| Overview Tim R. McVicar |
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Section 1 — Water balance modelling Section 2 — Soil–environment impacts Section 3 — Spatial information systems |
The chapters in this book summarise the results of a collaborative project between Chinese and Australian scientists to improve agricultural water uwse efficiency (WUE) and thereby increase agricultural productivity and sustainability in China and Australia. The project was externally funded by the Australian Centre for International Agricultural Research (ACIAR), with significant in-kind contributions from both the Chinese Academy of Science (CAS) and Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO).
The study focused on three main regions:
Figures 1 and 2 show the general locations of these regions, all of which require both water and soil conservation measures at farm and regional scales. In all three regions, using the available water resources more efficiently and preventing increases in soil degradation are essential to ensure long-term sustainability of agricultural productivity.
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Figure 1 Locations of the North China Plain and the Loess Plateau. |
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Figure 2. Location of the Murray–Darling Basin and main study sites discussed in the book. The insert shows the location of the MDB within Australia. NDTI = normalised difference temperature index |
The four broad aims of the project were to:
The project team focused on these four key issues, which are covered in the four sections of this volume.
Water balance modelling. The team working on this issue developed a model (WAVES) that could be used to estimate crop yield and to develop scenarios of water saving, recharge and waterlogging in different situations. The first step was to review the literature on water-saving agriculture and regional water balance, and to collate field data on climate, soil, hydrology and vegetation. The team then modified the plant growth component of the model in order to predict crop yield and develop indicators of plant stress that could be measured in the field. The model was subsequently used to develop water use efficiency measures. Chapters 1–7 deal with water balance modelling.
Soil–environment impacts. To study this issue, the project scientists developed soil impact models, by linking soil process understanding with both the water balance and the underlying regolith. In Australia, the focus was on salinity, waterlogging and sodicity, as these processes develop down a toposequence. On the NCP, the same issues are a major concern; the soil chemical properties change due to interactions with transient perched watertables. On the Loess Plateau, the focus was on evaluating indicators of erosion and nutrient levels. Chapters 8–15 deal with soil-environment impacts.
Spatial information systems. The team working on this issue collated the information from water balance modelling and soil environment impacts, compiled maps based on the data and developed methods to interpolate from sites to the regional scale. The first step was to review relevant research and assess what further data were needed for the project. The team then collected the additional information required, tested its integrity, used it to develop a generic GIS framework applicable to each of the study areas in China and Australia, and established methods for upscaling the data. Finally, GIS modelling techniques were used to assess WUE and soil degradation at regional scales. Chapters 16–23 deal with information systems.
Technology transfer. The first step in transferring technology was to establish the priority issues that needed to be assessed in the two countries. The team then developed extension packages that could be used by existing extension networks, integrated information common to both China and Australia, and ensured that relevant skills were transferred between scientists. An important focus of this work was the use of indicators to help farmers identify problems and to plan better options for land use. Chapters 24–29 deal with technology transfer. For farmers, manuals were developed; for policy makers (at local, regional and national levels), a series of indicators were established.
In Chapter 1, Lu Zhang et al. provide an introduction to water balance modelling suitable for most agricultural professionals. The authors discuss the concepts of water balance modelling, the matching of complex models with readily available data and the integrated WAVES model. In Chapter 2, Ming’an Shao et al. demonstrate the field-scale water balance for winter wheat on the Loess Plateau. In the following chapter, Xiying Zhang links water balance to irrigation scheduling on the NCP, giving practical recommendations on the number of irrigation events needed during the winter wheat growing season. Chapter 4 discusses the range of measures that can be used to define WUE in China and Australia, ranging from leaf-level biogeochemical analysis to landscape systems approaches. Cox and Pitman, in Chapter 5, measure and model the development of perched watertables down a toposequence (upper, mid- and toe-slopes) for three commonly grown pastures (cocksfoot, phalaris and lucerne) in southern Australia. They conclude that favourable changes to the water balance will occur if farmers plant lucerne on the upper and mid-slopes, and phalaris on the toe-slopes, rather than planting cocksfoot. Shaozhong Kang et al. simulate WUE for winter wheat in Chapter 6 and simulate the effects of limiting irrigation for winter wheat in Chapter 7. The authors found that using WAVES to predict WUE based on simulated above-ground production is much more accurate than using the model to simulate transpiration (Chapter 6); and that optimal scheduling of irrigation can be used to save water, while maintaining high agricultural production, hence increasing WUE (Chapter 7).
