Summer forages and legumes
Peter Tame, AusWest Seeds, Southern Qld & Northern Rivers NSW
We often think only of forage sorghum when someone mentions ’summer forage’. While it’s a big part of the feed platform today, there are many other options that could also be considered such as millet, and legumes such as cowpeas, lab lab and soybeans. Most of these can be utilised by grazing or cut for silage or hay and many offer regrowth potential. The quality of these crops can be variable and need to be managed well to achieve the best results.
Forage Sorghums
Today’s forage sorghum market offers a huge range of varieties and it can often be a maze
to navigate which variety is best for your circumstance.
Forage sorghums are bred from multiple crosses and combinations and hybrids of Sudan grasses,
sorghums, and sweet sorghums. With good nutrition and adequate moisture, forage sorghums can be
multiple grazed or cut for hay or silage. Sorghums are quick to establish, they use water
efficiently and produce good amounts of dry matter.
All forage sorghums need to be managed to obtain their best quality. Ideally they should be grazed between 650 and 1200mm height. If sorghums are left to grow beyond these heights they produce a lot of bulk but the quality dramatically declines.
Periods of plant stress due to cold or dry conditions increase the potential incidence of prussic acid poisoning. This can be a serious issue for animal health. To help minimise prussic acid poisoning risk and digestibility issues, graze or cut the forage at the heights mentioned above. The inclusion of a Sulphur lick block in the pasture can also be helpful.
Sudan crosses often have finer leaves and recover quicker after grazing or cutting for hay or silage. Sudan grass types still have the potential for prussic acid issues but are a lower risk than other forms.
FeedEx forage sorghum is a fine leaved hybrid forage Sudan x sorghum cross. Its fine stem lends
itself to grazing, hay and silage production. It has very good leaf to stem ratio with the
ability to recover quickly after cutting or grazing.
BMR Fuel® forage sorghum is a new variety in our range. It also has fine stems
with very quick regrowth potential with its Sudan x sorghum cross. What is special about Fuel is
it is a BMR, Brown Mid-Rib, variety. The inclusion of this gene can produce quality feed with
lower levels of lignin (Indigestible fibre) compared to conventional types.
Nudan Sudan grass is also a fine stem quality forage at the top end of the market. It has
established a strong reputation for quality hay production and grazing. Its finer stems allow a
quicker dry down and has a lower prussic acid risk.
Millets
Millets can be a safer option than forage sorghum as they don’t have any issues with prussic acid. However millets will not produce the same volume of dry matter as forage sorghums as the potential for millets to recover from grazing or cutting for hay is generally low.
Millets can be useful to fill feed gaps through early spring and autumn. The dual purpose types Japanese and Shirohie will germinate in cooler soil temperatures (14 – 16 degrees) than other millets and forage sorghums. Both these varieties have rapid early growth and can be grazed in four to six weeks at 250-400 mm of growth. Both varieties are quick to mature and should be grazed early to maximise quality.
The variety Siberian is not as cold tolerant as Japanese and Shirohie. It performs best with soil temperatures similar to forage sorghums at 18 degrees. Its early growth is not as quick as Japanese and Shirohie but it has a longer growing season which really peaks in the warmer conditions. Due to its longer production window it also produces more dry matter. It has a prostrate growth habit with a higher tillering capability and has the ability to recover from grazing well, maintaining good palatability and quality.
Pearl millet types require soil temperatures of 18 degrees and rising. These types will produce higher levels of dry matter and are suited to grazing and hay production.
Other varieties of millet can be very quick maturing and don’t produce large volumes of dry matter.
White French, for example, is not very palatable and can cause photosensitivity issues for stock.
Nutritional inputs of millets are lower than forage sorghums with Nitrogen preplant levels of 30 – 50 kg/ha being required for most reasonable dryland crop production.
Summer legumes
Cowpea varieties include Red Caloona, Buff, and Ebony. Red Caloona has good resistance to Phytophthora root rot and are generally grown along the coast. Buff varieties do not provide the same resistance levels as Red Caloona but can be higher yielding. As such they are generally grown away from coastal regions. Cowpea’s early growth rate is quicker to reach grazing height (approx. 8 weeks) than lab lab by about four weeks. With sufficient moisture they are often capable of two grazings. Plantings can be as early as September and October as the soil temperatures reach 18 degrees.
The most popular lab lab varieties are Highworth and Rongai. There have been other shorter season varieties released but they generally only produce about 70% of the dry matter of these two lines. Lab lab has better resistance to Phytophthora root rot than cowpeas and can handle heavier soil types well. It can be multiple grazed three or more times if conditions allow. While lab lab is a little slower to reach grazing height than cowpeas by about four weeks, its longer growing window enables lab lab to produce more dry matter.
Highworth has a purple flower and an erect growth habit. It is quicker to flower than Rongai by about three weeks. This variety is often grown away from the coast on the central and western Downs. Rongai has a white flower and has the longer growing phase. Both varieties of lab lab are late in flowering resulting in the crops generally being frosted before they produce any grain.
Soybean can also be used for grazing, hay or silage. For better production, longer season varieties, such as Hayman, can be a good option. Planting for these purposes as opposed to grain production, can start in mid-November to December. Soybeans do require good soil moisture and tend to be centered in the higher rainfall regions. However soybean don’t recover as well from grazing as cowpeas and lab lab and should be grown out to semi-pod fill before grazing.
Legume inoculation
For best results legume crop seed should be inoculated. As they are legumes nitrogen fertiliser
is usually not needed. However other elements such as phosphorous are important. Nitrogen
fixation is an important by product of growing legumes along with the improved protein content
and forage quality.
The table below shows some indications of feed quality of these legumes in general terms by NSW
DPI:
| Crop |
ME (MJ/ kg DM) |
Protein % (Whole Plant) |
| Cowpea | 10.7 | 18 |
| Lab Lab | 9.0 | 18 |
| Soybeans | 9.4 | 15 |
| Forage Sorghum | 8.2 | 9 |
There are a range of suitable summer forage grass and legume crops that can be grown for grazing and hay or silage production. The choice of crop/s depends on the livestock enterprise and the end use required. In the current conditions where many areas are in severe drought the primary need will be for quick feed where pasture and fodder supplies have been exhausted. The forage sorghums, sudan grasses and millets have usually been the crops of first choice. Seed shortages of these will mean producers may need to look at other options such as the legumes cowpeas, lab lab and soybean if they are in suitable environments for these crops.
Animal health risks such as prussic acid poisoning and nitrate poisoning can be worse in drought conditions. Careful management of summer crops will be required to minimize these risks.
References:
NSW Department of Primary Industries: Summer legume forage crops: cowpeas, lab lab, soybeans