热带农业生态系统土壤肥力与植物养分综合管理研究进展

The greatest challenge for tropical agriculture is land degradation and reduction in soil fertility for sustainable crop and livestock production.Associated problems include soil erosion,nutrient mining,competition for biomass for multiple uses,limited application of inorganic fertilizers,and limited capacity of farmers to recognize the decline in soil quality and its consequences on productivity.Integrated soil fertility management(ISFM) is an approach to improve crop yields,while preserving sustainable and long-term soil fertility through the combined judicious use of fertilizers,recycled organic resources,responsive crop varieties,and improved agronomic practices,which minimize nutrient losses and improve the nutrient-use efficiency of crops.Soil fertility and nutrient management studies in Ethiopia under on-station and on-farm conditions showed that the combined application of inorganic and organic fertilizers significantly increased crop yields compared to either alone in tropical agro-ecosystems.Yield benefits were more apparent when fertilizer application was accompanied by crop rotation,green manuring,or crop residue management.The combination of manure and NP fertilizer could increase wheat and faba bean grain yields by 50%–100%,whereas crop rotation with grain legumes could increase cereal grain yields by up to 200%.Although organic residues are key inputs for soil fertility management,about 85% of these residues is used for livestock feed and energy;thus,there is a need for increasing crop biomass.The main incentive for farmers to adopt ISFM practices is economic benefits.The success of ISFM also depends on research and development institutions to provide technical support,technology adoption,information dissemination,and creation of market incentives for farmers in tropical agro-ecosystems.     

适宜施氮量降低京郊小麦-玉米农田N2O排放系数增加产量

为明确京郊地区小麦-玉米轮作农田的N_2O排放特征,寻求既能减少N_2O排放又保证粮食产量的切实有效措施,以京郊地区冬小麦-夏玉米轮作农田为研究对象,运用静态箱法对8个施氮水平的农田N_2O交换通量进行了连续一年对比研究,每季作物施肥量分别为N0(0 kg/hm~2),N1(50 kg/hm~2),N2(100 kg/hm~2),N3(150 kg/hm~2),N4(200 kg/hm~2),N5(250 kg/hm~2),N6(300 kg/hm~2),和N7(400 kg/hm~2)。在N0-N7施氮量条件下冬小麦季N_2O排放量为0.08~0.52 kg/hm~2;夏玉米季0.26~3.70 kg/hm~2。整个轮作周期,小麦季各处理N_2O排放损失率为0.05%~0.13%;玉米季0.78%~1.02%。在京郊地区冬小麦-夏玉米轮作体系中夏玉米季氮肥施入农田土壤后,土壤N_2O排放通量高于小麦季。京郊农田土壤N_2O排放通量表现出明显的季节性和日变化规律。综合考虑本试验条件下施肥量、N_2O排放量和京郊地区潮土农田小麦-玉米产量,研究认为该轮作体系中每季作物的施肥量为N4(200 kg/hm~2)比较合理,可为合理施肥及估算中国农田温室气体排放量提供参考。     

Agricultural production,greenhouse gas emissions and mitigation potential

During the next three decades, Asia will remain the largest food consumer (increasing from 40 to 55% of the global consumption between 2000 and 2015) and the largest source of greenhouse gas (GHG) from agriculture (about 50% of the total emissions). The growth of food demand in Africa and South America will cause substantial increase in GHG emissions by the agri-food sector, unless improved management systems are adopted. The higher food consumption rate (kJ person⁻¹ day⁻¹) around the world is primarily a result of improved crop production and higher percentage of animal products in diet. The latter will, however, result in more CH₄ emissions. The growing use of N fertilizers is also a concern. The part not taken up by crops (more than 50%) is either lost through leaching or released to the atmosphere as N gases including nitrous oxide. Between 2000 and 2030, the total GHG emissions are expected to increase by about 50%, with further impact on weather and climate. Mitigation techniques such as improved feed quality for a better digestibility, improved manure management, greater N use efficiency, better water management of rice paddies and/or by increasing the role of agro-forestry in agriculture, have to be considered in order to minimize the impact of agriculture on climate.     

