Building on a solid start – Farmers Guardian

Jack Richardson, Farmacy, Lincolnshire

Planting began in good conditions during late March, although soils were still relatively cold. This could increase the rhizoctonia solani risk, as the longer it takes potatoes to emerge, the more time there is for the pathogen to infect tubers via stolons. In-furrow azoxystrobin or seed treatments based on flutolanil should help protect crops though.

The hike in fertiliser and fuel prices has prompted difficult conversations and the inevitable temptation to find savings. Some growers have questioned the value of that extra pass with the cultivator, while others are seeking opportunities to reign back nitrogen. This may be possible where soil mineral nitrogen is high, especially after peas or veg, but generally there is little room for manoeuvre in such a high value crop.

Getting the most from any applied fertiliser is crucial and for nitrogen the aim should be to apply it early to build yield. Typically, 50-75 per cent of total nitrogen is applied in the base fertiliser, with a foliar top up during tuber initiation. Equally, placement phosphate fertiliser is widely used at planting, providing a useful kick-start to growth, especially if soils are cold or dry.

Given limited post-emergence chemistry, early pre-emergence weed control, ideally within a week of planting, should be a priority. We have seen good results from the broad control offered by metribuzin and aclonifen, which on weedier sites can be topped-up with pendimethalin, or prosulfocarb for grass-weeds. Before crops emerge, glyphosate is also an option if needed.

Andy Finnamore Hutchinsons, Cornwall

A relatively kind winter and early spring has seen planting progress apace in the South West, with many growers now well into planting maincrop varieties and most of the crisping crop now planted in good conditions. The earliest first earlies that went in before Christmas are due for lifting imminently.

For maincrop growers, the focus is on early pre-em weed control. Most will be using metobromuron plus metribuzin, although clomazone and prosulfocarb are useful options where cleavers are a particular issue. Pyraflufen-ethyl offers good contact weed control, although as with pre-em glyphosate (check approvals), great care is needed to make sure there is no sign of crop emergence.

While growers have been shocked by the rise in costs, most were already committed to the 2022 crop, so inputs are unlikely to differ too much for this season at least.

Much emphasis is placed on seedbed fertiliser, with most growers band placing at least 75 per cent of total nitrogen in the base dressing, together with high levels of phosphate and potash, such as in 14-14-21 fertiliser products.

This will usually be followed with a slow-release foliar nitrogen at late tuber initiation, along with phosphate, potash, magnesium and trace elements where required.

Early blight risk is nearly always considered high in the South West, especially in crops planted under plastic during February. Waiting until potatoes are touching in the rows before starting blight control has long gone, so many programmes now commence from 50 per cent emergence onwards, depending on conditions and risk.

Stronger chemistry

Typically, early programmes alternate between cyazofamid and mandipropamid, although the stronger chemistry of fluopicolide + propamocarb hydrochloride may be brought in if risk is particularly high, or in the rapid growth phase.

Products with the strongest curative and kick-back activity, such as those based on oxathiapiprolin, are generally reserved for later in the season and may be useful if spray intervals are likely to be stretched from seven to nearer 10 days due to weather or management logistics around cereal harvest, for example. Mancozeb will also feature in blight programmes to offer multisite activity.