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Rapeseed meal, a nutritious organic fertilizer (OF), contributes to improving soil environment and crop productivity. However, there are also problems, namely slow fertilizer efficiency and low nutrient utilization during the growing season. This 2‐year field trial was conducted to explore the effect of biochar addition on improving the nutrient availability of OF through a comparative study of various biochar application rates under rice‐rapeseed rotation conditions. The findings revealed that, compared to the individual application of chemical fertilizers (CF), OF alone decreased rice yield (2%/2%) and rapeseed yield (6%/10%) in 2019/2020. Compared with OF, combining biochar (15 t ha−1) with OF (OF + B15) significantly increased rice yield (17%/10%) and rapeseed yield (25%/20%) in the first/second year. Additionally, OF + B15 still increased rice yield (14%/7%) and rapeseed yield (12%/13%) for two consecutive years compared to CF. The co‐application of biochar and OF had positive impacts on soil physicochemical properties and enzymes. Compared to OF, OF + B15 elevated soil organic carbon (SOC) by 57%–81%, soil catalase 19%, invertase 14%–20%, urease 17%–19%, and phosphatase 13%–17% during rice season, and similarly increased SOC by 77%–90%, soil catalase 14%–16%, invertase 14%–20%, urease 18%–24%, and phosphatase 16%–17% in rapeseed season. Biochar addition improved soil conditions and enzymatic activities, and the available nutrient supply of OF. Also, the co‐application of biochar and rapeseed meal surpassed the effect of chemical fertilizer alone on the growth and yield of crops. Therefore, biochar coupling with organic fertilizer is an effective fertilization strategy based on resource recycling, which promotes both crop yield and sustainable agriculture. [ABSTRACT FROM AUTHOR]

Dry direct-seeded rice (dry-DSR) is an efficient, resource-saving and environmentally friendly cropping system. The employment of water-saving and drought-resistant rice (WDR) for dry direct-seeding can better meet the needs of dry-direct seeding systems. However, the decline in seedling emergence rate and poor seedling growth are the main bottlenecks under current direct-seeded rice production. Seed treatment is a sustainable and effective technique to overcome these issues. Therefore, growth chamber and field experiments were conducted to assess the impact of poplar wood vinegar (WV) priming and rice straw biochar (BC) coating on emergence, establishment, growth, physio-biochemical events, and ultimate yield. We treated the seeds of WDR viz., Hanyou 73 with WV, BC, and co-treatment WV + BC. The results showed that seed priming with 1:50 WV concentration and coating with 20% BC content was the optimal ratio for promoting germination and seedling growth. The field evaluation indicated that individual WV and BC markedly promoted the final emergence by 58% and 31%, respectively, while co-treatment WV + BC increased by 67%. Likewise, WV and BC significantly enhanced total seedling biomass by 26% and 10%, respectively, and the respective enhancement of WV + BC was 31%. For ultimate yield, WV and BC produced 12% and 19% higher grain yield, respectively, whereas WV + BC yielded 20%. The above results revealed that WV and WV + BC were the most effective treatment. Our findings may provide new avenues for advancing pre-sowing seed treatments facilitating the stand establishment and grain yield of dry direct-seeded rice. [ABSTRACT FROM AUTHOR]

