Considerations for tillage after drought

Mahdi Al-Kaisi
Integrated Crop Management News and Iowa State University Extension

The dry, warmer-than-normal growing season presents significant challenges for managing soil and crop residue this fall.

Excessively dry soil conditions make field preparation and fall tillage challenging, even though a dry soil condition is preferred for conducting tillage operations. The advantage of having low soil moisture for tillage is reduced soil compaction and field ruts from equipment traffic.

However, disturbance under dry conditions destroys soil structure and increases the potential for erosion after rain events. It can also lead to a loss of organic matter, top soil and nutrients in the soil.

A lack of soil moisture, especially in the top 12 inches where most tillage occurs, can produce unfavorable conditions for soil fracturing. The excessive dry soil conditions can produce large soil clods that are not easy to break with secondary tillage in the spring.

Additionally, tilling excessively dry soils can be costly in terms of fuel and time use as compared to soils with normal field moisture at field capacity. The effectiveness of incorporating crop residue may be limited and the lack of moisture will reduce the breakdown of crop residue.

The best option for managing dry soils and crop residue under dry conditions is to limit soil disturbance and keep residue on the soil surface. Crop residue can help mitigate drought conditions by trapping rain and snow moisture to recharge the soil profile for the following season.

It has been documented that keeping residue standing with no-till on the soil surface can trap 70% more of the water in rain or snow melt than conventional tillage. The water storage capacity of soil will be greater than that with conventional tillage, where soil structure is destroyed.

Conservation practices also play a major role in managing soil moisture. The absence or reduction of soil disturbance in no-till both minimizes soil moisture loss from the soil’s surface and maximizes soil moisture storage. They also enhance beneficial properties such as increased water infiltration, maintenance of soil macropores and reduction of surface runoff during rain events, thus increasing soil moisture storage.

Generally, every tillage pass can cause the loss of 1/4 inch of soil moisture. However, this number varies based on texture, organic matter content and the amount of residue on the soil surface.

To account for unpredictable weather patterns and ensure maximum soil moisture storage, precaution should be exercised in using tillage to manage dry soils this fall, and farmers should keep residue upright on the soil surface to increase the soil profile moisture recharge.