The livestock manure was piled up without any management at D1 and D2 in Fig. 1a until it was transported for treatment. Three agro-livestock farming areas were additionally chosen in South Korea to validate the suggested hydrochemical index in a similar condition with pervasive agricultural contamination and feedlots and livestock mainly consisting of cows. The bedrock units in the sites A , B and C are Precambrian biotite gneiss, Jurassic biotite granite, and Cretaceous conglomerate and shale, respectively , which were covered with colluvium or alluvium similar to the study area with weathering products overlying silicate bedrock . The study area and the three agro-livestock farming areas A to C have a temperate climate with four distinct seasons and are influenced by the East Asian monsoon. The average annual rainfall for the past 30 years in the study area and the sites A to C were 1,286 mm, 1,223 mm, 1,371 mm and 1,349 mm, of which 67%, 66%, 64% and 67% occurred from June to September, respectively . In the study year of 2013, the annual rainfall of the study area and the sites A to C were 1,019 mm, 1,092 mm, 1,062 mm and 1,236 mm with 57%, 51%, 62% and 56% of the annual rainfall occurring from June to September, respectively . Food security is a core concern of the United Nations from the Millennium Development Goals to the Sustainable Development Goals . Population growth, supply–demand imbalances, hunger and poverty have always been long term challenges to food security and sustainable development . According to the United Nations , the global population is projected to rise to 9.7 billion in 2050, with a slow rise to 10.9 billion by the end of the century. This would cause food demand to increase by nearly 70% globally in 2050 . Between 720 million and 811 million people worldwide were hungry in 2020, and 9.9% of the population were undernourished .
In addition, as global climate change intensifies and affects plant diversity , drought and extreme weather events have a greater impact on traditional agriculture, hydroponic fodder system threatening agricultural production in large regions of the world . Cultivated land is the material basis for agricultural production which acts as an important carrier of food security and sustainable development by serving various functions, including food supply, environmental regulation, and ecological services . Cultivated land use is closely related to agricultural development, social stability, and ecological security, which directly affects global environmental change and the sustainable development of regional societies and economies . Driven by food demand and agricultural modernization, cultivated land use has been became more intensive around the world. Although it helps to increase food production, but often associated with the use of a large number of agricultural chemicals and waste, and the increase of agricultural water. Intensive use of cultivated land is now generally recognized to be unsustainable and harmful to the environment and caused a potential human health problem . Under the circumstances of increased demand for food and its byproducts, limited potential of new cultivated land, and increased ecological constraints, it is necessary to produce more sustainable products from existing cultivated land and with lower environmental costs, to meet future food demand, protect natural land, and increase services of the ecosystems . Sustainable intensification has been widely discussed as an effective way to coordinate the demand for land products and functions, protect the ecological environment, and reduce marginal land development . Thus, the sustainable intensification of cultivated land use has become an inevitable requirement to resolve the contradiction between increasing food demand and resource and environmental constraints, improve the service value of cultivated land ecosystems, and realize the transformation of regional cultivated land use according to local conditions . Cultivated land use is also the sum of economic, social and ecological relations formed between man and land in the process of agricultural production and development. In the traditional agricultural countries represented by China, whose main agricultural management form is still family management by small farming households.
Farming households are the most basic micro-socioeconomic subjects and independent decision-making units in cultivated land use. They are at the core of the contradictions among population, economy, resources, and the environment . Therefore, as the largest group of cultivated land use in China, farming households’ behavior and activities directly affect the direction of cultivated land use transformation. Rapid progress in urbanization, industrialization and agricultural modernization, rural social structure and economic form is producing transformation and reconstruction. It directly affects the adjustment of agricultural structure, occupational differentiation of farmers, large-scale operation and technological innovation, and finally reflects on the livelihood of farming households, which makes the farming households’ livelihood types gradually show the characteristics of diversity . Consequently, the farming households’ livelihood transition mainly manifested as the fundamental transformation of the occupation or industry that they depend on for survival and life, as well as the evolution of their dependence on agriculture and cultivated land. To be specific, it directly expressed as the gradual transition of farming households’ livelihood types and the increases in the diversification and non-agricultural degree of livelihoods.With more and more support and promotion of SI, a large number of theoretical and empirical studies have been carried out . Targeted SI researches based on land use perspective need to be further enriched and deepened . As the important land for agricultural production and food security, cultivated land should be the focus of SI. As the SICLU becomes the requirement of coordinating the contradiction between growing food demand and resource and environmental constraints . Non-agricultural and diversified livelihoods have become the inevitable trend of farming households’ livelihood transition at present. These are all scientific questions that need further exploration: How to define the concept and connotations of SICLU? How to carry out quantitative analysis and evaluation? How to form a scientific understanding of SICLU from the perspective of farming households? What enlightenment does it bring to the transformation of cultivated land use and protection? Therefore, 359 questionnaires of farming households in the Qufu County of the Shandong Province, China were used as research samples to: 1) clarify the concept and connotations of SICLU; 2) establish a SICLU evaluation system by means of emergy analysis; 3) evaluate the SICLU level of the sample farming households; 4) and explore the differences between farming households with different livelihood types. This study aimed to provide a reference for understanding the process law of SICLU on a microscale and guide various farming households to optimize the mode of cultivated land use. The earliest SI research dates back to a 1983 workshop. It reported on sustainable intensification of tidal swamp lands in Indonesia by the Research Group on Agroecosystems . But its definition and principles were not clear at the time.
