Common Harvest Mistake:

Leaving Too Much Residue in Windrows

We used to say that residue management started at harvest, but now days it is more prudent to say that residue management is an ongoing process. Knowing how much residue you are likely to have at the end of the harvest and making plans now to modify equipment to handle that residue will make residue management much easier.

Proper distribution of residue behind the combine is important. Wide combine headers (>15 feet) and high residue production with today’s varieties are two reasons a well adjusted combine is critical to high residue farming. Without special attachments or modifications, combine headers of 20 to 30 feet or more are not adequately equipped to spread today’s volumes of residue uniformly.

The most common mistake made in the harvesting operation is to allow crop residue to accumulate in windrows behind the combine. This accumulation causes the soil under the windrows to stay wetter and cooler longer in the spring. Planting into windrows and chaff rows can result in uneven stands, because seeds take longer to germinate and grow, resulting in significant yield reductions. Other problems associated with improper combine residue distribution include:

• Unsatisfactory weed control from herbicide interception.
• Poor performance of planters, drills and tillage equipment (particularly in a no-till system).
• Poor seed soil contact (usually from hair pinning of residue into the seed row).
• Excessive residue laying directly over the seed furrow, resulting in an allelopathic effect (natural chemicals or toxins from related plant types that could inhibit germination or growth).
• Increased pest infestation (from insects and rodents).
• Increased weed seed concentration.
• Poor plant nutrient uptake (from fertilizer tie up or interception).

To avoid these problems, make sure you always check the residue distribution patterns of your equipment, whether it is new or used. The other thing you can do is to consider incorporating some residue spreading attachments. A straw spreader uses rotating blades or rubber batts to throw or deflect whole pieces of crop residue. While the spreader typically distributes the residue more uniformly, the straw chopper can provide more residue cover, since it chops the residue into small pieces before spreading. A straw spreader is effective in handling fine materials primarily from harvest of small grains.

Surprisingly, chaff makes up nearly half of the harvested materials of some crops. The chaff usually does not reach the straw spreader or straw chopper because it drops to the ground from the combine sieves. With high yielding varieties with a lot of residue, the potential for creating heavy windrows is great. Chaff is easily distributed but because it is lightweight, it is hard to spread beyond 20 to 25 feet.

The most commonly used chaff spreading attachments are hydraulically driven single or dual spinning disks that have rubber batts attached. Generally, single disk spreaders are most effective for headers under 20 feet, while dual spreaders are more effective for wider headers.

Rainfall, high temperatures, fall tillage, or knifed in fertilizer applications can all speed the decomposition of crop residues between harvest and planting. As long as moisture is available, decomposition can occur when temperatures are above 50°F. Even when air temperatures drop below freezing, snow can actually act as an insulator and allow decomposition to continue.

Residue from canola, beans, peas, fall-seeded cover crops, potatoes, sugarbeets, and sunflower decomposes at a faster rate than residue from alfalfa, corn, grass hay, oats, sorghum, or wheat.

—Jim Bauder, Montana State University extension soil and water specialist

Color and Small Grain Maturity

With uneven maturity common in many fields, you may have to wait for late grain to mature, while hoping ripe grain does not shatter. Looking at head color and kernel color will enable one to cut as soon as late grain is mature.

Here’s how it works:

 Lack of green in the flag leaf - the uppermost leaf - indicates that a wheat or barley plant has reached 95% of its ultimate yield and that the final stage of development is under way.

 Green disappears from the glumes (bracts at the bases of the spikelets) about 1 1/2 days before maturity.

 Lack of green in heads and the darkening of a pigment strand in each kernel, seen most easily when kernels are cut open crosswise, signal 100% maturity. The pigment strand begins to appear about a half day before physiological maturity.

A whole field won’t lose its color at the same time, so check thoroughly. Also, check bottom kernels on heads because top kernels lose green first.  For color photos showing grain maturity, visit www.ag.ndsu.nodak.edu/aginfo/procrop/hrs/color07.htm .

– NDSU Extension Services

ND, MN IPM Crop Survey Results

Weekly summaries of the IPM field crop survey results are posted on the NDSU IPM web page at:  www.ag.ndsu.nodak.edu/aginfo/ndipm/ .  This site provides maps indicating weekly survey results for diseases and/or insect pests of wheat, barley, canola, sunflower and soybean. Links to additional information about these pests are provided as well.

The Minnesota Department of Agriculture Plant Pest Survey and Crop Pest Fact Sheets can be found online at www.mda.state.mn.us/pestsurvey/default.asp .

Follow the APPLES Sequence When Tank Mixing
The NDSU Extension Service recommends the A.P.P.L.E.S. sequence for adding herbicide formulations to a tank partially filled with water: Agitate, Powders soluble, Powders dry, Liquid flowables and suspensions, E mulsifiable concentrates and Solutions. Add surfactants, petroleum oils, MSO (methylated seed oil) type and other adjuvants last.

How much residue do tillage implements bury?
Tillage implements vary considerably in how much residue they bury. The approximate percentage of the residue cover remaining on the soil surface after a single pass of different tillage and planting implements follows. These figures may vary with travel speed, tillage depth and residue condition.

