How Drought Affects Soil Health

Dr. Mahdi Al-Kaisi, professor of agronomy and Iowa State University Extension and Outreach soil and water specialist, published a great article on the impacts of drought on soil health and management practices that can help reduce drought effects.

Drought conditions during most of the growing season in Iowa can have a profound impact on soil heath, just as when we have extreme wet conditions. The effect of drought can be noticed very clearly on crop performance when the lack of water availability is severe. This water stress can affect soil chemical, physical, and biological activities that are essential for plant and soil health.

One of the obvious effects of drought on soil health is the lack of nutrient uptake by crops, as water is the major medium for moving nutrients into plants as a result of water uptake. The increase in soil temperature associated with lack of soil moisture has an impact on microbial activities and nutrient processing, both of which are important for plant use for biomass and grain production. Microbial activities in soil generally are controlled by soil moisture and temperature. The departure from the optimum ranges of soil moisture (water field capacity) and soil temperature (approximately 76-86o F), which varies for different microbial communities in soil, can alter microbial activity. Changes in soil temperature during drought conditions can affect soil organic matter (SOM) decomposition and increase the release of carbon dioxide. Also, during this process additional mineral N, mostly in the form of nitrate, will be released in the soil system. This change in soil environment affects the stability of SOM and subsequently, affects the soil biological system.

The most profound effect that can be experienced in cropland is the excess release of nitrate which may not be utilized by crops due to the lack of moisture available for the plant to uptake nutrients. This shift in biological and chemical processes during the growing season influences many other relationships that are essential for crop performance, quantitatively and qualitatively, by changing activities that are important to nutrient cycling such as, enzymatic activities, change in soil chemicals concentrations, etc.

Management practices to reduce drought effects
In order to moderate future drought event’s effect on soil health, several practices can be valuable to enhance soil health by improving soil physical, chemical, and biological properties:

  1. Crop residue: crop residue can provide important benefits like improving soil moisture with an increase in soil water infiltration during and off-season as well as increase recharge of the sub-soil profile. The other benefit of residue is the moderation of soil temperature, where crop residue acts as an insulation layer by increasing soil surface reflectance to sun radiation (i.e., change in Albedo, the ratio of the light reflected by surface to that received by it, where residue color is lighter than soil surface). These benefits of crop residue have direct impacts on soil biological and chemical properties by reducing soil temperature and the slowdown of organic matter mineralization. The increase in soil organic matter can increase soil water storage capacity (Fig. 1). The other benefit of moisture conservation and its availability to crops during drought periods is the increase of utilization of nutrients and reduction of nutrient concentration in soil and loss during off-season rain events.
  2. Cover crops: cover crops have many benefits that are critical, especially during drought conditions. The way that cover crops provide such benefits during drought conditions is based on the cumulative effects of cover crops during previous seasons, where they promote better soil biological and physical conditions. It is well documented that cover crops increased soil water infiltration and recharge of the soil profile by improving soil aggregate stability and soil porosity. Furthermore, cover crops contribute to the increase of the soil organic matter pool, which is essential for building soil health.
  3. Balanced crop rotation: crop rotation and diversity of crops within one year or over several years is one of the most important practices that enhance soil health and mitigate drought conditions during the growing season. The diversity of crops on the land can provide a rich soil environment for a healthy and diverse biological system. The inclusion of different crops such corn, soybean, alfalfa, small grain, etc., provides diversity of root systems that promote a wide range of microbial community, therefore enhancing soil nutrient and organic matter pools as compared to a mono-cropping system (i.e., continuous corn).

These practices, in addition to organic amendments, are important in mitigating unexpected drought conditions in the long-term. These practices, along with minimum or no-tillage, can reduce the prolonged impact of drought events by increasing soil resiliency. The degree at which soils in Iowa and the Midwest have absorbed the dramatic impact of drought events was due to the rich soil organic matter content. Factors which contributed to that are the temperate climate and vegetation base (i.e., prairie), which encourage greater organic matter accumulation. This unique soil quality provides high water storage capacity that sustains crop production. So, to sustain such soil quality, we need to maintain it through the implementation of soil health principles by adopting conservation systems.

figure_1_Al-Kaisi drought article 8-23-2017

The article was published by Integrated Crop Management News on August 23, 2017.

Liz Juchems

Articles from different North American regions offer same advice for soil health

Two articles from publications in vastly different agricultural regions—Canada and Mississippi—discuss the same issues that we face here, in between these geographical areas. Both articles contain excellent reasons why conservation practices are worth doing no matter where you live.

Up North

ILF Juchems 068In the article “Where Water Leaves the Farm,” published in Country Guide (“Canada’s oldest farm publication”), retired farmer Don Lobb offers his point of view on agricultural drainage. This story has a lot of data for the Lake Erie area, but the information on the science of soil health is the same for Iowa—everywhere actually.

“The modern role of subsurface cropland drainage (tile drainage) is much different,” says Lobb. “It’s root-zone soil moisture management. We want a favourable balance of air and water in the root zone, while also maintaining water at the base of the root zone to supply water during dry periods.”

Lobb also gives great reasons how tillage damages soil quality:

“Tilled soils have little or no soil aggregation, and clay soils are almost always compacted,” says Lobb. “With these conditions, subsurface drains can then contribute little to reduce run-off of water sediment and contaminants,” he continues. “When tillage-degraded soil cracks, water easily reaches subsurface drains. This does lead to water degradation in drains and outlet channels, and is really the outcome of bad soil management, not the use of subsurface drains.”