长期施肥对农田土壤氮素关键转化过程的影响

当前,如何合理施肥、提高作物产量、维持土壤肥力、并兼顾生态环境效应是农业研究的主要挑战之一。本文综述了长期施肥对农田土壤氮素关键转化过程的影响,主要从土壤氮转化过程的初级转化速率角度综述肥料(有机肥和化学氮肥)对土壤氮素关键转化过程的影响。土壤氮素矿化-同化循环是自然界氮循环过程中两个至关重要的环节,是决定土壤供氮能力的重要因素。总体而言,长期施用氮肥,尤其是有机肥能显著提高初级矿化-同化周转速率;长期施肥可以刺激自养硝化作用,且有机肥的刺激作用更明显;施用化学氮肥和有机肥均能提高反硝化速率,且有机肥的刺激作用高于化学氮肥。有机肥一直被提倡和实践用来改善土壤肥力和提高土壤固碳能力,无论是单施有机肥还是有机-无机配施,均能有效地减轻硝酸盐污染,改善土壤肥力并提高作物产量。但是有机肥的施用并不是多多益善,有机肥过多施用也会增加氮损失的风险。因此,本文综述了长期施肥对农田土壤氮素关键转化过程初级转化速率的影响,讨论了各个氮转化过程之间的联系,以期增强人们对长期施肥措施影响农田土壤氮素循环的理解,并为合理施用氮肥、提高氮肥利用率、减少与氮相关的环境污染提供理论依据。     

长期施肥对棕壤铁形态及其有效性的影响

【目的】利用沈阳农业大学棕壤肥料长期定位试验,研究不同施肥处理对耕层土壤酸碱度（pH）、氧化还原电位（Eh）和有机质的影响,探讨不同施肥条件下土壤游离态氧化铁、无定形氧化铁、亚铁总量和有效铁含量的变化以及与pH、Eh和有机质的关系。 【方法】本文选取试验处理为CK（不施肥）、N（氮肥）、NP（氮磷肥配施）、NPK（氮磷钾肥配施）、M（有机肥）、MN（有机肥与氮肥配施）、MNP（有机肥与氮磷肥配施）、MNPK（有机肥与氮磷钾肥配施）。在2014年大豆收获期,采集了不同施肥处理0-20 cm耕层土壤样品,分析了土壤pH、Eh、有机质含量以及游离态氧化铁、无定形氧化铁、亚铁和有效铁含量。 【结果】与1979年原始土壤相比,所有处理土壤pH显著降低了0.6~1.4个单位。不施肥处理土壤有机质下降了11.5%,化肥处理有机质略有下降,而有机肥处理有机质含量显著增加。所有处理有效铁含量显著增加,化肥有机肥配施增加幅度更大;与2014年不施肥处理相比,施用氮肥处理土壤pH最低,而氮肥配施磷、钾和有机肥中的一种或几种pH又有所上升,其中配施有机肥效果最明显;施用化肥处理土壤Eh增加,而施用有机肥处理Eh则下降。施用化肥土壤游离态氧化铁和有效铁含量增加,亚铁含量下降,而施用有机肥土壤游离态氧化铁降低,亚铁总量及有效铁含量增加。 【结论】经过长期耕作和施肥,土壤pH显著下降,有效铁含量显著增加。长期不施肥土壤有机质显著下降。施用氮肥土壤酸化趋势明显,磷、钾和有机肥配施能够缓解氮肥引起的酸化现象。施用有机肥显著降低土壤氧化还原电位,有利于氧化态铁向还原态铁转化,更有利于增加土壤有效性铁的含量。     

