Initial and subsequent effects of hydrochar amendment on germination and nitrogen uptake of spring barley

The application of hydrochars as soil amendments could be an option to ameliorate soil quality by enhancing nutrient and water‐holding capacity of sandy soils. But when hydrochar application is directly followed by sowing, it can decrease the soil mineral‐N concentration and the germination rate of crops. We currently lack evidence, whether these effects are persistent or transient and thus can be avoided by adjusting the application strategy, e.g., by prolonging the period between application and sowing. A set of pot trials with spring barley (Hordeum vulgare L.) was performed to study the initial and subsequent effects of different hydrochar amendments on germination, biomass production, and plant N availability. To this end, two subsequent cultivations of barley were grown on hydrochar‐amended soil–peat substrates. The first barley cultivation was sown directly after hydrochar application. After the harvest, the same substrates were cultivated with barley again. Germination, biomass production, and N concentration in the biomass were reduced when sowing directly followed the application of hydrochars. Differences in germination rate and biomass production between hydrochar treatments depended on the hydrochar feedstock. A recultivation of the hydrochar‐amended substrates 9 weeks after hydrochar application showed no significant effects on germination and biomass production. The N concentration in plants was still lower in the hydrochar treatments despite additional fertilization. The N immobilized during the first cultivation period was not released in the following weeks. We conclude that the germination‐inhibiting substances in hydrochars were removed in the weeks after soil incorporation. This is probably due to microbial degradation of hydrochar components and a consecutive immobilization of mineral N. Hydrochar amendment had only short‐term effects on germination and biomass production of barley that can be avoided by applying hydrochar at least 4 weeks prior to sowing. The N concentration in plants was persistently low even 4 months after hydrochar application which can only be redeemed by adjusting the fertilization strategy.     

Relationship between mineralization and immobilization of nitrogen influenced by various conditions of submerged soils

The relationship between mineralization of soil nitrogen and immobilization of added nitrogen in submerged soils were studied under various soil conditions in a laboratory experiment. Selected factors which constituted soil conditions were content of soil organic nitrogen, quantity of nitrogen addition, temperature, soil drying, puddling, and period of incubation. Each factor contained some treatments in it.

The ratio of mineralization to immobilization, M/I, was relatively constant under various soil conditions. The values of M/I were around 2 except the soil drying treatments, indicating that the amount equivalent to about half of mineralized nitrogen is immobilized simultaneously under nitrogen added condition. Even so, if considered in detail, treatments that stimulate the microbial activities were observed to have increasing effect on M/I.

The ratio of additional mineralization caused by nitrogen addition to immobilization, ΔM/I, is considered to be an index to know the influence of nitrogen addition on the quantitative change of soil nitrogen level. This value was around 1 in the soil without any application of organic matters, and around 0.6 in the soil receiving straw compost for 10 years. Factors that have close relations with the value of ΔM/I were soil organic nitrogen level, temperature, soil drying, and period of incubation.     

凋落物中次生代谢物对森林土壤可溶性氮的影响

通过外加性质不同的凋落物以及不同浓度的单宁酸,于武夷山不同海拔高度的森林土壤中进行培养,研究森林凋落物中次生代谢物对土壤可溶性氮(N)的影响。结果显示,土壤经加入凋落物处理,其可溶性N含量降低。加入杉木凋落物使红壤可溶性N含量降低12.0%～27.5%,杉木较竹叶凋落物处理降低作用显著(p0.05);对黄红壤添加不同浓度单宁酸处理显示,与对照比较,高浓度单宁酸可显著(p0.001)降低土壤可溶性N含量,降低幅度在40.6%～48.1%,而低浓度单宁酸对土壤可溶性N的影响不显著。表明植物凋落物,尤其是杉木对土壤可溶性N的影响很可能与其本身单宁酸含量差异有关,从而影响了土壤可溶性有机N和无机N的转化。     

Effects of amendments and fertilization on plant growth,nitrogen and phosphorus availability in rehabilitated highly alkaline bauxite‐processing residue sand

