Sunflowers and faba beans are among the crops on trial for use as silage. Anne Lee reports.

A herd of Mid-Canterbury cows have had an extra drop of sunshine this past winter with the addition of sunflowers to their daily diet.

The novel silage was part of an onfarm trial by both the user and grower of the crops with a sunflower-barley wholecrop cereal silage mix tested along with a mix of faba bean and barley wholecrop cereal silage.

The experimental silages were mentioned in February as an aside to a report on Tom Mason of Terracostosa, a 3600-cow equity farming operation spanning five coastal Canterbury farms. (Dairy Exporter, February 2018, page 81)

At that stage the crops had recently been cut and ensiled but silage quality and full costings weren’t yet available.

The ultimate proof – that of the eating – also hadn’t been done.

Now both silage mixes have been enthusiastically consumed by cows as the daily entrée to the winter fodder beet diet and with quality, yield and cost data in, both Tom and growers of the specialist crops, arable farmers John Evans and Kai Tegels, have given them the thumbs up.

John and Kai have doubled the area of each they’re sowing this season to 10 hectares of each crop, fine-tuning the agronomy and trialling two varieties of bean.

‘Fodder beet already has low protein levels so I was looking for something that could replace the straw and the fibre it provides but also give us a bit more protein.’

Tom’s happy to buy the resulting crops for use in the novel silages again this season given the cows like it, the cost has come out on par with cereal silage alone and he’s getting the added benefit of more protein in the feed.

Added protein is why John and Kai came to test plant the crops for silage in the first place after questioning their neighbour over what, as a dairy farmer, Tom might be looking for that they could grow.

“Fodder beet already has low protein levels so I was looking for something that could replace the straw and the fibre it provides but also give us a bit more protein.

“We needed to be able to dust it with minerals and of course the cows had to like it.

“We also had to make sure the cost was going to be right,” Tom says.

He had barley, grown as a whole crop cereal silage available, but it too had low protein levels.

John works closely with the Foundation for Arable Research (FAR) and Plant and Food scientist Dr John de Ruiter.

Discussions with them led him to investigate both the Faba bean and sunflower crops.

Faba beans

The beans were sown in mid-May following a wheat crop.

Ideally John says he would have sown it a little earlier, at the end of April or early May.

The ground was cultivated and the seeds were spun on at a rate to give about 40 plants/square metre.

They needed two fungicide sprays for chocolate spot and an insecticide spray for black bean aphid during their growing period.

They were also thirstier than the sunflower crop and required 250mm of water in total with irrigation events from the end of October through to December 10, timed according to soil moisture readings via neutron probe.

The ideal stage to cut the crop for silage is when the pods at the base of the plant have started to firm up and go black, with pods mid-way up the plant still green and some flowers still present at the top of the plant.

Unlike whole crop cereal silages, which are cut at the right drymatter for ensiling, the beans need to be cut and wilted to get the drymatter right.

“We stopped irrigating on December 10 and gave it no more water before it was cut two weeks later,” John says.

It was windrowed, left on the ground to wilt for two days and then picked up by a standard silage chopper.

The length of time the beans are wilted for can vary but the aim is to have the drymatter at about 31-32% drymatter, de Ruiter says.

“You can’t leave it too long because the leaves will dry out and drop off.

“It’s a bit of a balancing act between the stems and soft beans drying out enough and not drying the leaves out too far,” he says.

John used Wizard as the variety sown in autumn but it’s also possible to sow the crop in spring. This season he’s sown both a spring variety Ben and the autumn variety Wizard in autumn to test the yield differences.

The wilted and chopped bean crop was delivered to the bunker at the same time the whole crop cereal crop was delivered so both were mixed in as the stack was made.

Sunflowers

The sunflower crop was sown on October 20 using a precision drill after the paddock had been sprayed out, cultivated and a good seed bed prepared before drilling.

John used a sowing rate to achieve a high plant population of 90,000 plants per ha.

When sunflowers are grown for seed the sowing rates are much lower as the plants are in the ground longer and high plant populations are at risk of lodging.

Soil temperatures need to be 12C and climbing so mid-October is probably the earliest John would sow it.

“But depending on where it fits in a rotation you could sow it any time from the up until December,” he says.

He used an open-pollinated variety sown to produce bird seed but is aiming to source a hybrid variety this season.

A pre-emergence broadleaf herbicide was used and the only other weed control used was inter-row cultivation when the crop was 300mm high.

They held off irrigating to force the plant to send its tap root down into the soil profile but then played catch-up to get soil moisture levels up through December.

In total the crop received 125mm of irrigation.

John says the sunflowers appear to be better scavengers of nutrients than maize and no additional nitrogen was required based on leaf test analysis.

The crop was only in the ground for two months and was cut in late December when the sunflowers were flowering and before seeds had developed.

De Ruiter says that again there’s a trade off when making silage as leaving the crop longer through to seed development means the stems become woody and thick making it difficult to ensile well.

Table: Silage and crop data

John says the sunflower crop grown for silage on its own isn’t a great returning crop on a per-hectare basis because of the lower yields but as a filler in a rotation it could have a place.

While he’s not sure about ensiling it on its own, de Ruiter says both crops can be.

He’s carried out trials ensiling them separately in tubes.

The faba bean silage is dark and doesn’t look appealing but providing it’s wilted properly it is of good quality.

His quality tests give similar results to John’s but there can be variations as with any silage.

He also points out that while there could be benefits to the cows of added protein over winter when fed with the fodder beet, the higher protein in the silages may have a detrimental effect on nutrient nitrogen loadings limiting the nitrogen budget benefits of the fodder beet.

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