Giving maize and potato crops a head start

Article taken from Agronomist & Arable Farmer, May 2017, written by agronomist Bob Smart.


Young maize is a poor competitor at the best of times and any growth check from cold soils can make the problem worse.

Weeds are, therefore, a real threat and must be controlled early on. They compete for sunlight, shading the young maize leaves and reducing the amount of light reflected from the soil surface.

This light is key to early crop vigour and any reduction can damage final yield prospects from the four-leaf stage. Pre-emergence endimethalin at l,200-l,400g provides an excellent start to the proramme, offering cheap and effective weed control to keep the crop clean from the start. A lot of maize has been introduced in this area as a spring break to help control black-grass, another good reason for using pendimethalin.

I'll add Remix, a paraffinic oil and application aid that reduces spray drift and which keeps the pendimethalin in the few centimeters of soil where it's doing most good. Using pendimethalin may also allow rates of post-emergence chemistry to be reduced. The post-emergence chemistry is relatively expensive, so it can save money, and there is less risk of stressing young maize.

I recommend MaisTer (foramsulfuron + iodosulfuron) + adjuvant Mero at the four- to six-leaf stage where black-grass is present and to control broad-leaved weeds, otherwise use Elumis (mesotrione + nicosulfuron) at 1-1.51/ha.

Growers should consider spraying N-Lock, a nitrogen stabiliser, just before final seedbed cultivation so it can be worked into the soil. Applied at 2.51/ha it can be tank-mixed with glyphosate. It can also go on post-emergence, in which case it needs rain to wash it in.

N-Lock slows down the conversion of ammonium into nitrite, reducing leaching and ensuring more nutrient is available later, when the plants really need it.

Maize uses half its total N requirement after flowering, and 60kg/ha can be lost between drilling and that time.

Potato growers will also be considering weed control. Around 80% of potatoes in this area are grown on rented land, so you need to make some enquiries to see what weeds you'll be dealing with. I'll base my programmes on Soleto (metobromuron) as it has excellent safety and no buffer restrictions. Soleto mixed with Artist will be my preferred option, offering very good broad-spectrum weed control as well as grass-weed activity. I'll add Remix to pre-emergence recommendations, to ensure even distribution of chemical.

I prefer to apply residuals 10-14 days post-planting onto settled seed-beds, then follow up with diquat around emergence, rather than putting everything on at once just before potatoes emerge. Blight protection will begin with Ranman Top (cyazofamid) at 0.51/ha at the rosette stage.

This gives excellent control of foliar blight and early zoospore activity in the soil. I'll follow with Consento (fenamidone + propamocarb) during the rapid-growth phase and later introduce Revus (mandipropamid) and Infinito (fluopicolide + propamocarb), as necessary.

My customers will have ingredients needed for various blight programmes in the spray shed, so we can adjust according to blight pressure and product rainfastness. The all-important T2 timing in wheats will be next on the list. I'll be using Priaxor (fluaxapyroxad + pyraclostrobin), Eclipse (epoxiconazole + fenpropimorph) and chlorothalonil.

With a solid TO and TI already applied, I will adjust rates according to disease pressure and variety.

Bob Smart is an agronomist with Agrovista, based in Leicestershire (


09 May 2017

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