Central South too wet to drill

Paddocks had only just become passable after an unusually wet April and now some fear they will not get back on again until spring. Where crops have been sown agronomists say slugs are having a field day.

"Slug pellet use has gone through the roof," Mid Canterbury agronomist Roger Lasham told Rural News.
"Where people have gone on with pellets before any damage has been done it's not too bad but if they're late they'll never get those plants back."

He says growers should be vigilant and while there's still a prospect of some warm dry weather use metaldehyde-based baits as they're less toxic to non-target species. Once it gets cold and wet a switch to methiocarb may be necessary for a faster knockdown.

Some of his clients have hardly any winter cereal sown, while others are drilled up: it all depends on the farm situation. For those with crops such as potatoes, carrots or onions to lift, the wet's been "a double whammy."

In one case potato lifting had just started again when this week's rain hit and it would be the weekend at least before they could get back in the paddock, he predicted.

One technique worth considering to get cereals in, particularly where wheat seed is on farm and is approaching the latest safe sowing date for the cultivar, is broadcasting, says Lasham.

"It's something I've had a lot of success with in the past. If you've got an accurate spreader and can travel then really there's little issue. The only worry would be follow-up herbicides are a bit more difficult."

The reason is seed may not be buried deep enough to be safe from residual herbicides, particularly as such products will be highly active in the wet conditions. The risk is particularly great if rain follows soon after application.

"You want two days before rain after an application ideally."
Where ground is still to be worked ahead of the drill, don't be afraid to leave a rougher seedbed than usual and ideally don't work it until you can be confident of getting it drilled before it rains again.

"A rough seedbed will take the rain better."

PGW's grain production manager Nick Brooks said there were "sheets of water" lying in paddocks in coastal Mid Canterbury after the latest rain and some growers haven't planted anything yet.

"The window is closing for a lot of people, particularly for those on heavy land. If we don't get 10-14 days of dry weather now a lot of the winter planting is going to have to be put off until spring."

For those with varieties that have a high vernalisation requirement, ie early latest safe sowing date, that poses a problem.

"There might be some cases where people need to switch away from true winter feed wheats because it is getting so late."

Wheats such as Discovery (or KW31 as it was in FAR trials), Raffles and Morph have no such problems being safe to sow from late April through to September, and while they may be a little lower yielding than earlier sown feeds, as premium two milling wheats they should sell for a better price.For later spring sowing Sensus would be an option.

FAR's Rob Craigie says trial results with the premium two type milling wheats Brooks mentions show a 0.6t/ha yield penalty on average between sowing in May and August, but being trials, they would have been sown into good conditions in May. The difference between a muddled in crop now, and one put into a good seedbed come August or early September might be much less.

There's also "a trade-off" with yield loss and lower growing costs, with savings on fungicides, slug baits and aphicides likely with the later sowing.
As for broadcasting, FAR's series of non-inversion tillage trials 2003 to 2008 showed yields could match drilled crops, but percentage establishment was generally lower so seed rates needed to be increased to compensate. Broadcasting into a crop residue in particular was prone to poor emergence.

"Broadcasting was more successful if a stale seedbed had been created."

Brooks notes that prior to the wet autumn an increase in winter barley sowing had been expected but with growers prioritising first wheats and herbage seeds, that increase seems highly unlikely now.

"You've really got to get barley in within the next week to ten days so that it is reasonably well established before winter. It might just be too late for it already."

Met Service and NIWA data gives a glimpse of just how wet it's been. In the past 30 days Met Service records show 161mm of rain's fallen in Oamaru, 158mm in Christchurch, 138mm at Fairlie, 121mm at Ashburton, and 116mm in Timaru.

NIWA's latest climate summary states some Central and North South Island areas received three to five times the normal rainfall for April, and the outlook for May-July rain "is near-normal for all regions, except the east of the South Island where normal or above normal rainfall is forecast."
With soils in the east of the south saturated already, that's not what any farmer wanted to hear.