The rain event we experienced last Thursday in the Coastal Bend was worth millions of dollars, although it was not enough to put an end to the current drought. The rain did, however, reinvigorate our plants while at the same time greatly improving the mood for all those folks who depend on the land to make a living.
Cotton in many fields has started to bloom, which is the most critical stage when it comes to the amount of moisture the cotton plant uses. Drought before bloom can reduce the number of fruiting branches produced by first bloom. However, drought is rarely severe enough to cause fruit shed before bloom. As the crop begins to bloom, it must begin filling bolls. This process causes the increases the plant's demand for water dramatically as more and more bolls are produced.
When cotton begins to bloom it can be using from one-fourth to four-tenths of an inch of water per day. The dry conditions early in the season forced the cotton plant to send roots deep for moisture, which helps explain why some of the cotton looks as good as it does.
Drought following bloom has the greatest effect on cotton yield and lint quality, so we need this new rainfall trend to continue.
Grain sorghum is known as a drought-tolerant crop; that’s why it’s so well adapted to the local region. Grain sorghum’s ability to perform under dry conditions can be attributed to the sorghum plants rolling leaves as they wilt, reducing transpiration and the waxy covering over the leaf protecting it from drying.
Sorghum’s extensive root system, which can extend to 6 feet in a friable soil, also is an advantage. Much of our sorghum is at peak water use stage now, which can be as high as four-tenths of an inch per day during early bloom and then is reduced to just less than three-tenths of an inch per day during grain fill. About 75 percent of water use will occur in the upper half of the root zone. Under stress conditions, when the upper zone becomes water-limited, the crop will use significant deep water, which, thankfully, we had some of this year.
Corn has been hurt the most by the current drought. During pollination the corn plant requires the most water and is most sensitive to drought stress. Grain is not produced without pollination because fertilization by pollen initiates seed (kernel) production.
Drought stress can disrupt pollination in many ways, with the most frequent being by disrupting the "nick," or synchronization of pollen shed and silk emergence. Tassel and pollen formation take priority over silk and ear formation. Drought stress prior to tasseling will delay silk emergence. By the time the silks from the tip of the ear emerge from the husks, pollen shed may have ended. This leads to ears with barren tips (nubbins), or, in extreme cases, ears with no kernels at all. We have already seen some evidence of this locally.