WHEN Robert Goose lifts his first early crop he has just a few days to prepare seedbeds for his second crop of first earlies, grown on the same land in the same year. The result is a total yield of 40t/ha (16t/acre).
He manages 1,200ha (3,000 acres) at Deben Farms for Velcourt, at Shottisham, near Woodbridge. This year he is cropping 130ha (325 acres) of potatoes with 15ha (38 acres) of second crop. In previous years second cropping has been up to 25ha (63 acres); the reduced area this year reflects an uncertain market and the availability of suitable land.
The technique allows better use of the farms most valuable asset – the soil, and better use of equipment dilutes fixed costs.
"This is early land in an early area and as we have water for irrigation we can exploit early potatoes," Mr Goose says.
"While some local growers follow first early potatoes with dwarf beans or sweetcorn, we opt for more of the same for part of our crop.
"But because a lot of seed is needed for two crops, double cropping is expensive and technically difficult to get just right. With a lot invested we cannot afford to get it wrong."
The farms 965ha (2,412 acres) of arable land comprises three soil types; 240ha (600 acres) of silty clay loam, 607ha (1,500 acres) of sandy loam to loamy sand, and 118ha (295 acres) of blowing sand.
Potatoes are on the lighter land on a 1 in 5, or wider, rotation. Typically this starts with potatoes, then wheat or barley, with sugar beet in the third year, wheat or barley in the fourth. Dried peas or linseed round off the cycle before a return of potatoes. On the silty clay a wheat, beet, and rape rotation is used.
First earlies account for 56ha (140 acres), second earlies for 50ha (125 acres), with seed crops making up the remainder. About 20ha (50 acres) of the first crop of first earlies, and 12ha (30 acres) of the second earlies are grown under perforated polythene covers.
Potato land is ploughed, ridged and de-stoned in spring. Liquid fertiliser is applied between ploughing and ridging – the amount is tailored to the needs of each field and each variety.
After soil testing aldicarb (Temik) granules are applied where needed at planting to deter cyst nematodes.
Varieties used for the first crop include Rocket, Colmo and Maris Bard. Once grown farm-saved seed is put in on a 2-row bed arrangement.
"The seed-rate used depends on seed size, for the 35-45g grade, we plant sufficient to give a target population of 100,000/ha," Mr Goose explains.
"We start planting in late February as soon as a sensible early opportunity arises when soil conditions are reasonable and soil temperature acceptable. If we are covering the crop we only put in what we can cover the same day."
A pre-emergence treatment of linuron herbicide is sufficient to control weeds. It is possible to irrigate over the top of perforated polythene, the amount used is determined by neutron probes.
Where covers are used they are removed as soon as crop growth becomes restricted or the soil moisture deficit critical, usually this is about half way through the season.
Lifting starts in late May when the yield averages about 20t/ha (8t/acre).
After the land is cleared it is immediately ploughed, fertiliser is applied, and planting is done without delay to conserve soil moisture. If the land is very dry a little irrigation water is put on to get the crop away. No more aldicarb is needed for the second of the two back-to-back crops.
Varieties used for this follow-on crop include Maris Peer, Carlingford, and Charlotte.
About half the seed is home grown, the rest bought in. It is delivered in mid-winter and held in a cold store where it is kept apart from the first early material, so the day degree requirement for individual varieties can be regulated. Two to three weeks before it is needed it is taken out and warmed up so the eyes are open at planting.
This job starts around 10 June and is staggered to meet the market requirements with harvests ranging from mid-August until late October. The target yield is also 20t/ha (8t/acre).
Blight is a slight threat to the first of the twin crops which may be given up to two fungicide sprays. But the fungus poses a much greater threat to the second crop as the soil is warm and moist and plants are unusually small and vulnerable when the blight pressure is highest.
At 60% emergence a contact-acting fungicide is applied to ensure the fungus is not allowed to gain in the crop. Then systemic materials are applied at 10 day intervals whilst new growth is being formed, before a tin-based compound finishes off the blight control programme, just before the crop is burnt off with acid.
The other major threat to Deben Farms early potatoes is black scurf. This is controlled by a fungicide seed-dressing, and use of clean land.
All the farms first earlies are grown for pre-packing for the major supermarkets, and the second early crop is planted with Estima, Remarka, and Saxon for the early set-skin baker trade.
"Double cropping with potatoes is a high risk business which has to be managed properly. We are always learning something new to help us achieve what the quality-conscious supermarkets demand," Mr Goose concludes.
Double cropping, double profits? It is not without risks, but it can be rewarding as this Suffolk grower shows.