After wet weather through March and April caused some significant delays to maincrop planting, 草榴社区 Guardian catches up with two Hutchinsons agronomists to see what this means for agronomy over the coming weeks.
South east - George Baxter, Cambridgeshire Fens
Generally, progress is around two to three weeks behind normal in this region, so with a shorter growing season, it will be more important than ever to ensure nothing impedes establishment.
Particular caution should be given to post-emergence herbicide applications, based on actives such as metribuzin and rimsulfuron, to varieties that are susceptible to adverse crop effects.
There are of course, good reasons why such chemistry may be needed, so the risks of not applying a post-em must be carefully weighed against the risks of setting crops back in an already later season. This can only be determined on a field-by-field basis.
Nutrition
Early nutrition has been key this season, mostly in the seedbed, however this will be supported with foliar nutrition as growth accelerates. Phosphites are really useful early on to build root development, while methylated ureas can help retain green canopy later in the season.
Soils in this region are particularly prone to manganese and magnesium deficiency, so these two nutrients are another focus, with requirements based on historic crop need, and in-season tissue testing.
The aim is to generate as many viable tubers as plants can sustain, although in a later-planting season, yield potential is often the first to be compromised. Tailoring nutrition can help mitigate the impact, but be realistic about what crops can sustain.
If the unsettled conditions continue, blight pressure could be high this season, so robust rates, of the correct products, at the right time, are fundamental.
There is a good range of blight chemistry available, and while it is useful to have a plan, avoid being too prescriptive, and adapt product choice to risk at the time. One possible exception is during rapid canopy development, when scheduling the more systemic chemistry, such as benthiavalicarb + oxathiapiprolin, or fluopicolide + propamocarb, is recommended to ensure new growth is protected.
North west - Archie Boase, Cheshire
Planting delays in the north west are typically two to four weeks on many farms, and while warming soils should help crops get away quickly once in, it is vital to keep pushing them on to make up for lost time.
As mentioned, foliar phosphites can help root and stolon development, thereby improving the plants water and nutrient scavenging ability through the growing season.
Applying foliar nitrogen, as methylated urea, is also beneficial in supporting canopy development, providing a valuable top-up to seedbed nitrogen where required. Nitrogen demand typically peaks around tuber initiation and the start of bulking, so this is an ideal time to consider additional nitrogen if needed.
Tissue testing is an accurate way of assessing nutrient requirements for individual crops, and is best done a couple of times during rapid canopy development when demands are greatest, although a final test once canopy growth stabilises can also be useful.
While the focus is often on macro nutrition, we must not overlook other nutrients, such as manganese, magnesium, zinc, and calcium. Deficiencies will compromise plant health, development, and potentially cause tuber quality issues - such as internal browning due to insufficient calcium. Calcium deficiency is best addressed by soil amendments though.
Cost effective
Recent wet weather has kept blight risk high, so Hutton criteria must be monitored carefully and crops treated from emergence onwards where necessary.
Chemistry such as mancozeb and cymoxanil can be cost effective early in the season, but once canopy growth accelerates, more systemic products based on fluopicolide + propamocarb hydrochloride, or mandipropamid, are preferred to protect new growth. Where blight risk is particularly high, benthiavalicarb + oxathiapiprolin is the go-to option given its excellent efficacy.
Once growth stabilises, there is a range of options, although it is worth retaining a couple of cyazofamid applications for the end of the season given its strong tuber blight activity.
Do not overlook alternaria either. This caused some issues in unirrigated crops that became stressed in hot, dry conditions last year, especially susceptible varieties like Markies, although difenoconazole proved effective at managing the risk.
As always, stay flexible and adapt blight programmes to the season, utilising a range of chemistry with different modes of action. This is vital to manage risks from new blight strains, such as 43_A1, which has insensitivity to CAA-inhibitor chemistry (e.g. mandipropamid), and although is not yet in the UK, is present elsewhere in Europe.
