不同氮水平对马铃薯块茎和土壤NO_3^--N含量的影响

[目的]为马铃薯科学施肥提供理论依据。[方法]设置N1:传统氮肥施用量;N2:80%推荐氮肥施用量、N3:推荐氮肥施用量、N4:120%推荐氮肥施用量4个氮水平,研究不同水平对马铃薯块茎和土壤NO3--N含量的影响。[结果]马铃薯块茎内NO3--N含量随施氮量的增加而增加,但均未超标。N2处理马铃薯产量最高,块茎NO3--N为431.56 mg/L。随着施氮量的增加,氮淋失程度加深,土壤中的NO3--N含量逐渐增加。各处理土壤NO3--N含量随土层的加深有不同程度的递减。N2处理的氮素供应与马铃薯对N素的吸收基本达到了平衡。[结论]随着氮水平的提高,马铃薯块茎和土壤中的NO3--N含量均呈上升趋势。

Nitrogen cycling and environmental impacts in upland agricultural soils in North China： A review

The upland agricultural soils in North China are distributed north of a line between the Kunlun Mountains, the Qinling Mountains and the Huaihe River. They occur in arid, semi-arid and semi-humid regions and crop production often depends on rain-fed or irrigation to supplement rainfall. This paper summarizes the characteristics of gross nitrogen（N） transformation, the fate of N fertilizer and soil N as well as the N loss pathway, and makes suggestions for proper N management in the region. The soils of the region are characterized by strong N mineralization and nitrification, and weak immobilization and denitrification ability, which lead to the production and accumulation of nitrate in the soil profile. Large amounts of accumulated nitrate have been observed in the vadose-zone in soils due to excess N fertilization in the past three decades, and this nitrate is subject to occasional leaching which leads to groundwater nitrate contamination. Under farmer＇s conventional high N fertilization practice in the winter wheat-summer maize rotation system（N application rate was approximately 600 kg ha–1 yr–1）, crop N uptake, soil residual N, NH_3 volatilization, NO_3~– leaching, and denitrification loss accounted for around 27, 30, 23, 18 and 2% of the applied fertilizer N, respectively. NH_3 volatilization and NO_3~– leaching were the most important N loss pathways while soil residual N was an important fate of N fertilizer for replenishing soil N depletion from crop production. The upland agricultural soils in North China are a large source of N_2O and total emissions in this region make up a large proportion（approximately 54%） of Chinese cropland N_2O emissions. The “non-coupled strong ammonia oxidation” process is an important mechanism of N_2O production. Slowing down ammonia oxidation after ammonium-N fertilizer or urea application and avoiding transient high soil NH4＋ concentrations are key measures for reducing N_2O emissions in this region. Further N management should aim to minimize N losses from crop and livestock production, and increase the recycling of manure and straw back to cropland. We also recommend adoption of the 4 R（Right soure, Right rate, Right time, Right place） fertilization techniques to realize proper N fertilizer management, and improving application methods or modifying fertilizer types to reduce NH_3 volatilization, improving water management to reduce NO_3~– leaching, and controlling the strong ammonia oxidation process to abate N_2O emission. Future research should focus on the study of the trade-off effects among different N loss pathways under different N application methods or fertilizer products.

土壤中反硝化酶活性变化与N_2O排放的关系

研究施肥条件下，土壤反硝化酶活性硝酸还原酶（ＮＲ）活性、亚硝酸还原酶（ＮｉＲ）活性及羟胺还原酶（ＨｙＲ）活性在玉米生长季节中的变化及其与土壤含水量、硝态氮含量、Ｎ２Ｏ排放之间的关系．结果表明，３种还原酶都有明显的季节变化规律并受土壤水分含量及施肥的影响．通过研究３种反硝化酶活性与土壤含水量及Ｎ２Ｏ排放量之间的关系后指出。

有机种植条件下水肥管理对番茄品质和土壤硝态氮累积的影响

采用田间试验方法研究了北京郊区主要蔬菜作物—番茄在大棚有机种植条件下,不同有机肥投入量与灌溉量对番茄产量与品质以及土壤硝态氮累积的影响。结果表明,与当地习惯的水肥管理相比,减半量有机肥投入不会显著降低番茄产量,而且能降低硝态氮、重金属和有机酸的含量,有效地改善果实品质,并增加番茄果实中可溶性糖、Vc、番茄红素等营养元素的含量;还能显著降低土壤中硝态氮累积量。在施肥量相同的条件下,减量灌溉也有同样的结果,但效果不如减量施肥明显;过量施用有机肥可造成番茄果实中硝酸盐含量和镉、铬、锌等重金属含量超标。说明在番茄的有机种植中,保证产量和品质的前提下开展节本增效还有很大空间。

