Abstract:Nitrogen fertilizer is essential for food security, but its excessive application leads to reactive nitrogen emissions, causing severe environmental issues. In the new era of promoting green development, clarifying Chinas reasonable nitrogen fertilizer demand and pathways for reducing chemical nitrogen fertilizer is crucial for agricultural transformation and upgrading. This study comprehensively analyzes the yield potential and nitrogen demand of 31 major crops in China and determines the reasonable nitrogen fertilizer demand under the conditions of food security and ecological sustainability by combining the nitrogen surplus levels under optimized management for different crops. Under the green development framework, the total reasonable nitrogen nutrient demand in China is 31 million tons, with a reasonable chemical nitrogen fertilizer demand of 19.04 million tons, accounting for 61% of the total demand. Future pathways for rational nitrogen fertilizer application in China should consider nitrogen fertilizer quota, increasing organic nutrient input and substitution ratio, increasing the planting proportion of leguminous crops to enhance biological nitrogen fixation potential, and optimizing nitrogen fertilizer product structure. Under these pathways, the potential for reducing chemical nitrogen fertilizer ranges from 26% to 53%. Specifically, under reasonable nitrogen input conditions (nitrogen quota), increasing the organic nutrient substitution ratio to 40% could lower the chemical nitrogen fertilizer demand to 14.28 million tons, with a reduction potential of 44%. Further increasing the planting area of leguminous crops (enhancing soybean-maize rotation ratio) could reduce the chemical nitrogen fertilizer demand to 13.6 million tons, with a reduction potential of 47%. Finally, optimizing the nitrogen fertilizer product structure could further reduce the reasonable chemical nitrogen fertilizer demand to 12.13 million tons, with a reduction potential of 53%. This studys evaluation of reasonable nitrogen fertilizer demand and exploration of green development pathways for nitrogen fertilizer will aid in implementing more scientific management systems and provide scientific support for the upgrading of Chinas nitrogen fertilizer industry.

Abstract:Building healthy soil is a prerequisite for the improvement of cultivated land productivity. It is fundamental for meeting the challenges of food security and environmental protection as well as realizing the agricultural green development and a community of shared future. The core of building healthy soil is to realize the soil ecosystem multifunctionality. In the new era of ecological civilization construction, research on the evaluation and cultivation of soil multifunctionality, and the underlying mechanisms have become hotspots and frontiers of global soil health initiatives. In this paper, we systematically review the concepts of soil functions, soil ecosystem services and soil ecological multifunctionality. The impact of soil biodiversity on soil multifunctionality and the synergies and trade-offs between soil functions are discussed as well. Also, the approaches to evaluating and quantifying soil functions are summarized. Finally, we put forward the pathways of healthy soil cultivation based on the integrated regulation of soil multifunctionality beyond the single pursuit of high grain yield. Different strategies to increase soil multifunctionality are proposed: adjusting the way of land use and agricultural structure at the national scale, coordinating resource allocations at a regional scale, constructing agricultural infrastructure and landscape pattern at the landscape scale, and optimizing the field soil management practices to improve soil health and multifunctionality at the field scale. It is necessary to explore the maintenance mechanism of soil multifunctionality at different temporal and spatial scales, and to combine modern technologies with relevant policies and implementation plans for functional soil management, emphasizing the multi-dimensional role of soil multifunctionality in sustainable environmental policy and management. It will provide important support for the coordinated development of mountain, water, forest, farmland, lake and grass life community, and the implementation of the national strategy of carbon peak and carbon neutrality.

Abstract:In China, N fertilizer use efficiency (NUE) is quite low as affected by its high-input intensive production mode in agriculture. A considerable portion of the nitrogen fertilizer applied to the cropping systems is lost to the environment as ammonia (NH3), nitrate (NO3), and nitrous oxide (N2O) as greenhouse gas, thus raising agricultural production cost and aggravating environmental pollution. Nitrification is the key transformation process of nitrogen cycling in soil, and is closely related to nitrogen loss in farmland. Some plants can produce and secrete compounds that inhibit nitrification and are called biological nitrification inhibitors (BNIs). Thu use of such BNIs may be an efficient and environment-friendly nitrogen management strategy. Here, a review of recent key developments in the field of biological nitrification inhibitors at home and abroad was presented, elaborating significances, substance types, functions, secretion and mechanism of BNIs secreted by roots. Researches in the past, particularly with focus on tropical pasture grasses and sorghum, held that releasing of BNIs was a nitrogen-preserving survival mechanism plants used to adapt to low-nitrogen environments in natural ecosystems. This paper suggests that BNIs are equally important in the high-N-input agricultural ecosystems and that a certain number of food crop varieties also have high BNI activity. In addition, BNIs that are produced by plants may evolve as specific responses to nitrifying environments. The mechanisms of BNIs secretion under waterlogged and aerobic conditions are quite similar, but differ somewhat, for instance effect of the parts of the root system exposed to NH4+ and pH. The hypothetic mechanism that BNIs released from plant cell membranes is proposed, for example, 1, 9-decanediol might be released via the ATP-binding cassette (ABC) transporter or members of the multidrug and toxic compound extrusion (MATE) transporter family. In terms of action targets, BNIs may regulate more ammonia-oxidizing microbial species and enzyme sites than the synthetic nitrification inhibitors (SNIs). Prospects of how to make use of BNIs in improving nitrogen utilization and reducing environmental pollution in agriculture are also discussed, such as high BNI-activity plants (such as pasture)-crop rotation, nitrogen fertilizer synergist, use of BNI traits for crop genetic improvement. For future researches, emphases should be laid on the following aspects:(1) to explore BNI functions and BNIs types in cultivation of important crops, and take into account interaction between BNIs substances; (2) to further reveal mechanism of known BNIs substances inhibiting nitrification, in addition to AOA and AOB, attention should be paid to response of the newly discovered Comammox, including other nitrogen transformation processes such as denitrification, and evaluation of potential loss of ammonia via volatilization caused by BNIs; (3) to investigate key genes and molecular genetic mechanisms regulating BNIs secretion through genome-wide association analysis (GWAS); and (4) to explore effects of BNIs in different soil conditions and with different crops in improving agriculture by field experiments, which hopefully may serve as reference for the developing of future BNIs technologies and products, improving the quality of agricultural produces, and promoting the green development of modern agriculture.

Abstract:Agriculture green development (AGD) is the future for modern agriculture, and soil health is the cornerstone of AGD. This article summarized the connotation, research progress and trend of soil health in domestic and overseas. By summarizing the main management strategies for healthy soil cultivation, this paper puts forward novel ideas and approaches for promoting soil health, and discusses the challenges and opportunities for soil health engineering. The cores for the promotion of healthy soils are: eliminating the limiting factors of soils; increasing the content of soil organic carbon and nutrient use efficiency; exploiting the biological potentials; promoting synergistic interactions between above-ground and below-ground. The aim of soil health engineering is to synergize the production and other ecosystem services delivered by soils by optimizing the internal regulatory processes whilst minimizing the external inputs. The cultivation of healthy soil needs holistic engineering, which requires comprehensive integration of whole industry chain in the nexus of external input, crop production, products-processing, and waste recycling. Meanwhile, cross-disciplinary innovation, government-farmer-research-extension institute collaboration, and policy support and incentive systems are crucial for realizing soil health towards AGD.