Wood vinegar is formed by the condensation of smoke produced during the production of biochar. It mainly contains acetic acid, butyric acid, catechol, and phenol. Wood vinegar has a compound effect of promoting crop growth similar to plant growth regulators and is environmentally friendly. Moreover, it can enhance the biological and abiotic resistance of crops. In this study, foliar spraying was carried out systematically in the field with the hybrid variety of Huayouza 9 for two years to study the effects of wood vinegar and its compounds on the growth of rapeseed (Brassica napus L.). We applied four treatments with tap water as a control (CK), namely wood vinegar diluted 400-fold (M), M mixed with gibberellin (T1), M mixed with sodium D-gluconate (T2), and M mixed with melatonin (T3). They were sprayed in the seedling stage and overwintering stage, respectively. The results showed that the seed yield, the leaf area index, and the number of pods per plant of rapeseed treated with M increased by an average of 9.58%, 23.45%, and 23.80% in two years as compared to the CK, respectively. Compared with M, the seed yield of rapeseed treated with T1, T2, and T3 increased by an average of 7.88%, 6.90%, and 1.32% in two years, respectively. The treatments also improved the quality of rapeseed. In particular, the glucosinolate content of rapeseed treated with T2 and T3 decreased by an average of 12.83% and 6.72% in two years compared to the CK, respectively. The four treatments selected in the current study improved the resistance of rapeseed at the low temperature of 2–6 °C by increasing the activity of superoxide dismutase and proline and soluble protein contents, as compared to the CK. Besides, all treatments containing M reduced the incidence of Sclerotinia sclerotiorum and Peronospora parasitica (downy mildew) in rapeseed. More specifically, the T3 treatment significantly decreased the infection rate of these two diseases mentioned above by an average of 17.33% and 12.14% in two years compared to the CK, respectively. Therefore, the study and application of wood vinegar due to its compound effects on crop growth and yield is of great importance to sustainable agriculture, crop ecology, and environmental protection.

Seed germination and stand establishment are the first steps of crop growth and development. However, low seed vigor, improper seedbed preparation, unfavorable climate, and the occurrence of pests and diseases reduces the germination rate and seedling quality, resulting in insufficient crop populations and undesirable plant growth. Seed coating is an effective method that is being developed and applied in modern agriculture. It has many functions, such as improving seed vigor, promoting seedling growth, and reducing the occurrence of pests and diseases. Yet, during seed coating procedures, several factors, such as difficulty in biodegradation of coating materials and hindrance in the application of chemical ingredients to seeds, force us to explore reliable and efficient coating formulations. Biochar, as a novel material, may be expected to enhance seed germination and seedling establishment, simultaneously ensuring agricultural sustainability, environment, and food safety. Recently, biochar-based seed coating has gained much interest due to biochar possessing high porosity and water holding capacity, as well as wealthy nutrients, and has been proven to be a beneficial agent in seed coating formulations. This review presents an extensive overview on the history, methods, and coating agents of seed coating. Additionally, biochar, as a promising seed coating agent, is also synthesized on its physico-chemical properties. Combining seed coating with biochar, we discussed in detail the agricultural applications of biochar-based seed coating, such as the promotion of seed germination and stand establishment, the improvement of plant growth and nutrition, suitable carriers for microbial inoculants, and increase in herbicide selectivity. Therefore, this paper could be a good source of information on the current advance and future perspectives of biochar-based seed coating for modern agriculture.

Leaf nitrogen (N) concentration plays an important role in biochemical and physiological functions, and N availability directly influences rice yield. However, excessive N fertilization is considered to be a root cause of environmental issues and low nitrogen use efficiency. Therefore, the selection of appropriate nutrient management practices and organic amendments is key to maximizing nitrogen uptake and maintaining high and sustainable rice production. Here, we evaluated the effects of different 15N-labelled nitrogen sources (urea, ammonium nitrate, and ammonium sulfate at 315 kg ha−1) with or without biochar (30 t ha−1) on paddy soil properties, root growth, leaf gas exchange, N metabolism enzymes, and N uptake in the early and late seasons of 2019. We found significant differences among N fertilizer sources applied with or without biochar (P < 0.05). Across the seasons, the combination of biochar with N fertilizers significantly increased soil organic carbon by 51.21% and nitrogen availability by 27.51% compared with N fertilizers alone. Correlation analysis showed that rice root morphological traits were strongly related to soil chemical properties, and higher root growth was measured in the biochar treatments. Similarly, net leaf photosynthetic rate averaged 9.34% higher, chlorophyll (Chl) a concentration 12.91% higher, and Chl b concentration 10.05% higher in the biochar treatments than in the biochar-free treatments across the seasons. Notably, leaf 15N concentration was 23.19% higher in the biochar treatments in both seasons. These results illustrated higher activities of N metabolism enzymes such as NR, GS, and GOGAT by an average 23.44%, 11.26% and 18.16% in the biochar treatments across the seasons, respectively. The addition of biochar with synthetic N fertilizers is an ecological nutrient management strategy that can increase N uptake and assimilation by ameliorating soil properties and improving the morpho-physiological factors of rice.

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.

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.