricultural Engineer, Department of Agriculture and Biosystems Engineering and Michael Tidman

Minimize the effects of soil compaction
The impact on yield from soil compaction has been reported to be as much as 10 to 20 percent in unfavorable years. A major effect of soil compaction is the alteration of the soil's physical (bulk density, soil strength, and porosity) and the hydraulic (infiltration rate and movement of water within the soil profile) properties. Changes in the soil's physical properties alter the ratio of water to air in soil. Plant roots require air as well as water to develop a healthy root system.

The main causes are field traffic and machinery, and to a lesser extent, livestock. Soil compaction is most likely to occur when soil moisture is at or near field capacity.  Under these conditions, aggregates can be "lubricated" by water and readily reposition themselves through the air spaces under heavy traffic and when farm equipment is used.

Minimize field-wide compaction by using controlled traffic lanes. Avoid driving loaded grain carts randomly through the field, because most damage occurs in the first pass of the implement. Grain tank extensions on combines also add to the load on soil.  Check wheel and tire size and pressure. Larger wheels and tires allow better flotation, whereas lower tire pressures reduce the load on the soil. Increase the tire's "footprint" with larger wheel diameters. Spend the extra time with your implement and tire dealer to obtain proper tire size and set tire pressure, the extra time this fall may pay off quickly next year through higher yield potential soil conditions.

Source:  Soil compaction may be cutting into your yield; ICM Newsletter 7/8/2002.  Mark Hanna, Extension Agricultural Engineer, Department of Agriculture and Biosystems Engineering, and Mahdi Al-Kaisi, Assistant Professor, Department of Agronomy and Michael Tidman

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