Agronomy Update April 2019
Posted on April 12, 2019
By Dave Dyson, Agronomist
As the days get longer and temperatures rise, the drive to get in the field becomes more overpowering. The long-term forecast shows the higher precipitation pattern that we’ve seen so far this year is likely to persist into spring. In addition, according to NOAA, the temperature gradient is amplified more than normal this early spring, meaning a colder north and warmer south. This will help fuel spring storms and keep weather active. The outlook through May calls for temperatures near or slightly below normal with precipitation above normal. These conditions, along with an itchy trigger finger on spring fieldwork, could spell trouble for the health of your soil.
If fields are still wet, avoid the urge to begin fieldwork until they dry out. Soil compaction is most likely to occur when soil moisture is at or near field capacity, when soil pores are filled with equal amounts of air and water. Under these conditions, aggregates can be "lubricated" by water and readily reposition themselves through the air spaces under heavy traffic and farm equipment.
The most devastating and longest lasting compaction is deep subsoil compaction. The chief reason for subsoil compaction is high axle loads driven over saturated soils (figure 1). The definition of an axle load is the total load supported by one axle, usually expressed in tons or pounds. Farm equipment with high axle loads will cause deep compaction.
Figure 1: Research from Penn State University indicates axle loads of 10 tons or more have a significant increase in subsoil compaction.
Deep sub-soil compaction can only partially be alleviated with subsoil tillage, and at considerable cost. Freezing/thawing and drying/wetting cycles have not been shown to improve soil compaction at this depth. Research from Penn State University shows yields can be reduced by up to 15% with this type of compaction and will last up to 12 years. Subsoil compaction should be avoided at all cost. Soils that are near or at their water holding capacity will act as a hydraulic ram and will drastically increase the chances of both surface and subsoil compaction.
Several factors can indicate soil compaction, including stunted plants, slow infiltration, ponds of water, high surface runoff, soil erosion under normal or light rainfall, and evidence of poor root system establishment. Poor root development can cause a crop to have a nutrient deficiency, and compaction can result in reduced potassium uptake. According to Iowa State University, the impact on yield has been reported to be as much as 10 to 20 percent. Changes in the soil's physical properties alter the ratio of water to air in the soil. Plant roots require air as well as water to develop a healthy root system.
If your fields show signs of soil compaction, it is important to determine the depth of the soil compaction. To do this, take a soil probe or spade and push it into the soil to determine the level of compaction by the level of resistance. Compaction layers near the top three to six inches of soil are generally associated with excessive surface pressure. Compaction at deeper depths is primarily associated with axle weight or deep ruts.
Once you have determined where and how dense the compaction layer is, the decision to till or not to till will be upon you. First and foremost, you must have a level soil surface for planting, so tillage will be mandatory if the soil is not level. If tilling the soil to level out the ruts from last fall is required this spring, make sure the soil is dry before you run a tillage pass. If a tillage pass is done on wet or saturated soil, you will compound the problem by making another compaction layer. Try waiting for soils to dry before starting field work, but watch the calendar. If the calendar gets too late due to continuous spring moisture, no-till planting may be your best option for the 2019 cropping season.
Starter fertilizer, in the form of an in-furrow or a 2x2 application, will pay dividends in a wet/cool planting situation. The restricted root growth due to multiple compaction layers in the soil may cause your plant to rely completely on the starter fertilizer until V5. The V5 stage is critical for the corn plant because at that stage the corn plant has determined the maximum number of rows of kernels the ear will produce. Roots that are restricted by compaction tend to form into a “mohawk” formation (figure 2). This formation of roots can only get nutrients from a band of fertilizer placed close to the seed trench. The Andersons can provide you with a high-quality, low-salt starter fertilizer that is safe for your seed’s germination, and it also will provide vital nutrients to your plant’s restricted roots.
Figure 2: This picture from Pioneer Seeds shows restricted corn roots, called “mohawk” roots.
By Jessica Stacy, Product Specialist
The addition of a high-quality, low-salt starter provides essential nutrients to the crop early in the season allowing the crop to maximize its genetic potential, even in the face of adverse conditions. PureGrade® starter fertilizers are seed safe and will effectively deliver nutrients to the young root system in immediately available forms ready for uptake. Extensive research has been conducted on PureGrade.
The above trials were conducted in Ohio, Wisconsin and Nebraska. Season Pass® Plus with AVAIL® was applied at 5 gallons per acre. Between the three sites, an average increase of 9.9 bu/acre was observed.
The application of PureGrade GoldStart® 6-24-6 at 5 gallons per acre provided necessary nutrients early in the season to the crop, resulting in an average of 8.58 bu/acre advantage compared to the untreated check. This trial was conducted in eight geographies across the nation.
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