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Opportunities for Precision Agriculture in Crop Protection

NDVI image taken with small unmanned aerial system Stardust II. Mosaic of 299 images acquired in one flight.

2 Mar 2017

SCI Agrisciences Group has been discussing progress in the application of precision agriculture technologies, particularly directed at crop protection. Precision agriculture uses information and communications, engineering and decision support systems to reduce the variability in farming operations. The aims are to increase productivity and profitability, and to reduce environmental impact.

Early adoption
The development of precision agriculture commenced in the mid-1990s as a result of the wide scale availability of Global Positioning System (GPS) services delivered from satellites. The first applications were yield mapping with combine harvesters and soil nutrient mapping, leading to phosphate and potassium fertiliser application according to the spatial variability in a field.

This was followed by imaging of growing crops leading to variable application of nitrogen fertiliser. Sensors are used to record the images from visible band and near infra-red cameras on satellites, aircraft, drones or from tractor-based units. Soil structure mapping is also carried out using electric conductivity equipment, which can be used to operate spatially variable sowing rates. Automatic tractor guidance systems using GPS are now widely adopted in the UK.

Most of the developments in precision agriculture have, so far, been applied to crops including cereals and oilseed rape in Europe, as well as maize and soya beans in North America. However, there are potential opportunities in vines and in orchards. Commercial adoption of precision agriculture in crop protection is relatively limited. Some services are offered to farmers and a number of projects are currently underway that could widen opportunities.

Some recent developments
The prevalence of blackgrass (Alopecurus myosuroides) in winter wheat in the UK, which is increasingly resistant to herbicides, has prompted interest in mapping the occurrence of this weed in the field, enabling the patch spraying of expensive herbicides. The best time to collect images of blackgrass is before harvest, although this means that the first opportunity to variably apply herbicides is in the following crop. The eyeWeed project, co-funded by Innovate UK and involving the University of Reading and several industrial collaborators, has looked at the detection of blackgrass in cereals at a much earlier stage of the crop using cameras mounted on ground-based farm machinery (especially sprayers). A prototype sprayer which will permit ‘real time’ herbicide application is now being evaluated.

Potato cyst nematodes (Globodera spp.) are an important economic pest in potatoes in parts of the UK and control measures with granular nematicides are very costly. By taking soil samples and recording egg counts, it is possible to draw-up maps showing the variability in infestations and a few agronomy companies in the UK offer such services. However, the first remedial action by patch application can only be operated when the next potato crop is planted in the same field, which may need to be several years later.

Another technology under development is the application of hyperspectral imaging. Using special sensors, it is possible to record differences in the spectrum of reflected light from the leaves of crops. These differences relate to the fluorescence of chlorophyll and the presence of zeaxanthin, and can indicate variations in the health of the crop and the extent to which it is suffering from drought or disease-related stress. Specialist companies in the USA offer services, primarily for research purposes, based on hyperspectral sensors. There has been some evidence that foliar disease incidence can even be detected before it is visible to the human eye.

A project currently underway, involving the University of Cambridge and industrial collaborators, Blightsense, is aiming to develop a rapid acoustic biosensor device for in-field identification of air-borne spores of Phytophthora infestans, the causative agent of potato blight.

The wider application of precision agriculture in crop protection will depend largely on the technical performance and economic viability of these evolving sensor technologies.

Bruce Knight, Innovation Management

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