8 March 2002

Choose seed carefully to get most from forage crops

Refreshing your memory of forage crop agronomy

and variety choice could make the difference

between a successful or poor yielding sheep feed.

Jeremy Hunt asks an agronomist for advice

ADHERING to a simple list of priorities, including varietal choice and crop nutrition could help sheep producers achieve far more from their forage crops.

James Hague, technical director at the Kingshay Farming Trust in Somerset – which produces an annual report on forage crop varieties – says forage crops are generally regarded as the poor relation.

"No one would go into a local merchant and ask for grass, wheat or barley seed without specifying a variety, yet stubble turnips or swede seed is widely bought without any preference shown.

"There are some excellent new varieties of stubble turnips, kale and fodder beet. Spend some time evaluating these new seeds and making a sound decision.

The difference between getting variety right and getting it wrong could mean losing up to 50% of potential yield."

Mr Hague advises accurately calculating the area of forage crop required. "Get the variety right, give plenty of thought to crop location in terms of stock access, make sure crop nutrition is optimal and ensure the crop is ready to graze exactly when you need it."

But Mr Hague warns that forage crops are not only able to take 620kg/ha (250kg/acre) of slurry, but are also very susceptible to pests. "These are highly palatable crops at 10-12% dry matter, but there are plenty of takers besides livestock.

"Slugs, bean weevils and pigeons can quickly wreak havoc on a crop, so do not leave anything to chance. Deal with pest problems swiftly by walking forage crops at least once every two days," he advised.

Maincrop turnips are widely used because they are adaptable, says Advanta Seeds forage crop specialist Martin Titley. They can be grown on a wide variety of soil types, but losing valuable moisture from the seed-bed will adversely affect germination and ultimately yield.

"Most maincrop turnips are now sown using precision drills, which require a level seed-bed.

"When drilling in April and May, it is important to avoid compaction by employing minimum cultivation methods.

"But many sheep producers do not drill turnips until late May or even June when conditions can be dry and loss of moisture from the seed-bed can be excessive. In this case, aim to complete seed-bed cultivations as early as possible," says Mr Titley.

Maincrop turnips are ready to use within 12-15 weeks of drilling. They have a higher dry matter (DM) content than stubble turnips and are more winter hardy. "The crop will produce an average dry matter yield of 5.5-6t/ha at 80-10% DM, a digestibility of 15-17% and metabolisable energy of 10-11 MJ/kg DM," he adds.

Stubble turnips, which should be sown 12-14 weeks before they are required for grazing, are becoming more popular in northern England as an autumn-sown crop, with drilling completed by late July.

"High seed rates – we recommend 1.75-2.5kg/acre when drilling into broken stubbles – are likely to produce a crop with more foliage and less bulb growth. This helps when weed suppression is important or the crop is sown late," says Mr Titley.

Stubble turnips demand about 75kg/ha (30kg/acre) of nitrogen and 37kg/ha (15kg/acre) of phosphate and potash. But because of the crops tendency to take up large amounts of nitrates, closely monitor soil nitrate levels.

Flea beetle is the most common pest to hit stubble turnips during establishment, he adds.

"A ewe will consume about 11kg of stubble turnips in a 2-3 hour grazing period. An autumn-sown crop producing 40t DM/ha should provide one days grazing for 1000 ewes for every hectare of crop," says Mr Titley.

Sheep producers in the north and west have the most favourable cool and moist conditions to grow swedes. But, like turnips, it is essential to ensure moisture retention in the seed-bed for maximum germination and strong root development.

Agonomists agree that row spacing in swedes is critical and should be 38-42cm (15-16.5in) apart. The space between seeds should be about 15cm (6in). But research may lead to recommendations for specific spacings for individual varieties, allowing growers to achieve maximum root development.

Mr Titley advises growers to use treated swede seed to avoid damage from common diseases, such as clubroot and mildew. Average dry matter yield ranges from 7-10t/ha (3-4t/acre) at 9-13% DM, with a crude protein of 10-11% and digestibility of 82D.

The crop should be sown from April-June at a rate of 370g-860g/ha (150g-350g/acre) when precision drilled, 2.5kg/ha (1kg/acre) if direct drilled and 5kg/ha (2kg/acre) for broadcast sown, say agronomists. &#42

FORAGE CROPS

&#8226 Evaluate new varieties.

&#8226 Refresh agronomy techniques.

&#8226 Need plenty of nutrients.