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PRECISION AGRICULTURE - PERSPECTIVES
FOR THE MAURITIAN SUGAR INDUSTRY
I Jhoty and J C Autrey
Mauritius Sugar Industry Research Institute
Precision agriculture, (precision farming or site-specific management) is a form of mechanized agriculture that relies upon satellite-based navigational technology to map spatial variability enabling a more judicious use of inputs. It can provide the basis for improved yields and reduced costs of production. Devices such as the Global Positioning System (GPS) and yield-mapping systems, mounted on agricultural machinery, are used for data collection. Some applications of precision agriculture are described together with the characteristics of the hardware and software involved. Possible applications to sugar cane in the mauritian context are discussed with a view to demonstrating how precision agriculture can lead to lower costs and decreased environmental impact.
Keywords: Precision-agriculture, sugar industry, mapping spatial variability, Global Positioning System, Geographical Information Systems, Mauritius.
From use of extensive land and simple tools, agriculture has progressed to intensive use of land with sophisticated farm machinery. In the recent past, the green revolution brought a tremendous change in agriculture enabling an increased capacity for crop production. Despite achievements made in fertilizer production, plant breeding, crop protection methods, etc, crop production planning has not been totally mastered. Information and engineering technologies presently available are likely to make crop production planning more precise. Crop production is achieved on an "as needed basis" allowing a cost-effective business approach through minimum inputs. This new approach is called Precision Agriculture. It represents a great leap forward for agricultural production and could lead to significant improvement in crop productivity. In the mauritian context, at a time when the sugar industry is facing critical issues such as competitiveness and the need to reduce costs of production, Precision Agriculture may be expected to contribute towards meeting these objectives.
What is precision agriculture ?
The concept of Precision Agriculture was formulated in 1986 (Fairchild 1994). It is based on the fact that variability of soil fertility, soil depth, micro-relief, microclimate, weed species, etc are natural and site-dependent and therefore have a direct bearing on crop production (Kharural et al. 1996; Earl et al. 1996; Gerhards et al. 1996). Crop production is achieved from “prescribed” inputs made on an “as needed basis” and calls upon the support of information and engineering technologies as micro-computers, geographical information systems (GIS), global positioning system (GPS) and automatic control of farm machinery. Instead of managing fields with average requirements or with general types of recommendation, fields can now be managed by variable rates of inputs that are specific to the site conditions. By this method, crop yield can be better controlled and low-yielding areas can be better managed resulting in increased productivity. It will also result in a judicious use and economy of inputs as well as being environment friendly. Extra inputs of fertilizers or biocides in non-desired areas will then be avoided thereby minimizing risks of pollution. Further aspects on the philosophy, technology and benefits of Precision Agriculture have been reviewed by (Graham and Dawe 1995) and (Toft and Dorward 1995). Precision Agriculture has been developed and applied mainly in Europe and the United States particularly in wheat, barley, corn and soybean. But its application is being extended to other crops such as potato, cotton, sugar beet and sugar cane. Other names used in lieu of Precision Agriculture are Precision Farming, Prescriptive Farming, Variable Rate Farming, Site-Specific Management, Soil Specific Crop Management, Farming by Computer, Farming by satellite, Computer-assisted Agriculture, Automated Agriculture, Farming by Foot, Cyberfarm, etc.
Information and engineering aspects of precision agriculture
Precision Agriculture has been made possible because of impressive progress achieved in information and engineering technologies. These technologies are associated with the four phases of Precision Agriculture: observation, interpretation, evaluation and implementation. In the observation phase, referenced spatial variable data are collected with the help of yield-mapping systems (sensors), aerial photographs and satellite imageries together with a global positioning system (GPS). Databases are compiled within a geographical information system (GIS), essential for managing the huge amount of information. In the interpretation and evaluation phases, processes involve data querying, spatial analysis, and generation of models for soil behaviour/crop performance with appropriate software tools while control measures are also formulated. In the final phase of implementation, control is achieved with variable rate applicators/spreaders for applying inputs on an “as needed basis”. Integrating the different processes and controls involved in the four phases in a well designed Decision Support System is vital.
