Millets generally produce less dry matter than forage sorghums but have higher quality feed, particularly for smaller animals such as sheep. Millets also present a better fattening and hay/silage option than forage sorghum. They can be more difficult to establish than the larger seeded sorghums and can be grazed 5 to 7 weeks after sowing but do not tolerate harsh grazing.
There is no prussic acid poisoning risk, but there is a photosensitisation risk with millets. Paddock selection is important, beware of residual herbicides. There are also few herbicides available for in crop weed control. Millet can run rapidly to head in hotter weather so grazing management is important. It is also frost sensitive.
In conclusion, summer forage crops of forage sorghum or millet offer quick and high levels of dry matter production, however careful attention to nutrition and available soil moisture is key to quality production and will drive your choice of crop. Generally speaking if soil moisture is limited or summer rainfall unreliable, then millet is a safer option for a lower risk of stock poisoning and higher quality feed from less moisture. However if starting soil moisture and nutrients is less limiting and in crop rainfall favourable further options for higher dry matter production and prolonged grazing options are available by using forage sorghums.
For further information about varieties available, sowing rates and varieties suitable to your enterprise contact your local territory manager.
Soil nutrition and fertiliser use
Second only to soil moisture, poor plant nutrition is one of the most common reasons for poor forage crop performance. Nitrogen deficiency is the most common deficiency in many soils.
Both forage sorghum and millet crops have a high requirement for nitrogen, particularly if the seasonal conditions are favourable. Top dressing between grazings or hay cuts is often required to sustain optimum growing conditions. Other key nutrients include phosphorus, sulphur and potassium.
Nutrient removal from the soil can be very high, for example, a dryland crop of forage sorghum yielding 10 tonne per hectare of dry matter will remove the practical equivalent of the below fertiliser per hectare:
Crop rotation factors
The paddock must be selected ensuring that there are no residual chemicals in the soil. This can be exacerbated by drier conditions with a lack of rainfall maintaining residuals in the soil which can affect plant establishment. For example, any Metsulfuron used in a fallow period, or the use of atrazine and/or metalochlor must be considered in the rotational choice for the next crop.
Unless irrigation is available most situations will require a fallow to have adequate starting soil moisture for a summer forage crop, particularly in areas were summer rainfall is unreliable.
Forage sorghum is the most productive and fastest growing forage. It can produce large volumes of feed relatively quickly. As a general rule, forage sorghum can be sown when the frost risk has passed and soil temperatures have reached at least 16°C at the intended sowing depth at 9am in the morning.
Forage sorghum can be grazed once the crop has established secondary roots, reaches 50 cm in height and is unstressed. If the crop is stressed, there is a high risk of prussic acid and /or nitrate poisoning. Forage sorghum will generally reach grazing height eight weeks after sowing. Several cuts or grazings are possible in good conditions.
Hybrid Forage Sorghum (Sorghum x Sudan grass hybrid)
Available varieties: Feedex, BMR Fuel
Sudan Grasses (Sudan grass x Sudan grass hybrid)
Available variety: NuDan
Lower prussic acid risk
Sweet Sorghums (Sweet sorghum x Sweet sorghum)