Down South

In the article “Improving Water Use Efficiency Starts With Caring for the Soil,” published in Delta Farm Press, the scarcity of water to nourish crops in Mississippi magnifies the issue of water quality.

“Here in the Mississippi Hills we have to make the most of the water we receive as rainfall during the winter months as well as during the growing season. Very few of the farmers in this region have the capability to provide supplemental water to their crops, so our efforts to increase water use efficiency are not optional but necessary.”

Again, healthy soil is of highest importance for success:

“…we have been forced to learn every practice that can allow our soils to store as much water as possible and that will allow our crops to extract and use as much of that stored water as possible. The strategies involved in this program begin with the soil and include the standard practices of soil fertility, such as liming and fertilizing according to current soil tests, and improving the quality of the soil to raise organic matter levels and increase the activity of beneficial soil organisms such as mycorrhizae and earthworms.”

DSCN9201The two articles have great points, written in plain English, on improving soil health through no-till, cover crops, and allowing time for these practices to take effect.

Although they focus on land far from us, there are many points that we can apply to Iowa farmland.

— Carol Brown

No-till & crop residue benefits flow chart

On yesterday’s No-Till Farmer website, editor Frank Lessiter posted a flow chart showing the benefits of no-till and crop residue. The chart sums up the numerous benefits in few words and little space.


Read the complete story here: Check out the many benefits of retaining crop residue in a no-till system

Carol Brown

A Cover Crop Snapshot

In the last two weeks, Iowa Learning Farms team members have visited five of our cover crop demonstration sites located on ISU Research Farms to check on spring cover crop growth and prepare our suction lysimeters for water monitoring this spring.

I posted photos from my trip to the Armstrong Research Farm on March 27, but now that we’ve been to each site, I thought it would be interesting to see a snapshot of how our cover crops (specifically, the over-wintering cereal rye) are doing across the state.

Here are the pics in chronological order of our visits:






How are your cover crops doing this spring?  We’d love to see your spring cover crops photos… share with us on Facebook, Twitter, or send via email to

Ann Staudt

Top 10 Webinars #6: Biochar’s Contribution to Sustainable Bioenergy Production

March 2012 Screenshot

Today, the Top 10 Most-Watched Webinars series presents “Biochar’s Contribution to Sustainable Bioenergy Production,” hosted by David Laird, a professor in the agronomy department at Iowa State University. Here’s my preview:

1. When farmers harvest residue for biofuel production, they are promised short-term gains (sales, temporary yield increases), but they also face the prospect of long-term losses (degraded soil quality, reduced agricultural productivity).

2. If residue is harvested, biochar can help maintain soil quality by putting lost nutrients back in.

3. So, the pyrolysis-biochar platform may help make residue harvesting more sustainable.

Watch the full webinar here.

– Alex Kirstukas

Spring Cover Crop Biomass Sampling

As part of the ILF cover crops research, we have been busy installing lysimeters and we have also been collecting cover crop biomass samples. Given the harsh winter weather and cool spring, the cover crop growth was spotty across the state this spring.  Where the cover crops managed to survive, the cereal rye is the only one to successfully overwinter this year within the mixture plots.

Below are some photos taken during the biomass sampling process Friday, May 9th at the Sutherland Research Farm in Northwest Iowa.

20140509_121659Cereal rye overwintered as part of a three species mixture: rye, rapeseed, and radish

20140509_121707Single species plot – cereal rye

20140509_124046Step 1: Biomass sampling frame is tossed at random within the plot and using scissors, the rye biomass (plant material) is clipped close to the ground and placed in a paper bag.
This is done twice per plot.

20140509_124531Step 2:  The two sample bags per plot are then used to estimate the pounds per acre biomass of the cover crop for the entire plot.
Step 3: Back in the lab, the rye is dried and weighed to calculate the pounds per acre.

The aboveground biomass is as important as what’s growing underneath the surface. The rye (or other cover crop) covering the soil reduces the impact of energy when a raindrop falls on the land. By hitting the biomass first, the force of the rain is lessened and allows the water to infiltrate the soil gently.

Liz Juchems

Two stories offer perspectives on residue management

The article “Tips for Making No-Tilled Corn-on-Corn Successful” was published recently on the No-Till Farmer website. Author Laura Allen includes quotes from farmers from all over the central midwest and also Iowa State University Agricultural Engineer Mark Hanna, faculty advisor for Iowa Learning Farms. The farmers and experts offer advice on all stages of the corn-on-corn growing process from fall harvest through spring planting. Part of the article talks about soil health and residue breakdown.

“Once residue is present in the field, the soil microbes get to work decomposing the residue, says Doug Miller, vice president of Midwest Bio-Tech, a company that distributes liquid biological and enzyme treatment products for crops and crop residue. ‘As soon as you’ve got residue in the field, it’s more or less like opening up the buffet line for the microbes. They’re going to multiply very rapidly and start to work in seeking out carbon, which is their main fuel source,’ Miller says.”

“Myths and Facts About Residue Breakdown” is in today’s Integrated Crop Management News. ISU agronomy professor and former ILF leader Mahdi Al-Kaisi explains the results of his research study on the effects of residue breakdown through tillage and nitrogen application.

“There were no differences in the rate of residue decomposition as a result of N application of different N rates.  These results show that applying N fertilizer to facilitate residue decomposition is not effective.”

“Environmentally, both tillage and N application are not very sustainable practices; tillage can contribute to soil health and water quality deterioration by increasing soil erosion potential, sediment loss and water quality degradation, as do N applications, where no growing plant can utilize it.” – Al Kaisi