Precision Agriculture for Sustainability and Environmental Protection

Margaret Oliver, Thomas Bishop, Ben Marchant, Margaret Oliver, Thomas Bishop, Ben Marchant

• Publisher: Routledge
• Year: 2013
• ISBN:
  9781136468247
• Edition: 1
• Topic: Ciencias biológicas
• Subtopic: Ecología

Precision agriculture (PA) involves the application of technologies and agronomic principles to manage spatial and temporal variation associated with all aspects of agricultural production in order to improve crop performance and environmental quality. The focus of this book is to introduce a non-specialist audience to the the role of PA in food security, environmental protection, and sustainable use of natural resources, as well as its economic benefits.

The technologies covered include yield monitors and remote sensing, and the key agronomic principles addressed are the optimal delivery of fertilizers, water and pesticides to crops only when and where these are required. As a result, it is shown that both food production and resource efficiency can be maximized, without waste or damage to the environment, such as can occur from excessive fertilizer or pesticide applications. The authors of necessity describe some technicalities about PA, but the overall aim is to introduce readers who are unfamiliar with PA to this very broad subject and to demonstrate the potential impact of PA on the environment and economy.

Chapter 3 of this book is freely available as a downloadable Open Access PDF at http://www.taylorfrancis.com under a Creative Commons Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND) 3.0 license.

Part 1

Precision agriculture and food security

1 An overview of precision agriculture

Margaret A. Oliver

Introduction

The world population is growing and is forecast to reach around 9 billion by 2050 and more than 10 billion by 2100 according to a United Nations press release of May 2011. The competition for land by a myriad of users means that land available for agriculture is likely to decrease despite technological improvements that might extend the boundaries of land that can support agriculture. Therefore, with the population continuing to increase farmers must try to produce more from less land while at the same time protecting the environment and ensuring food security. Recent research has suggested that the global demand for cereals will increase by 75 per cent between 2000 and 2050 (IAASTD, 2008). A larger world population increases the challenges we face to manage land in such a way so as to sustain it and the wider environment in a healthy condition for future generations. Much of the progress in increasing yields to meet the growing population and also higher standards of living in many parts of the world in the middle part of the twentieth century stemmed from improvements in crop varieties bred to give larger yields and produce less waste, for example straw from cereals (Gale and Youssefian, 1985).

In 2009 38 per cent of the Earth’s land area was agricultural (land occupied by arable crops, under permanent crops and permanent pastures) (FAOSTAT, 2011), and of this less than a third is used for arable crops (11 per cent of the world’s land area). The arable land provides us not only with food, but also with fibre for clothing, household and industrial goods, and fuel. The FAO (2010) estimates that >75 per cent of the Earth’s land area is unsuitable for rainfed agriculture and that only 3.5 per cent is suitable for agriculture without any physical constraints. In developed countries land is being withdrawn from cultivation for building, manufacturing industry, roads and so on, and consequently agriculture must be intensified to maintain production. In many developing countries there is scope to bring new land into production with technological advances and new crop varieties. However, this is not true for parts of Asia, where almost all cultivable land is already in use. Where it is possible to extend the cultivable area, such as in Brazil, this is at the expense of native forest, which has an important role in the global ecosystem. Intensification of agriculture and changes in land use can have serious consequences for the environment by increasing soil erosion, desertification, salinization and flooding, all of which are increasing in many parts of the world. I discuss these issues briefly later in this chapter.

Crops of all kinds remove nutrients from the soil, but not evenly – their effects vary from place to place. The nutrients removed need to be replaced by the application of fertilizers and or manures to the soil. Crop yields increased substantially in the second half of the twentieth century: between 1961 and 1999 global production of the major cereal crops doubled (Wiebe and Gollehon, 2006). This increase has been mainly in developed countries and without additional land; it is the result of several factors such as improved crop varieties, greater use of fertilizers, herbicides and pesticides, increased use of irrigation, improved understanding of the processes involved in crop production and technological advances. The latter have enabled a better understanding of processes by monitoring crop development, weeds and pests. Research and plant breeding have led to genetic improvement of crops, which has probably contributed most to the increase in crop yields of the last half century (Eggli, 2008). Plant breeding has modified plants so that the harvest index (HI), that is the ratio of harvested biomass to the total crop weight, is greater. A good example of plant breeding to achieve a larger HI was the breeding of new short-stemmed cereal varieties in the 1960s in which the amount of straw was greatly reduced and more energy was used for the grain (Gale and Youssefian, 1985). Improvements from plant breeding have also changed the crop-growing seasons, improved the use of nitrogen and resistance to certain diseases, contributed to better storage and transport and so on. The disadvantages, however, are that some of the newer cultivars require more fertilizer, pesticides and water, and these increase input costs to the farmer and create problems for the environment. Water is becoming increasingly scarce because of the many competing uses for it. Agriculture consumes large volumes of water for irrigation, and as the shortages and costs of water increase, irrigation must be managed more carefully (see Chapter 10). Genetic engineering of crops is also playing a major part in increasing yields and resistance to diseases and other stresses (Chivian and Bernstein, 2008).

