PCN picture looks better with ICM approach
Norfolk potato grower, Pete Legge, believes he has finally got a handle on PCN control, with a switch to Nemathorin in combination with a comprehensive ICM agronomy programme that is seeing long-term egg counts declining - along with reduced effects on the growing crop, yield and tuber quality.
At the core of the farm’s approach has been a greater focus on soil testing - and tailoring the crop’s agronomy to the results. That has included seeking out clean land, extending rotations, adopting resistant or tolerant varieties, split field cropping and better targeted use of a nematicide.
A third generation of the Legge family, based at Further Fen Farm, Southery near Downham Market, Pete highlighted the potato business has built to around 400 hectares of the crop per year, with around 25% grown on owned land and the rest primarily on long-term rental arrangements.
“We are now sampling all potato fields - both our own and long-term rented land - on one hectare grids, and using GPS technology to build up a better picture and understanding of the PCN populations,” he reported. “We have even started doing some pf:pi counts, pre and post cropping." (below).
"We can evaluate what is working best for us, particularly with the different varieties,” added Pete.
They switched to Nemathorin for all the farm’s nematicide treatment after on-farm trials demonstrated that it was just as effective as oxamyl on the black fen soils, and gave better results on sand and silt soils that are increasingly being cropped.
Armed with the knowledge of PCN levels, he says they are better able to adjust cropping and variety selection to individual field situations, even to the extent of taking fields out of the rotation if PCN populations are too high, or being more selective in fields that are rented.
After conducting variety trials on the farm, they have now adopted G. pallida resistant varieties including Eurostar, Performer and Arsenal, into the cropping – primarily grown on fields with the lowest PCN burden. However, Daisy, Markies and Agria now make up the bulk of the cropping.
A change in marketing strategy, to diversify end uses, has also facilitated the growing of different varieties, highlighted Pete. Around 25% of the farm’s output is destined for pre-pack; 40% for crisping and processing, with the remainder bagged for retail and chip-shop trade.
“Variety can certainly help with PCN management and we are keen to continue, but there is a yield penalty and we are very mindful that they have to be both marketable and commercially viable against non-resistant varieties.”
“That’s enabled us to take a more proactive approach to PCN,” he added.
“We’ve pushed the rotation out to one in six or seven years, and we are prepared to invest in nematicides where we can see the long-term benefit in managing PCN populations.”
Soil testing, by the labs of Richard Austin Associates, has revealed the farm’s PCN population is now almost exclusively G. pallida - which may be a legacy of the extensive area of Maris Piper cropping in the past. Nematicide efficacy against prolonged hatching of G. pallida populations is a key consideration in managing population numbers.
The nematicide is applied on a Standen bed tiller, with the same set-up on the front of the farm’s primary belt planter, and back-up cup planter. Pete pointed out all the operators are PA4G certified, and have regularly undertaken the Nemathorin Incorporation Test, using rice grains to check incorporation depth and consistency on different soil types and conditions. Applying Nemathorin at the rate of 30kg/ha, compared to 55kg/ha with oxamyl previously, was easier and faster with the Surefill system, he added.
He highlighted that with last year’s cold slow start to the season the early planted crops - principally on the PCN free land and where no nematicide was used - were uncharacteristically slow to emerge for up to five weeks. However as soil conditions improved and where Nemathorin was used, on around 40% of the farm’s cropping, the crop’s emergence was faster and even within three weeks.
“PCN is our number one soil pest,” said Pete. “But, providing we can retain all the measures we now have, combined with the ability to get an accurate picture of what is happening, we are confident that we can maintain viable cropping in the future.”