Cereal trials reveal large variation in crop yields

FAR CEO Nick Pyke discusses pea crop management at Steve Wilkins’ farm in northern Southland.

14-04-2010 | Robert Pattison

The performance of cereal crops depends on many factors, from sowing techniques through to harvesting according to Southland trials.

The Foundation for Arable Research (FAR) has done on-farm trials for autumn and spring-sown wheat and barley crops over several years in Southland. The mean yields for the past four years show there is a large variation in crop yields between different cultivars.

The three top-performing wheat cultivars have been Wakanui, Einstein and Phoenix. Two new autumn varieties, Richmond and KWW34, also performed well.

The top-performing spring barley cultivars were Snakebite, Tavern and Doyen.

About 60 cropping farmers from South Otago and Southland attended a FAR field day in February to look at the performance of autumn and spring-sown oat, barley and pea crops on three farms in northern Southland.

FAR cereals project manager Rob Craigie says cultivation techniques, soil health and crop management from sowing to harvesting can have a significant impact on crop yields and margins. It seems getting crops in the ground is just one challenge. Lessons are still being learned from cultivation through to harvesting.

Cropping farmers John Gardyne, Steve Wilkins and Gary Collins all say every aspect of growing crops is a balancing act. Many issues that affect crop yield are farm and paddock-specific. Targeted fertiliser inputs and chemical treatments for disease control to specific parts of a paddock are equally important.

Craigie says achieving the best cropping margins is highly dependent on the timing of fungicide treatments to plant growth stages to maximise protection against the wide range of diseases.

A two-year trial in Southland comparing fungicide treatments to determine the best margin over fungicide cost (MOFC) showed that a one-spray programme gave good control of scald on most barley cultivar varieties. The crops were treated at growth stages GS30-31 (rows closed, leaf 3-4 emergence), GS33 and GS49 (awn emergence).

However, a single spray strategy for autumn barley varieties is less effective because the plants are more susceptible to a wider range of diseases than wheat. To be fully effective, spray treatments need to occur when the lower leaves, particularly before flag-3, emerge at the GS30-31 stage.

The main diseases to watch for are powdery mildew, scald, net blotch and leaf rust. It seems that if the weather prevents one disease developing, another one will take its place.

Crops sown late in April/early May can be susceptible to wet weather disease, particularly scald (rhynchosporium secalis) which builds up over the winter. Treating with prothioconazole (Proline) as the main triazole for barley crops has reduced the need to apply late tillering sprays.

To protect early sown crops that are susceptible to scald and leaf rust, FAR is recommending a treatment of 400ml Proline and 500ml Acanto at GS30-31. Then a follow-up spray at GS39-49 (flag1, first awns) with 200ml Proline and 250ml Acanto/ha.

Craigie suggests that where crops have been irrigated an increased application rate of Acanto can be beneficial.

Crops sown late May/early June are generally more resistant to diseases such as leaf rust. This means there is less need for a strobilurin partner. Protection can be achieved using a mix of Proline and carbendazim (Protek). The recommended application rates are 400ml Proline and 500ml Protek/ha at GS30-31, then a follow-up spray of 200-400ml Proline (depending on whether the crop is irrigated or dryland) with 500ml Protek/ha at GS49.

Not just diseases and insects affect crop yield. Sowing dates, ground conditions, soil moisture, temperature and weather conditions and harvesting can also have a significant effect on crop performance and yield. Bird control is important because they can cause significant damage.

North Chatton cropping farmer John Gardyne has also tested taking a second crop of oats. He says making use of the seed from wind shake and what falls out the back of the header increases their cropping efficiency because tillage and fuel costs are minimal for establishing the second crop. The main thing is not to panic if it appears there is little plant regrowth after harvest. There is a huge variation across a paddock and they were told about five times to plough it up.

They tested one paddock last year and it yielded 6t/ha when harvested in April. It was so successful they left five paddocks (25ha) for this year. The paddocks were harvested in March and yielded 220 tonnes (8.8t/ha).

Gardyne says the paddocks are managed like an emerging oat crop. It is critically important to graze before the plants develop their nodes. If the node is nipped off the plant will not be able to develop a seed head.

The paddocks are shut up after harvesting in March and kept as a green feed crop for winter. The stubble is left standing and he delays grazing the regrowth until the crop canopy is nice and leafy. One paddock was not grazed over winter and there was virtually no difference in yield compared with the crops that were grazed.

The crops are generally free of weeds, but it is important to control any grass weeds around the outside of the paddock. These are sprayed with glyphosate (Round Up).

To cover the seed the paddocks get a light stir up with power harrows or a set of discs with a packer roller on behind. They also chase a mob of ewes over the paddocks with a huntaway to trample the seed in. Then the paddocks are shut up for winter feed and don't get grazed until August.

Managing nitrogen (N) inputs is also important. If urea is applied before the plants have finished tillering the chances are the crop will be too dense and it will fall over. One kilogram of N is equal to about 25kg of grain.

To protect against disease the crops were sprayed four times (monthly) with fungicides between September and December.

Gardyne says it is also important to be vigilant and watch for wild oats. The best control method is to remove them from the crops by hand picking.

After harvesting last year's crop of regrowth oats in April the paddock went straight into wheat.

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