It is difficult to wait. Time is ticking and you have corn to plant. However, with wet soil conditions in many areas, performing tillage and planting before soils are fit can have many negative impacts from now through harvest. Machinery used in wet soils can increase the risk of restricted root growth and seedling diseases. It can also cause soil structural damage such as compaction from tillage and traffic as well as sidewall compaction during seed placement.
Compaction from Tillage and Traffic
Wet soils in the spring are very susceptible to compaction. Disking or field cultivating fields before they are fit can lead to a compaction layer just below the depth of tillage. The weight of tractors used in tillage or planting can also cause a compaction layer just below the soil surface. This type of compaction leads to shallow root systems because roots cannot penetrate the compaction layer.
Sidewall compaction occurs when furrow sidewalls are smeared by the combination of double-disc openers and excessive down-pressure on the gauge wheels of the planter. This can cause poor seed to soil contact, which has several negative consequences including reduced germination and poor stands, and uneven emergence. When emergence is uneven, larger plants compete with smaller plants for light, water, and nutrients. The smaller plants are effectively weeds because they have little yield potential, resulting in lower overall yields at harvest.
Symptoms of Compaction
Above ground symptoms often include stunted plants, leaves with premature yellowing or death, or wilted or curled leaves. These symptoms are attributed to the root system not being able to access the moisture and nutrients, even if they are in ample supply. Below ground symptoms are smaller root systems that appear abnormal when they grow around the compaction layer to follow the path of least resistance (Figure 2). Compaction symptoms can be similar to those from other issues such as herbicide carryover, fertilizer deficiency, or insect damage. Look for patterns to help determine the actual cause of the symptoms.
Restriction of Roots
Root growth is reduced not only because of compaction but also because of low soil oxygen availability. Nutrient deficiencies such as potassium and nitrogen may occur due to slow root growth and poor root exploration. Restricted root development can also increase lodging and have a negative impact on yield, especially if the latter half of the growing season is hot and dry.
During years when adequate water and nutrients are available, compaction usually will not have a great impact on grain yield. When the crop is water or nutrient stressed, however, compaction can cause further stress to the crop and ultimately result in reduced yields.
The best way to reduce the effects of soil compaction is to avoid field operations when soil moisture is close to field capacity. Compaction will be less severe when tillage, fertilizer application, and planting occurs under dry conditions. Other in-season considerations that can help reduce the effects of compaction include:
- Using proper tire size and correct pressure—over inflation not only reduces the tire footprint, thus increasing compaction, but also reduces traction.
- Practicing controlled traffic—all farm equipment is driven in the same paths to minimize the amount of land traveled.
- Removing excess weights that make tractors heavier than necessary.
Keep in mind the impact wet planting can have on corn development as you decide when to enter your fields for planting or scouting this spring. Consider long-term management practices such as improved drainage, use of cover crops, and reduced tillage that can help create better soil structure and minimize future yield losses.
Al-Kaisi, M., et al. 2009. Not too early to think about spring moisture conditions, consideration for soil compaction. Iowa State University. www.extension.iastate.edu (verified 4/4/14); Take steps to reduce compaction before spring planting. 2010. Ag Answers. Ohio State Extension and Purdue Extension. www.agriculture.purdue.edu (verified 4/4/14); Thelen, K. 2006. Managing corn and soybean fields submerged by recent heavy rains. Michigan State University. Available online at http://msue.anr.msu.edu (verified 4/4/14).