The effects of organic–inorganic amendments and nitrogen‐phosphorus (NP) fertilization (NH₄NO₃ plus Ca (H₂PO₄)₂) on ryegrass (Lolium rigidum) growth, and nitrogen (N) and phosphorus (P) availability in highly alkaline bauxite‐processing residue sand (BRS), were examined in a pot experiment. The BRS used was either unamended (control) or amended with organic (e.g. greenwaste compost and biochar) or inorganic (e.g. zeolite) materials at a rate of 10% v/v. BRS from 15 years of rehabilitation (15YRRH) was also used as the second control. NP fertilizer was applied at different rates. The experimental set up was arranged in a two factorial complete randomized design. BRS with zeolite and 15YRRH at NP fertilizer rates of 2.0 and 2.5 t/ha produced the highest dry matter, leaf N concentration and N uptake by ryegrass, which were significantly higher (P < 0.05) than the other treatments, suggesting the potential of zeolite in providing stability of applied N fertilizer in BRS. Further, BRS with biochar at NP rates 2.0 and 2.5 t/ha can also be suitable amendments as they enhance growth and also improved the N and P supplying capacity of BRS. Ryegrass leaf P concentration and P uptake were above the critical P values in the 15YRRH compared with organic–inorganic amended BRS, suggesting that time is important for better P uptake from the residue. It is concluded that zeolite and biochar combined with appropriate NP fertilizer rates can improve plant growth and provide a source of nutrients for ryegrass establishment in bauxite residue storage areas. The results need to be tested in field conditions before being advised in farming practice.     

不同氮磷钾肥对土壤pH和镉有效性的影响

采用土壤培养方法研究了不同氮、磷、钾肥对土壤pH和镉有效性的影响。结果表明,在培养60 d时,所有氮肥处理均降低了土壤pH,增加了Cd的提取量;但高量尿素和氯化铵处理土壤pH降低最多,提取的Cd也最多;硫酸铵提取的Cd较对照增加最小。所有磷肥处理均引起土壤pH小幅降低,但对土壤Cd提取量的影响以普钙稍大。3种钾肥处理均降低了土壤pH,其中氯化钾在0 d时提取的Cd在所有钾肥处理中为最高,其提取能力15 d后逐渐消失,试验结束时所有钾肥处理对Cd提取量均低于对照。本研究进一步表明,在土壤Cd含量处于污染临界值附近或已受Cd污染的土壤上,应避免施用高量的酸性肥料如尿素、氯化铵、普钙,以及其他酸性物料。在常用磷、钾肥中,磷酸二铵和硫酸钾在Cd污染土壤上施用更为适合。     

生物炭对植烟土壤氮素形态迁移及微生物量氮的影响

为了在植烟土壤中施加生物炭,以及在不同氮素水平下验证生物炭对土壤氮素的淋洗及迁移的影响.采用大田试验,设计5个处理,在磷肥和钾肥施用量相同的基础上,除对照(CK)处理不施生物炭与氮肥外,其余4个处理都添加1 600 kg/hm2的生物炭,施氮量分别为(N0)0、(N1)37.5、(N2)52.5和(N3) 67.5 kg/hm2,对植烟土壤氮素在0～20、20 ～ 40和40 ～ 60 cm土层施加生物炭,研究全氮、碱解氮、硝态氮和铵态氮质量分数的影响及其迁移规律,以及0～20cm土层微生物量氮的变化特征.结果表明:植烟土壤施用生物炭降低了0～ 20 cm以下土壤氮素质量分数,提高了植烟土壤对氮素的固定能力.与CK相比,增施生物炭的N0在0～20 cm以下土层,土壤全氮、碱解氮、硝态氮和铵态氮质量分数降低率最高达到11.21％、49.07％、42.29％和31.35％.而施氮量对植烟土壤全氮、碱解氮和铵态氮的影响,主要集中在0 ～ 20 em土层,且土壤氮素质量分数随施氮量的增加而增加,以N3处理各氮素指标质量分数相对最高,其全氮、碱解氮和铵态氮质量分数最高分别为2.10 g/kg、261.86 mg/kg和49.80 mg/kg.土壤硝态氮质量分数随土层加深而下降,在0 ～ 20 cm土层,以N3处理最高,达264.90 mg/kg;但不同氮水平下,硝态氮质量分数在20 ～ 40 cm土层差异较其他土层更显著.施用氮肥对植烟土壤氮素的影响主要表现在烟草移栽后前30 d.增施生物炭可以提高烟草移栽后60 d时土壤微生物量氮;而施氮量对微生物量氮熵的影响主要表现在烟草移栽30 d之后.施氮量对植烟土壤氮素的影响主要表现在0～20 cm土层,且在烟草生育前期效果显著.生物炭可以明显抑制植烟土壤本身及低量氮肥施用下氮素淋失迁移,但在高量氮肥施用下的抑制作用不明显.在豫中烟区,以生物炭配施氮肥67.5 kg/hm2施肥措施,最利于植烟土壤氮素提高.     