Biochar application as an organic amendment has been practiced to reduce soil acidity, enhance nutrient utilization, and improve crop growth and yield. However, uncertainties remain about the long-term effects of organic amendment and chemical fertilizers under crop rotation to ensure the sustainability and conservation of soil fertility and nutrient requirements of crops. A three-year field trial of rice-rapeseed rotation was conducted to investigate the effects of biochar (0, 3, 9, 15, 30, and 60 t ha−1) coupled with compound fertilizer NPK (15-15-15) at the ratio (N: P: K 1:0.8:0.8) for rice and (N: P: K 1:0.5:0.5) for rapeseed. The results showed that biochar amendment consistently improved the soil physiochemical properties such as soil pH, soil organic carbon and soil total porosity, soil enzyme activities, nutrient uptake, and yield of rice and rapeseed compared to plots with no biochar. Compared to control, plots treated with biochar at 30 t ha−1 increased the activity of urease up to 52 % and 39 % and invertase by 15 % and 32 %, while biochar at 60 t ha−1 increased the activity of soil catalase by 34 % and 32 % and alkaline phosphatase by 35 % and 41 % respectively under rice and rapeseed cultivation in the last two years of the study. The findings of the study revealed that coupling of biochar 15 t ha−1 with compound fertilizer significantly improved the grain yield of rice by 12 % and rapeseed by 22 % in the first year, and biochar amendment at 30 t ha−1 improved rice yield by up to 14 % and 22 % and rapeseed up to18 % and 21 % in the last two years. However, compared to 15 and 30 t ha−1, 60 t ha−1 biochar was ineffective and reduced the nutrient uptake and yield throughout the study. The soil conditions, growth, and yield of rice and rapeseed were improved in control plots with no biochar in the last two years, indicating crop rotation's positive effect. Altogether, our findings suggest that crop rotation under the combined application of biochar and chemical fertilizer is a promising approach to ensure soil fertility and crop productivity on a long-term sustainable basis. • Chemical fertilization depleted soil's chemical and physical properties. • The nutrient capacity and delivery performance of organic fertilizer were insufficient. • Biochar promoted soil quality and compensated nutrient delivery of organic fertilizer. • Biochar with organic fertilizer under crop rotation enhanced nutrient utilization and crop production. [ABSTRACT FROM AUTHOR]

Compensating nitrogen input and increasing nitrogen utilization efficiency (NUtE) are necessary for sustainable crop production. Research studies on the co-application of biochar and nitrogen to promote rapeseed growth, soil fertility, and improve nutrient utilization efficiency are found to be limited. This study aims to examine the integral effects of biochar and nitrogen over soil fertility, rapeseed growth and nitrogen utilization efficiency. The experiment was conducted in a completely randomized design to assess various morphological, physiological and biochemical traits of rapeseed and soil chemical properties under the application of four nitrogen levels (0, 75, 225, and 450 kg ha−1 equivalent to 0, 133, 400 and 800 mg nitrogen pot−1) and four biochar levels (0, 5, 10, and 15 MT ha−1 equivalent to 0, 10, 20 and 30 g biochar pot−1 soil by weight basis). The results of this study showed that the integral application of biochar at 30 g pot−1 and nitrogen at 800 mg pot−1 at 45 days after sowing (DAS) and 60 days after sowing (DAS) compensated the amount of nitrogen and increased soil organic carbon (SOC 69%), total nitrogen accumulation (TNA) (93% and 62%), leaf biomass (60% and 33%), stem biomass (20% and 22%) and photosynthesis (20% and 17%) at 45 DAS and 60 DAS, respectively as compared to a single application of nitrogen. However, under the conditions of no nitrogen or 75 kg ha−1 nitrogen application, the application of biochar to promote the growth of rapeseed plants is limited due to the less nitrogen supply. In contrast, the application of nitrogen at 800 mg pot−1 and biochar at 10 or 20 g pot−1 showed that the growth of early seedlings was adversely affected due to high nitrogen concentration in soil. The findings of the present study imply that within the appropriate nitrogen application range, the interaction of biochar and nitrogen might have an economical approach towards better utilization of nitrogen and sustainable crop production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Drought stress negatively affect the sustainable crop production in various ways. • Moisture deficits drastically reduced crop yields and regional economies. • Understanding the drivers of yield levels under deficient water is required. • Biochar with high carbon is being recognized by scientists for its potential role. • Biochar improve soil status and enhance utilization of soil water and nutrients. The depletion of soil fertility and freshwater reservoirs in dry and arid conditions of the world are alarming for food and crop productivity. Although many research studies have explored the effect of biochar on plant growth and soil fertility, however, information on the role of biochar on rapeseed under drought stress is limited. The current study was conducted to investigate the effect of biochar on photosynthesis, antioxidants activities, osmolytes contents, growth and yield of rapeseed under drought stress. Rapeseed plants at the flowering stage were subjected to two moisture conditions, no stress (NS) and drought stress (DS) along with four biochar treatments (B0:0, B15:15, B30:30 and B60:60 t ha−1). Drought stress negatively affected rapeseed growth due to the over-production of hydrogen peroxide (H 2 O 2) by increasing 45 %, malondialdehyde (MDA) 21 % and electrolyte leakage (EL%) 40 % in (BO + DS) treatment as compared to control (BO + NS). However, the addition of biochar at 30 t ha−1 alleviated the hostile effects of drought stress in rapeseed to reduce the contents of MDA, H 2 O 2 , EL by increasing the activities of superoxide dismutase (SOD) by 63 %, peroxidase (POD) 48 %, and catalase (CAT) 62 % compared to stress-controlled treatment (BO + DS). The results revealed that biochar could alleviate the harmful effects of drought stress by enhancing the activities of antioxidants, osmoprotectants, soil fertility, and the physiological processes of rapeseed which indicate that the biochar application might be a sustainable strategy to enhance rapeseed growth under drought stress. [ABSTRACT FROM AUTHOR]

