Minimizing nitrogen environmental impacts in intensive greenhouse vegetable production systems in Shandong, China (NIVEP)

大约中国消费的所有蔬菜中，有三分之一是由所谓的日光温室里的小农户生产的。然而，农民过度使用化肥，特别是氮肥，两个生长季节每年2000公斤N公顷的施肥量是相当正常的，也不是例外。这造成了并正在造成巨大的环境问题：土壤酸化和盐碱化，土壤生态功能退化和病原体增加，杀菌剂、农药和硝酸盐在表层和下层土壤中积累，地下水的硝酸盐污染，以及温室气体N2O损失增加。该项目的总体目标是描述和量化不同管理的温室土壤与常规管理的耕地土壤相比，植物和/或微生物的氮去除、氮固定过程和气态氮损失的变化。因此，该项目旨在确定土壤恢复和减少集约管理温室蔬菜生产系统土壤的水文和气态氮损失的可行方法。在总体目标的基础上，确定了以下子目标：1)利用时间序列方法量化日光温室土壤表层(0~1m)和下层(1~3m土层)C、N储量的时间动态变化。2)量化了集约管理日光温室蔬菜系统土壤剖面中实际和潜在反硝化速率随管理和土地利用历史的变化。3)评价厌氧土壤侵染和在底土中添加DOC去除表层和底土中过量NO3-的效果。因此，追踪底土产生的N2O的去向可能对土壤-大气N2O通量有贡献。4)确定不同的日光温室土壤恢复措施和管理方法的潜力，如生物炭和/或秸秆的施用以及滴灌在提高土壤健康、土壤氮素保持潜力和氮素利用率以及减少温室气体排放和温室蔬菜生产系统的水文氮素损失方面的有效性。

Approx. 1/3 of all vegetables consumed in China are produced mostly by smallholders in so called solar greenhouses. However, farmers are overusing fertilizers, specifically N based fertilizers, and application rates >2000 kg N hectare and year in two growing seasons are rather normal and not the exception. This has caused and is causing tremendous environmental problems: soil acidification and salinization, degradation of soil ecological functions and increase occurrence of pathogens, accumulation of fungicides, pesticides and nitrates in top- and subsoils, nitrate pollution of groundwater, and increased losses of the greenhouse gas N2O. The overall objective of the project is the characterization and quantification of changes in plant and/ or microbial N removal, N immobilization processes and gaseous N losses for differently managed greenhouse soils as compared to conventionally managed arable soil. Thus, the project aims at the identification of feasible approaches for soil restoration and mitigation of soil hydrological and gaseous N losses from soils of intensively managed greenhouse vegetable production systems. Based on the overall objectives the following sub-objectives have been defined: 1) Quantification of the temporal dynamics of topsoil (0 to 1 m) and subsoil (1 to 3 m soil depth) changes in C and N stocks of solar greenhouse soils using a chronosequence approach. 2) Quantification of changes in actual and potential denitrification rates in soil profiles of intensively managed solar greenhouse vegetable system as affected by management and land use history. 3) Assessment of the effectiveness of anaerobic soil infestation and DOC additions to subsoils for removing excess NO3- from top- and subsoils. Thereby, tracing the fate of subsoil produced N2O for its possible contribution to soil-atmosphere N2O fluxes. 4) Identification of the potential of different solar greenhouse soil restoration measures and management methods such as biochar and/or straw application as well as drip irrigation for its effectiveness in increasing soil health, soil N retention potentials and NUE efficiency as well as reducing greenhouse gas emission and hydrological N losses from greenhouse vegetable production systems.