施氮量对土壤无机氮分布和微生物量氮含量及小麦产量的影响

在高肥力土壤条件下,研究了施氮量对土壤无机氮分布和微生物量氮含量及小麦产量的影响。结果表明,小麦生长期间,施氮处理0100.cm土层硝态氮积累量显著大于不施氮处理;当施氮量大于150.kg/hm2时,随施氮量增加,0100.cm土层硝态氮积累量显著增加;随小麦生育进程推进,施氮处理上层土壤硝态氮下移趋势明显,至小麦成熟时,施氮1952～85.kg/hm2处理60100.cm土层硝态氮含量显著大于其它处理。小麦生长期间,0100.cm土层铵态氮积累量较为稳定,施氮处理间亦无显著差异。与不施氮肥相比,施氮提高小麦生长期间040.cm土层土壤微生物量氮含量;当施氮量小于240.kg/hm2时,随施氮量增加,土壤微生物量氮含量增加。小麦的氮肥利用率随施氮量增加而降低;施氮1051～95.kg/hm2,收获时小麦植株吸氮量、生物产量、子粒产量和子粒蛋白质含量提高;而施氮量大于240.kg/hm2时,小麦生育后期的氮素积累量降低,收获时植株吸氮量、生物产量和子粒蛋白质含量降低。说明本试验条件下,施氮1051～50.kg/hm2可满足当季小麦氮素吸收利用,获得较高的子粒产量和蛋白质含量。继续增加施氮量,土壤微生物量氮含量增加,但土壤中残留大量硝态氮,易淋溶损失。     

洱海北部地区水稻氮肥投入阈值研究

为了研究洱海北部地区水稻合理的氮肥投入阈值。本试验通过连续两年的大田定点监测和室内分析, 研究了不同施氮处理条件下对水稻产量、 水稻氮肥利用率、 田面水可溶性总氮（DTN）、 土壤氮素表观盈余率（SNASR）等的影响。结果表明,施氮量对水稻产量的影响呈二次曲线关系,施氮能显著提高水稻产量,但当施氮量达到304.34 kg/hm2后,水稻有减产风险;增施氮肥能显著提高水稻地上部分器官对氮素的吸收,但收获指数逐渐减少;在施入氮肥后的9 d内,施氮量与田面水DTN浓度相关系数在0.609**以上;当施肥量在228.26~304.34 kg/hm2时,水稻产量范围在9969~10212 kg/hm2,SNASR在50.05%~79.65%之间,田面水DTN在施肥后9 d内的平均含量为78.40 mg/L~108.58 mg/L。因此,在当前生产条件下,水稻推荐施氮量为228.26~304.34 kg/hm2,能保证水稻稳定高产,且环境可承受。     

Driving factors of soluble organic nitrogen dynamics in paddy soils: Structure equation modeling analysis

