A decade of trials to evaluate and develop a homegrown protein alternative to GE soya are finally starting to be realised in commercially grown crops.

PGG Wrightson says it expects to market close to 2500t of field beans this year and is hoping to be able to increase contracted tonnage for the 2011 harvest.

“We had talks with Tegel earlier this week and we are talking with another potentially major buyer,” grain trader Tom Patrick told a recent field day audience.

However, trials and grower reports continue to highlight the crop’s variable nature.

“There are still some failure beans around this year but there are also some good crops,” says FAR’s Nick Pyke.

Yields of up to 6t/ha have been achieved in trials.

The field day looked at FAR’s trials in a commercial crop of cultivar Ben on Eric Watson’s farm near Ashburton.

“This is pretty much bean-central for us because most of the trials we have anything to do with are here,” says Pyke.

Cultivar, fungicide and sowing date/rate work is all in progress, and already some noticeable differences are emerging.

For example, June 6-sown plots and the similarly early-drilled surrounding crop are only a little over waist height and already senescing, while August 16-sown plots are head-high and largely still green.

In turn, that appears to have affected pod distribution, early-sown plots being packed with pods near the base of the stem whereas the August-sown plots have pods more widely spaced and starting about 50cm up the stem.

“There’s a definite difference in the internode length and they [pods] are starting much higher up on these later sown plots. But what’s that going to mean for yield, who knows?”

Crop density appears a likely cause of the height differential, with August sown plots having 2.2-2.4 tillers per plant at slightly higher plant counts (40-52ppm) than the 1.6-1.8 tillers per plant on the early sown (31-52ppm).

However, what caused that difference in tillering is the question: traditional wisdom is earlier sowing leads to more tillering.

One thing speakers were united on was the danger of sowing too early.

Seed is large, with thousand grain weights up to 700g for some cultivars, which can cause problems in some drills and, at about $1000/t, makes seed a significant input cost.

“The average seed rate in our commercial crops was 200kg/ha,” says PGW’s Nick Brooks.

The cost of importing seed free of bruchid beetle – a pest not present in New Zealand – is another reason why that seed cost is high, even though PGW is writing the cost off over three years, he adds.

However, other growing costs are modest. “It needs virtually no fertiliser [it’s a legume so fixes its own nitrogen] and only a few fungicides.”

Weed control is based around pre-emergence products such as simazine, Gardoprim (terbuthylazine) or trifluralin. Basagran (bentazone) is “pretty much the only option post emergence,” says PGW agronomist Chris Nottingham, who had considerable experience with the crop in the UK prior to emigrating to New Zealand 16 months ago.

Fungicide programmes are built around carbendazim (as in Protek) plus a triazole and/or strobilurin to combat key diseases chocolate spot, rust and ascochyta, though disease free seed and soil are the keys to the latter of that list.

FAR’s trials are “primarily looking at chocolate spot”, says Pyke, with Proline (prothiaconazole), Comet (pyracolostrobin) and Amistar (azoxystrobin) being tested in combinations with carbendazim applied at start of flowering and a fortnight later.

Before the field day, 8% of leaf area was affected by chocolate spot in the untreated, compared to 1-2% in all treated areas.

“They all seem to have done the job and the treated now possibly has slightly more leaves left too.”