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China is facing a great challenge with grain demand. Meanwhile, the decline of farmland quality will affect the quality and safety of food. The existing methods of farmland quality monitoring are characterized by a long time period and a lack of detailed spatial information of farmland quality. They could not provide the data that meet the requirements of farmland quality monitoring. This study explored a new methods and mobile laboratory for farmland quality monitoring. A farmland quality monitoring indicator system consisting of the variables or predictors that can be fast measured spatially and temporally was first developed. In this study, a framework which integrated satellite remote sensing monitoring, unmanned aerial vehicle(UAV) monitoring, wireless sensor network(WSN) monitoring and in situ measurement method into a farmland quality monitoring mobile laboratory was built. This study also explored the integration of remote sensing, UAV, WSN and ground-based monitoring methods through middleware technologies that connect various components of the system. Moreover, this study developed of a farmland quality monitoring mobile laboratory with an optimal design of routines for fast collection of data. A on-site test was carried out in the area of farmland upgrade and reconstruction program, which took less than 2 hours to quick test 13 indicators for 5 sampling points showed higher efficiency and on-site analysis capability compared with traditional farmland quality monitoring method. This study overcame the gaps that currently exist in the traditional farmland quality monitoring methods, realized comprehensive and multi-scale monitoring of farmland quality, promoted the effectiveness of monitoring cultivated land, and enhanced the capacity of farmland management and protection.

Optimizing the layout of monitoring sample points according to the spatial distribution characteristics of cultivated land quality can improve the monitoring efficiency and accuracy of cultivated land quality. In this paper, the environmental factors that change synergistically with cultivated land quality were selected as auxiliary variables, the spatial variation characteristics of cultivated land quality were analyzed by geostatistics, and the layout scheme of cultivated land quality monitoring sample points was optimized by Cokriging method. The results showed that the interpolation accuracy of 66 monitoring points obtained by Cokriging under the optimal(5 km×5 km) grid interval was better than that of ordinary Kriging under the small(2 km×2 km) grid interval; Under the same grid layout, the interpolation accuracy of monitoring points obtained by Cokriging method was better than that of ordinary Kriging. This shows that the Cokriging method combined with easily obtained auxiliary variable information can optimize the layout of cultivated land quality monitoring points, obtain the sample point scheme with fewer monitoring points, reduce the cost and improve the accuracy of cultivated land quality monitoring.

Cultivated land is the oldest and most extensive human-land system formed by human civilization through the transformation of the earth's surface for thousands of years. The ability of cultivated land system to maintain stable production and healthy environment is reflected in the quality characteristics of cultivated land, under certain technical and economic conditions within a certain period of time, and the development and utilization value is expressed as the resource attribute of cultivated land. This paper clarifies the cultivated land system, the quality of cultivated land and cultivated land resources, on the basis of cognitive connotation and evolution process. The "nature-humanity" constituent elements and their coupling relationship of cultivated land resources are analyzed, characteristics and formation mechanism of "horizontal-vertical" structure, "production-ecology-living" function synergy and transformation relationship. The exchange process and response mechanism of "matter-energy-information", and the service value and evolution law of "economy-ecologysociety", the cognitive system of cultivated land resources is constructed, which is "two-dimensional factor-triple function-multiple value". A new way of systematically recognizing cultivated land resources is proposed, deconstructing the internal mechanism and external value of cultivated land resources, service farmland protection and quality improvement and natural resource assets "two unified" management, to support the construction of a new pattern of resource utilization and cultivated land protection under high-quality crossdomain development.