Agronomy Update - East

Article taken from Farmers Guide, May 2017.

 

A long spell of cold nights, coupled with plenty of rain over the Easter weekend, means soils have been very slow to warm up over recent weeks.

Ideally, maize needs to be drilled into a seedbed that remains at 10°C or above to avoid being stressed. At the time of writing (third week of April) readings were just 7-8°C, and the long-­range forecast suggested the run of cold nights would continue.

Much of the crop is sown by contractors who have large areas to cover. Added to this, most maize varieties in the east tend to be the bigger and later ones with FAO values of 210 or more, so they need to be in the ground early to maximise their potential. Drilling therefore has been continuing apace over the past fortnight.

These cool soils will put the crop under stress from the word go. Seedlings will expend more energy to emerge and establish and are very likely to suffer from cold shock. Many stands are likely to turn yellow soon after emerging, as roots struggle to grow and provide sufficient nutrition for the young plant.

Work at our Great Ellingham trials last year, when conditions were even more stressful, showed a low-rate application (10-litres/ ha) of MZ28, a non-scorching foliar nitrogen product, gave these yellow crops the kick-start they needed.

MZ28 is usually applied at 8 - 10 true leaves to aid cob production, but applying it at 10 - litres/ha when the crop has 4-true leaves helped plants to green up and regrow, putting them in a much better position once soils did warm up.

This also helps keep herbicide programmes on track. Weeds are much less sensitive to soil temperatures, so in cool conditions pose even more of a threat than usual. However, stressed crops cannot be sprayed with herbicide as they are easily damaged.

Pre-emergence

Pendimethalin applied pre-­emergence will be critical this season. It provides good broad-spectrum control of most problem weeds and will optimise post-emergence herbicide performance. I'll apply 1 ,200 - 1,400g/ha together with Remix, an adjuvant and application aid that keeps the active in the top few centimetres of soil where it does most good.

I'll also be advising adding N-Lock with the pre-emergence herbicide. This is a nitrogen stabiliser that slows the conversion by bacteria of ammonium bagged nitrogen for up to six weeks.

This ensures enough nitrogen will remain near the soil surface to fill cobs - maize uses half of its total N requirement after flowering, and 60kg/ha can be lost between drilling and that time. On average, we've seen a nine per cent yield increase at our Great Ellingham trials over the past three years.

Post-emergence herbicide treatments are ideally applied at the 4-leaf stage. However, if crops are stressed you can hold off to six leaves in the case of Maister (foramsulfuron + iodosulfuron), or eight for other treatments.

Product choice will depend on weed spectrum. For broad-­leaved weeds I'll use Callisto (mesotrione) or Calaris (mesotrione and terbuthylazine), but be aware of following-crop restrictions, particularly sugar beet.

Where broad-leaved weeds and grasses need controlling, Elumis (mesotrione + nicosulfuron) at 1.0 - 1.5-litres/ha provides exceptional broad-spectrum activity. An alternative that will control single R-resistant black-grass as well as a range of other grass weeds and broad-leaved weeds is Maister + Buctril (bromoxynil), at 150g/ha and 0.6-litres/ha respectively.

 

Craig Green is an agronomist with Agrovista, based at Great Ellingham, Norfolk (craig.green@ agrovista.co.uk)

 

11 May 2017

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