The intensification of agriculture to produce larger yields and poor agricultural management have tended to degrade the environment resulting in losses of soil and pesticides from fields. In addition, over-application of nitrogen and phosphorus has led to losses of these nutrients into surface and groundwaters and also on to land where they are not required. This has made us aware of a need to manage land in a sustainable way such that farmers can provide the food and other raw materials that we require, but at the same time ensure that the land remains in a condition suitable to continue farming it for future generations. There is a general consensus that farmers need to do their job so that we can all eat and clothe ourselves, but at the same time farmers need to maintain the soil and water in a healthy condition. This means maintaining a good soil structure, organic matter and nutrient status, pH and biodiversity, and limiting the losses of soil itself, nitrogen, phosphorus and pesticides into the environment elsewhere. Therefore, farmers must understand how their actions might lead to soil erosion and compaction, and losses of plant nutrients and other agrochemicals from their land by surface, vertical and lateral flows so as to sustain the quality of the soil and water (Hatfield, 2000). Although organic farming achieves some of these goals, it is not without drawbacks, and it cannot feed a growing world population. More promising solutions are the return to a more integrated approach to farming (Marsh, 2000; Tinker, 2000) and precision agriculture (PA) or site-specific management (SSM). Integrated farming aims to minimize inputs to achieve good yields, and furthermore to apply them only when necessary (Spedding, 2003). The basis of this approach is to integrate beneficial natural processes into modern farming practices and to minimize pollution (Tinker, 2000). Crop rotation is essential in an integrated system; it ensures a better nutrient balance than with monoculture and also some resistance to diseases. The other solution, PA, is to some extent linked with the intentions of the integrated approach because it aims to apply inputs (fertilizers, seeds, pesticides, water and so on) at the rate at which they are required rather than uniformly. The concepts of PA and sustainability are inextricably linked (Bongiovanni and Lowenberg-DeBoer, 2004). With uniform management a single application rate of fertilizers, seeds, pesticides, lime, water, etc. is used for the entire field, with the result that some parts are likely to receive too much and others too little. This could lead to increased pollution of ground- and surface waters, and greater pressure from weeds, pests or diseases (Froment et al., 1995). Precision agriculture in arable farming is the subject of this book, and in the next section I shall describe the background to it and its many components

Precision agriculture

In looking for specific definitions of precision agriculture, I came across this statement by Rick Heard (2006): ‘If you ask 10 people what is their definition of precision agriculture you would probably get that many different answers in return.’ The term ‘precision agriculture’ appears to have been used first in 1990 as the title of a workshop held in Great Falls, Montana, sponsored by Montana State University. Before this, the terms ‘site-specific crop management’ or ‘site-specific agriculture’ were used. The first two international conferences on what we now regard as ‘precision agriculture’ referred to site-specific management in the title, but by the third conference in 1996 the term ‘precision agriculture’ was used. By the mid 1990s, ‘precision agriculture’ became the preferred term for what we know as modern precision agriculture, a concept that first emerged in the USA in the 1980s.

There is a tendency to consider PA as a modern concept related to agricultural systems in parts of the developed world; however, it is not (see Chapter 3). Precision agriculture has been practised by farmers since the early days of agriculture. Farmers divided their land into smaller areas, the characteristics of which they knew well, and they grew crops where the conditions were most suitable. The early farmers managed their land precisely to ensure that they produced enough food for their families as do subsistence farmers of today; it was a matter of life or death. In Britain there is evidence of small fields that were relatively uniform, each of which could be managed as a unit, and that have since been joined to form much larger fields that are consequently more variable (see Frogbrook et al., 2002, for an example). Modern PA, however, may help both farmers of the developed world with large farms and farmers in Africa and Asia with smallholdings to achieve greater yields and to manage their land better (McBratney et al., 2005).

