Summer Feed
Technical
Insight 805

SUPER SWEET SUDAN (SSS)

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FORAGE SUDAN X SUDAN GRASS

PRODUCT DESCRIPTION

Ideal for grazing new Super Sweet Sudan (SSS) has superfine stems and a prolific tillering habit. High quality small seed means you sow less kilograms on every hectare. Leaves are superfine and super sweet making SSS an excellent choice for silage or hay. Highly palatable at all stages of growth. Suitable for use in dairy, beef and sheep farm systems. 

Bettagraze (Left) and SSS (Right)
Bettagraze (left) and SSS (right)

SSS requires a minimum soil temperature of 18°C at 5cm depth for quick germination and establishment. Generally, sowing is not recommended before late November – early December.

SITE SELECTION

SSS prefers a deep soil with good moisture holding capacity and a medium to high fertility status. The crop fits well into a pasture renewal programme. Forage sorghum and sudan grass hybrids may be susceptible to herbicide residues. Check with your local Pioneer Representative before establishing crops in paddocks which have been recently sprayed with products other than glyphosate.

SOIL FERTILITY

A soil test is recommended to identify nutrient status and any possible deficiencies. The levels of P and N are important and a specific fertiliser recommendation should be obtained from your local merchant, fertiliser representative or Pioneer representative, based on the results of the soil test and the requirements of the crop.

The ideal soil pH range is 5.5 - 7.0, and the phosphate level should be greater than 20 ppm. Lime should be applied and incorporated during seedbed preparation. An application of 150 - 200 kg/ha DAP at sowing should provide sufficient fertility for the establishment of the crop. A top-dressing of up to 60 kg/ha of nitrogen may be required following the first cut or grazing.

GROUND PREPARATION

Effective weed control is important for SSS establishment and yield. Currently there are no post-emergence herbicides registered for sorghum in New Zealand therefore it is critical to (1) ensure the seed bed is weed-free and (2) to plant when the soil temperatures are high enough to ensure rapid SSS growth. Pasture should be sprayed-out with glyphosate and then grazed hard three to five days later. The ground should be ready for cultivation 7 - 14 days after spraying. A fine and firm seedbed is essential to promote establishment and weed control.

SOWING DATE

SSS should be sown 35 - 45 days before it is required for silage or grazing, although not before the soil temperature, at 5 cm depth, reaches 18oC and is rising. In most areas and seasons this temperature will not be reached until late November or early December.  SSS is an excellent crop to follow cereal silage or a late pasture silage cut in mid to late November.

SSS should be drilled and rolled into a fine moist seedbed at 15 - 25 kg/ha to a depth of 2.5 – 3.5 cm. Avoid planting deeply as the seed size is small. Crops planted at higher rates will have thinner stems and a higher yield potential. Broadcast sowing is not recommended. There have been mixed results with direct drilling.

TIMING OF UTILISATION

SSS can be grazed or cut. Feed quality will be maximised when the crop reaches around 1 metre in height. SSS will become rank and lose quality if left too late before grazing or cutting.

GRAZING

SSS should be grazed by break feeding to stock. Back-fencing is essential to minimise plant damage and allow quick re-growth in the grazed portion of the crop and to avoid crop toxicity. For maximum re-growth potential aim to leave a grazing residual of 15 cm. The crop can be recut or grazed after 4 - 5 weeks when it is at least 0.8 m and no more than 1.2 m in height.

FEED VALUE

The drymatter content of SSS that is 0.8 - 1.0 m in height is typically between 13 - 17% DM with 15% being a good average figure to use to determine cow crop allowance. Forage sorghum and sudan-grass products are bulk feeds with an average energy content of 9.0 - 10.0 MJME/kgDM depending on crop maturity at harvest time. A well-established crop that is between 0.8 - 1.0 m in height will have a drymatter yield of 3.5 - 4.5 tDM/ha per cut.

SILAGE

SSS can be made into pit, bunker or round bale silage. It is always recommended to cut using a mower-conditioner and wilt in the paddock for a maximum of 48 hours. SSS can be made into hay although it must be planted at high populations to ensure thin stems which will dry more quickly.

HORSES

Forage sorghum and sudan grass hybrids can cause major health problems for horses. They should not be grazed by horses or fed to them as hay or silage.

AUTUMN MANAGEMENT

Frosted SSS can be toxic. Always spray out SSS crops before autumn frosts and/or regrassing.

NITRATES

Any crop that grows rapidly has the potential to accumulate nitrates. Nitrate levels are higher in rapidly growing SSS crops that have been planted in high fertility paddocks. Nitrate levels also rise in crops that have been drought stressed or frosted. SSS should be sampled and analysed before grazing/cutting if nitrate build-up is suspected. If you suspect nitrate poisoning, contact your veterinarian immediately.

PRUSSIC ACID

Sudan x sudan grass hybrids have lower levels of prussic acid than forage sorghum or forage sorghum x sudan grass hybrids. Prussic acid poisoning is rare in New Zealand. Sudan grass is always low in sulphur and feeding sulphur will reduce the risk of prussic acid problems. Aim for a dietary sulphur level of 0.2%. Supplementation of sulphur is recommended if the pasture sulphur is low (less than 0.25%) and/or you are feeding more than 50% of the diet as SSS To supplement sulphur feed 40 grams of either zinc sulphate or magnesium sulphate per cow per day.

Factors which increase the level of prussic acid include:

Young plants: Avoid grazing crops under 0.8 m high.
Drought: Severe moisture stress.
Frost: Levels rise after light frosts. If crop is killed by frost, wait 5 days to graze.
Nitrogen: High available soil nitrogen may lead to higher levels, as does large amounts applied.
Low phosphorus: High available soil nitrogen may lead to higher levels, as does large amounts applied.
Re-growth: Cutting or grazing is a stress on plants, wait until plants are at least 80 cm high.
Herbicides: Applying 2,4-D may raise HCN level.

There is currently no acceptable method for testing for prussic acid in New Zealand. If you suspect that your crop has high levels of prussic acid, talk to your local veterinarian or local Pioneer representative before feeding it. 

SSS ECONOMICS

The table below gives the estimated growing costs ($/ha) for SSS.

2016/17 estimated costs (excl GST)SSS Costs($/ha)My Costs($/ha)
Spray out pasture (glyphosate @ 3 l/ha + application) $70  
Lime (1 t/ha + spreading ) $100  
Fertiliser (DAP @ 150 kg/ha + application) $170  
Cultivation $400  
Planting $160  
Pioneer® brand SSS @ 20 kg/ha $222  
Total crop costs $1,122  
  10 11 12 13 14 15 16
SSS DM cost (c/kgDM) 11.2 10.2 9.4 8.6 8.0 7.5 7.0

All costs are estimates only.
The costs and benefits of regrassing have not been included.

 

 



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The information in this publication is general in nature only. Although the information in this publication is believed to be accurate, no liability (whether as a result of negligence or otherwise) is accepted for any loss of any kind that may arise from actions based on the contents of this publication.

© 2017, Genetic Technologies Limited. No part of this publication can be reproduced without prior written consent from Genetic Technologies Limited.

Revised: Sept 2016
Expires: Sept 2017