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Wednesday, July 30, 2014

Drought more than skin deep

Sunday, December 11, 2011

I have made a habit to periodically check the US Drought Monitor to see if our abnormally dry condition had changed. I noticed that we were considered to have made it back to normal in the November 29 report. This report is located at http://droughtmonitor.unl.edu/.

One of the features that I like on the Drought Monitor site is the forecast. The monthly and three month forecasts are available. The December, January, and February forecast estimates above normal temperatures and slightly above normal precipitation.

We had a severe drought last year and it was broken this spring due to the rainfall and flooding during planting season. According to the U.S. Drought Monitor as of August 2, much of our prime cotton region in Missouri was considered abnormally dry. Only the southern portions of Butler, Dunklin, and Pemiscot Counties were not affected by drought. However, even in these areas, the non-irrigated cotton showed considerable moisture stress. It is easy to see the difference for all crops that are located outside of the center pivot circle.

While we have more moisture now that at the same time last year, we will need rainfall to replenish the subsurface areas. I receive news releases from the University of Missouri Cooperative Media Group each week. This week, the article was entitled, ?Missouri drought more than skin deep.? It was written by Roger Meissen who is a Senior Information Specialist. The article featured Dr. Randy Miles, MU soil scientist and Dr. Mike Collins, director of plant sciences in the College of Agriculture, Food, and Natural Resources. The article might explain what happened in many of our Southeast Missouri crop fields.

With the major drought last year, much of our subsoil moisture was depleted. While some was replenished with the excessive rainfall in April and May, the hot dry conditions following planting this year soon reduced the amount of moisture that was available to plants.

When we have plenty of moisture early during plant development, all plants generally will put the majority of their roots into the moisture. In some years, when we just have enough moisture to get the roots started, the plant will put down deeper roots. Deeper roots mean that the plants have more access to water during the growing season. Even if the crop is irrigated, most of the water applied by center pivots only promotes roots near the surface. So during hot, dry summers like we have experienced during the past two years, the crops need to be irrigated more frequently to keep the crops growing normally.

In the article related to moisture, Dr. Miles noted that in droughty areas, he sampled the subsoil and found that it was very dry. This meant that the crop was depending only on the surface moisture. In no-till corn, the roots are generally 5-6 feet deep. So when the surface water was depleted, the crop did not have sufficient moisture to complete grain fill. Thus, the field yields less than its potential.

With some of the complaints this year of the cotton not yielding up to expectations, I suspect that last year?s drought might have been part of the problem. Any time that a crop does not meet expectations, the yield components could help us understand what was happening. For example, the yield of any given area is based on the number of plants, the number of bolls, the number of seed, and the lint per seed. In addition, the lint can have a greater thickness which could lead to a micronaire or ?mic? problem. Usually, we would like for the cotton to have the highest micronaire possible without going into the penalty range.

We can only speculate since we don?t have the yield component data for some of these fields. There are a lot of things that can happen during the course of the season. However, the cotton plant is very competitive and can compensate for problems during the early season. If the stand is too thin, the plant will grow larger and produce more bolls. The cotton plant is capable of producing up to five times more blooms than it can reasonably set. So the key is to set as many as the plant can support. In order for the plant to maintain its fruit, it must have plenty of moisture. Good agronomic and crop protection practice will protect the blooms and bolls set.

My guess is that if we had sufficient bolls, we still might not have had as much yield due to motes. Generally we have about 28-35 seed per boll. Motes are unfertilized ovules or seed in which the seed developed ceased due to environmental stress.

The two main reasons for environmental stress are heat and the lack of moisture. We see this every year in the non-irrigated cotton. Some of the motes are removed when the seed cotton is cleaned. Motes have shorter fibers and in general the fiber is not very well developed.

A three year research study conducted in Texas concluded that the seed size was one of the most important factors of within boll variation. The larger the seed, in general, there were more fibers attached to the seed. This also tends to lead to higher yields.

While cotton prices have dropped from their highs, there are still plenty of opportunities for crop producers. Cotton acreage has been projected to be up again this next year.

University of Missouri Extension programs are open to all

Dr. Michael R. Milam is an agronomy specialist and county program director with University of Missouri Extension in Dunklin County.

At Your Service
At Your Service