A typical approach for mapping yield variations in the field consists of a combine harvester or a side trailer equipped with a yield monitor sensor for measuring flow rate of crops (volume for grain and mass for crops such as potato, sugar beet and sugar cane). A GPS field guide system is mounted on top of the harvester to give correct positions in latitudes / longitudes / altitudes (or Eastings and Northings) as the harvester moves along rows. The GPS is a satellite-based navigational technology that receives signals from 24 satellites in space and computes the position (in x, y, and z) of any point on the surface of the earth. Yield variations will be recorded and shown as a map. Mapping spatial variables related to soils is achieved by grid sampling and geo-statistical methods (Franzen et al. 1996; Mohamed et al. 1996). However, other rapid and automatic methods are being explored by using mobile systems (soil chemical sensors mounted on small vehicles) to measure chemical properties of soils like organic matter, soil moisture, nitrate levels, etc (Borgelt 1992; Lui et al. 1996; Wright 1996). The GPS is a part of the system for referencing the points where measurements have been made. Weeds and other biotic factors may be mapped with the aid of aerial photographs or satellite imageries. For variable rate applications (of fertilizers, ameliorants, and biocides), the tractor is equipped with variable rate applicators or spreaders and a GPS field guide system to show the areas where variable rates need to be applied. Other applications involve digital terrain modeling (Bell et al. 1994; Verhagen et al. 1994; Haneklaus et al. 1996), and soil dynamic modeling techniques for characterization of uncertainty in soils (Mays et al. 1994), or water and chemical fluxes and crop growth (Bouma 1994). The modeling techniques provide information on soil behaviour for minimizing inputs and leaching / run-off of agrochemicals.
Other technologies like the video image analysis have been reckoned to provide capabilities for detecting patterns related to soil sampling and mapping (Beverly et al. 1995) and voice recognition systems developed for automatic recording of spatial variable data while operating a tractor / combine harvester (Dux et al. 1997). The success of Precision Agriculture will be assured if the necessary mobile sensor for mapping soils and biotic factors become commercially available, as manual sampling of these factors has proved to be costly and impractical.
The sugar industry
Precision Agriculture has already been applied in the sugar industry. In Florida, grid soil sampling techniques have been adopted to produce rate application maps for fertilizer, lime and calcium silicate slag to be used with rate controllers. Yield mapping is carried out by means of infrared photography and satellite imagery (Lockhart and Murray 1997) but a field worthy yield sensor monitoring system is not yet available. In Australia, however, the development of yield monitors has been a primary concern. Mass flow rate measurements for a prototype yield monitor has received attention (Cox et al. 1996a; Cox et al. 1996b; Cox et al. 1997). For the 1998 cane crop, three yield monitors attached to harvesters have been evaluated for their potential to map yield variations (Cox 1998). Furthermore, a workshop was organized in June 1997 to overview the application of Precision Agriculture and its benefits to the Australian sugar industry (Bramley et al. 1997).
On the manufacturers' side (Cameco, Case IH), investigations are going on to provide the necessary facilities to cane harvesters for the operation of yield monitoring systems (Mondet, pers. comm.; Taske ,pers. Comm. ; Willet ,pers. comm.).
Perpectives for Mauritius
Can Precision Agriculture be applied to the sugar industry in Mauritius ? The following aspects must be taken into account to meet comprehensively this question :
- Crop mechanization,
- Spatial variability of resources,
- Reduction of costs of production and competitiveness,
- Environment protection,
- Databases and GIS, and
- Research needs.
The necessity to mechanize cultural operations, including planting and harvesting, has been recognized. This situation has stemmed from shortage of labour. Programmes of mechanization mostly on large sugar estates’ land have been initiated and are on going. In this implementation process, fields and roads have been re-designed and land planed (by means of cut and fill techniques) to allow the efficient use of machines. Precision Agriculture is much easier to introduce than if there were no mechanized operations. Yield monitoring and variable rate applications for fertilizers and biocides can be tested and adopted. The investment in Precision Agriculture will therefore involve only additional costs of equipment like yield sensors, GPS field guide systems, and variable rate applicators. These costs have been calculated to be minimal compared to heavy investment in machines (Cox DRV 1997).
