In this month’s Texas Row Crops Newsletter, Drs. Gaylon Morgan and Ronnie Schnell, Extension Agronomists with AgriLife Extension offered some timely thoughts on managing waterlogged cotton, corn, and sorghum. This is a rather timely topic give that we have receive around 30 inches of rain in Corpus Christi since the first of the year. This is around 20 inches above normal and the wettest start to the year on record dating back to 1887, according to John Metz with the National Weather Service. And before we get to critical of our bountiful rainfall Metz also pointed out that at this time last year we had just over seven inches of precipitation.
With a moderate-strong El Nino predicted there is a greater than 40% probability of above normal rainfall and below normal temperatures through next spring according to Metz. With this in mind, Drs. Morgan and Schnell reminded us that oxygen is required by plants for respiration, including above ground (shoots) and below ground (roots) plant tissue. Respiration is the process where plants metabolize sugars, producing energy needed for growth and development. Soil contains about 50% pore space that is occupied by air and water. Flooding increases the proportion of pore space occupied by water and reduces exchange of air between the soil and atmosphere. Deep ponding has the same effect on above ground tissue. Oxygen does not easily move through water so saturated or flooded conditions will limit oxygen availability to plant tissue, especially roots. This can have detrimental effect on plants.
The growth stage of the crop will influence the plant’s ability to withstand flooded conditions. Younger plants are more susceptible to damage or death by flooding, especially when the growing point is at or below the soil surface. Younger plants are easily submerged compared to older, taller plants. Higher temperatures will exacerbate the effects of flooding. Stand loss at early growth stages is a major factor in yield loss.
Saturated soils also inhibit nutrient uptake. An obvious response for some producers may be to apply foliar nutrients to remediate observed or anticipated nutrient deficiencies. Foliar applications of nutrients may result in a slight improvement in appearance, but are not likely to result in an economical yield increase. Soil nitrates (plant available form of nitrogen) also can be lost from the soil as a gas once anaerobic conditions occur. As a result, supplemental N may be needed in some cases to meet plant needs for the season. Therefore Dr. Morgan suggests, producers review the Mississippi State University publication titled “How to Estimate Nitrogen Loss resulting from Saturated Soils”. However, in most cases once waterlogged conditions subside and sunshine returns, normal plant growth and nutrient uptake will resume, and nutrient deficiency symptoms typically will go away. Regardless, plants cannot compensate for this lost time and crop harvest will be delayed as a result.
After the soil begins to dry out, there will likely be the urge to apply plant growth regulators (PGRs) to control plant size and possibly promote earlier maturation. However, we must keep in mind that waterlogged conditions also inhibit plant hormones, which contribute to growth and leaf expansion. So, be cautious about applying PGRs too soon after waterlogged conditions, because applications too early could further decrease the yield potential, especially for some varieties. Please consult with the seed company about the recommended PGR regime for each variety.
The flooding and waterlogged soils will definitely delay crop development; however, once established, cotton is a tough plant that can compensate for many adversities. So, do not give up on our 2015 cotton crop too early is a final thought from Dr. Morgan.
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