中国农作物秸秆综合利用潜力研究

针对秸秆分区布局规划不完善,导致地区性、季节性、结构性秸秆过剩,资源浪费与环境污染问题突出,研究秸秆综合利用规划理论,提出"一主多元、农用优先"秸秆综合利用途径。中国秸秆综合利用潜力总量8.76亿t,比2015年增加利用量1.56亿t,其中秸秆肥料化、饲料化和能源化利用量分别增加8 722.4万t、5 122.3万t和1 720.1万t。通过肥料和饲料化利用,可直接和间接替代化肥潜力氮肥(N)1 481.6万t、磷肥(P2O5)419万t、钾肥(K2O)1 885.1万t,节本增效节约化肥成本约685.9亿元(折合98.5元/t秸秆);通过能源化利用,可替代煤炭等化石能源5982.4万t(标准煤),可减排二氧化碳1.5亿t、二氧化硫448.7万t、氮氧化物224.3万t,烟尘4068万t,经碳排放交易经济效益可达20.25亿元(折合16.9元/t秸秆),环境和经济效益显著。     

氮肥与氮转化调控剂配施降低夏玉米-冬小麦农田N2O排放

针对农业生产中氮肥施用不合理导致氮肥利用率低、N_2O排放增加及经济效益下降等问题,采用田间试验法研究了不同氮肥与氮转化调控剂配施模式的夏玉米-冬小麦一年两作农田N_2O排放特征及经济效益。结果表明:与农民施氮肥处理(FN)相比,各推荐施氮处理在夏玉米季和冬小麦季的N_2O平均排放通量分别降低29.2%~65.4%(P0.05)和26.9%~74.9%(P0.05),N_2O排放总量分别降低1.05~2.72(P0.05)和1.10~2.47(P0.05)kg/hm~2;整个轮作季纯收益增加967.5~3 887.0元/hm~2。同等施氮量条件下,与推荐施氮处理(RN)相比,夏玉米季推荐施氮配施双氰胺处理(RN+DCD)和推荐施氮配施吡啶处理(RN+CP)分别使N_2O平均排放通量降低41.5%(P0.05)和31.2%(P0.05);而在冬小麦季则分别下降63.0%(P0.05)和65.7%(P0.05);整个轮作季RN+DCD和RN+CP处理N_2O排放总量分别降低了52.5%(P0.05)和49.0%(P0.05),纯收益分别增加312.6和708.9元/hm~2。夏玉米季,土壤N_2O阶段排放峰值出现在三叶期-拔节期和大喇叭口期-抽雄期;而冬小麦季土壤N_2O阶段排放峰值出现在播种-冬前苗期和返青-拔节期。考虑作物产量、N_2O排放以及经济效益,RN+DCD和RN+CP处理经济效益较高,N_2O排放总量较少,是兼顾作物产量、农民收入及大气环境的推荐氮肥管理措施。     

A simple process-based model for estimating ammonia emissions from agricultural land after fertilizer applications

Abstract. Fertilizer applications to agricultural land are a significant source of ammonia (NH₃) emission to the atmosphere, accounting for approximately 10% of the total emissions from agriculture. Current estimates of emissions from fertilizer applications use 'fixed' emission factors. This paper describes a model in which the emission factors are expressed as a function of the important influencing variables: fertilizer type, soil pH, land use, application rate, rainfall and temperature. Total emission in 2002 for the UK were estimated by running the model for a 'standard UK' scenario, viz. 28.7 kt NH₃-N, which compares well with the UK inventory estimate of 30.4 kt NH₃-N. Differences exist in the estimates for specific fertilizer types, with the mean emission factor for urea applications to grassland, in particular, being lower by use of this model (13% compared with 23% of applied N for the UK inventory). Emission estimates were most sensitive to temperature and fertilizer type. Scenario testing showed that significant reductions in emission could be achieved by replacing urea with other forms of N fertilizer, by combining urea use with a urease inhibitor, or by modifying some management practices.     