In the first chapter of this section (Chapter 8), Fitzpatrick introduces the physical processes of soil salinity (primary, secondary, seepage and transient), sodicity, acidity and erosion (both wind and water). The author introduces most of the processes discussed in detail in the remaining chapters of the section. In Chapter 9, Fitzpatrick and Merry develop a soil–regolith and soil–water landscape model that can be used along toposequences in southern Australia to describe and predict degradation processes; the model allows landholders to better understand how various land-use options can help to prevent degradation. In Chapter 10, Liu Guobin et al. assess the ecosystem rehabilitation of a small catchment (8.3 km2) on the Loess Plateau from 1938 to 1997, using a weighted indicator method. Merry et al. (Chapter 11) discuss the GIS-based prediction of soil profile salinity and alkalinity for 80 km2 of the Adelaide Hills. Results agreed well with conventional soil mapping. In Chapter 12, Chunsheng Hu evaluates the soil fertility from 1949 to 1998 for Luancheng County on the NCP. Conclusions for sustainable management are drawn, highlighting the need for the rational use of both inorganic and organic fertiliser within the bounds determined by understanding of the biogeochemical cycling. Renzhao Mao et al. (Chapter 13) report variations in the chemical properties of saline soils. Techniques include using ratios of the principal anions and X-ray diffraction, linked with remotely sensed data, to provide practical guidelines for managing saline and sodic soils, again on the NCP. In Chapter 14, Yinli Liang et al. describe the dual effects of soil moisture and soil nutrients, and their interactions, on crop productivity for different growing stages of winter wheat and summer corn on the Loess Plateau. The authors conclude that when crop yields are improved by increasing soil fertility, water management becomes critical. In Chapter 15, Cox describes the results of monitoring the concentrations and total loads of 12 elements from 1994 to 1996 for the Keynes catchment in the Adelaide Hills. Cox draws conclusions on the design of drainage systems for discharge areas to take into account the characteristics of sediment runoff (including concentrations, total loads and particle size distributions).
This section of the book looks at the use of spatial information technologies to apply measures of water balance and soil processes to larger areas than those considered in the previous two sections. McVicar et al. (Chapter 16) introduce temporal-geographic information system (TGIS) approaches, developing the ‘data construct’ concept as a means to assess the suitability of data for use in regional agricultural sustainability monitoring. They also provide a beginners guide to the physics of remotely sensed data. In Chapter 17, Cox and Davies compare point and catchment-scale measurements of soil saturation duration in the Mount Lofty Ranges. They conclude that, for dry years, soils on upper slopes will remain wet for longer than will soils on lower slopes, due to the processes governing soil–water interactions. In Chapter 18, McVicar et al. report the results of monitoring regional WUE for 60,000 km2 of the NCP from 1984 to 1996, for both the winter wheat and summer corn growing seasons. Using readily available data they show that average winter wheat WUE increased from 7.0 kg/ha/mm in 1984 to 14.3 kg/ha/mm in 1996. In Chapter 19, McVicar and Jupp develop a method for mapping moisture availability, using the example of the 1.1 million km2 MDB. The method relies on using the high spatial density of remotely sensed data as the backbone of the spatial interpolation in a ‘calculate-then-interpolate’ framework. Again working in the MDB, Bradford and Lu Zhang (Chapter 20) extend an annual water balance model to assess the impact of land-cover changes on water yields. They assess pre-European, current and potential conditions (if large tracts of the MDB are replanted, as is currently being considered), and show the changes on a catchment basis. They conclude that replanting may reduce the water yields by up to 40 mm/year in some of the high-rainfall catchments in the MDB. In Chapter 21, Davies et al. upscale assessments of land degradation from points to 80 km2 of the Adelaide Hills, extending detailed process knowledge from toposequences to the larger area using a weighted overlay spatial modelling approach. Results can be used to target farm-management action for the larger area. Yang Qinke et al. (Chapter 22) use spatial modelling techniques to predict regional soil erosion from the Loess Plateau. The methodology relies on readily available data and was applied to 15,000 km2, illustrating that regional soil erosion can be assessed rapidly for national and provincial policy. In Chapter 23, Yang Qinke et al. apply a 15-variable GIS-based model to assess cropland taxation rates. In China, farmers are taxed at different rates depending on the quality of the land they farm; thus, being able to update changes is important to the micro (farmer) and macro (China) economies. The method developed could be extended to larger areas.
