How to Grow Sorghum (Sorghum bicolor) From Seed

Choosing Sorghum Varieties To Grow

The first thing to consider when choosing a type of sorghum to grow is its end use. Depending on the end use, there are three options to consider:

• grain (milo) to grow for their seeds, primarily used as food for humans and cattle;
• forage to grow for livestock feed due to their high biomass yield and nutritional quality;
• sweet to grow for their high sugar content and then process into syrup or ferment into ethanol.

Once you have narrowed down your list of varieties by the end use, it's time to think about how well they'll do in your growing regions. This includes factors like sorghum soil requirements, drought tolerance, pest and disease resistance, and its average growing season. Another important consideration is yield potential.

Bed Preparation

Sorghum is an annual, frost sensitive grass that prefers full sun and tolerates a wide variety of soils. Sorghum is a heavy feeder; add an organic fertilizer to the soil before planting and a side dressing of nitrogen about 6 weeks after planting. Drought tolerant once established.

When choosing a variety to grow, assess the variety's adaptability to local conditions. About a month before the planned sowing dates, prepare the field to ensure good seed-to-soil contact and moisture retention. Plant at warm temperatures and try to space seeds at a uniform distance and depth.

Successful sorghum growing starts with proper field preparation. First, clear all plant residue, debris, and weeds. Follow with deep plowing, 8–12 inches (20–30 cm), to break soil compaction. Next, harrow to achieve uniform soil texture. In wet-prone areas, construct elevated rows (ridges) for better drainage. Schedule these operations at least one month ahead of planting sorghum.

Planting

Sorghum should be direct seeded outdoors once the danger of frost has passed and temperatures have warmed. Optimal soil temperature for germination is 55-80˚F. Sow seeds 1/2” deep and 1-2” apart in rows that are 2' apart. Seeds will sprout in 7-15 days. Thin seedlings so that mature plants are 8" apart.

This warm-season crop can grow well in high temperatures and is hence well-suited to hot climates. At 59°F (15°C), most seeds will germinate within 10 to 12 days, while higher temperatures of 77–82°F (around 25–28°C) can lead to faster emergence, typically within 5 to 6 days. Temperatures below 15°C (59°F), as well as water scarcity, could impede germination and early growth, and temperatures of 77–86°F (25–30°C) throughout the growing season promote plant growth and boost yields.

Late spring to early summer, ideally after the last frost, is when it's best to plant sorghum. Ensure the soil temperature reaches a minimum of 60°F (15°C) for successful germination. Late planting might cause drought stress and reduce the time available for plants to develop productive tillers. In warmer regions, sorghum planting can also occur from September to early October to grow as a second-season crop.

Seeds can be sown either by broadcasting or drilling. Even though broadcasting is much faster, particularly over vast areas, it doesn't work well for commercial crop growing because of uneven seeding rates. Drilling involves using a seed drill to place seeds directly into the soil at a specific depth and spacing. This method ensures that seeds are planted uniformly and at the correct depth, which is crucial for optimal germination.

Sorghum planting spacing influences how plants compete for resources, how successfully they suppress weeds, and how convenient it is to carry out routine agricultural operations. To balance these parameters, stick somewhere between 10 and 30 inches (25 and 75 cm). The optimal planting depth for sorghum seeds is typically between 1 and 2 inches (2.5 and 5 cm). In sandy soils, deeper planting may be acceptable, while in heavy soils the depth should not exceed 1 inch (2.5 cm) to ensure proper seed-to-soil contact and quick germination.

Sunlight and Temperature

While the crop needs full sun to grow healthy, it can tolerate some shade, especially in scorching climates. Plant sensitivity to light varies by growth stage. It can handle high temperatures and intense sunlight during the vegetative stage but may become more sensitive during the reproductive stage (e.g., during flowering). Too much sun, especially combined with a dry spell, during this time can negatively impact flower formation and grain yield.

Soil

The crop grows best in loamy soils that drain well. While it can handle sandy soil, it does better where there's clay in the lower layers to hold water. The plant won't get hurt if the field floods briefly, but longer waterlogging will impact your yield. The optimal soil pH for sorghum is between 5.5 and 7.5. Unlike many other grains, it can handle some salinization and alkalinity but struggles in acidic conditions. Before planting, plow deep and work in some compost or aged manure to improve your soil.

Sorghum is a moderate to heavy feeder, particularly in terms of its nitrogen requirements. So, you'll need to apply NPK fertilizers to achieve the desired yields. And to protect those yields from threats, monitor for sorghum diseases, weeds, and insects regularly and implement integrated pest management strategies.

Sorghum Fertilizer Recommendations

Nitrogen (N), phosphorus (P), and potassium (K) should be the primary nutrients applied based on the results of soil tests. Average recommended rates are 71–107 lb/ac (80–120 kg/ha) of nitrogen and 36–53 lb (40–60 kg/ha) of both phosphorus and potassium. To improve nutrient uptake and decrease runoff, it's best to apply P&K fertilizers for sorghum at planting and divide N fertilizers between planting and the early stages of plant growth.

Supplement NPK fertilizers with sulfur, magnesium, and zinc. Sulfur enhances nitrogen use efficiency, while magnesium and zinc support overall plant health.

Sorghum Weeds, Pests, Diseases And Their Control

Commercial sorghum farming faces three major threats: weeds, pests, and diseases. Weeds pose the greatest risk during the first one to one and a half months after emergence, directly competing with young crops. Although narrower spacing — 12–20 inches (30–50 cm) between rows — naturally suppresses weed growth, pre-emergence herbicides and mechanical weed control are often necessary.

Key pests include sorghum midge, aphids, shoot flies, earhead bugs, and stem borers. Plants are particularly vulnerable during flowering and grain fill. Pest damage often goes beyond yield reduction; for example, midge and earhead bug feeding results in distorted, lightweight seeds that bring lower market prices.

The crop suffers from over 50 diseases, from root rot to head mold. Anthracnose, downy mildew, charcoal rot, and grain mold are particularly damaging.

How Long Does Sorghum Take To Grow?

Temperature directly affects how long the crop grows. In warm conditions above 68°F (20°C), early varieties sprint to harvest in 90–110 days, while medium varieties in 110–140 days.

Harvest

For molasses, harvest sorghum stalks 2 weeks after immature seeds begin the milk stage. Seeds are milking if a white liquid oozes out when pierced. Harvest sorghum for grain when the seeds are fully mature. Cut seed heads with several inches of stalk still intact. Hang seed stalks to dry for a week before threshing and winnowing plants to separate seed from chaff.

Sorghum harvest usually occurs during July–August (first-season crop) or November–January (second-season crop) when kernels reach physiological maturity. Key indicators of maturity include a visible black spot at the kernel base and 20–25% grain moisture content. Grain combines can effectively handle sorghum harvesting when calibrated to separate out leaves and stalks.

The final step is drying your grain to less than 13% moisture content before storing it in a well-ventilated facility. Under normal conditions, grain has a storage life of 6–12 months, or possibly longer, giving crop producers the leeway to manage market fluctuations and find suitable buyers.

Seed Saving

Perfect, self-pollinating flowers are held in panicles (flower heads), which dry on the plant for easy harvest. Wind pollination is possible with very open flowers, though rare. Dry panicles can be cut individually as they are ready, and screened and winnowed to clean for storage.