10 April 1998

Know your soils well for a sound precision future

GET to know your soils properly before applying other precision farming techniques.

That was the clear message from a recent Shuttleworth Alliance meeting in Beds.

But with fields rarely uniform there is still plenty of debate about how and where to begin looking and sampling.

Soil conditions accounted for up to 90% of the variation in crop performance, so it made as much if not more sense to understand, and if possible monitor, what was going on beneath field surfaces as above, suggested chairman and consultant, Chris Dawson.

"We must take more note of the soil because that is what drives crop variability. We really need to know whether we can improve it with cultivation practices. That is precision farming just as much as matching nitrogen to crop need."

"If you understand your soil you are well on the way to getting a good crop," added the Soil Surveys Ian Bradley. Fertility strongly related to soil structure, which often accounted for yield map patterns, he explained.

Clues lie in the size and pattern of clods and the presence of structureless layers or pans. "Colour tells you how water is behaving. Lots of grey suggests waterlogging." The presence or absence of roots is another useful pointer.

Despite constant advice to examine soils regularly at depth too few growers did so, the meeting heard. The intense interest in soil pits at agricultural shows proves the point, claimed Dr Bradley. "You have only got to dig a hole and you fill it with farmers in minutes!"

A key problem was variation within fields, explained Margaret Oliver of Reading University.

Soil conditions explain up to 90% of variation on yield maps, so it pays to take a closer look, urges Cranfield Universitys Dick Godwin. Soil coring is a relatively cheap and quick way to get a feel for ones soils and to show where to dig exploratory pits, Alliance delegates heard. Herts grower John Dingemans said that even after a soil survey the technique had thrown up some surprises.

ALLIANCE MEETING POINTS

&#8226 Too few farmers know what is going on under their fields. (Dick Godwin.)

&#8226 Under a square metre of wheat there may be 30km of roots. (Peter Barraclough.)

&#8226 There is little benefit in soil sampling at less than 24m if that is corrective treatment tramline size. (Grower.)

&#8226 Crops differ markedly in rooting capacity. Wheats produce about six times more root/cc of soil than potatoes. (Dr Barraclough.)