In recent years, heavy metal pollution in farmland soil has become a crisis due to human activities or natural impacts, with particular emphasis on cases from China, where this issue is prominent, greatly affecting crop production and food safety. In the context of a low heavy metal (HM) content in farmland soil, which is difficult to monitor in real time, effective and rapid monitoring of soil plays a decisive role in subsequent targeted protection measures. To this end, this paper provides a narrative review of the application of spectral sensing technology on the basis of the quantitative inversion of heavy metal content in farmland soil using different platforms (ground, airborne, and spaceborne). The sensing process evaluates the mechanism by which soil produces different weak spectral features from the perspective of the heterogeneity of farmland soil. Different methods used for the quantitative inversion of heavy metals (by studying the correlation between soil heavy metals and organic matter, clay minerals, metal oxides, crop vegetation index, etc.) and their feasibility were clarified. At the same time, relevant research on key technologies used in various processes—such as follow-up pretreatment, spectral feature extraction, and the establishment of inversion models for spectral data of different farmland soil types—was summarized, with a primary focus on cases in China. Finally, the challenges, applications, and research directions related to heavy metal spectral inversion in farmland soil were discussed.

In recent years, in order to save land resources and ensure biosecurity, multi-storey buildings for pig rearing are replacing traditional flat-floor methods in pig farms domestically and internationally. However, the precision, stability, and adaptability of pig feed transportation in multi-storey buildings have brought certain challenges to the development of large-scale pig raising. The uniqueness of this paper lies in the comprehensive review of recent research advances in various transportation machinery and feeding systems from the perspective of both pig feed transportation and feeding systems compared to other papers that singularly present pigs’ feed transportation machinery or feeding systems. In addition, this paper provides an outlook on the potential for coupling power sources for pig feed transportation and pig transportation, providing insights for future research and development. First, the paper comprehensively reviews feed transportation machinery in multi-storey pig rearing, highlighting their advantages and challenges. Then, it explores the commonly used feeding systems in large-scale pig rearing and their limitations. Finally, the paper summarizes the current issues in pig feed transportation in multi-storey buildings and examines future development trends.