Forage sorghum planting and grazing guide

When farmers look at diversifying their livestock feeding rotation, forage sorghum often comes up as a cost-effective alternative for summer grazing. And with good reason. It produces a relatively large amount of forage in a short period of time, responds well to high temperatures and requires minimal attention. It’s the perfect choice for intense grazing that helps livestock producers fill the Summer gap or simply reduce pressure on other pastures. In this forage sorghum guide we’re going to be talking about how to grow it and how to graze it, to ensure you end up with high quality feed that helps you maximise weight gain, in less time.

Main types of forage sorghum

Forage sorghums can be grouped into three main categories including sorghum-sudan grass, sorghum-sweet hybrids and dual-purpose hybrids. When selecting a forage sorghum that best suits your operation, it’s important to begin thinking about the choices during the Winter months and to book your seed early. Here’s a list of the key features of each type to help you select the right variety for your needs:

Sorghum X Sudan Grass hybrid type 

• Suitable for grazing, hay and silage
• Suitable for cattle and sheep grazing
• Can plant early (some varieties can be planted when soil temperature is 14°C)
• Highly productive with fast regrowth
• Fine stems make it good for hay making
• Quick recovery from grazing or cutting
• Range of varieties with different flowering times
• Graze at 80 – 90 cm

Sorghum X Sweet Sorghum hybrids

• Ideal for grazing and pit silage
• Suitable for cattle (in particular beef cattle)
• Flexible planting options (all-round season) plant at 17°C soil temperature
• Thick stems with high sugar content make it very palatable
• Slower growing and late flowering
• Ideal for late Summer carry over feed
• Some varieties carry extra sugar traits which can lead to higher weight gains due to digestibility of the leaf and low lignin
• Graze at 80 – 90 cm

Dual purpose hybrids (Sorghum X Sorghum hybrid)

• Suitable for grazing, grain production or silage (ideal for pit silage)
• Maize substitute
• Grain bearing with tall forage
• Produces high energy silage (ME or Metabolisable Energy)
• Good growth after cutting
• Can grow 1 – 2 m high
• Graze at 80 – 90 cm

Planting guide

If you’re trying forage sorghum for the first time, there are a few important planting details that are unique to a sorghum crop and critical for success. Early paddock selection is key, along with preparing your soil with good seed beds and a pre-emergent herbicide. Some key planting tips when it comes to planting forage sorghum include:

• Soil: Forage sorghums perform best on heavier soils because of their greater water-holding capacity, supplying the plant with moisture through the warm growing season.
• Sowing temperature: Seed should be planted when the soil temperature is above 14°C for Sudan and above 17°C for other types. Place a thermometer into the cultivated soil at planting depth at around 9am and take an average over 7 days.
• Sowing depth: The ideal depth for planting forage sorghum is 3 – 5 cm. It’s best to plant as shallow as possible, but deep enough for adequate moisture for germination.
• Row spacing: Row spacing for forage sorghum varies depending on your region but can be sown in 15 cm – 1 m rows. For hay production narrower row spacing is better.
• Sowing rates: Seed should be planted at an average count of 30,000 seeds/kg. Marginal dryland varieties should be planted at a rate of 3 – 5 kg/ha and favourable dryland varieties should be planted at a rate of 5 – 10 kg/ha.
• Irrigation: Forage sorghum fits well into dryland and limited irrigation situations. Sorghum that is irrigated is usually done at > 15 – 25 kg/ha.
• Fertiliser: High yielding crops like sorghum require fertile soil to achieve optimum growth and feed quality. Nitrogen is the most limiting nutrient for forage sorghum production and should be applied up front prior to planting, as well as after cutting to boost regrowth. As a rule of thumb, a fertiliser program like grazing oats is a good guide.
• Weed control: As with most crops, keeping paddocks free from weeds will reduce competition and maximise soil moisture so make sure you have a strategy in place before you plant. Once established however, forage sorghums will compete well against weeds

Grazing guide

Once your crop is established, you’ll need to consider the best approach to grazing. In general, forage sorghum is better suited to cattle grazing, as it can quickly get too high for sheep. It also offers an almost complete ration for animals with lower energy requirements, which makes it well suited to dry cows or heifers. Some additional tips for grazing forage sorghum include:

• Introducing stock: As a general rule, livestock should have a full stomach so they don’t gorge themselves. For peace of mind, watch your stock closely in the first couple of hours and monitor at least twice a day for the first few days.
• Animal health: There is a slight risk of prussic acid or nitrate poisoning from forage sorghum. In hot and dry conditions, sorghum can become stressed causing the plant to accumulate these toxins. The best way to manage the risk is to feed hungry stock with hay before allowing them to graze as mentioned above. If in doubt, it’s always best to test crop for nitrate levels before using as fodder. As sorghum is also low in sulphur, it’s a good idea to supplement stock with lick blocks when grazing. Salt blocks with 10% sulphur are generally recommended.
• Height: Depending on the variety, grazing should start at a height of 80 – 90 cm to maximise forage quality, which declines rapidly as the crop develops. The crop should always be grazed while in vegetation stage before the plant becomes advanced and less palatable.
• Timeframe: The grazing timeframe also depends on the variety, but generally ranges from 7 – 12 weeks after planting.
• Rotation: Forage sorghum is best suited to short rotational or strip grazing. It’s recommended to allow for regrowth and remove stock before the crop is below 15 cm.

Final thoughts

For farmers looking for cost-effective ways to produce forage in a dry environment, forage sorghum is a great option. It can do some impressive things in a short window, with little water and without costing farmers a fortune! And with Summer fast approaching, now is the time to think about options for planting and buying next season’s seed.

To ensure you are on the right track with selecting the best forage sorghum for your livestock operation, talk to one of our team today.