Environmental Degradation and Dryland Agro-Technologies in Northwest China

Preface

Environmental Degradation and Dryland Agro-Technologies in Northwest China is a documentation of past and present research, training and extension experiences on the subject matter in the arid and semi-arid lands of Northwest China. Some of the issues addressed herein include: environmental degradation; conservation farming systems; water and nutrient management options; soil and water management training; soil erosion control; and soil fertility and crop productivity. These issues are expounded on both from the national (China) and Regional (Loess Plateau) perspectives.

The information provided herein was obtained through a review of all relevant literature and field consultations/discussions/ interactions with leading authorities (professors) at the Northwest Agricultural University, Northwest Institute of Soil and Water Conservation and Regional Academies of Agricultural Sciences (SAAS,GAAS,QAAF, and NAAF), local scientists, technicians and farmers in Northwest China. The facts and figures presented are based on their experiences of many years. Indeed, from the content, it is very evident that a lot of good research, training and extension work pertaining to many aspects of dryland agriculture have been done in Northwest China. Available agro-techniques within Northwest China are either traditional or newly developed through scientific research at various relevant Institutions. The development of appropriate and effective agro-techniques is done by Experimental Stations belonging to Universities and Institutions such as NWAU, NWISWC and Regional Academies of Agricultural Sciences such as SAAS, GAAS, NAAF and QAAF.

Soil and water management training, dissemination of research information and demonstration and extension of agro-techniques in Northwest China has been area based and specifically focused on the three major soil problems of severe soil erosion, low soil fertility and low soil moisture with a view to improving crop productivity within the Loess Plateau Region. Among the many agro-techniques that farmers have adopted in Northwest China are four that have significantly impacted on soil fertility and crop productivity. These four agro-techniques are: Use of rectangular fertilizer pits in balanced fertilization applications, Shaanxi Province; Water saving irrigation using underground waters wells (Shui Jiaos), Gansu Province and Ningxia Autonomous Region; Soil saving damlands (Gu di) in valley bottoms of small gullies, Northwest China; and Improved soil water storage by mixing nutrient rich red clay soil and light grey silty loam soils, Ningxia Autonomous Region.

Another environmental problem in Northwest China is that of severe wind erosion due to vegetation degradation. Vegetation degradation is attributed to overgrazing, deforestation for fuelwood and timber; and the changing cropping patterns from perennial to annual crops. These factors have contributed to the denudation and occurrence of gully erosion in the Loess Plateau Region.

Thus as population pressure increases and the land resources base continues to shrink due to degradation, Chinese farmers are increasingly becoming aware about the importance of protecting their environment and improving food production through better conservation farming practices. The pictoral illustrations of farming and other household income generating activities in Northwest China presented in this document serve to confirm this change in the attitudes of Chinese farmers.

This publication will benefit immensely all those research scientists and frontline extension workers associated with farmers and farming activities. There are lessons to be learnt and plausible remedial conservation measures to be adopted elsewhere from these experiences in Northwest China.

Prof. Elijah K. Biamah

Professor of Environmental and Water Systems Engineering, School of Engineering, University of Nairobi, Kenya.

Chapter One

1.Environmental Degradation and Resource Conservation in China

1.1Introduction

1.1.1Country Background

China is a country of both water scarcity and abundance because of the imbalance in the distribution, timing and location of precipitation. The total annual water resources available in China are 2,800 billion m³. With a population of 1.3 billion, the available water per capita water is less than 2,200 m³, one quarter the world average (Shan et al. 2000). Over 80% of the water resources are concentrated in the southeastern part of China where the arable area is only 35% of the country’s total arable area of 95 million ha. In contrast, the water resources in the northern parts of the country account for less than 20% of the total, whereas arable land accounts for 65% of the total (Xi-Ping Deng et al., 2006).

Of the total arable area, 50 million ha, or about 50 % of the total, is irrigated, mainly in the southeast where the water resources are more abundant. The water used in irrigation accounts for 80 % of the total water use in China, but as 80% of the food is produced on irrigated farmland, this water is important in feeding the large population (Yang et al. 1999). Dryland agriculture (crops and pastures) accounts for more than 70% of total farmland in northern and north-western China, including the vast rainfed areas to the north of the Qinling Mountains and Huaihe River. Twenty five million hectares are located in the Loess Plateau, while the North China Plain has 16 million hectares of arable land and produces about 20% of the nation’s food (Xi-Ping Deng et al., 2006).

With its large population, China cannot maintain food security without irrigation. In northern and northwestern China where natural rainfall does not match the needs of crops in both quantity and temporal distribution, supplementary irrigation is used to increase yields and provide the food needs of the nation. However, excessive-use of diverted river flows and groundwater has caused severe environmental problems. For example, since 1972 the Yellow River in northern China has dried up in the winter months for several years to the extent that water did not reach the sea and in an extreme drought year failed to reach the sea for 7.5 months (MWR, 2000). In the North China Plain where groundwater is the primary source of water for irrigation, the groundwater level has declined rapidly from about 10 m below the soil surface in the 1970s to about 30 m in 2001 (Zhang et al. 2003). Moreover, inefficient use of water is a notorious phenomenon in irrigation systems. It is estimated that in the North China Plain about half of the water is lost to leakage during transfer to farmers’ fields (Liu and He 1996). Of the water reaching the field, losses of water are also substantial. Flood irrigation is predominant and more efficient irrigation systems such as sprinklers and drip irrigation is negligible (Xi-Ping Deng et al., 2006).

China’s population will increase by 12 million people annually over next half century. To support this growing population, food production has to be based on improving water use efficiency and further expansion of irrigation. Given the severe shortage of water resources in North China, the expansion of irrigated land is expected to be limited. Therefore, increasing water use efficiency in both irrigated agriculture and promoting dryland farming through water conservation and efficient use of rainfall will play significant roles in maintaining food security (Xi-Ping Deng et al., 2006).

1.1.2Land Cover and Population

The People’s Republic of China covers an area of 9.6 million km² of which two thirds consists of hilly and mountainous areas. These hilly and mountainous areas account for 47.8 percent of the country’s cultivated land, 40 per cent of its grain yield and most of the country’s forests, orchards and medicinal herbs production. The wide range of natural resources and climatic conditions present in these hilly and mountainous areas makes them suitable for both crop and livestock production (Gao Bowen et al., 1989).

Figure 1.1. Location map of China showing major cities and rivers (Biamah, 1994; 1996).

The population of China as of 1994 was more than 1.2 billion, 22% of the world’s population. This extremely high population has overstretched the limited available land resources and hence resulted in rather low availability of land per capita. China has only 7% (100 million ha) of the world’s total cultivated area and as a result of the very high demographic pressure, less than 0.1 ha of land is available per person. Some 33 million ha of land under cultivation is sloping land (hilly and mountainous areas). Given the very low land per capita, sufficient food production can be sustained through effective prevention and control of soil erosion, rational land use and conservation and increased land productivity (Shi Liren et al., 1990).

1.1.3Climate and Land Use

The climate varies widely and includes: tropical, sub-tropical, temperate, temperate-frigid zones and humid, sub-humid, arid and semi arid zones. Dominated by a continental monsoon climate, precipitation in north China is generally low and concentrated in a few months for the year. Annual rainfall gradually decreases from about 600 mm in the North China plain to 440 mm in the Loess Plateau (between Xi’an, Taiyuan, Yinchuan and Lanzhou in central China) to less than 300 mm in the northwest of China (Fig. 1.2). About 70 % of the annual precipitation is in the form of storms in the four months of June, July, August and September (see Fig. 1.3) (Xi-Ping Deng et al., 2006).