10 November 1995

Rotation is key to conversion without stock

Organic arable farming without a livestock enterprise to maintain soil fertility has long been tricky. Now researchers at Elm Farm think they have a solution. Andrew Blake reports

ALL-ARABLE conventional farms can go organic without losing money provided they adopt the right approach.

That is the conclusion from an eight-year experiment at Elm Farm Research Centre in Berkshire using red clover to build fertility.

After two full cycles of three different four-year rotations, the trials suggest organic farmers can get acceptable gross margins without introducing livestock.

For all-arable growers the money to set up a stock enterprise, the traditional organic entry, is a big barrier, says researcher Dr Hugh Bulson. "You can be looking at nearly £3000 a head, including quota, buildings and fencing, to establish a suckler cow herd."

Commercial trial

The stockless work began in 1987 on a commercial farm in Kent and in replicated field plots at Elm Farm. Rotations were chosen so every course was present each year to avoid seasonal effects distorting the end picture.

The three rotations and their gross margins are shown in Table 1. Two of these (B and C) compare well with conventional gross margins, says Dr Bulson (see Table 2).

"Some of our expectations proved correct, but there were also some surprises."

Well established red clover, flail-cut several times a season, at a height of 40cm (16in), is the key.

"Red clover has a phenomenal ability to accumulate nitrogen above ground – weve measured about 400kg/ha a year." The theory is that when ploughed down the residues break down gradually to release N and other nutrients for following crops.

Crop performance suggests this is indeed happening. "Were quite encouraged that the N seems to be being released fairly uniformly over the rotations. Nutrient availability is the key." However, he acknowledges the risk of leaching.

New work on composting garden waste from Newbury Town Council could offer a fresh source of potash and other nutrients.

Crop sequence can seriously affect viability. Attempting to grow two wheats running is asking for trouble – in terms of weeds and sheer low yield, probably from poor soil structure and nutrient availability, says Dr Bulson.

This year, in rotation A, first wheat after red clover yielded 4.78t/ha (1.9t/acre). "Weve got up to 5.4t/ha in some years." And wheat after potatoes in rotation B stayed relatively clean to give 4.69t/ha (1.88t/acre).

But the second wheat in rotation A was "very poor" at 2.24t/ha (0.9t/acre). Even at £200/t the organic milling wheat price cannot compensate for such low output, he suggests.

"We thought we would run into weed problems – and we were right. But even where we took the weeds out by hand in a separate experiment, the yield didnt get back to the level it was after potatoes. That suggests weeds are symptomatic of a poor crop rather than its cause."

Good establishment is critical. According to Dr Bulson it accounts for 80% of yield variability over the years. "Farmers are always telling us how important it is." Recent trials suggest Amazones RPD combination power harrow/drill boosts establishment and helps young cereals compete with weeds, he says.

Useful weed control

Other pointers have emerged. Potatoes and winter oats in the same rotation give useful overall weed control. "And winter beans can be a valuable break, allowing two winter wheats to follow."

So, how should conventional growers react to the Elm Farm work? "The experience to date has been encouraging," he says. "While the work is still experimental, the results have given a sound basis from which to develop.

"Fixed cost structures of all-arable organic and conventional farms are broadly similar. With the underpinning of area aid many more growers could now gradually introduce organic farming as part of a carefully planned conversion."

Pure red clover is not the most practical entry, he admits. Instead he advocates a 50/50 clover/grass mixture under the voluntary set-aside derogation. "It is probably worth sacrificing some nitrogen accumulation to keep on top of weeds and boost soil structure."

Organic premiums, particularly for the wheat and oats, clearly underpin the economics, he concedes. "But the market for organic grain is strong and the potato market is growing. It appears that prices are holding up and farmers should have no problem selling. At the moment there is still plenty to go at."

Varieties used in Elm Farm organic trials

Winter wheatMercia (Pastiche

& Spark better)

Winter oatsSolva

Spring oatsDula

Winter beansBourdon

PotatoesSante (for blight resistance)

Table 2. Conventional gross margins – average performance £/ha (£/acre)

Winter wheat for milling680 (275)

Winter oats for milling685 (277)

Spring oats for milling590 (239)

Winter beans545 (221)

Potatoes (maincrop)1174 (475)

Source: Farm Management Pocketbook – Nix (1995 edition)

Table 1. Elm Farm stockless organic rotations and gross margins £/ha (£/acre)

Rotation ARotation BRotation C

Yr 1 Red clover174 (70) Red clover174 (70)Red clover174 (70)

Yr 2 Winter wheat 1140 (461) Potatoes1239 (501) Winter wheat 1122 (454)

Yr 3 Winter wheat632 (256)Winter wheat1032 (418) Winter beans637 (258)

Yr 4 Spring oats407 (165)Winter oats617 (250) Winter wheat 776 (314)

Average588 (238)766 (310)677 (274)