The perfect seedbed?

The perfect seedbed
A successful crop year after year requires proper care of the soil seedbed.

When someone thinks of the ideal seedbed, the first thing they probably think of is how it is tilled, but in reality the ideal seedbed encompasses several things. For the ideal growing environment, soil needs to have proper drainage (can be achieved with tiling), contain nutrients and organic matter, be free of weed seeds and needs to be the right consistency for the seed to germinate and the crop to grow. The optimum soil makeup is: 50% soil particles, 25% water and 25% air. Soil with a composition of less than 50% air and water is compacted.

Soil composition

The consistency of the soil is also a big factor in how a plant will thrive. Seed germination requires both water and oxygen so different enzymatic processes can occur. Therefore, the seed needs to have enough contact with the soil to get the water but enough space around it where oxygen can be present (seed to soil contact). This is why we typically want a loose soil to plant in, coarse blocks of soil could mean that your seed does not have contact with much soil at all. Loose soil also allows for the carbon dioxide that is formed during respiration to escape.

Composition of ideal and compacted soil.

Composition of ideal and compacted soil

The consistency of the soil is also a big factor in how a plant will thrive. Seed germination requires both water and oxygen so different enzymatic processes can occur. Therefore, the seed needs to have enough contact with the soil to get the water but enough space around it where oxygen can be present (seed to soil contact). This is why we typically want a loose soil to plant in, coarse blocks of soil could mean that your seed does not have contact with much soil at all. Loose soil also allows for the carbon dioxide that is formed during respiration to escape.

Solutions

Irrigate dry areas and install drain tile for wetter areas. Make sure you are not tilling or planting in conditions that are too wet. A simple ribbon test can be used to determine if you should till or plant. If you can create a ribbon, the soil is too wet, if it crumbles, the soil is ready for tillage.

Hard pans can cause roots to struggle, forcing them to reach down deeper for water. Occasional deep tillage, also known as subsoiling can help breakup a hard pan.

Diseases

One reason that crop rotation is suggested, is that many diseases that affect dicot plants like soybeans, sunflower, cotton, or canola are different from those of a monocot like corn, wheat, barley or rye. By rotating crops, the disease life cycle has a better chance of being broken.

Weeds

Many people do not realize just how long weed seeds can remain dormant in the soil. For example, common purslane seeds are viable for over 20 years and black mustard can survive over 40 years. This is one of the main reasons removing weeds before they can produce seed is critical.

Insects and Nematodes

An ideal seedbed would be free of major pests, which is another reason that crop rotation is beneficial. Planting continuous corn will allow for pests, such as corn rootworms, to thrive. Likewise, continuous planting of soybeans will result in higher soybean cyst nematode populations. By alternating crops, you are limiting the primary food source for the pest, causing the pest population to decrease.

Tillage Recommendations

Use the ribbon test to ensure soil is dry enough to till.

Use the appropriate primary tillage tool to adequately manage residue and compaction. Remember, chisel plows can reach shallow compaction while rippers may be needed to reach deeper compaction.

Determine which type of secondary tillage tools and attachments to use to ensure proper seed to soil contact.

Compaction Load

Depth of compaction as axle load increases. (Tire pressure remained at 12 psi for all tire sizes.) Larger surface area – for all equipment, the larger the surface area of the tires/tracks, the better spread out the weight will be. This includes making sure your tires are properly inflated for the field, not the road. Source: Adapted from Soil compaction: causes, effects and control, University of Minnesota Extension (http://www.extension.umn.edu/agriculture/tillage/soil-compaction/).

Compaction free

Compaction can do damage for years. Farmers should be mindful of how many passes they perform, how heavy machinery is, how dispersed the weight of the tractor/sprayer/etc. For example, tracks distribute weight better than tires and duals distribute more weight than single tires. Highly inflated tires have less contact with the ground than less inflated tires, resulting in more compaction.

Solutions

  • Use lighter weight equipment that can still perform the task at hand. For example, Gleaner® S77 combines are 7,060 lbs. or 23.5% lighter than a Case IH™ 7230 and 14,690 lbs. or 49% lighter than a John Deere™ S670 combines of the same class. Either drive over a field less, or create designated paths for the equipment to travel. It will increase compaction in these areas, but you sacrifice soil quality and yield in smaller, defined areas instead of over the entire field. 80% of compaction occurs on the first pass over soil so additional passes add little additional compaction.
  • Make sure you properly inflate your tires. The pressure needed for roading a tractor is higher than needed in the field. Use tractors with on-the-go tire inflation technology.


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