Soil soluble organic nitrogen (SON) is one of the most active components in soil nitrogen pools; however, limited information is available with regard to its driving factors, as well as their pathways and degrees of influence. In this study, structural equation modeling was used to analyze the driving factors, their significance, and pathways that affected SON dynamics in a waterlogged experiment of two typical paddy soils incubated for 80 d after green manure application. Soil pH, Eh, microbial biomass, enzyme activity, and SON dynamics were used to construct the structural equation model. Results showed that soil microbial biomass carbon (MBC), protease, glutamine, and initial organic matter (OM) directly and significantly affected soil SON with path coefficients corresponding to 0.405, 0.547, 0.523, and -0.623 (P < 0.01), respectively. Soil microbial biomass carbon and initial OM affected the SON dynamics indirectly through protease and glutamine activity. In addition, pH indirectly affected SON dynamics by glutamine activity. It is implied that soil MBC, protease, glutamine, and initial OM are the key factors affecting SON dynamics in the waterlogged paddy soils after green manure application. Our research indicated that structural equation modeling could provide an effective method to clearly recognize the impact, significance, and pathways of multiple factors on SON dynamics in paddy soils.     

控制排水和施氮量对旱地土壤氮素运移转化的影响

为了研究控制排水和氮肥共同作用对旱地土壤氮素运移转化的影响,在湖北荆州丫角排灌试验站进行微区对照试验,以控制水位水平(30、50、100cm)和3个施氮水平(H:68.25/145.6kg/hm2;C:52.5/112kg/hm2,L:36.75/78.4kg/hm2,前面数值是施磷酸二铵量,后面为施硫酸钾复合肥量)为试验变量,组合成H30、H50、H100、C30、C50、C100、L30、L50、L100等9个处理测定了土壤剖面分层NO3-N、NH4+-N含量。对观测结果进行分析表明,常规施氮水平下,自由排水处理各土层NO3-N含量最高、50处理各土层NO3-N含量最低;低施氮水平下30处理NH4+-N含量最高;同一水位处理高施氮水平NH4+-N含量最低。同一施氮水平下,控制水位30cm的NH+4-N含量大于50cm的NH+4-N含量大于100cm的NH+4-N含量。同一施氮水平下实行控制排水可以增加氮素稳定性;实行控制水位处理时,不需增加或减少施氮量、常规施氮条件下氮素稳定性保持最高;而在自由排水时,减少施氮量,能够增加耕层土壤氮素稳定性。     

过量施氮对旱地土壤碳、氮及供氮能力的影响

【目的】过量施氮会影响土壤有机碳、氮的组成与数量,进而改变土壤供氮能力,但关于西北旱地长期过量施用氮肥后土壤有机碳、氮及土壤供氮能力变化的研究尚缺乏。本文在长期定位试验的基础上,通过分析不同氮肥水平特别是过量施氮条件下土壤硝态氮,有机碳、氮和微生物量碳、氮的变化,探讨长期过量施氮对土壤有机碳、氮及供氮能力的影响。【方法】长期定位试验位于陕西杨凌西北农林科技大学农作一站。在施磷(P2O5)100kg/hm2的基础上,设5个氮水平,施氮量分别为N 0、80、160、240、320 kg/hm2。重复4次,小区面积40 m2,完全随机区组排列。种植冬小麦品种为小堰22。本文选取其中3处理,以不施氮为对照(N0)、施氮量N 160 kg/hm2为正常施氮(N160),施氮量N 320 kg/hm2为过量施氮(N320),分别于2012年6月小麦收获后和10月下季小麦播前采集土壤样品,进行测定分析。【结果】过量施氮导致下季小麦播前0—300 cm各土层硝态氮含量显著增加,平均由对照的2.8 mg/kg增加到15.5 mg/kg;同时,0—60 cm和0—300 cm土层的硝态氮累积量分别由对照的47.2和108.9 kg/hm2增加到76.5和727.7 kg/hm2。过量施氮也增加了夏闲期间0—300 cm土层土壤有机氮矿化量,由对照的72.4 kg/hm2增加到130.7 kg/hm2。但过量施氮未显著增加土壤的有机碳含量,却显著增加了土壤有机氮含量,过量施氮0—20、20—40 cm土层土壤有机碳分别为9.24和5.39 g/kg,有机氮分别为1.05和0.71 g/kg,较对照增加52.2%和54.3%。同样,过量施氮未显著影响0—20、20—40 cm土层土壤微生物量碳含量,其平均含量分别为253和205 mg/kg,却显著提高了0—20、20—40 cm土层土壤微生物量氮含量,由对照的24.1和7.5 mg/kg提高到43.6和16.1 mg/kg。【结论】过量施氮可以显著增加旱地土壤剖面中的硝态氮累积量、夏闲期氮素矿化量、小麦播前土壤氮素供应量和土壤微生物量氮含量,但对土壤有机碳和微生物量碳没有显著性影响,同时过量施氮增加了土壤硝态氮淋溶风险,故在有机质含量低的黄土高原南部旱地冬小麦种植中不宜施用高量氮肥,以减少土壤氮素残留和农业投入,达到保护环境和培肥土壤的目的。     

