Jim Angel’s latest post regarding “Dryness Across Illinois” is helping to shed light on some of the challenges we’re seeing so far this summer on the Wolske Urban Farm.

As a result of the below-normal rainfall, crops and vegetation have had to rely more heavily on soil moisture to grow. This is causing a rapid depletion of soil moisture in the top 8 inches. As those reserves are used up, roots will have to go deeper to tap into soil moisture at lower levels. Corn and soybeans have much deeper root systems than lawn grass and can do fine even after the grass has turned brown.

University of California Davis Vegetable Root Depth Chart helps to further consider in the vegetable garden issues of concern as depletion of soil moisture. If you’re noticing some varieties of a given crop, for instance tomatoes, seem to be doing well than another, it’s probably because that plant’s root system is deeper. In a year like this, that matters more.

• In Champaign, our 4″ soil moisture has a value of .17. Anything below .2 is very dry. For a vegetable like Mache, this would be a significant issue. For others, we need to look deeper, though.
• In Champaign, our 8″ soil moisture has a value of .24, which is in the dry range, nearing the very dry range, thereby impacting radishes and maybe some onions.
• Our soil moisture value at 20″ in Champaign is still only .27, closer to the .3 minimum value for soil moisture in good shape. Quite a few vegetable crops have some or all of their varieties impacted at this level.

Indeed, these values bring home confirmation of the rapidly drying soil conditions being seen in the Wolske Urban Farm and other vegetable gardens in the neighborhood. While plants may not seem like they’re not needing water quite yet, failure to do so means these plants are rapidly increasing the depletion of soil moisture deeper down in the soil.

Especially for gardeners in parts of Illinois seeing very dry soil moisture as listed in Jim Angel’s post, now is a good time to start providing a deep 1.5″ watering of the vegetable beds once every 5-7 days, or whatever balance is needed if the fortunes come our way and rain does give at least some of that moisture back to the soil.