Implications of climate change for tillage practice in Australia

The world is experiencing climate change that in no way can be considered normal, and the challenge that this brings to agriculture is twofold. The first challenge relates to the continuing need to reduce greenhouse gas emissions that generate the changes to climate. Australia's National Greenhouse Gas Inventory estimates that agriculture produces about one-quarter of Australia's total greenhouse gas emissions (including land clearing). The main gases emitted are carbon dioxide, methane, and nitrous oxide. These gases are derived from high-value components within the agricultural production base, so reducing emissions of greenhouse gases from agriculture has the potential to provide production and financial benefits, as well as greenhouse gas reduction. Methane essentially derives from enteric fermentation in ruminants. Nitrous oxide and carbon dioxide, on the other hand, are strongly influenced, and perhaps even determined by a range of variable soil-based parameters, of which the main ones are moisture, aerobiosis, temperature, amount and form of carbon, organic and inorganic nitrogen, pH, and cation exchange capacity. Tillage has the potential to influence most of these parameters, and hence may be one of the most effective mechanisms to influence rates of emissions of greenhouse gases from Australian agriculture. There have been substantial changes in tillage practice in Australia over the past few decades – with moves away from aggressive tillage techniques to a fewer number of passes using conservative practices. The implications of these changes in tillage for reducing emissions of greenhouse gases from Australian agriculture are discussed.

The second challenge of climate change for Australian agriculture relates to the impacts of climate change on production, and the capacity of agriculture to adapt where it is most vulnerable. Already agriculture is exposed to climate change, and this exposure will be accentuated over the coming decades. The most recent projections for Australia provided by the CSIRO through the Australian Climate Change Science Programme, indicate that southern Australia can expect a trend to drying due to increased temperatures, reduced rainfalls, and increased evaporative potentials. Extremes in weather events are likely also to become more common. We anticipate that climate change will become an additional driver for continued change in tillage practice across Australia, as land managers respond to the impacts of climate change on their production base, and governments undertake a range of activities to address both emissions reduction and the impacts of climate change in agriculture and land management.     

农作措施对中国稻田氧化亚氮排放影响的研究进展

农业是全球最主要的温室气体排放源之一,稻田不仅是全球重要的甲烷(CH4)排放源,亦是氧化亚氮(N2O)的重要排放源。灌溉、施肥、耕作等农作措施能够改变稻田生态系统土壤微环境,影响土壤硝化与反硝化过程,进而影响N2O的排放。目前,关于农作措施对农田生态系统N2O排放特征研究很多,但系统地综述农作措施对稻田N2O排放影响的研究还比较少。该文着眼于中国的农业发展趋势,基于稻田灌溉、施肥及耕作等方面的新技术,综合分析新型农作措施对中国稻田生态系统N2O排放的影响及其机制,为相关研究提供参考。在此基础上,提出了中国稻田生态系统N2O排放深入研究的方向:1)加强研究新型农作措施下稻田N2O产生及排放途径;2)系统研究稻田生态系统直接与间接N2O排放的影响及其机制;3)开展农作措施集成技术对稻田生态系统N2O排放影响的研究;4)加强模型模拟的调参验证并进行相关预测分析。     

生物炭及炭基硝酸铵肥料对土壤化学性质及作物产量的影响

为了促进生物炭研究和农用,采用盆栽试验研究了两种生物炭基氮肥及相应生物炭对土壤部分化学性质、养分状况及作物产量的影响。试验结果表明：施用生物炭基氮肥可显著提高土壤有机碳含量,提高土壤pH值、阳离子交换量、土壤速效磷、速效钾和矿质态氮含量,增强土壤保肥能力,促进作物增产。生物炭对土壤化学性质和养分状况虽有一定改善作用,但作物增产效应不明显甚至减产。因此,将生物炭与肥料复合制成生物炭基肥料不但可以保持生物炭改良土壤的功能,还可促进作物生长和增产,有利于生物炭农用效益的提升。     

