选择深圳市郊区常年连作菜地，采用田间小区试验方法，设置对照、常规施肥、减量施肥10%、优化施肥（减量施肥50%，氮磷钾优化配比）等不同处理，研究不同肥料用量和养分配比条件下减施化肥对蔬菜生长及土壤肥力的影响。试验以叶菜为供试蔬菜，连续种植2茬。结果表明，与不施肥处理相比，施肥显著增加蔬菜产量和氮、磷、钾养分吸收量，肥料增产贡献率为32.3%~37.7%，且化肥减施与常规施肥处理之间肥料贡献率无显著差异。常规施肥模式下蔬菜氮、磷、钾养分利用率分别为13.98%、5.39%、31.95%，优化施肥相比常规施肥显著提高蔬菜磷肥和钾肥利用率1.87倍、26.3%。施肥对土壤pH、有机质含量无明显影响，常规施肥、减量施肥10%提高土壤碱解氮含量12.27%~27.83%、有效磷含量26.49%~44.24%、速效钾含量13.17%~35.30%。与常规施肥相比，优化施肥显著降低土壤有效磷含量19.96%~23.65%、速效钾含量22.29%~23.23%。各处理土壤综合肥力指数为1.34~1.43，均属于II级水平，连续2茬短期施肥管理对土壤肥力指数无显著影响。总体上，常年连作菜地系统优化施肥即化肥减施50%并优化氮磷钾养分投入比例，可在蔬菜产量不降低的情况下维持土壤肥力水平，降低土壤有效磷累积导致的面源污染风险。

\nNitrogen recommendations for individual corn fields are less accurate than desired.

Increasing the inputs of nutrients has played a major role in increasing the supply of food to a continually growing world population. However, focusing attention on the most important nutrients, such as nitrogen (N), has in some cases led to nutrient imbalances, some excess applications especially of N, inefficient use and large losses to the environment with impacts on air and water quality, biodiversity and human health. In contrast, food exports from the developing to the developed world are depleting soils of nutrients in some countries. Better management of all essential nutrients is required that delivers sustainable agriculture and maintains the necessary increases in food production while minimizing waste, economic loss and environmental impacts. More extensive production systems typified by ‘organic farming’ may prove to be sustainable. However, for most of the developed world, and in the developing world where an ever-growing population demands more food, it will be essential to increase the efficiency of nutrient use in conventional systems. Nutrient management on farms is under the control of the land manger, the most effective of whom will already use various decision supports for calculating rates of application to achieve various production targets. Increasingly, land managers will need to conform to good practice to achieve production targets and to conform to environmental targets as well.

The current political, social, and economic conditions place, more than ever, the need to sustainably supply nutrients for plants, integrating low-impact, crop-adapted, variable-rate-application fertilizer solutions, at the center of attention. Fertilization plans should be based on the monitoring of soil fertility to address the proper rate of fertilizer application along with the development of techniques able to increase nutrient uptake efficiency. Monitoring and modelling analysis of the effects of agronomic management in different pedoclimatic conditions can provide several advantages, that include higher nutrient efficiency, increase in plant growth and yield, decreased fertilization costs, increased profit, reduced environmental impact. This approach should enter into a framework of precision farming methodologies for the distribution of nutrients adopted at different levels (region, farm, field, plot), to obtain the maximum efficiency of inputs.

Reactive nitrogen (N) plays a pivotal role in supplying N to plants and soil microbes, but it has negative environmental impacts through influencing the quality of water and air, which in turn influences human health. Thus, there is an urgent necessity to maximize N benefits while reducing the negative impacts on the environment. Improving crop N use efficiency (NUE) is required for environmental conservation and agricultural sustainability. Thus, the pivotal objective of this article is to introduce the modern developments and imminent prospects of improving crops NUE using various complementary methods. Here, the approaches of site-specific N management, use of synthetic and biological nitrification inhibitors, microbial nitrate (NO3−) immobilization stimulation, and stimulation of the dissimilatory nitrate reduction to ammonium (DNRA), adopting agroforestry system, breeding techniques, quantitative trait loci (QTL) mapping, omics approaches, and potential new targets and overexpression of N-related genes were presented as effective approaches to improving NUE. Optimal rate, time, application methods, using specially formulated forms of fertilizer, and using nitrification inhibitors are the most agricultural practices linked with improving NUE. The fertilizer recommendations could be often justified across the field rather than a uniform application using spatial variability of nutrient content. Restoring soil NO3−retention capacity and adopting agroforestry system can also be promising ways to improve NUE. Furthermore, the use of genetic modification or the development of new cultivars that use N more efficiently is critical. In addition, omics data, including transcriptomics and metabolomics, not only advance our current understanding of N reactions but also help us move towards strategies, which are more effective in improving NUE and enhancing crop production. In conclusion, this article strongly advocates the use of integrated approaches with a private insight of genetics and agricultural management when managing N.