The National Research Council of the USA (1997, p. 17) gave a clear definition of modern PA as follows: ‘Precision agriculture is a management strategy that uses information technologies to bring data from multiple sources to bear on decisions associated with crop production.’ It suggested that PA has three components: obtaining data at an appropriate scale, interpretation and analyses of the data, and implementation of a management response at an appropriate scale and time. The intensity and resolution of some of the spatial information involved in PA mean that the revolution to modern PA is essentially about a change in the scale of operation and management. In addition, individuals, governments, non-governmental organizations (NGOs) and land managers have become increasingly aware of the effects of land use on environmental systems or ecosystems. The ability to determine within-field variation and to manage it to improve the economy of agricultural activities and to mitigate their effects on the environment is central to the concept of PA. The data used in PA are often at a fine spatial resolution, for example data from yield monitors, proximal sensor data, remotely sensed data, digital elevation models and so on. There are also many data on soil and crop properties at much coarser scales.

At the heart of PA is the fact that the soil, weather and microclimate vary both spatially and temporally. As there is no simple definition of modern precision agriculture, I shall give its aims. The need for precision agriculture, both old and new, arises because soil, drainage, insolation and topography are rarely uniform over farms or within fields. Heterogeneity is a feature of land (and of the broader environment), so one should not expect to manage the land uniformly. Precision agriculture aims to apply nutrients, soil ameliorants such as lime, water, pesticides and herbicides only where and when they are needed. The purpose is to optimize agricultural production, that is to improve productivity, crop quality and food safety, to improve farm economy and food traceability (Peets et al., 2009) and at the same time reduce undesirable impacts on the environment and improve sustainability. This can be achieved by varying inputs and types of tillage across fields. Farmers in many parts of the world are required by law to manage their land so that groundwater is not polluted. Precision agriculture can help to fine-tune existing management to reduce the leaching of N, for example (McBratney et al., 2005). Precise management entails an understanding of crop requirements for profitable yield, how efficiently the crop uses nutrients, how much the soil can provide and the temporal patterns of nutrient uptake. This requires soil information, but there is also much ongoing research on the use of the plant to indicate its nutrient status and requirements. For example, multispectral sensors such as Quickbird (Bausch and Khosla, 2010) and hand-held sensors such as Greenseeker (Inman et al., 2007) can provide information that will help farmers to optimize N fertilizer inputs. Most pesticides are used for weed control, and with a better understanding of weed dynamics their use could be much better controlled (see Chapter 9). Variation in time and space must be characterized properly (see Chapter 7), and this is inextricably linked with the technological advancements I describe below.

History of modern precision agriculture

Spatial variation in the soil and the environment more generally has been known about since mankind started to manage the land. The soil is remarkably variable, as a result of variation in the soil’s parent material, microclimate, drainage, landscape, previous uses and so on. Consequently crop development, yields, quality, pests, weeds and diseases vary spatially and temporally. It is this variation that PA aims to understand and manage in a local or site-specific way, essentially the variation within fields.

The work of Gilbert and Lawes in the latter part of the nineteenth century and their successors at Rothamsted Research, Harpenden, UK, could also be considered as precision agriculture because they wanted to assess the benefits of various combinations and amounts of crop nutrients and also of different crop varieties. The aim was to increase yields, something which applications of cheap fertilizers could achieve, and there were no concerns about their impact on the environment until the last quarter of the twentieth century. Until the 1980s precise or site-specific management was at the farm level, and the management unit was the farm. The soil of any one field was sampled to determine the mean value of crop nutrients and pH, and these were amended uniformly over the field. Similarly, crop yield was based on the total weight taken from the field.

In the mid 1970s to early 1980s farmers became increasingly aware of the potential benefits of better record-keeping and understanding of soil and crop input requirements (Robert, 1999). Robert also described the outcome of a study in the late 1970s by CENEX (Farmers Union Central Exchange, Inc. in the USA) and the Control Data Corporation that showed that farmers were beginning to realize ...