Anne Verhallen, Soil Management Specialist, OMAFRA, Ridgetown
Recent heavy rain storms have had many growers scrambling to get excess water off their fields. Most crops can’t survive long under water. For unplanted acreage, the ponded water and sediment poses a continued drainage problem.
Temporary flooding of fields does more than just cover the crop and soil with water. Rain carries soil and crop residues as it collects in low-lying areas. We have had extended ponding in many fields. As the water flows into the low areas, sand particles drop out of the water first, often on the outside edges of the low area. Silt particles drop out within a few hours while the clay particles stay in suspension for days as the water sits, eventually creating a skin of clay in a wet area. The accumulation of fine soil particles and the weight of the water in the flooded area can cause the soil to seal and exhibit poor soil structure. The result — poor air and water movement at the soil surface and crusting. It is going to be tough to get many of these low spots to dry out this year.
Meanwhile if there was a crop planted in the field, the crop roots are in soil that has very little available oxygen. Crop tolerance to low oxygen and high carbon dioxide levels vary depending upon plant species and age. Often the first effect of temporary flooding is the increase in resistance to water movement through the roots. Plants have difficulty in taking up water and may appear wilted. The old roots often die and there may be a lag as new adventitious roots form.
The key to managing temporary flooding is to get the water off as quickly as possible and open up the soil at the first opportunity. Use a light cultivation to open the soil surface and improve aeration.