Petroleum hydrocarbon (PHC) contamination of soil is a widespread global environmental concern due to the persistence and recalcitrant nature of PHCs. The PHCs are highly toxic and their removal from the terrestrial ecosystem is necessary to maintain soil as well as human health. Here, a pot experiment was performed to examine the impact of Enterobacter sp. MN17 and biochar addition on the growth of mungbean plants and PHCs removal from diesel-polluted soil. For this purpose, soil was contaminated artificially with diesel to achieve a final concentration of 5000 mg kg−1. Untreated and Enterobacter sp. MN17 treated mungbean seeds were sown in pots. Sugarcane bagasse biochar was applied as an amendment in respective pots along with the recommended levels of essential nutrients. Results showed that PHCs significantly suppressed the seedling emergence as well as agronomic and physiological attributes of mungbean as compared to un-contaminated controls. However, the co-application of Enterobacter sp. MN17 and biochar significantly reduced the phytotoxicity of PHCs to mungbean plants and effectively increased the seedling emergence, shoot and root length, shoot fresh and dry biomass, root fresh and dry biomass of plants up to 24%, 54%, 52%, 52%, 54%, 55% and 60%, respectively as compared to controls. Similarly, 30%, 57%, 64%, 36% and 57% increase in chlorophylls contents, transpiration rate, stomatal conductance, sub-stomatal conductance, and photosynthetic rate, respectively were observed in their combined application as compared to respective controls. Furthermore, the co-addition of biochar and Enterobacter sp. MN17 could remove 69% and 85% higher PHCs from unplanted and planted pots, respectively, than that of their respective controls. Our results suggest that the co-application of biochar and Enterobacter sp. MN17 may be useful in enhancing plant growth and eliminating PHCs from contaminated soil.

In China, maize-soybean relay-intercropping system follow the two main planting-patterns: (i) traditional relay-intercropping; maize-soybean equal row planting, where soybean experience severe maize shading on both sides of plants, and (ii) modern relay-intercropping; narrow-wide row planting, in this new planting pattern only one side of soybean leaves suffer from maize shading. Therefore, in this study, changes in morphological traits, cytochrome content, photosynthetic characteristics, carbon status, and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were investigated at 30 days after treatment (DAT) in shade-tolerant soybean variety Nandou-12 subjected to three different types of shading conditions; normal light (NL, all trifoliate-leaves of soybean plants were under normal light); unilateral shade (US, all right-side trifoliate-leaves of soybean plants from top to bottom were under shade while all the left-side of trifoliate-leaves from top to bottom were in normal light); bilateral shade (BS, all trifoliate-leaves of soybean plants were under complete shade). Compared with BS, US conditions decreased plant height and increased stem diameter, leaf area, and biomass at 30 DAT. Biomass distribution rates to stem, petiole and leaves, and photosynthetic characteristics were markedly improved by the US at all sampling stages, which proved to be a better growing condition than BS with respect to shade tolerance. The enhanced net photosynthesis and transpiration rates in the left-side leaves (LS) of soybean plants in US, when compared with the LS in BS, allowed them to produce higher total soluble sugar (by 70%) and total soluble protein (by 17%) at 30 DAT which reduce the adverse effects of shading at right-side leaves (RS) of the soybean plants. Similarly, soybean leaves under US accumulated higher proline content in US than the leaves of BS plants. Soybean leaves grown in shading conditions (LS and RS of BS and RS of US) developed antioxidative defence-mechanisms, including the accelerated activities of SOD, POD, APX, and CAT. Comparatively, soybean leaves in US displayed lower activity levels of the antioxidative enzymes than the leaves of BS plants, showing that soybean plants experienced less shade stress in US as compared with BS treatment. Overall, these results indicate that the association of improved photosynthetic characteristics, sugar and protein accumulation and optimum antioxidative defences could be an effective approach for growing soybean in intercropping environments.

Influences of planting density and nitrogen rate have been investigated frequently in targeted wheat (Triticum aestivum L.) research. Few studies have investigated interactions between these inputs. The objective was to determine the combine effect of N and seeding rates on culm morph‐physiological traits for lodging tolerance and grain yield. The experiment used a split‐split randomized block design using two wheat varieties ‘AnNong0711’ and ‘YanNong19’, split by four seeding (180, 240, 300, and 375 × 104 ha−1) and four N rates (0, 180, 240, and 300 kg ha−1). Lodging traits of plant height, culm height center of gravity, and internode length, increased (p < .05) however, stem diameter, wall thickness, and stem breaking strength decreased with increasing N and seeding rate. Stem breaking strength was negatively correlated with culm height center of gravity (r = −.869, p = .01), internode length (r = −.872, p < .01), and lignin (r = −.746, p < .01) but positively correlated with internode diameter (r = .715, p < .05) and wall thickness (r = .696, p < .05). Culm lodging index and cellulose showed positive correlation (r = .807 and .913 respectively) with lignin. Compared to YanNong19, AnNong0711 showed higher grain yield and culm lodging index of 9 and 20.49%, respectively. For improved grain yield, 180 plants m−2 was optimal in surface combinations with 210 kg N ha−1 for AnNong0711 and 200 kg N ha−1 for YanNong19. These combinations of seeding and N rates could successfully mitigate lodging and improve grain yield.

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