施氮量、土壤和植株氮浓度与小麦赤霉病的关系

【目的】赤霉病已成为影响小麦产量和品质的重要病害之一,为了解施用氮肥对小麦赤霉病的影响,本文通过研究不同施氮水平下小麦赤霉病的发病情况,探索施氮、土壤供氮、植株氮浓度与小麦赤霉病的关系。【方法】采用田间小区试验,以多穗型豫麦49-198(YM49-198)和大穗型周麦16(ZM16)为供试品种,设N 0、120、180、240、360 kg/hm25个施氮水平(N0、N120、N180、N240、N360),根据"小麦赤霉病测报技术规范"调查小麦赤霉病的发病情况。【结果】土壤硝态氮含量及0—90 cm土层土壤硝态氮累积量均随施氮量的增加而增加,小麦收获期N0、N120、N180处理0—30 cm土层硝态氮含量及0—90 cm累积量差异不显著,但显著低于N240和N360处理。两个品种小麦赤霉病病穗率和病情指数(DI)随施氮量的增加而增加,各处理间差异显著;豫麦49-198施氮处理的病穗率和DI比不施氮处理分别增加29.5%~132.0%和35.9%~225.2%,周麦16施氮处理的病穗率和DI比不施氮处理分别增加42.4%~161.8%和41.7%~206.9%;两个品种小麦N180处理赤霉病的病穗率和病情指数与N0、N120差异较小,显著低于N240和N360;周麦16较豫麦49-198发病严重,各处理的病穗率和病情指数比豫麦49-198分别高出7%~25%和28.0%~63.6%。小麦赤霉病病穗率和DI与硝态氮含量显著正相关,与0—90 cm硝态氮累积量呈线性正相关。孕穗期、开花期和灌浆期茎基部硝酸盐含量和拔节期~开花期植株的全氮含量各处理间差异较大,且与小麦赤霉病病穗率和DI显著线性正相关。【结论】土壤硝态氮含量及累积量随施氮量增加而增加,小麦收获后施氮量低于N 180 kg/hm2时土壤中硝态氮残留较低,赤霉病发病较轻。小麦赤霉病病穗率和病情指数随施氮量的增加而增加,说明施氮量过高会加重小麦赤霉病病害;小麦拔节期~开花期的氮浓度过高会加重赤霉病病害,因此在这一时期,适宜的施氮量、土壤硝态氮和植株氮浓度在赤霉病发生年份可以减轻病害,综合考虑土壤硝态氮残留、产量和赤霉病害等因素的适宜施氮量为N 180 kg/hm2。     

Differences in isotopic fractionation of nitrogen in water-saturated and unsaturated soils

