27 March 1998

Place potato fertilisers if you want best results

By Edward Long

POTATO growers can cut fertiliser costs by up to 30% and boost yield and quality by choosing the right product, tailoring rate to need and placing part of the requirement alongside seed tubers at planting.

That is the opinion of Mark Law of Wisbech-based Law Fertilisers. "General ADAS recommendations must be thrown away and the needs of each crop assessed individually to take account of pH, soil type, organic matter, type of fertiliser and the method of application," says Mr Law.

Growers who broadcast over 200kg/ha (160 units/acre) of phosphate are wasting money, he adds. Only 50kg/ha (40 units/acre) is needed for a 50t/ha (20t/acre) crop, because potatoes are "shy" feeders and phosphate is almost immobile in the soil and quickly locked up.

Nitrogen rate must be tailored to need after allowing for residual amounts in the soil and the amount likely to be mineralised from organic matter, Mr Law continues. Varieties vary in their need for N and rates should be matched to both soil and crop maturity targets, he says.

Trace elements also need considering. "Modern market demands for quality tubers are increasing the need for trace element applications to prevent deficiencies interfering with crop marketability. But these tend to be applied late as a "fire-brigade" operation and often focused on just manganese."

Foliar applications are inappropriate, as a lot of trace elements are not translocated between leaves, so have to be taken up by roots, he explains. But high phosphate indices can leave trace elements locked-up in the soil.

Placement of trace element enriched fertiliser is an important part of Mr Laws drive for improved efficiency. "We like to place a quarter to a third of the crops nutrient need at planting and broadcast the rest before or after the crop is put in.

"But it is absolutely vital not to place potash due to the damaging effects of its chlorine component. This can cause scorching, increased risk of blackleg and a reduction in the availability of other nutrients."

Together with some nitrogen, a little phosphate is needed for early root growth and canopy development.

The Wisbech company has a fleet of 2-4 row applicators, which it will fit to planters and calibrate. Basal programmes, including magnesium, cost £50-£100/ha (£20-£40/acre). Placement of fertiliser, manganese, calcium, boron, sulphur, copper and zinc costs a further £25-£63/ha (£10-£25/acre).

"One Cambridgeshire potato grower with 55 acres of Piper for chipping has cut his costs by 30% by placing part of his fertiliser this year. And by putting trace elements into the soil he is preventing rather than curing deficiency troubles," says Mr Law. &#42

Placing a tailor made fertiliser blend alongside seed potatoes at planting can boost output and cut costs, says Wisbech-based Mark Law.

Early N vital to give beet a flying start

Sugar beet growers are under constant pressure to reduce nitrogen rates. But sufficient must be available early in the season to get the crop off to a flying start. Failure to achieve this will compromise sugar yield.

It is important for growers, and British Sugar, to balance the amount provided to the actual need of individual crops, says Mark Law of Cambs-based Law Fertilisers of Wisbech.

Traditionally N rates have been too low in a dry year and too high in a wet one when a lot of mineralised N becomes available, he says.

"The amount put on must match the needs of the soil and season. It is vital to achieve good establishment, so there must be sufficient N early on. Beet seed can only survive for about 10 days on its own reserves. If not given some top-up help it will suffer. An early growth check will saddle a crop with a legacy of reduced yield and quality."

He also suggests trace elements should go on either at or before drilling as they are taken up by plants in the first third of their growth cycle.