Some herbicides (e.g., phenoxy or atrazine) applied at this time may cause florets to abort resulting in a “blasted” head. During this period, plants are especially sensitive to any type of stress such as temperature extremes, nutrient deficiencies, or water deficits or excesses, any of which may reduce potential seed numbers. This stage continues through head exertion. In the rapid growth stage, 40 to 65 days after emergence, growing point differentiation occurs and the panicle or head begins to develop. During this period of development, water and nutrient uptake are low, and only about 25 percent of the total crop nutrient demand will be absorbed. As plants slowly develop their root systems and absorb water and nutrients, leaf tissue expands and produces carbohydrate energy for future growth. Plant growth requires energy, but it takes time to produce carbohydrates with a few small leaves which are subject to destruction by wind, hail, frost, insects and pests. Emergence and early plant growth are highly dependent upon growing conditions. The seedling development stage begins at germination and ends 30 to 35 days after emergence when plants have five to six mature (fully expanded) leaves. Like any other crop, sorghum responds to optimum growing conditions and good management. Although sorghum can survive and produce seed under adverse conditions, yields can be greatly reduced by environmental stress and poor management. Many producers falsely believe that sorghum is “tough” and requires little management. Stress in any stage of development will reduce yield potential. Plant growth in each stage of development is dependent on the previous stage. Since both the number and weight of seed determine yield, it is important to understand the plant processes that influence seed development. Like other crops, seed production in sorghum is a one-time event and all root, leaf and stem development is directed toward completion of the reproductive cycle. Information related to weed and insect control is not addressed in this publication, but can be found in Suggestions for Weed Control in Sorghum (B-5045) and Managing Insect and Mite Pests of Sorghum (B-1220). A brief summary of the basic growth processes and important interactions follows to assist in making better production decisions as conditions in the field change. All are important factors in determining crop yield. Only after decades of research, the effects and interactions of fertility, row and plant spacing, planting date, environmental conditions (water, temperature, etc.), insects, diseases and hybrids are better understood. ![]() Many people try to put the growth, development and eventual yield of the grain sorghum plant into a simple formula, when it is a complex series of many processes and interactions. *Associate Professor and Extension Agronomist Assistant Professor and Soil Fertility Specialist Associate Professor and Extension Agronomist, The Texas A&M University System. ![]() By: Charles Stichler, Mark McFarland, and Cloyce Coffman*
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