Spatial variability of resources
Spatial variability of soil / climate/ biotic parameters may be important for realizing variable rate applications being given the size of farms. This is so because the geological nature of parent materials has given rise to considerable variations of landform over small areas. A clear example is the hummocky and chaotic topography in the north, east and west of the island. For this type of landform, soil depth is very limited on hummocks while in the troughs soil is deeper. Evidently, the soil fertility, water availability, organic matter content, etc will also vary according to soil depth. On the other hand, microclimates are dominant features and favour variable leaching conditions or weed growth. These variable parameters and seasonal variations will certainly influence yield potential. The extent of influence has to be determined. It has been observed that the greater the spatial variability of environmental parameters the greater is the opportunity for cost-effectiveness of Precision Agriculture (Forcella 1992).
Reduction of costs of production and competitiveness
Cost-benefit analysis has been conducted for crops and variable rate applications. Net benefits have been demonstrated in certain cases and not in others (Earl et al. 1996; Hammond 1992; Snyder et al. 1996). Furthermore the higher the crop value and the number of controlled inputs, the greater the possibility for benefits to be derived from Precision Agriculture (Swinton and Ahmad 1996). In the sugar industry, results of cost-benefit analysis are not available yet. However, the benefits expected have been reviewed and appraised (Bramley et al. 1997). In Mauritius, as the primary aim of the sugar industry is to be competitive and to cut down costs of production, the contribution of Precision Agriculture cannot be overlooked. It should be a part in the overall strategy to increase productivity at minimum costs.
The public has a concern over the excessive use of agrochemical products that could harm the environment. Though environmental pollution by agrochemicals is far from being a critical situation in Mauritius (Autrey and Ng Kee Kwong 1997), Precision Agriculture would be an appropriate management system to regulate applications of agrochemical products. It will demonstrate that over application of agrochemical products in non-desired areas can be avoided and that off-site export of the products will not take place or might be negligible and kept well below accepted tolerance values.
Databases and GIS
Data management using GIS or expert systems for Precision Agriculture is a dominant aspect of Precision Agriculture (McGrath et al.1994; Usery et al. 1995). Valuable spatial data on the characteristics of land, climate and crop for sugar cane fields have already been compiled (Land Index Databases) while also a highly performing GIS for the management of the sugar cane land (GISCANE) is also operational at the Mauritius Sugar Industry Research Institute (Anon 1992; Jhoty 1995). For the initiation of Precision Agriculture this represents an important asset. Only additional data related to Precision Agriculture would need to be compiled.
Research on Precision Agriculture is progressing in many countries aiming at making it a routine practice. In the mauritian context, research should concentrate on yield variations, spatial variability, variable rate applications supported by economic analysis. The best approach would be to constitute a working group involving resource persons of different disciplines to look into the various factors and issues that would influence Precision Agriculture. As the research progresses it will then be possible to provide answers to such questions as:
- Can spatial variability be managed to allow variable rate applications?
- What are the interacting factors that affect yield most on small areas?
- How precise variable rate inputs can be applied to the desired area?
- As a result of the effective management of variable rate inputs, can there be reduction of costs of inputs?
- What are the costs to be involved and how cost-effective can Precision Agriculture be?
- Will it involve other changes in management of fields?
- Will this method of farming be possible for the small planters’ community?
- In spite of success, what will be its rate of acceptance by the planting community?
Precision Agriculture should be a part of the action plan aiming at making the industry more competitive, productive and compliant with environmental regulations. Its associated technology is being continuously improved and as agricultural machines will soon be equipped with the appropriate tools it will be possible to assess the real potential of Precision Agriculture. On-going programmes of crop mechanization and the availability of agricultural information database management systems favour its introduction. Furthermore, Precision Agriculture offers the possibility for a real multidisciplinary approach towards increasing productivity and should be evaluated without delay.
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