Temporal variations in δ¹⁵N of NH₄⁺ and NO₃⁻ in water-saturated and unsaturated soils were examined in a laboratory incubation study. Ammonium sulfate (δ¹⁵N=−2.6‰) was added to 25 g samples of soil at concentrations of 160 mg N kg⁻¹. Soils were then incubated under unsaturated (50% of water holding capacity at saturation, WHC) or saturated (100% of WHC) water conditions for 7 and 36 d, respectively. During 7 d incubation of unsaturated soil, the NH₄⁺-N concentration decreased from 164.8 to 34.4 mg kg⁻¹, and the δ¹⁵N of NH₄⁺ increased from −0.4 to +57.2‰ through nitrification, as evidenced by corresponding increase in NO₃⁻-N concentration and lower δ¹⁵N of NO₃⁻ (product) than that of NH₄⁺ (substrate) at each sampling time. In saturated soil, the concentration of NH₄⁺-N decreased gradually from 162.4 to 24.2 mg kg⁻¹, and the δ¹⁵N values increased from +0.8 to +21.0‰ during 36 d incubation. However, increase in NO₃⁻ concentration was not observed due to loss of NO₃⁻ through concurrent denitrification in anaerobic sites. The apparent isotopic fractionation factors (α_s/p) associated with decrease in NH₄⁺ concentration were 1.04 and 1.01 in unsaturated and saturated soils, respectively. Since nitrification is likely to introduce greater isotope fractionation than microbial immobilization, the higher value for unsaturated soil probably reflected faster nitrification under aerobic conditions. The lower value for saturated soil suggests that immobilization and subsequent remineralization of NH₄⁺ were relatively more dominant than nitrification under the anaerobic conditions.     

Variations of soluble organic nitrogen and microbial nitrogen in deciduous forest soils along an urban-rural gradient

Soluble organic N and microbial N pools in terrestrial ecosystems have been less studied than those of inorganic N. Therefore, cross-system variation in their pool sizes and seasonal dynamics, both absolute and relative to inorganic N pools, needs to be quantified so that their ecological importance in different ecosystems can be evaluated. We measured extractable soil organic N (ESON), microbial biomass N (MBN), and the net production rates of ESON in red oak-dominated remnant forests, along an urban-rural gradient in the New York City metropolitan area. We were interested in (1) determining the seasonal dynamics of ESON and MBN, and (2) examining whether the contrasts in land use (urban, suburban, rural) surrounding these forest remnants were associated with different amounts of ESON and MBN. This field-based study was conducted continuously for 16 months. Yearly average ESON concentrations ranged from 60 to 140 mg kg⁻¹ soil organic matter (SOM), 3-4 times those of inorganic N, and average MBN ranged from 600 to 1100 mg kg⁻¹ SOM. There was a considerable MBN increase in spring in all plots across the gradient. The average increase expressed on an areal basis (to a depth of 7.5 cm) ranged from 1.75 to 4.19 g N m⁻². The N incorporated into the microbial biomass in spring was gradually released later in the growing season (the mean MBN decrease ranged from 1.11 to 3.82 g N m⁻²). The spring MBN increase could be an important retention mechanism for conserving soil inorganic N when plant N uptake may be low. The amplitude in the seasonal dynamics of ESON was far less than that of inorganic N, as was that of net ESON production rates when compared to net N mineralization. These suggest a closer coupling of plant N uptake with inorganic N, much more than with ESON. Both ESON and MBN were significantly higher in rural soils than in urban soils, and both concentrations were positively correlated with SOM content. The variation in ESON, MBN, or SOM associated with this urbanization gradient suggests that the form of N exported, the plant N budget and soil N retention mechanisms may be differentially affected by urban, suburban and rural land uses.     

聚丙烯酸盐类土壤改良剂对燕麦土壤微生物量氮及酶活性的影响

以燕麦田土壤为研究对象,探讨了聚丙烯酸盐类土壤改良剂及其复配(聚丙烯酸钾、聚丙烯酰胺、腐植酸钾、聚丙烯酸钾+腐植酸钾、聚丙烯酰胺+腐植酸钾)对燕麦田土壤微生物量氮及土壤酶活性的影响。结果表明,不同土壤改良剂均能提高土壤有机质、碱解氮、速效磷和速效钾的含量,各指标分别比对照增加了8.24%～30.22%、7.60%～19.29%、5.15%～29.45%和27.86%～68.86%;土壤改良剂能促使燕麦全生育期内0～10、10～20和20～40 cm各土层的土壤微生物量氮含量显著提高,聚丙烯酸钾+腐植酸钾和聚丙烯酰胺+腐植酸钾复配处理较其各单施效果显著,随土壤深度的增加土壤微生物量氮逐层递减;与对照相比,土壤改良剂能显著提高燕麦全生育期各土层过氧化氢酶活性,在抽穗期活性最高,且以聚丙烯酸钾+腐植酸钾较高;但对于脲酶,聚丙烯酸钾+腐植酸钾、聚丙烯酰胺+腐植酸钾和腐植酸钾3个处理在苗期显著低于对照,在抽穗期和成熟期高于对照,两种酶活性均随土壤深度的增加逐渐降低。     