稻草还田与不同耕作方式对麦田土壤脲酶和土壤无机氮的影响

采用小区试验研究稻草还田与不同耕作方式对麦田土壤脲酶、铵态氮、硝态氮含量的影响.结果表明：稻草还田与耕作方式影响了土壤铵态氮的分布,在小麦不同生育期影响不同.稻草还田有利于提高小麦对硝态氮的吸收,降低了小麦拔节期至灌浆期土壤10～20 cm土层硝态氮含量.耕作方式对土壤硝态氮含量影响因小麦生育期不同而不同.稻草还田使小麦抽穗期、灌浆期0～10 cm土层脲酶活性降低,应增加氮肥施用.

陇东旱地苹果园不同地面覆盖模式的水分与养分效应

为完善和改进果园树盘起垄覆膜集雨保墒模式,提高土壤墒情,探寻更加有效的果园保墒措施,该研究以17 a生苹果园为研究对象,设置常规树盘起垄覆膜行间清耕模式(F),在F基础进行改进的树盘起垄覆膜+行间覆草模式(F+W)和树盘起垄覆膜+行间覆草+膜侧添加渗水穴模式(F+W+H)2种改进模式,以不起垄不覆盖为对照(CK),采用定点试验,连续3 a(2015年干旱、2016年秋旱和2017年常年降雨)开展苹果花前、果实膨大期及采后的水分效应,以及养分效应和树体生长发育响应研究。结果显示:3种覆盖模式可不同程度增加0~200 cm土层的含水率,以2017年最显著,2种改进模式可缓解300~500 cm土层水分消耗,降低休眠期无效蒸散,3 a三种覆盖模式果园土层总蒸散量均极显著(P<0.01)低于CK,由低到高顺序为F+W+H、F+W、F、CK。2015年和2016年采后覆盖模式0~300 cm土层硝态氮累积量均极显著(P<0.01)低于CK(比CK低34.4%~39.6%)。3种覆盖模式增加果实中氮磷钾养分吸收,以钾最突出。F+W+H、F+W和F 3 a平均产量分别较CK提高13.1%、13.0%和8.3%。综合各种效应,以2种改进覆盖保墒模式F+W+H和F+W较优。

河北省典型保护地蔬菜土壤硝态氮的含量和分布

调查了定州市和永年县蔬菜大棚和拱棚施肥情况 ,并采集土壤样品测定了土壤硝态氮含量。结果表明 ,蔬菜土壤硝态氮含量定州市平均比永年县高出 1 3 3～ 38 9mg/kg。表层土壤的硝态氮含量 ,定州市变化幅度 60～ 2 0 0mg/kg ,平均 94 2 5mg/kg ,永年县变化幅度为43 0～ 64 7mg/kg之间 ,平均 5 5 4mg/kg。保护地蔬菜土壤 0～ 1 0 0cm土层积累了大量的硝态氮。其中定州市蔬菜大棚土壤 1m土层内硝态氮含量平均为 80 7 0 6kg/hm2 ,永年县平均为430 32kg/hm2 ,均高于大田作物。容易造成土壤硝态氮积累和淋溶。

生物炭和有机肥对华北农田盐碱土N_2O排放的影响

基于山东滨州地区冬小麦-夏玉米轮作大田试验,探究了施用生物炭和有机肥对夏玉米季土壤氧化亚氮(N_2O)排放的影响,为盐碱土壤N_2O增汇减排提供理论依据.试验按照不同处理氮、磷、钾含量相同原则,设置对照CK[N:0.2t·(hm^2·a)^(-1),P_2O_5:0.12 t·(hm^2·a)^(-1),K_2O:0.2 t·(hm^2·a)^(-1)]、C1[5 t·(hm^2·a)^(-1)生物炭]、C2[10 t·(hm^2·a)^(-1)生物炭]、C3[20 t·(hm^2·a)^(-1)生物炭]、M1[7.5 t·(hm^2·a)^(-1)有机肥]、M2[10 t·(hm^2·a)^(-1)有机肥]这6个处理.结果表明,施加生物炭和有机肥对土壤N_2O排放影响趋势基本一致,排放高峰均出现在施肥(基肥和追肥)后,累积排放量占整个生育期排放量的近一半;与CK相比,C1、C2分别降低N_2O排放的45.3%、31.6%,而C3、M1、M2分别增加了17.3%、37.4%、27.6%.施加生物炭和有机肥均会对土壤N_2O排放产生影响,施加生物炭可以降低N_2O排放,而施加有机肥则促进了N_2O排放.因此,生物炭对减少农田N_2O排放具有巨大潜力.