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Soil compaction is one of the main limiting factors for sustainable agriculture. Efficient methods for detecting the distribution of soil compaction at a field scale are urgently needed in precision agriculture. We evaluated the possibility to detect soil compaction from measurements of apparent electrical conductivity (ECa) by using electromagnetic induction (EMI) and maize traits at a ~1 ha field parcel. The soil was Luvisol, and soil compaction‐related properties, such as bulk density (BD), penetration resistance (PR), soil texture, soil salinity, soil moisture and maize traits, were measured at ten locations across the field based on ECa variability. In this site‐specific study, no good correlation between soil compaction properties (i.e. BD and PR) and ECa was found but soil clay content was positively related to ECa in the sublayer (P = 0.08). The variation in the unmanned aerial vehicle (UAV)‐derived maize canopy height was significantly negatively correlated with soil compaction and a negative relationship between dry above‐ground biomass and BD and PR existed at 25–50 cm layer. In addition, ECa and UAV‐derived maize canopy height was negatively correlated (Spearman's rank correlation coefficients of −0.67 in the 0–25 cm layer) under the rather dry conditions prevailing during this study. Overall, as could be expected, detecting soil compaction with ECa was challenging under heterogeneous terrains, while maize traits had a better correlation with spatial variability of soil compaction. Owing to its sensitivity to the integral variation of multiple soil properties, ECa was a good indicator of maize canopy height. [ABSTRACT FROM AUTHOR]

• Maize root penetration was greater following white mustard below 30 cm depth. • Maize root distribution was restricted at out-row positions under strip tillage. • Strip tillage could sufficiently loosen top soil for maize production. • Maize biomass was marginally higher under strip tillage with white mustard combination. Soil compaction is a serious threat to agricultural production because of an expanding agricultural mechanization. Conservation tillage and use of pioneer plants can be an environmentally solution to alleviate the adverse effects of soil compaction. Root penetration into compacted soil of two winter cover crops with different rooting patterns, i.e. tap-rooted white mustard (Sinapis alba L.), and fibrous-rooted winter rye (Secale cereal L.), and of maize (Zea mays L.) in the consecutive growing season was assessed. Additionally, the effects of two spring tillage methods were evaluated, i.e. strip tillage and intensive tillage (by mouldboard ploughing). Winter rye showed significantly higher root penetration than white mustard in the top 15 cm, while an opposite trend was observed at 20–45 cm depth. After one season, maize root penetration was significantly greater following white mustard than winter rye at 30–40 cm depth. Strip tillage, like intensive tillage, could sufficiently loosen soil for adequate maize growth even though maize root distribution was restricted to tilled rows in contrast with intensive tillage. In conclusion, white mustard already showed positive short-term effects on maize growth, whereas strip tillage did not negatively affect it. Combining both is a viable option to reduce the negative impact of soil compaction on maize growth. [ABSTRACT FROM AUTHOR]

[Display omitted] • Topsoil compaction affected topsoil water content but not maize growth. • The detriment of subsoil physical properties was worse in the headland zone. • Subsoil compaction restricted root growth and increased nitrogen leaching risks. • Subsoiling promoted maize growth and its effects can be detectable after ∼ 2 years. Mechanical soil compaction increasingly occurs in arable land but the state and effects of historical compaction from regular operations are still poorly documented. Therefore, a typical field was selected and the effects of both newly formed topsoil compaction and historical developed subsoil compaction (below 30 cm) on soil physical and hydraulic properties, soil water movement, soil mineral nitrogen leaching potential and crop parameters were evaluated on a Luvisol under a winter rye (Secale cereale L.) and summer maize (Zea mays L.) rotation system. Three subsoil compaction levels were included, i.e., a i) highly compacted headland zone, and a moderately compacted in-field zone ii) without and iii) with deep tillage by subsoiling in the winter of 2016. Topsoil compaction on the other hand was induced by one machine pass with a rotary cultivator in addition to the regular machine passes during field preparation for the summer maize season of 2017, and compared with a control without extra compaction. For subsoil compaction treatments, both visual evaluation and lab or field based measurements indicated that soil physical and hydraulic properties were deteriorated in the headland compared with in-field zones. As a result, both winter and summer crop above-ground biomass were decreased in the highly compacted headland zone because of the restricted root growth, which further increased the risk of soil mineral nitrogen leaching. The alleviation effect of deep tillage remained after ∼ 2 years, which significantly increased maize height in the extremely dry and hot summer of 2018. For topsoil compaction, one traffic pass with a rotary cultivator increased topsoil penetration resistance and water content but summer maize above-ground biomass was not affected. Overall, prevention and alleviation of subsoil compaction are essential in increasing the resistance and resilience to the continuing deteriorating climatic conditions. [ABSTRACT FROM AUTHOR]

• Median root system width was the key root trait in alleviation compacted soil. • Root alleviated macropores exerted in vertical direction more than in lateral direction. • Root growth explained one-third of macropores change under compacted soil. • Modern soybean varieties were more effective in alleviating compacted Mollisol. Soil compaction is the main form of soil degradation in agricultural systems. It leads to decreased infiltration and limited root growth. Plants can alleviate soil compaction through various mechanisms connected to root growth. However, it remains unclear whether plant breeding can improve the root traits of modern cultivars and their ability to alleviate compacted soil. The aim of this study was to determine the responses of soybean (Glycine max L. Merr.) roots to soil compaction and to observe the difference in soil alleviation by using soybean varieties bred before and after the development of mechanical agriculture in the Mollisol region of Northeast China. Five soybean varieties, bred from 1941 to 2003, were planted and subjected to either soil compaction or no compaction. Root traits and soil macropores were characterised by screening the root system (Shovelomics method) and by adopting dye-tracing methods. The properties of roots in soybean varieties showed noteworthy differences, although no clear breeding trends were detected. Compared with no compaction, the root lengths of all varieties decreased significantly when grown in compacted soil. Moreover, soil compaction decreased the vertical macroporosity and increased the heterogeneity of horizontal macropores. The modern soybean variety alleviated soil compaction by enabling the creation of more macropores, which were located deeper in the soil, compared to the older varieties. Overall, root growth was responsible for approximately one-third of macropore changes observed under compacted soil conditions, and the alleviation effects were greater in roots growing vertically than those observed in roots growing laterally. The observed variability of soil compaction alleviation among different soybean varieties could be considered in agriculture by breeders to select the varieties which decrease soil compaction. [ABSTRACT FROM AUTHOR]