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  4. 1998
  5. May

Before Planting Your Grain Sorghum

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Hybrid Selection. Proper hybrid selection is an important factor in having a successful season. Producers can enjoy higher yields with the careful selection of a hybrid that is best adapted to their farming situation.

Maturity and stalk strength are the main factors to consider. Maturity is the most important characteristic to consider when selecting the proper hybrid. A full-season hybrid will out yield a short-season almost every time. Also, standability is usually greater with the full-season hybrid. Always try to plant the latest maturing hybrid that you can taking in account the length of the growing season, moisture availability and your cropping rotation. To maximize production, a hybrid should be physiologically mature two weeks prior to the first hard freeze of the fall. Lack of moisture can damage late hybrids more than a freeze.

Yield can be greatly influenced by genetics and/or environmental conditions. Therefore, it is important to look at other positive traits of the hybrid that can lead to higher yields, such as insect and disease resistance. Things to remember are the probability of a repeat pest problem and the ability of the hybrid to withstand altered management practices to avoid the pest.

Planting Management. Planting date should be timed so that flowering does not occur during the hottest period of the summer. Moisture stress can cause poor stalk formation, which can lead to lodging.

Planting early or delaying planting in the spring helps to avoid injury during this stressful period of the season. Also, a shortseason hybrid can be planted early to avoid drought stress and take advantage of the moisture early in the season. Planting too early when soil temperature is below 60°F can result in poor germination. Early grain sorghum usually has more vegetative growth and is taller.

If planting early, a starter fertilizer should be banded with or close to the seed to enhance early plant vigor. Late grain sorghum increases the risk of a freeze damaging the crop before it has reached maturity. When planting late always use a full-season hybrid to increase yield potential.

Seeding rates should be determined by rainfall amounts. For example, if rainfall were 30-40 inches per year, a plant population of 50-60,000 plants per acre would be desirable. However, if under irrigation, a plant population of 70? 80,000 should be considered. Seed spacing within the row should be determined by plant population and row width as shown in the table below.

Seeding depth should be no more than 1 inch in heavy soils or in sandy soils with good soil moisture. Seed can emerge from a depth up to 2 inches; however, germination is slow and percent germination decreases substantially.

Fertility. Fertility requirements for grain sorghum are similar to those for wheat and corn. Grain sorghum is very responsive to nitrogen. Since nitrogen is related to yield, it is needed more than any other nutrient.

Phosphorus is important in stand establishment, uniformity of maturity, root formation and grain test weights. Potassium promotes standability (stalk strength). Poor potassium levels can result in lodging.

Secondary nutrient requirements vary among different soil types. Zinc is usually needed in fertile soils where yields are traditionally high. Sulfur may be required in sandy soils or soils in which organic matter levels are low. Liming is recommended when the soil pH falls below 6.0. Grain sorghum is not very responsive to liming, but a soil pH of 5.5 or less can lead to drastic yield reductions. Fertility and lime requirements are best determined by soil testing and establishing a realistic yield goal.

Weed Management. Before planting grain sorghum, a weed management plan should be developed. The field should be free of weeds prior to planting. This can be accomplished by tillage (in a conventional cropping system) or by using herbicides (in a no-till system).

A preemergent herbicide, such as Dual or Lasso, should be applied to control grasses and small-seeded broadleaf weeds, such as pigweeds. Atrazine can be tank-mixed with these preemerge herbicides to enhance broadleaf weed control. For best results, these herbicides should be applied within two weeks of planting and should be lightly incorporated to ensure activation. It is important to purchase Concept or Screen treated seed to avoid herbicide injury. Always consider what crop is next in the rotation. Atrazine and some other herbicides have a long life in the soil and can cause crop injury the following crop season.

A postemergent herbicide, following a preemergent treatment, can be applied when the crop is in the three to six leaf stage. There are several postemerge herbicides available including atrazine, Buctril, Peak, Permit, Banvel and 2,4-D. It is critical to properly identify the targeted weed and make sure the weed height is within the critical level described in the label.

A common mistake is to apply postemergent herbicide late when the weed is too tall to control. This drastically lowers the overall performance of the herbicide and increases the possibility of weed competition. The use of Banvel and/or 2,4-D increases the risk of crop damage. However, these herbicides are inexpensive and offer excellent weed control.

Banvel and/or 2,4-D should be used at low rates when the crop is less than 8 inches in height to avoid serious crop injury. Cultivation is an alternative method of weed control in grain sorghum planted in wide rows. It is a good idea to cultivate areas of the field where a herbicide performed poorly.

Insect Control. There are a number of insects that attack grain sorghum, but infestations will vary from season to season. Greenbugs are usually of concern since they are widespread due to the amount of wheat that is grown in the area. Insect resistant hybrids and timely applications of insecticides will help reduce the risk of crop injury due to insect infestations. It is critical to scout fields regularly to stay ahead of a potential insect problem.

Planning and preparing a crop management plan, covering everything from hybrid selection to weed control, will lower risk while increasing overall production.