6 November 1999


Britain leads Europe when it comes to adopting precision farming techniques. Peter Hill provides a summary of the current state of the art.

Soil sampling

GET to know your soils better. That is the message from enthusiasts of precision farming to growers considering a first step with the new technology.

With GPS guidance providing accurate sampling positions and equipment geared to doing the job quickly, soil mapping to give an accurate picture of soil type and/or soil nutrient and pH status is one of the most common practical uses of precision farming technology.

Pinpoint sampling also holds the promise of reducing the cost and environmental impact of soil pesticides, and commercial services claiming to do just that are already available.

The system hinges on GPS-guided soil sampling to detect the presence of pests such as nematodes, then GPS-guided pesticide application to control them.

Potential savings are enormous; but so, too, is the cost of not getting it quite right.

Fertiliser and lime

Having determined with greater precision the soil nutrient pattern of individual fields, fertiliser rates can be targeted accordingly. In many cases, growers who have adopted this approach, using either their own machinery or more likely a contract application service, find they make significant savings in fertiliser usage.

Such savings are not guaranteed. After all, there is not always significant variation in nutrient status. But where that is the case, at least the fertiliser is applied at appropriate rather than blanket rates across fields and should therefore be used by the crop more effectively.

Contract application charges can be offset by applying two years worth of fertiliser in one go. Or farmers can do their own thing, either applying the two nutrients in separate passes (rather expensive), by using spreaders on one tractor (a popular solution) or buying Amazones novel twin-compartment mounted spreader which has two sets of spinning discs.

Although variable rate potash and phosphate application are proving both justified and practical, the picture is more complex as far as nitrogen is concerned. Trials evaluating the potential for variable rate N based on current methods of soil N assessment, crop removal and so on have shown no appreciable gains.

Where top dressing rates are calculated by calculating the needs of the growing crop, however, variable rate N is showing a lot more promise, with yield improvements and fertiliser cost savings won over conventional practice in trials.


The technology is now available but few, if any, growers are using it. Because there is no clear view whether, under given circumstances of variety, target market and seedbed condition and drilling dates, seed rates should be increased or decreased, let alone by how much.

At least growers know it can be done and the electronic drill control systems essential for GPS-guided sowing do allow broad-brush manual variation in light of obvious differences in soil type or seedbed condition.

From the machinery aspect, all it takes is a GPS monitor to handle position and application rate data, a compatible implement controller to turn application rate demands into machine settings, and electric drive to the seed metering system to achieve the required rate.

Several drill manufacturers can put together such packages, using either third-party electronics from the likes of RDS and LH Agro, or matching their own electronic systems to GPS terminals such as AGCOs Fieldstar unit.

Precision-sown crops may also benefit from GPS-guided seeding technology which Kleine has pioneered in respect of sugar beet and Amazone with maize.

With the root crop, the most likely reason for adjusting seed rates using the electronically-driven seeding units is to avoid over-large roots in rows alongside tramlines – and that does not need GPS technology. But with forage maize trials already suggesting that changes in plant populations based on soil potential can result in yield gains, the technology may yet have a place on such drills.


The idea of using GPS-regulated irrigator controllers is still in its infancy but does hold the promise of more economical water usage when irrigating across different soil types with different water retention characteristics.

And it would help ease management of irrigation to vegetable and salad crops in some cases if systems could be set up to irrigate different crops at different rates in one continuous operation.


It is not so much the sprayer itself as providing it with a mapped target that is the challenge for precision farming technicians in the realms of crop protection.

With direct injection of pesticides readily available (if still quite expensive), it takes only a little ingenuity and engineering to produce a system that can select which of several pesticides are applied at any given moment, and at what rate.

Some (though barely a handful) are already in use on commercial farms. The real problem comes in mapping the target in order to provide digital product and rate instructions.

Weeds hold most promise, at least those that are clearly visible in crops at certain times of year and which tend to occur in distinctive clumps – such as wild oats and blackgrass. Trials have shown significant savings in pesticide use (through strategic reductions in application rate as well as switching the spray on and off as appropriate) when the target is accurately mapped.

But given the level of seed return from such weeds, the penalties for inaccurate mapping or application can be severe.

Crop mapping

With almost all combines now available with yield and moisture mapping systems, it is at harvest that most use is being made of precision farming technology.

Yield maps provide the evidence of in-field crop performance variations – in terms of both yield and gross margin – that encourages growers to investigate their causes and try remedies to even them out.

Much has been learned about yield mapping technique; and future developments may allow growers to readily map grain quality characteristics. But there is still a need to hone yield map interpretation skills.

Researchers hope to help by using computer power to work through and refine the mass of data generated by yield maps, to identify common trends and help users better identify field areas worth investigating more closely or managing differently.

Root and other non-combinable crops are also getting the yield mapping treatment; their high value and high input costs makes them ideal candidates given that small yield improvements and/or cost reductions can have a significant effect on the bottom line.

Weigh cell trailers and weight cell-mounted web rollers have both demonstrated sufficient accuracy to be of value, and some examples of the latter are already in commercial use on farms, mostly in Canada.

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