Precision farming of cereal crops: A five-year experiment to develop management guidelines

Abstract

Precision Farming is the term given to a method of crop management by which areas of crop within a field may be managed with different levels of input.  The benefits of so doing are three-fold:

i.                     the economic margin from crop production may be increased by improvements in yield or a reduction in inputs,

ii.                   the risk to environmental pollution from agrochemicals applied at greater levels than those required by the crop can be reduced,

iii.                  greater assurance from precise targeting and recording of field applications to improve traceability.

It is an excellent example of where both economic and environmental considerations are working together.

This five-year study, principally involving five fields in Southern and Eastern England, covered a total of thirteen soil types that represented approximately 30% of the soils producing arable crops in England and Wales.  The overall aim of the project was to determine guidelines to maximise profitability and minimise environmental impact of cereal production using precision farming.  The objectives were:

i.                     To develop a methodology for identifying the causes of within-field variation in crop performance.

ii.                   To develop practical guidelines required to implement precision farming technology to achieve best management practice.

iii.                  To explore possibilities of using remote sensing methods to enable decisions to be made in 'real time' during the growth of the crop.

iv.                 To determine potential economic benefits of using precision farming technology for cereal production.

v.                   To collaborate with a range of farmers with interests in precision farming to ensure that research findings are appropriate for adoption.

The study concentrated on the interaction between soil/water variability and nitrogen applications.  The harvest years 1995-97 (which included a harvest before the formal start of the programme) concentrated on identifying the in-field variability and the development of the 'real time' sensing techniques.  Studies in harvest years 1998-2000 compared spatially controlled inputs with uniform agronomic practice.  A number of techniques were used to decide upon the variable application strategy.  These included information on:

i                       yield variability from historic yield maps,

ii                     variability in shoot density in the spring, and

iii                    variability in the subsequent development of the canopy (green area index);

the latter two enabling the development of the concept of 'real-time' agronomic management.

The major outcomes of the project were as follows:

i.                     Yield maps are indispensable for targeting areas for investigation and treatment by precision farming practices and subsequent monitoring of results.  They provide a valuable basis for estimating replenishment levels of P and K fertilisers. However, they do not provide a useful basis for determining a variable nitrogen application strategy to optimise management in a particular season.

ii.                   The possible extent and potential causes of yield variability can be determined using low capital cost yield mapping systems together with electro-magnetic induction techniques to assess variation in soil factors such as texture and water-holding capacity.  An objective methodology has been developed to use these techniques to determine within-field management zones.  Both individually and together these systems provide a means for assessing the degree of variability within a field and provide a basis for targeting soil and crop sampling points, which is the only cost-effective method for commercial use.

iii.                  The spatial variation in canopy development within a field can be estimated using an aerial digital photography (ADP) technique developed by Cranfield University for this project for 'real-time' agronomic management.  This technique can be extended from field-scale to farm-scale for crops of similar varieties and planting dates.  The processing of data from cameras mounted in light aircraft is sufficiently fast to enable application rate plans to be produced and implemented in near real-time.  The technique can be used as a basis for determining the most appropriate application rate for nitrogen, and as a guide for herbicide and plant growth regulator application.  It is feasible to adapt the system for use with tractor-based systems.

iv.                 The application of nitrogen in a spatially variable manner can improve the efficiency of cereal production through managing variations in the crop canopy.  Depending upon field and year, between 12% and 52% of the area of fields under investigation responded positively to this approach.  In 2000 seven out of eight treatment zones gave positive economic returns to spatially variable nitrogen with an average benefit of £22 ha-1.

v.                   Simple nitrogen balance calculations have shown that in addition to a modest increase in yield, the spatially variable application of nitrogen can have an overall effect on reducing the nitrogen surplus by approximately one third.

vi.                 Common problems, such as water-logging and fertiliser application errors, can result in significant crop yield penalties.  Precision farming can enable these problems to be identified, lost revenue to be calculated and resultant impact on cost-benefit to be determined.  This provides a basis from which informed management decisions can be taken.  It is critical that these problems are corrected prior to the spatial application of fertilisers and other inputs.

vii.                At current prices, benefits from spatially variable application of nitrogen outweigh costs of the investment in precision farming systems for cereal farms greater than 75 ha if basic systems costing £4,500 are purchased, and greater than 200-300 ha for more sophisticated systems costing between £11,500 and £16,000.

viii.              Integrating the economic costs with the proportion of the farmed area that has benefit potential enables the break-even yield increase to be estimated.  Typically a farmer with 250 ha of cereals where 20% of the farmed area could respond positively to spatially variable nitrogen would need to achieve a yield increase of 1.1 t ha-1 on that 20% to break even.

ix.                 The net effect of combining the benefits of spatially variable application of nitrogen (£22 ha-1) with the benefits from both the spatial application of herbicides (up to £20 ha-1) and fungicides (up to £20 ha-1), found from other studies, should provide valuable returns from the adoption of precision farming concepts.  However, this should not be considered as a simple sum of maximum levels quoted.

These economic advantages linked to the environmental benefits should improve the longer term sustainability of cereal production.