不同氮源及秸秆添加对菜地土壤N_2O排放影响

在饱和田间持水量WFPS(water-filled pore space)为75%、温度为25℃的条件下,用室内培养研究设施菜地土壤在不同氮肥种类(硝酸钙CN,碳酸氢铵AB,硫酸铵AS,尿素U,对照CK)和有无秸秆添加情况下N2O的排放特征。培养17天的结果表明,各种肥料类型中,对照和硝态氮肥处理最先出现N2O排放高峰,铵态氮肥处理出现较晚。无论有无秸秆,碳酸氢铵(AB)处理的累积排放量都最高,分别为4.206±0.899和2.159±0.256μg g-1干土,铵态氮肥处理N2O排放量明显高于硝态氮肥。添加秸秆后各处理N2O排放明显增加,比未施秸秆增加1倍多(CN处理除外)。不同处理(CK除外)的N2O累积排放量与时间的关系都可用y=aLn(x)+b表示(P<0.001)。实验还发现,施用氮肥会导致土壤酸化,添加秸秆可改善土壤酸化现象。     

Impacts of land management on fluxes of trace greenhouse gases

Abstract. Land use change and land management practices affect the net emissions of the trace gases methane (CH₄) and nitrous oxide (N₂O), as well as carbon sources and sinks. Changes in CH₄ and N₂O emissions can substantially alter the overall greenhouse gas balance of a system. Drainage of peatlands for agriculture or forestry generally increases N₂O emission as well as that of CO₂, but also decreases CH₄ emission. Intermittent drainage or late flooding of rice paddies can greatly diminish the seasonal emission of CH₄ compared with continuous flooding. Changes in N₂O emissions following land use change from forest or grassland to agriculture vary between climatic zones, and the net impact varies with time. In many soils, the increase in carbon sequestration by adopting no-till systems may be largely negated by associated increases in N₂O emission. The promotion of carbon credits for the no-till system before we have better quantification of its net greenhouse gas balance is naïve. Applying nitrogen fertilizers to forests could increase the forest carbon sink, but may be accompanied by a net increase in N₂O; conversely, adding lime to acid forest soils can decrease the N₂O emission.     

基于农业投入的重庆农业碳排放时序特征及减排措施研究

农业越来越成为世界上碳排放的主要来源之一,已引起全世界的高度关注。基于农业投入的化肥、农膜、农药、用电量以及柴油5个方面碳源,测算了重庆市1996—2010年近15a的农业碳排放,结果表明:(1)近15a,重庆市农业投入的碳排放呈明显增长趋势,农业投入碳排放总量增长分为三个阶段:增长率下降的缓慢增长阶段、环比增长起伏的波动增长阶段和迅猛增长阶段。(2)近15a,重庆市农业投入的碳排放强度处于明显增长阶段,增长率达到120.32%;2007年以后碳排放环比增长与碳排放强度环比增长趋于吻合。(3)近15a,农业生产中化肥使用导致的碳排放在整个农业投入的碳排放中始终占据绝对支配地位,但呈下降趋势。农村用电碳排放所占比例仅次于化肥使用的碳排放,且呈增加趋势,由1996年的22.1%增加到2010年的38.69%。农膜、农药、农用柴油的使用导致碳排放量增加,但是在全年当中所占比例基本稳定。最后,立足研究结论,提出了未来重庆农业减排的措施,以期为重庆低碳农业发展提供借鉴和参考。     

长期定位施肥条件下黄土旱塬农田作物产量、水分利用效率的变化

以始于1979年的黄土旱塬黑垆土长期5种肥料试验为基础,研究了小麦、玉米一年一熟轮作条件下旱地作物产量及水分利用的变化。结果表明,无论气候年型如何,作物平均产量和水分利用效率大小依次为：有机无机肥结合（MNP）>秸秆还田与化肥配合（SNP）>单施化肥（NP）>单施农家肥（M）>单施化肥氮（N）>不施肥（CK）;MNP和SNP施肥方式在旱地农业生产中具有显著的增产和提高水分利用效率的作用,2种施肥方式下小麦平均产量较CK增加189%和158%,水分利用效率提高193%和 165%,玉米平均产量较CK增加125%和99%,水分利用效率提高121%和96%。随着试验年限的延长,化肥尤其是氮肥的增产效果受降水影响年际之间波动性很大, 但无机氮磷结合农家肥、无机氮磷配合秸秆还田能有效减缓产量的波动,起到抗逆减灾和稳定产量的作用。有机无机肥结合（MNP）和秸秆还田与化肥配合（SNP）是实现旱地有限水资源高效利用和旱地农业可持续发展的施肥方式。     