温度对土壤吸附有机肥中可溶性有机碳、氮的影响

可溶性有机碳、氮(Soluble organic carbon or nitrogen,SOC和SON)可被土壤吸附.土壤可溶性有机碳、氮组分复杂,土壤对可溶性有机物吸附的不均一性会导致可溶性有机物组分的变化,大部分疏水性化合物被吸附,而亲水性化合物被释放进入溶液中[1].因此,可溶性有机碳、氮在土壤中的吸附,直接影响其在土壤-水系统中的迁移和行为[2-3].林地土壤中含有相当数量的可溶性有机养分,因此,关于林地土壤对可溶性有机养分的吸附特性,国外研究者已开展了不少研究.研究表明,可溶性有机碳吸附特性与土壤性质如pH、表面积、有机碳、铁铝氧化物和黏粒含量等因素有关[4-5].关于农业土壤对可溶性有机碳的吸附特性的影响,国内也开展了一些研究,主要集中在pH、铁铝氧化物含量等对吸附影响方面[6-9].     

猪场废水灌溉对潮土硝态氮含量变化的影响

该文应用猪场废水处理工艺中3个阶段的出水（原水—猪圈舍干清粪后冲洗直接流入积水池的水;厌氧水—原水经厌氧池处理后的出水;仿生态塘水—经曝气和植物吸收处理的厌氧水）与地下水1︰5（体积比）配比和厌氧水不同灌溉量进行冬小麦小区灌溉试验,通过监测土壤硝态氮含量动态变化和残留量筛选适宜的混合水类型和厌氧水灌溉量,为制定合理的猪场废水灌溉制度提供理论依据。试验结果表明：应用3种混合水灌溉0～100 cm土壤剖面硝态氮含量随深度增加呈现“S”形变化趋势,小麦收获后各层土壤硝态氮含量均比初始值有所增加;收获后3种混合水灌溉处理0～100 cm土层中的硝态氮累积量比拔节期均有很大增加,仿生态塘水︰地下水1︰5处理变化幅度最小,较适宜灌溉;厌氧水灌溉量与土壤中硝态氮淋溶量和残留量成正相关关系,中灌水量（500 m3/hm2）较适宜。灌浆期灌水大大增加了收获后土壤中的硝态氮含量,灌浆期宜使用地下水灌溉。     

黄土高原典型土壤全氮和微生物氮剖面分布特征研究

为阐明黄土高原典型土壤全氮和微生物氮含量随土壤类型、土层和土地利用方式变化规律,研究了从北向南依次分布的干润砂质新成土(神木)、黄土正常新成土(延安)和土垫旱耕人为土(杨陵)等典型土壤的全氮和微生物氮含量的变化特征。结果表明,不同土壤类型、不同土层全氮和微生物氮含量存在显著差异。从南到北,全氮和微生物氮含量显著下降(P0.05)。对同一土壤类型,全氮和微生物氮含量在060.cm随土层深度增加下降很明显,60120.cm有轻微下降,120.cm以下低而稳定。微生物氮含量随土壤类型的变化趋势与全氮完全相同,其与土壤全氮、有机碳及微生物碳含量均存在极显著正相关关系(P0.01)。土壤微生物氮与全氮比值变化在0.42%9～.44%之间。虽然土地利用对土壤全氮和C/N比影响不显著,但却显著影响微生物氮含量和微生物氮与全氮的比值;与农田土壤相比,草地土壤微生物氮含量和微生物氮与全氮比值均明显增加。这一结果说明微生物氮含量和微生物氮与全氮比值更能有效、快速地反映土壤质量的变化。     

