Research advances on indicators and detecting methods of arable land compaction

Soil compaction has become one of the most serious obstacles restraining the sustainable use of arable lands. Many studies were carried out on soil compaction at home and abroad, but the results are not comparable due to the limited research conditions. This paper reviewed the soil compaction indicators and the detecting methods reported at home and abroad. The main results are as follows: (1) A single compaction indicator is often hard to quantify soil compaction degree completely. At field scale, combining soil penetration resistance with water content could characterize the actual degree of soil compactness. At scale as large as a region, the precompression stress method should be considered to approach soil compaction limits and the potential risks of soil compaction. (2) All the reported detecting methods showed advantages and disadvantages, affected by indoor or field detecting condition. Soil structure method and precompression stress method is often recommended for indoor detection as they could reflect soil compaction sensitively. The penetration resistance method and geophysical method are usually used to determine soil compaction degree in field condition. More researches should be strengthened in the future: (1) the effects of soil compaction on crop root morphology, distribution of aboveground photosynthesis products, and the feedback mechanism of crops on soil compaction; (2) Systematic evaluation of soil compaction by combining the soil physical indicators with soil mechanical indexes in conjunction with research scales; (3) Elimination of the influence of the spatial heterogeneity on field compaction detection.