Biological nitrogen fixation for fertilizer-limited crop production

有机农业在加拿大是一个迅速扩张的市场，它的增长速度比非有机部门快。加拿大是第六大有机食品消费市场，2020年，加拿大消费者购买了价值超过70亿美元的有机食品。2019年，加拿大有7500多家有机企业，约占农业用地总量的2%，对有机食品的需求超过了目前的生产能力。与传统农业相比，有机农业的产量差距是一个重大挑战，主要原因是禁止使用合成氮肥。农民们在外包天然肥料（如粪肥、有机残留物和堆肥）方面很有创意，但这些都很昂贵。在作物上接种固氮菌（如氮螺旋菌属）是增加有机作物氮输入的一种高效、低成本的替代方法。这些细菌不仅将大气中的氮固定在植物上，而且还产生促进植物生长的分子（植物激素、维生素、次生代谢物）、铁载体和有机酸，这些分子可以溶解土壤中的磷酸盐，促进根系生长和植物的健康和恢复力。固氮细菌已经研究多年，尽管它们在南美被广泛商业化，但在北美的使用仍然很少。在北美可用的少数氮螺旋藻产品通常来自南美洲，由于与加拿大的条件和土壤不相容，它们对加拿大作物的影响往往不一致。从加拿大土壤中分离和鉴定固氮螺旋菌菌株和其他固氮菌株，开发适用于加拿大作物的微生物接种剂产品，将提高产量并降低投入成本。我们建议从加拿大土壤中分离和鉴定固氮细菌，并基于这些分离物开发接种剂，以提高加拿大有机种植系统的氮水平。主要成果将是增加有机作物的产量，以满足对有机食品的需求，同时促进环境的可持续性。

Organic agriculture is a rapidly expanding market in Canada, and it is growing faster than the non-organic sector. Canada is the sixth-largest organic consumer market, and in 2020, Canadian consumers bought more than $7 billion worth of organic food. There were more than 7,500 organic operations in Canada in 2019, accounting for roughly 2% of total agricultural land, and the demand for organic food outstrips current production capacity. The yield gap of organic compared to conventional agriculture is a major challenge and is primarily attributed to the prohibition of synthetic Nitrogen fertilizer. Farmers have been creative with outsourced natural fertilizers such as manure, organic residues, and compost, but these are costly. The inoculation of crops with N2-fixing bacteria such as those from the genus Azospirillum is an efficient and low-cost alternative to increase the input of N to organic crops. These bacteria not only fix atmospheric nitrogen to the plants, but also produce plant growth promoting molecules (phytohormones, vitamins, secondary metabolites), siderophores, and organic acids that solubilize phosphates in the soil, promoting root growth and plant health and resilience. N2-fixing bacteria have been studied for years, and although they are widely commercialized in South America, their use in North America is still rare. The few Azospirillum products that are available for use in North America commonly originate from South America, and their effects on Canadian crops are often inconsistent due to incompatibilities with Canadian conditions and soils. Isolating and characterizing Azospirillum strains and other N2-fixing isolates from Canadian soils and developing microbial inoculant products that are suitable for Canadian crops will increase yield and reduce input costs. We propose the isolation and characterization of N2-fixing bacteria from Canadian soils and the development of inoculants based on these isolates for improvement of N levels in Canadian organic cropping systems. The major outcome will be to increase the production of organic crops to supply the demand for organic food products while contributing to environmental sustainability.