施用铵态氮对森林土壤硝态氮和铵态氮的影响

对取自武夷山的红壤、黄壤、黄壤性草甸土分别在对照(CK,N 0 mg/kg)、低氮(LN,N 50 mg/kg)、高氮(HN,N 100 mg/kg)3种氮(N)水平处理下开展培养实验,研究施加NH4+-N对森林土壤N转化的短期影响.结果表明,添加NH4+-N可显著(p＜0.05)降低土壤NO3--N含量4.5％～25.7％,但LN与HN处理差异不显著,NO3--N降低可能与NO3--N反硝化和异氧还原有关;然而,黄壤性草甸土NO3--N没有降低.与培养前比较,在第56天红壤NO3--N含量显著增加5倍左右;桐木关黄壤增加40％左右,而黄冈山25 km黄壤仅在CK处理下增加16％,但是黄壤性草甸土显著降低;结果显示LN与HN处理土壤NO3--N含量变化幅度小于CK.与CK相比,LN和HN处理红壤NH4+-N分别显著(p＜0.05)升高24.1％ ～ 96.5％和68.7％～114.1％,且随培养进行没有累积,可能与微生物固N有关;桐木关NH4+-N分别升高17.6％ ～ 39.6％和37.6％～95.8％ (p＜0.05),LN处理黄冈山25 km黄壤NH4+-N只有第7天升高17.8％ (p＜0.05),HN处理第7、14、28、42天显著升高17.5％～48.6％(p＜0.05).LN处理黄壤性草甸土的NH4+-N在前3周显著降低11.6％～28.5％ (p＜0.01); HN处理在第7天和14天分别降低10.8％(p＜0.01)和7.5％,但是在第28～56天显著增加17.6％～20.4％(p=0.002).随着培养进行,CK处理红壤NH4+-N逐渐降低,桐木关黄壤、黄冈山25 km黄壤和黄壤性草甸土升高;LN和HN处理黄壤和黄壤性草甸土NH4+-N逐渐升高.可见,不同海拔土壤类型对NH4+-N添加响应存在差异.     

柳枝稷生物炭对来自不同地区的两种土壤上植物生物量和微生物动态的影响

Biochar amendments to soils may alter soil function and fertility in various ways, including through induced changes in the microbial community. We assessed microbial activity and community composition of two distinct clayey soil types, an Aridisol from Colorado (CO) in the U.S. Central Great Plains, and an Alfisol from Virginia (VA) in the southeastern US following the application of switchgrass (Panicum virgatum) biochar. The switchgrass biochar was applied at four levels, 0%, 2.5%, 5%, and 10%, approximately equivalent to biochar additions of 0, 25, 50, and 100 t ha^-1, respectively, to the soils grown with wheat (Triticum aestivum) in an eight-week growth chamber experiment. We measured wheat shoot biomass and nitrogen (N) content and soil nutrient availability and N mineralization rates, and characterized the microbial fatty acid methyl ester (FAME) profiles of the soils. Net N mineralization rates decreased in both soils in proportion to an increase in biochar levels, but the effect was more marked in the VA soil, where net N mineralization decreased from -2.1 to -38.4 mg kg^-1. The 10% biochar addition increased soil pH, electrical conductivity, Mehlich- and bicarbonate-extractable phosphorus (P), and extractable potassium (K) in both soil types. The wheat shoot biomass decreased from 17.7 to 9.1 g with incremental additions of biochar in the CO soil, but no difference was noted in plants grown in the VA soil. The FAME recovery assay indicated that the switchgrass biochar addition could introduce artifacts in analysis, so the results needed to be interpreted with caution. Non-corrected total FAME concentrations indicated a decline by 45% and 34% with 10% biochar addition in the CO and VA soils, respectively, though these differences became nonsignificant when the extraction efficiency correction factor was applied. A significant decline in the fungi:bacteria ratio was still evident upon correction in the CO soil with biochar. Switchgrass biochar had the potential to cause short-term negative impacts on plant biomass and alter soil microbial community structure unless measures were taken to add supplemental N and labile carbon (C).