Effects of Nitrogen and Phosphorus Fertilizers and Intercropping on Uptake of Nitrogen and Phosphorus by Wheat,Maize, and Faba Bean

Abstract

One‐third of all the cultivated land area is used for multiple cropping and half of the total grain yield is produced with multiple cropping in China. There have been numerous studies on nutrient acquisition by crops in legume/non‐legume intercropping systems, but few on nutrient uptake in cereal/cereal intercropping. This paper describes a field experiment in which integrated wheat/maize and maize/faba bean systems were compared with sole wheat and sole faba bean cropping to assess the effects of intercropping on nutrient uptake by wheat, maize, and faba bean under various application rates of nitrogen (N) and phosphorous (P) fertilizers. Results show that both N and P fertilizers and intercropping enhanced N uptake by wheat, while only P fertilizer and intercropping increased P acquisition by wheat. The advantage of N uptake by border rows of wheat intercropped with maize declined with increasing N fertilizer application rate, but that of P acquisition was not affected by P fertilizer. The amounts of both N and P taken up by maize intercropped with faba bean were much higher than those by maize intercropped with wheat throughout the period of intercropping. Both fertilization and intercropping did not influence the N and P uptake by faba bean.     

等养分条件下稻草还田替代双季早稻氮钾肥比例的研究

【目的】研究等量氮磷钾养分投入条件下,长期稻草原位全量还田配施化肥对双季早稻氮 (N)、磷 (P)、钾 (K) 养分吸收累积、转运及养分利用的影响,为南方稻区稻草资源有效利用,维持并提高土壤肥力及水稻合理施肥提供理论依据。【方法】以江西温圳国家级耕地质量监测点长期定位试验为研究对象,陆两优 996 为供试材料,在不施化肥和施用化肥基础上设稻草还田、稻草烧灰还田和稻草不还田共 6 个处理,除空白对照外,所有处理养分投入量相等。于 2015 年在早稻移栽期、分蘖期、幼穗分化期、抽穗期和成熟期取地上部植株样,分析水稻植株不同部位的 N、P、K 含量和累积量以及转运比例,并计算 N、P、K 养分利用效率。【结果】稻草还田提高了水稻产量,施肥条件下稻草还田处理比稻草烧灰还田和稻草不还田处理平均增产 2.9%～ 6.4%,比不施肥区产量增幅高达 23.8%～ 26.0%,且差异达显著水平。无论是施肥区处理,还是无肥区处理,与稻草烧灰还田和稻草不还田处理相比,稻草还田植株中 K 含量及 N、P、K 积累量在整个生育期均较高,而 N、P 含量在生育后期较高,N、P、K 积累量以施肥区处理大于相应的无肥区处理;稻草还田提高水稻 N、P、K 养分农学效率、回收率和养分偏生产力,且 N、K 差异达显著水平,同时显著增加 K 的收获指数;稻草还田还提高了抽穗至成熟期茎鞘中 N、P、K 的转运量、转运率及转移养分对籽粒的贡献率,而叶片各处理间差异不显著。【结论】稻草还田配施化肥能提高水稻产量,同时还可以调节 N、P、K 养分的积累和转运,提高养分的吸收利用效率。本试验条件下,稻草还田可替代化肥氮肥 (N) 29.5%、磷肥 (P₂O₅) 4.0% 和钾肥 (K₂O) 50.0%。综合考虑,稻草还田相比稻草烧灰还田而言是南方稻区土壤养分管理实现高效利用的有效途径之一。     

Effect of Stover Management and Nitrogen Fertilization on N<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> Emissions from Irrigated Maize in a High Nitrate Mediterranean Soil