In the introductory chapter for this section (Chapter 24), Walker introduces the concept, use and application of environmental indicators in assessing sustainable agriculture. The need for indicators that are well suited to different scales (national, regional/catchment and farm/site) is addressed, as is the linkage between issue, sustainability indicators and scale. The indicator method is the backbone for all technology transfer performed within the project. In Chapter 25, Walker et al. develop and test indicators of salinity for the Upper Murrumbidgee catchment. The indicators were developed using readily available regional databases in a GIS environment and results showed high agreement for selected biological and physical measures within the stream network. Reuter et al. (Chapter 26) use indicator methods to assess regional agricultural sustainability for three case studies and suggest how the methodology could be applied to the northern grains region of Australia. They conclude that available regional databases, possibly used within a decision-support package, provide the most suitable form of extension into the region. However, the authors acknowledge that the approach used will have to be modulated by scale and issue. In Chapter 27, Li Rui et al. discuss the use of experimental and demonstration areas to assist in technology transfer of ecosystem rehabilitation for the entire Loess Plateau. They discuss both economic and ecological impacts of the three identified stages of ecosystem rehabilitation. On the NCP, Xiaojing Liu et al. (Chapter 28) report how scientific knowledge has been turned into management action by reclaiming saline land in Nanpi County. The authors have developed and implemented a communication plan for each defined user group to ensure that technology transfer is effective and comprehensive. The methods can be applied to other surrounding counties experiencing saline soil development for the eastern portion of the NCP. Finally, Fitzpatrick et al. (Chapter 29) discuss ways to develop manuals suitable for operational use in the daily management of farms in Australia and China. Methods take into account the educational level of the end-users and provide highly visual techniques that are easily implemented at the farm scale. Examples are drawn from both southern Australia and China.
Here we provide general introductions to each of the three regions studied in this project.
The project work was carried out in the northern part of the China, in the NCP and Loess Plateau regions. The NCP is one of the great plains of China, comprising the alluvial plains of the Yellow, Huai and Hai Rivers. The Loess Plateau is one of the four great plateaus of China. These two regions include some of China’s most important agricultural land.
North China Plain
Figure 3 shows the main geographical features of the NCP, which includes parts of five provinces (Hebei, Henan, Shandong, Anhui and Jiangsu) and two cities (Beijing and Tianjin). It is a low-lying area of 303,585 km2, supporting a population of over 300 million.
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Figure 3. The main locations on the North China Plain. The plain is enclosed by the thick black line in the main map and is shaded black in the inset map of China. The Hebei Plain study area (Chapter 18) is shaded grey. |
The NCP comprises the alluvial plains of the Yellow, Huai and Hai Rivers. The main soil type is a loam of aeolian origin, which has been relocated by the rivers over geological time. It is bounded in the west by the Taihang Mountains; in the east by the Bohai and Yellow Seas, and the Tai Mountains; in the north by the Yanshan Mountains; and in the south by the Huai River.
Annual precipitation ranges from 550 to 650 mm, of which 50–75% falls between July and September. As the rainfall is low and variable, agricultural productivity is low without irrigation. With no reliable surface water for irrigation, groundwater is used, which is causing groundwater levels in the region to fall. The average water resource per capita and per area is about 14% of the average for China and the amount of groundwater available for irrigation is decreasing.
The NCP is one of the most important agricultural regions of China, accounting for up to 40% of national production for many of the major cereal crops and about 20% of the national food production. The land cover is almost exclusively ‘grass crops’, with an annual double-cropping system based on winter wheat and summer corn, both named after the season in which they are planted. Other summer crops include millet, soybeans, sorghum, peanuts, cotton and several other nongrain crops. Some rice is grown in the southern portion of the NCP, in Anhui and Jiangsu Provinces. Small plots of intensively managed market garden vegetables are grown throughout the year. Chapters 3, 12, 13, 18 and 28 of this volume refer particularly to the NCP.
Loess Plateau
The Loess Plateau lies in the centre of China, in the middle reaches of the Yellow River. It borders the Riyue Mountains to the west and the Taihang Mountains to the east; and extends from Qinling Mountains in the south to the Yin shan Mountains in the north. Figure 4 shows the main geographical features of the Loess Plateau.
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Figure 4. The main locations on the Loess Plateau. |
The Loess Plateau is the second of the three grand relief landform terraces in China. Morphologically, it consists of loess hills, sand-loess hills and loess tableland, with many gullies. The plateau has three main regions.
The plateau has a long history of cultivation, but natural and social factors have resulted in severe land-use problems, in particular, a low proportion of vegetation cover and severe soil erosion and desertification. Currently, some areas of the Loess Plateau that are most actively eroding are being replanted with perennial vegetation, grasses, shrubs or trees, depending on the available water resources. These replanting schemes acknowledge that if the environment is to be sustainably managed, those deriving livelihoods from the area must have adequate economic returns. The scheme has not only improved the regional economy and farming practice on the Loess Plateau, but also promoted rehabilitation of the regional ecosystem. Some 150,000 km2 of eroded land has been controlled by various conservation measures. The flow of sediments into the Yellow River has been reduced by about 300 million tonnes/year.