The quality and nutritional status of agricultural soils are depleting gradually, and biochar is widely used in soil quality improvement. A sustainable approach of biochar application needs a better understanding of its interaction with nitrogen application and the final effect on crop growth. In our study, the effect of different biochar application levels (0, 15, 30, and 60 tons ha−1) in combination with nitrogen fertilizer levels (0, 150, 300, and 450 kg ha−1) on soil properties, rice growth, and nitrogen use efficiency were investigated. The results showed that sole application of biochar (B60) did not promote the rice growth except the soil organic carbon (SOC), total nitrogen, total phosphorous, and available potassium compared with no biochar addition, while a single application of 450 kg N ha−1 (N450) adversely affected the rice physiological and yield traits by destroying rice leaf ultrastructure and reducing the stomatal length by 13%, stomatal width 3% and density 12%, plant height 5%, dry biomass plant−1 4%, spike weight plant−1 8%, and grain weight plant−1 9% compared to N300 unless it was treated in combination with biochar. Biochar can significantly compensate the toxicity of excessive nitrogen and deficiency of low nitrogen fertilizer on rice growth. Compared to a single application of B0+N450 (450 kg N ha−1), combined application of biochar and nitrogen B30+N450 could elevate rice plant nitrogen content by 13%, plant height 30%, aboveground dry biomass plant−1 136%, spike weight plant−1 34%, and grain weight plant−1 36% while increments in total nitrogen accumulation (TNA 79%%) and nitrogen use efficiency (NUE 35%) were noted in B30+N300 treatment. These results suggest that biochar amendment combined with a proper amount of nitrogen fertilizer is an effective approach to promote soil conditions, manage nitrogen utilization, improve plant growth and increase crop yield on a sustainable basis. [ABSTRACT FROM AUTHOR]

Heavy metals (HMs) accumulation in soil poses a severe threat worldwide for soil, plants, and humans. The accumulation of HMs in soil and uptake by plants leads to disrupt physiological and biochemical metabolisms. As a potential and sustainable soil amendment, biochar has attained huge attention to reduce HMs toxicity in soil and improve plant growth influenced by HMs stress. Despite an array of research studies, there is a lack of knowledge on how biochar interacts with HMs, moderate plant defence system, induce HMs stress signals pathways and promote plant growth. At first, the review highlights the possible effects of HMs on soil and plant and their consequences on plant signaling network. Secondly, the biochar's impact on soil physiochemical properties and the sorption of HMs on biochar surface through direct and indirect mechanisms are reviewed. Finally, the review shows the key roles of biochar in soil improvement to enhance plant growth and signaling response to HMs by enhancing the activities of antioxidants and reducing chlorophyll injury, reactive oxygen species (ROS) accumulation, and cell membrane degradation under HMs stress. However, future studies are needed to evaluate the role of biochar in diverse climatic conditions as well as the long-term effects of biochar on HMs persistency in soil and crop productivity. This review will provide new avenues for future studies to address and quantify the advancement in biochar's role in alleviating plant's HMs stress on a sustainable basis. [Display omitted] • Heavy metals (HMs) accumulation decline soil fertility and environment sustainability. • Biochar is being recognized by scientists for its potential role, mitigating HMs toxicity and improving plant growth. • Amendment of biochar modify physio-chemical and biological properties of soil. • Biochar increase HMs sorption in polluted soils and promote plant signaling against HMs stress. [ABSTRACT FROM AUTHOR]