Forage Sorghum

Forage sorghums perform best on heavier soils because of their greater moisture holding capacity, which is important when considering the sowing time. A well prepared seed bed will greatly assist crop establishment. Early preparation followed by a fallow period will give better weed control and produce a finer seedbed. Rough seedbeds will usually result in poor establishment. Dependent on the situation, sowing depth of 4-6cm will provide the best overall results. The key to a successful strike is to plant as shallow as possible but deep enough to ensure adequate moisture for germination. If irrigation is available then it is recommended to water the paddock and then sow into the moisture. The use of presswheels or rollers to provide good seed/soil contact is also recommended. Forage sorghums require fertile soils to achieve optimum growth and feed value. At sowing a rate of at least 150 kg/ha of D.A.P type fertiliser is recommended, higher rates will achieve higher yields. Following grazing or cutting, nitrogen, and or potassium can be applied to boost re growth.For local recommendations refer to your local adviser, fertiliser or seed distributor.

Overall there are few pests of great concern in establishment of forage sorghum. However, there are several insects that can be destructive in the early stage of crop germination and establishment. These are wireworms and cutworms. Please consult your local chemical distributor on products that can control these pests.

Like other members of the sorghum family, there is some risk of prussic acid poisoning if hungry stock graze on fresh young growth. Therefore it is essential not to graze the crop until it is at least 0.8-1.5 metres tall, depending on the variety. At this height the quality of feed is at its highest in terms of protein and energy. It is also recommended to supplement sulphur by using stock lick blocks, as trials have shown that all stock are sulphur deficient, which can affect their performance while grazing forage sorghum.

To achieve the best quality feed, rotational or strip-grazing methods should be used. With intensive forage crops electric fencing is useful, provided wires are visible to stock. To allow regrowth a back hot wire is advised, this enables regrowth from the previous grazed area. A similar situation occurs when grazing regrowth brassicas, for best regrowth remove stock before the crop is grazed below 15 cm, then allow crop to grow back to approximately 0.8 metres in height again whether it be for grazing or cutting. An application of approximately 50-100 kg/ha of Urea after each grazing or cutting will ensure quicker regrowth maintaining productivity and food quality. In southern Victoria the possibility of getting a second grazing or cut from forage sorghums usually is a bonus because crops generally are not sown until December when soil temperatures are high enough. Therefore there is only approximately 3-4 months of growing period before soil temperatures drop and plants cease growing. Regrowth crops that stop growing and haven't reached the recommended 0.8 metre height late in the season cannot be grazed or cut due to the risk of prussic acid poisoning.

 

Forage sorghum hybrids should not be sown earlier than mid October in most districts as the soil temperature has to be at least 16 degrees and rising. The only way to be sure of the soil temperature is to place a thermometer into the cultivated soil at planting depth at 9am. It is best to do this over a number of days to determine an accurate reading. The right soil temperature at sowing is extremely important, as it will affect your establishment.

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