Winter wheat and summer corn are the main crops. Average annual rainfall ranges from 300 to 600 mm, with over 60% occurring from July to September. As rainfall is low and variable, water is the most important factor limiting agricultural production in the region. Crops are irrigated with water pumped from the Yellow River or from collected rainfall. However, the amount of available water in the Yellow River has declined rapidly in recent years, so there is an urgent need to reduce irrigation in order to sustain agriculture in this area. The studies described in this book were carried out mainly in the highlands of the Loess Plateau and in Shaanxi Province in the south. Chapters 2, 6, 7, 10, 14, 22, 23 and 27 of this volume refer particularly to the Loess Plateau.
Most of the Australian research discussed in this book was carried out in the MDB, which is one of Australia’s most important and degraded water catchments. Much of the soils research is focused within the Mount Lofty Ranges. The catchments in the eastern portion of the Mount Lofty Ranges flow eastward, joining the Murray River; catchments in the west contribute directly to Adelaide’s water supplies.
Murray–Darling Basin
The MDB covers more than 1 million km2 and is one of Australia’s main regions of dryland and irrigated agricultural production. Extensive clearing of natural vegetation and intensive irrigation have greatly altered the water balance, leading to a range of land degradation problems, including waterlogging and salinity caused by rising groundwater tables. Figure 2 shows the main geographical locations of the MDB. Chapters 19 and 20 of this volume deal with management issues relevant to the entire MDB. Chapters 25 and 26 discuss specific areas of the MDB, including the Upper Murrumbidgee catchment, which covers 12,000 km2 in the area around the national capital, Canberra.
Mount Lofty Ranges
Figure 5 shows the main locations in the Mount Lofty Ranges, which cover about 5,000 km2 and lie east of Adelaide in South Australia. The climate is temperate, with cool, wet winters and hot, dry summers. Annual rainfall may be more or less than 500 mm, depending on the precise location. The region includes prime agricultural (crops, meat, wool, dairy) and horticultural lands, and is a major catchment zone for the regional water supply. Changes in the water balance components have led to severe changes in the physical and chemical characteristics of the duplex soils of the region, and these have resulted in decreased agricultural production. In particular, the mobilisation and deposition of iron, sulfur and clay in these soils pose serious threats of land degradation and water quality. Farmers and researchers are concerned about the potential salinity problem in the area: although only a small area is affected at present, land degradation is worsening and saline scalds are increasing.
Chapters 5, 9, 11, 15, 17 and 21 describe characteristics of soil and water in the Mount Lofty Ranges. Chapters 26 and 29 describe how indicators can be used to improve land management.
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Figure 5. The main locations in the Mount Lofty Ranges |
Specific outputs resulting from the project are:
A major benefit of the project has been the development of an integrated, holistic understanding of the landscape developed by the project staff and those to whom we have communicated our results. This integrated understanding is discussed in the Preamble and was the basis for the project attracting funding. By working together on the project, scientists from a variety of disciplines and technologies have developed a greater understanding of one another’s areas of specialisation.
The large number of chapters (11 out of 29) with coauthors from both countries illustrates the high degree of cross-fertilisation of ideas and techniques between the project staff. The ability of the Chinese members of the project team to report their findings in English is a notable achievement. If the reverse were to be the case (Australian scientists reporting findings in Chinese) the quality of the book would be much lower.
We expect that the results of this project will help to refine agricultural practices of the regions studied. Specifically, on the NCP, plot-scale research has shown how water can be used more efficiently, while at the regional scale a method has been developed to monitor such improvements. On the Loess Plateau, increases in WUE and reduced erosion potential have been studied at the plot scale and results have been scaled to larger areas that have impacted on regional policy makers. Within Australia, soil degradation has been scaled from soil-pits to regions via toposequences, with an understanding of how hill-slope hydrology controls variability, and guidelines have been developed at the farm scale. Additionally, some research has directly tackled ‘big picture’ questions, and the impact of these will be seen in refinement of information systems supporting policies related to regional agricultural management (e.g. climate variability, specifically drought). This research will also be useful in developing guidelines for replanting tracts of Australia to help in restoring the hydrologic balance, for regional salinity control.
On a different tack, the entire project team, especially the editorial team, would like to thank Dr Hilary Cadman and Sue Mathews from Biotext for the long hours and effort they have put into this publication, which have improved its quality enormously.
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