28 February 1997

Root crops next in line for yield map application

Latest goal for precision farming enthusiasts is yield-mapping root crops. Peter Hill reports progress to date

WHEN Massey Ferguson announced a year ago that it had successfully yield-mapped a 2.2ha (5.5-acre) crop of sugar beet it was clear that an important piece of the precision farming jigsaw could soon be in place.

Yield variability appears to exist in beet and other root crops just as much as in combineable crops.

High-value and high input costs make such crops especially relevant to precision farming techniques, says David Smith, new product development manager at Massey Ferguson.

To weigh the beet crop, load cells were fitted to an 8t MF700-series trailer. The weight of beet coming off a six-row harvester running alongside could then be recorded with position data collected by the MF tractors Fieldstar GPS receiver and data recorder.

The weighing system proved accurate, coming within 10kg (22lb) of weighbridge check recordings. Analysis of the data confirmed that yield variation was significant across the field.

One attraction of this method of yield-mapping is that it could be applied to any harvesting technique where crop is transferred continuously from the harvester to a trailer. Potatoes, carrots onions and forage crops could all benefit.

On-harvester weigher

Costs could be contained where only one or two trailers are used, but that is often not the case. A less versatile but often more practical solution would be to have a reliable weighing system on the harvester.

A handful of experimental systems have been tried in the US. But Britains RDS Technology has a system up and running, which some growers in Quebec province, Canada, are already using. The system uses load cells built into the last two idler rollers of the harvesters conveyor trace.

"We cant achieve the same accuracy as with combineable crops," accepts Peter Nelson, engineering director at RDS. "But, at 5%, it is close enough to provide a good indication of yield variability."

Ultimately, the firm hopes to offer a retro-fit kit that could be used on any root crop harvester with suitable location for the load cell rollers.

It may be possible to assume common influences on the performance of different crops within a rotation. That is one aspect of a three-year project started in 1996 to see whether there is any reliable correlation between cereal yield maps and sugar beet yields.

"With sugar beet coming up only occasionally in the rotation, it would take a long time to come up with reliable yield maps specific to the crop," points out Simon Fisher, of British Sugars Holmewood Hall research and development centre.

The Sugar Beet Research & Education Fund-supported project also has Silsoe Research Institute and IACR Brooms Barn as partners. It involves beet yield mapping (using MFs trailer system) and surveying soils, crop development patterns, fertiliser, plant population and disease.

Work is also underway to assess the benefits of applying root crop inputs at variable rates, starting with seed. One idea is to sow two or three sugar beet varieties in the same field. A more drought tolerant variety could be grown on lighter soils, for example.

With potatoes, the approach is more likely to involve variable spacing to account for differences in soil type. Technology for that is already to hand, says Andy Bone of Standen Engineering.

"The computerised tuber spacing adjustment on our potato planter could be linked to an electronic control map without much difficulty, to give variable seed spacing across a field according to the yield potential of different soils or underlying conditions," he says.

MFs Fieldstar system is already being used in tests for selective application of nematicide.

Variable irrigation

Work on variable rate irrigation is planned at the Scott Abbott Arable Crop Station, Sacrewell, near Stamford, this year. "After mapping our crops for the first time last year, we guessed that moisture availability could be a key element of yield variation on the shallow, brashy soils," says agronomist John Ward. "When we conducted a soil survey to assess likely water capacity, we found an almost perfect match with the yield maps."

A 64m (210ft) boom irrigator from Briggs Irrigation will be used to apply up to five different rates of water using the machines computer-regulated reeler to alter the speed of the boom wherever the soil characteristics differ. &#42

MFs trailer-based yield-mapping system for non-combineable crops has already been used on sugar beet and potatoes at Shuttleworth Farms.


PRECISION ROOTS


&#8226 Trailer-based yield mapping.

&#8226 Harvester load cells being evaluated.

&#8226 Vary beet variety with soil type.

&#8226 Potato spacing change with soil type.

&#8226 Selective nematicide application.

&#8226 Computer-controlled variable irrigation.