The generally accepted definition of SI was formally proposed in the 1990s . It was originally a cooperative project, for the purpose of establishing an adaptive agricultural system, increasing grain production, supporting livelihoods of the rural poor, and paying attention to the sustainability of the environment, society and economy. Over the past decade, SI has become increasingly prevalent . It also has been promoted as a necessary method for food production in the 21st century by the FAO, CGIAR, and other organizations . SI aims to use existing land intensively to produce a greater number of more sustainable products at a lower environmental cost. As a relatively open concept, SI does not require the predetermination of technology, composition, or design. It is also not limited to the specific development path or method . The goals of SI are to improve the ecological environment, increase economic output and social benefit, and create resource-efficient agriculture models with significantly better environmental performance than traditional intensive agriculture . Related studies have evaluated SI from various scales, ranging from global, country, region, farm, to individual households and perspectives by employing substance flow analyses, data envelopment analyses, carbon balances, and emergy analyses . According to the theory of man-earth relationship, cultivated land is the product of long-term human activities and the development and utilization of natural land. Cultivated land ecosystems have developed into cultivated land ecological-economic systems influenced by human activities, which have positive social benefits in ensuring food security, hunger reduction and poverty, evolving into the compound systems of “ecology-economy-society”. SICLU is not a simple addition of sustainable and intensification, but a combination of social, economic and ecological requirements, under the optimal arrangement and combination of cultivated land ecological, economic and social complex systems. It pays attention to the changes of cultivated land use pattern at macro level and the changes of recessive function form at micro level. Therefore, SICLU has been regarded as a complex and sensitive land use optimization activity that has evolved from static conditions to a dynamic balance integrated system . In this process, by positively regulating the land input/output relationship and alleviating the pressure of environmental response, SICLU overcomes the possible negative impact of intensive utilization on the environment considering resource constraints, forcing the land available to provide material production and service in a sustainable way . In addition, SICLU takes into account the instantaneous impact and cumulative pressure of the combined effects of climate change and human activities, to enhance resilience, self-recovery ability, and biodiversity of the cultivated land ecosystems . Intensive management refers to emphasizing the intensity and effectiveness of investments by improving management methods and technologies, scientifically increasing effective investment, changing management methods, fodder system optimizing management modes, reasonably determining management scale and regional layout, and strengthening the entire process management of agricultural production. 2) High yield efficiency refers to emphasizing the yield efficiency and quality by coordinating the spatiotemporal allocation of inputs and outputs, optimizing crop varieties and planting structures, strengthening supporting infrastructure construction, improving agricultural production links, introducing advanced production technology, improving land and labor productivity, and maximizing the comprehensive production efficiency in existing management areas.
Resource saving refers to emphasizing the rationality and scientificity of resource utilization by reducing invalid investments and unnecessary external inputs, coordinating the proportion of resource utilization, scientifically allocating the investment structure, reasonably and efficiently utilizing various resources, improving the efficiency of resource utilization, and avoiding additional waste. 4) Non-degradation of the ecological environment refers to emphasizing the ecological priority and protection by adhering to the principle of ecological priority and considering source control, minimizing negative impacts on the environment, and further improving the environmental carrying capacity and self-healing capacity of the soil ecosystem, enhancing ecological service functions, and protecting biodiversity. 5) Social sustainability refers to emphasizing social fairness and sustainability by coordinating local relations, ensuring food security, protecting farming households’ rights and interests, reducing resource waste, strengthening market mechanisms, ensuring intergenerational fairness and distributive justice, popularizing agricultural technology training, enhancing microcredit, and improving welfare. There are checks and balances and coordination among the five connotations of SICLU . While focusing on and realizing the one connotation, it will also have the impacts on the realization of other connotations. Of course, the impacts can be both positive and negative. To be specific, high yield efficiency is the direct driving force of cultivated land use to the agricultural businesses and intensive management is the desirable main method to improve output at present. This process inevitably takes the cost of resource consumption and interferes with the ecological environment. It is not conducive to the resource saving and the non-degradation of ecological environment. But extensive management or leaving land uncultivated could lead to yield decline. Meanwhile, food security, resource conservation and ecological environmental protection together constitute the foundation of social sustainable development. Therefore, high yield efficiency, resource saving and non-degradation of ecological environment all contribute to the social sustainability. Guaranteeing ecological benefit is the premise of SICLU. It requires strengthening the ability of cultivated land to resist external disturbances and recover itself, restoring and enhancing the ecological service function, and revealing the versatility of cultivated land use in food production, environment renovation, biodiversity protection, landscape shape and so on. 2) Optimizing economic benefit is the necessity of SICLU. It requires building a balanced system of “combination of use and conserve”, strengthening the overall allocation and systematic development of water, soil, seed, fertilizer, medicine, electricity and other factors.