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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]

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]

Nitrogen is an essential element for plant growth, and the relationship between leaf N content and photosynthesis has been widely studied in different species under steady‐state light. However, under natural conditions, the light intensity at the leaf level is always changing, inherently heterogeneous in time and space. Therefore, the effect of leaf N content on photosynthesis under dynamic light conditions needs further study. At present, the effects of leaf N content on leaf non‐steady‐state photosynthesis have not been reported in canola (Brassica napus L.). To clarify the relationship between leaf N content and the speed of the response leaf gas exchange to variations in light intensity, eight genotypes of canola varying in leaf N content were used to study the temporal response of gas exchange to a step increase in irradiance. We found there were significant differences in non‐steady‐state photosynthesis, physiological characteristics, and anatomical traits across genotypes (the maximum amplitude was about fivefold), despite the lack of contrast under normal, steady‐state photosynthesis. In addition, initial stomatal conductance to water vapor in the darkness and leaf N content per leaf area were negatively correlated with the time required to achieve 50% and 100% of the maximum photosynthetic rate. Contrarily, the time required to reach 50% of the maximum stomatal conductance was positively correlated with the time required to achieve 90% of the maximum photosynthetic rate across genotypes. It is concluded that the genotypes of canola with higher N content per leaf area show a faster induction of photosynthesis to fluctuating light conditions. [ABSTRACT FROM AUTHOR]

Low temperature is a main adverse factor affecting successful seedling establishment in the Yangtze River basin, and thus low‐temperature stress tolerance at the germination and seedling emergence stages is an important attribute for rapeseed (Brassica napus L.) production. The present study was conducted to evaluate the low‐temperature stress tolerance indices (STIs) of a large conventional rapeseed genotype population at the germination and seedling emergence stages. Twelve seed germination‐ and seedling emergence‐related indices were investigated under normal and low‐temperature conditions, and the broad‐sense heritability of these indices ranged from 25.4 to 57.6%. Therefore, the selection of genotypes with strong low temperature tolerance is a feasible way to guarantee seedling establishment. Using principal component analysis, the STIs during the seed germination and seedling emergence stages have been divided into three main categories: dry matter weight, germination speed and final germination percentage, and root length with a seedling vigor index. The top three genotypes ranked by comprehensive STI score were Huayou No. 2, SWU44, and 2012‐K8053; the bottom three genotypes ranked by comprehensive STI score were Chuanyou18, wx1025, and 97096. The results of the present study could provide valuable information for breeders to utilize the rapeseed germplasm resources in the Yangtze River basin to achieve the goal of low‐temperature resistance breeding. [ABSTRACT FROM AUTHOR]

Germplasm collections provide an extremely valuable resource for breeders and researchers. However, misclassification of accessions by species often hinders the effective use of these collections. We propose that use of high-throughput genotyping tools can provide a fast, efficient and cost-effective way of confirming species in germplasm collections, as well as providing valuable genetic diversity data. We genotyped 180 Brassicaceae samples sourced from the Australian Grains Genebank across the recently released Illumina Infinium Brassica 60K SNP array. Of these, 76 were provided on the basis of suspected misclassification and another 104 were sourced independently from the germplasm collection. Presence of the A- and C-genomes combined with principle components analysis clearly separated Brassica rapa, B. oleracea, B. napus, B. carinata and B. juncea samples into distinct species groups. Several lines were further validated using chromosome counts. Overall, 18% of samples (32/180) were misclassified on the basis of species. Within these 180 samples, 23/76 (30%) supplied on the basis of suspected misclassification were misclassified, and 9/105 (9%) of the samples randomly sourced from the Australian Grains Genebank were misclassified. Surprisingly, several individuals were also found to be the product of interspecific hybridization events. The SNP (single nucleotide polymorphism) array proved effective at confirming species, and provided useful information related to genetic diversity. As similar genomic resources become available for different crops, high-throughput molecular genotyping will offer an efficient and cost-effective method to screen germplasm collections worldwide, facilitating more effective use of these valuable resources by breeders and researchers. [ABSTRACT FROM AUTHOR]