Lots of rain last fall, long periods of snow cover reducing soil freezing, the potential for excessive spring moisture due to melting snow, Elwynn Taylor telling us were in the 19th year. What do they have to do with each other, extra compaction compounded by the threat of drought.
Causes of Compaction:
Raindrop impact - This is certainly a natural cause of compaction, and we see it as a soil crust (usually less than 1/2 inch thick at the soil surface) that may prevent seedling emergence. Having optimum amounts organic matter and calcium can alleviate crusting.
Tillage operations - Continuous moldboard plowing or disking at the same depth will cause serious tillage pans (compacted layers) just below the depth of tillage in some soils. Corn roots have a penetrating force of 350-400 lbs/sq in. Alfalfa roots can exert up 700 lbs/sq in. Many tillage compaction layers can exceed 750 lbs /sq in of force to penetrate.
Wheel traffic - This is without a doubt the major cause of soil compaction. With increasing farm size, the window of time in which to get these operations done in a timely manner is often limited. The weight of tractors has increased to 20 tons today, from less than 3 tons in the 1940's. This is of special concern because spring planting and fall harvest is often done before the soil is dry enough to support the heavy equipment.
Minimal Crop Rotation - The trend towards a limited crop rotation has had two effects: 1.) Limiting different rooting systems and their beneficial effects on breaking subsoil compaction, and 2.) Increased potential for compaction early in the cropping season, due to more tillage activity and field traffic.
A farmer in Minnesota that has been using SuperCal SO4 and deep tillage for a number of years has reported that his end rows are now higher yielding the middle section. I have recommended that he till half and not use SO4 on that half, use SO4 and not till on the other half. Since SuperCal SO4 “chemically” loosens the soil, and adds soluble calcium and sulfur, I expect higher return on the acres that receive SO4.
A little compaction is good, as it speeds the rate of seed germination because it promotes good contact between the seed and soil. Corn planters have been designed specifically to provide moderate compaction with planter mounted packer wheels that follow seed placement. Too little seed to soil contact can result in rootless corn syndrome.
Soil bulk density is a measure of the weight of the soil per unit volume. The greater the weight of a substance needed to fill up a certain amount of space the greater the density. The more air in a given space the lower the density. Think of a pound of feathers and a pound or rock. They weigh the same but the feathers will take up a lot more space (volume) than the rocks.
While soil bulk density is rarely measured it has a major impact on root growth.
Compacted soils have a very high bulk density reducing root growth. Soil compaction in the surface layer can increase runoff, increasing soil and water losses. SuperCal SO4 provides valuable calcium and sulfur increasing organic matter, and soil oxygen reducing bulk density. This increases water infiltration, and root proliferation, allowing your crop to access more nutrients and water, resulting in a healthier crop, better yields.