To obtain the percentage of residue remaining for a specific tillage system, multiply the percentages together for each tillage operation within the selected system. As an example, a tillage system using chisel plow with twisted spikes in the fall and a field cultivator in the spring for seedbed preparation will leave about 22% of the previous crop residue on the soil surface at planting time. The chisel plow will reduce the residue 50% and overwintering will reduce that amount to about 35 to 40% of soil cover. A spring cultivation will reduce that amount to about 21 to 24%, not enough for erosion control. As a comparison, the moldboard plow system incorporates almost all residues while the no-till system leaves most of the residue on the soil surface.

—NDSU Extension Service

Influence of tillage and other practices on surface erosion

Operation % Residue Left After Each Operation Spraying (Chem. Fallow) 100 Under cutter (Sweeps 24” or wider) 90 Chisel plow -- 14”-18” sweeps 85 -- 14”-18” sweeps 85 --   8” - 12” sweeps 80 -- Straight spikes 75 -- Twisted spikes 50 Disk (tandem or offset)   -- Blade less than 23” dia. 70 -- Blade 23” to 28” dia. 50 -- Blade over 28” dia. 30 Field Cultivator 60 Moldboard plow 5-10 Overwinter weathering 70-80 Source: NDSU

MT, SD Winter Wheat Recommendations on the Web

South Dakota State University winter wheat variety performance information and recommendations for 2003 can be found online at agbiopubs.sdstate.edu/articles/EC774-03.pdf .

In 2002, better-performing varieties in SDSU trials were Alliance, Arapahoe, Expedition, Millennium, Nekota, Tandem, Trego (white), Wahoo,and Wesley.  However, SDSU cautions that severe drought in many areas of winter wheat production led to a high amount of experimental error and a wide range in yields associated with test trials in 2002.

The best varieties for the past three years are Alliance, Arapahoe, Expedition, Millennium, Nekota, NuPlains (white),Tandem, Trego (white), Wahoo, and Wesley.

Montana State University winter wheat variety performance evaluation from 2002 field data and recommendations for 2003 can be found online at plantsciences. montana.edu/Crops/winterwheat/default.htm.

Winter Wheat Production Tips
One crop rotation to consider, particularly in the western Dakotas, is sunflower, barley, peas, and wheat, then back to sunflower, says Duane Berglund, NDSU extension agronomist. The challenge in very dry conditions is what you should plant following ‘flowers.  One idea might be fallow, followed by winter wheat. 

There can be advantages to growing winter wheat, including more efficient labor and machinery use, reduced weed problems (particularly wild oats), and often a higher yield potential.

Well-developed winter wheat is less likely to suffer from early season moisture stress than spring-planted small grains, since a well-developed root system enables the winter wheat crop to use sub-soil moisture.

Earlier crop development may also help in avoiding some disease and insect pressure. Winter wheat is no more resistant to scab than spring wheat, but with a three week developmental advantage it may avoid late infection periods that will affect spring wheat. As well, flowering in winter wheat will be complete before the orange blossom wheat midge emerges, and the crop will effectively avoid the pest.

Winter survival is the most critical factor in successfully producing a winter wheat crop in the Northern Plains. Residue and snow cover is important to maintain warmer soil temperatures in the crown area, just above the plant’s root system. NDSU research indicates that a minimum of 3 inches of snow cover is necessary to prevent winterkill due to low temperatures.

Several methods can be used to enhance snow cover: winter wheat can be no-till seeded directly into standing crop residues left to catch snow. Seeding into wheat or durum stubble will increase the risk of some diseases, but even this practice is often preferred to seeding into clean-tilled fields, particularly in more arid areas where disease is less of a problem, since the stubble will enhance moisture conservation and protection from cold weather.

The recommended seeding dates for winter wheat are September 10 to September 30 in the southern half of North Dakota and September 1 to September 15 in northern regions. Planting after the recommended dates may reduce winter survival and grain yields and also delay maturity of the succeeding crop. Planting prior to the recommended date unnecessarily depletes soil moisture reserves, increases risk of disease and may reduce winter survival.

More information on producing winter wheat in North Dakota can be found online at www.ext.nodak.edu/extpubs/plantsci/smgrains/eb33w.htm .

Managed Late-Season Weeds Can Provide Ground Cover

Late-season weeds may prove beneficial as ground cover on fallow or stubble fields over the winter. This is especially true in dry years, when limited plant residues are on the soil surface. 

Weeds that germinate and emerge after September 1 will likely not become mature and produce viable seeds prior to the first killing frost.  Otherwise, a herbicide treatment, clipping or mowing is an option for control of weeds and suppressing seed production.

Not all weeds make a good ground cover. Kochia and Russian thistle are examples of tumble weeds that often become entangled in fences and are a nuisance to remove. Therefore, these weeds would not be desirable as cover. However, foxtail or pigeongrass can be good ground cover because of their fibrous root system. Winter annual weeds that remain alive over winter also can make good ground cover, but would need to be controlled early in the spring before they bolt and the flowering stem begins to elongate. Winter annual weeds become much more tolerant to herbicides and more difficult to kill once they begin to bolt.

—NDSU Extension Service