Assess Soil Profile After Drought Recovery

Assess Soil Profile After Drought Recovery

To determine how much reserve moisture is being held in a soil profile after potential recovery from last year's drought, you can use two methods.

It is welcome news to see the potential recovery from last year's drought as the soil profile is fully recharged in most areas in the state. The moisture recharge of the soil profile is affected by many factors, such as soil texture, type of tillage, residue cover, soil slope, grass filter strips and many other conservation measures that enhance moisture recharge. The timing of rain events during early spring can cause significant damage to fields, especially if soil temperature is low (frozen soils), leading to significant erosion and surface runoff. Therefore, monitoring soil moisture is important.

HOW MUCH RESERVE SUPPLY? Monitoring soil conditions and soil moisture recharge in your fields will help you assess the effectiveness of certain tillage and other management practices in achieving potential yield and improving soil quality, says ISU Extension soil management specialist Mahdi Al-Kaisi.

The following information and observations come from Mahdi Al-Kaisi, an Extension soil management specialist in the agronomy department at Iowa State University.

How to determine the soil moisture status in the soil profile in your field
To determine the soil moisture status in a soil profile you can use two methods. One quick method is by monitoring your drainage tile flow. If the tile is running with considerable flow, that is an indication the soil is saturated and the excess water is moving through the soil profile by what we call "gravity flow," says Al-Kaisi.

The second method is to determine exactly how much water is held in the soil. To do this you must know your soil texture at different depths at least down to 5 feet in 1-foot increments and the soil moisture holding capacity at each foot. (You can obtain this information from the soil survey or by contacting the NRCS office in your area). After you obtain this information, add up the moisture available for the top 5 feet to determine the total amount of water in your soil profile.

Most Iowa soils can hold 10 to 12 inches of water in the top 5 feet of soil profile
Most soils in Iowa have fine-to-moderate soil texture and the amount of water held at field capacity will be approximately 10-12 inches of water for the top 5 feet. If this is the case in your farming situation, then it provides an excellent start for the growing season for both corn and soybeans. Generally, corn needs approximately 24 inches of available water for the entire season. So at this point in time, if our soil profiles are at field capacity, we have almost 40% to 50% of the water needed for corn production.

Post-Drought Livestock, Range And Pasture Insight. No single group of producers has been more impacted by the 2012 drought than those who raise livestock. Download our FREE report, 5 Post-Drought Strategies For A Better 2013.

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The other 50% or so must be provided through additional rain that hopefully will be spread evenly over the growing season. This is especially true during the high demand period for water use by the crop from June through August. However, the timing of rain during growing season is as critical as the amount of rain needed for crop production.

How farmers manage crop residue and intensity of tillage can help capture and store more water in the soil for use by crops later in the growing season
"This good moisture amount that we have received over the past few weeks brings some challenges we need to be aware of in terms of managing soil and planting to minimize potential damage and eventually negative impact on yield," says Al-Kaisi. "Maximizing potential precipitation capture during subsequent rain events is highly important and is affected by how we manage crop residue and the intensity of tillage. Slowing water movement across the field through conservation practices, such as grass filter strips and waterways, is a critical way of increasing water recharge and potentially mitigating any drought spells that may occur during the growing season."

Monitoring field conditions and soil moisture recharge will help assess the effectiveness of certain tillage and other management practices in achieving potential yield and improvement of soil quality. "Keeping a good record of your field conditions and operations early in the growing season may help explain positive or negative outcomes of the growing season for future management decisions/adjustments," he says.

Post-Drought Livestock, Range And Pasture Insight. No single group of producers has been more impacted by the 2012 drought than those who raise livestock. Download our FREE report, 5 Post-Drought Strategies For A Better 2013.

 

TAGS: Soybean USDA
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