A high soil nitrogen (N) content in irrigated areas quite often results in environmental problems. Improving the management practices of intensive agriculture can mitigate greenhouse gas (GHG) emissions. This study compared the effect of maize stover incorporation or removal together with different mineral N fertilizer rates (0, 200 and 300 kg N ha^?1) on the emission of nitrous oxide (N₂O) and carbon dioxide (CO₂) on a sprinkler-irrigated maize (Zea mays L.). The trail was conducted in the Ebro Valley (NE Spain) in a high nitrate-N soil (i.e. 200 g NO₃–N kg^?1). Nitrous oxide and CO₂ emissions were sampled weekly using a semi-static closed chamber and quantified using the photoacoustic technique in 2011 and 2012. Applying sidedress N fertilizer tended to increase N₂O emissions whereas stover incorporation did not have any clear effect. Nitrification was probably the main process leading to N₂O. Denitrification was limited by the low soil moisture content (WFPS <?54%), due to an adequate irrigation management. Emissions ranged from ??0.11 to 0.36% of the N applied, below the IPCC (2007) values. Nitrogen fertilization tended to reduce CO₂ emission, but only in 2011. Stover incorporation increased CO₂ emission. Nitrogen use efficiency decreased with increasing mineral fertilizer supply. The application of N in high N soils of the Ebro Valley is not necessary until the soil restores a normal mineral N content, regardless of stover management. This will combine productivity with keeping N₂O and CO₂ emissions under control provided irrigation is adequately managed. Testing soil NO₃ ^?–N contents before fertilizing would improve N fertilizer recommendations.     

有机肥与无机肥配施对菜地土壤N2O排放及其来源的影响

该研究采用同位素自然丰度法,通过室内培养试验研究北京地区菜地有机肥和无机肥配施对土壤释放N2O及同位素位嗜值SP（site preference）的影响,以期获得不同肥料及其配比下土壤N2O的来源及变化规律。结果表明：施用无机肥释放的N2O显著高于有机肥,其累积排放量是有机肥的6.63倍,且无机肥施用比例越高,排放量越大;各肥料组合在施用后7天内均以反硝化作用生成N2O为主,贡献最高达到78.89%,SP为6.97‰,之后硝化作用逐渐增强并成为主要途径,最高占比达76.48%,SP为25.24‰;培养期内施用无机肥可以促进反硝化作用,平均占比52.98%,SP为15.52‰,而有机肥会使硝化作用增强,平均占比71.35%,SP为23.55‰。因此,在北京潮褐土地区菜地土壤施用有机肥对N2O有良好的减排效果,可为蔬菜生产中肥料的合理应用提供科学依据。     

禾豆间作氮素高效利用机理及农艺调控途径研究进展

为保障粮食安全,农业生产中化肥使用极为普遍,但过量使用,往往引起地下水污染、温室效应加剧、生物多样性降低等多种环境和生态问题。禾豆间作系统由于不同作物生物学特性和氮素利用存在差异,进行合理调控可充分发挥生物固氮优点,从而减少化肥投入,提高生产效益,是一种稳产、高产、高效可持续的种植体系。该系统中"氮转移"、"氮阻遏"消减和氮素时空分异是目前研究的热点,也是促进豆科作物固氮、减少化肥投入的有效途径,可实现禾、豆两种作物对氮素的高效利用。特别是该系统中作物品种、施氮制度、空间布局以及种植密度等农艺措施是对种间关系进行调控的必要手段,合理优化可有效促进禾/豆间作竞争与互补协同作用,增强氮素协调利用,从而挖掘两种作物对氮素高效利用的生物学潜力。为此,本文基于前人研究成果和农业可持续发展观点,重点综述了国内外有关禾豆间作氮素高效利用主要机理及相关农艺调控途径的研究现状,旨在为构建简易、高产、高效、氮肥节约型禾豆间作模式提供有力的科学依据和理论支撑。