Decomposition in a peaty soil improved for pastoral agriculture

Abstract. The rates of CO₂ production and decomposition of ¹³C-enriched Lolium perenne leaves and roots in soil from the surface five cm of two upland stagnohumic gley soils were measured in laboratory experiments. One of the soils had been limed (pH 6.8) 13 years earlier. The other was unlimed (pH 3.7). Liming increased the rate of CO₂ release from soil to which no L. perenne had been added. About 30% of the ¹³C in L. perenne leaves remained in both limed and unlimed soil after 224 days. By contrast, less ¹³C-remained in the limed soil amended with L. perenne roots (44%) than in the limed soils (55%). Although the daily rate of CO₂ from the plant material-amended soils was initially greater in the improved than in the unimproved soil, it subsequently declined more rapidly.     

施肥对农田土壤螨季节性变化的影响

对农田土壤螨季节性变化进行试验研究结果表明,农田土壤螨1年有2个发生高峰,即春季5月份高峰和秋季8－9月份高峰。EM堆肥区土壤螨数量年波动平缓,稳定性高;化肥区土壤螨数量年波动性大,中气门目击壤螨7月份后才出现。     

Nitrogen transformations in a peaty soil improved for pastoral agriculture

Abstract. Microbial transformations and chemical distribution of N were compared in two upland stagnohumic gley soils at the same site. In 1981 one soil was improved for more intensive agriculture by lime and fertilizer applications and reseeding with a grass/clover mixture. The other soil (referred to here as unimproved) was also reseeded in 1981, but no lime was added and the sward has subsequently reverted to rough grazing land. Improvement resulted in greater soil microbial activity. The improved soil showed greater rates of denitrification, net N immobilization and N fixation (acetylene reduction) and contained more microbial biomass N than the unimproved soil. However, no major differences in the distribution of organic N fractions were detected. This indicates that a large amount of the soil N present before improvement did not undergo mineralization and remained unavailable to plants.     

The effect of industrial aerial pollution on the composition of soil solutions in podzols

The composition of soil solutions is a sensitive indicator of the technogenic transformation of podzols of the Kola Peninsula under the impact of aerial pollution. The soil solutions have been obtained using Rhizon vacuum samplers. A sharp rise in the concentrations of heavy metals and sulfates is registered in the solutions from polluted soils. The leaching of organic substances, potassium, sodium, calcium, magnesium, manganese, and zinc from the litter horizons of polluted soils considerably increases. The ratios between the element concentrations in solutions from the litter horizons to those from the illuvial horizons become narrower, which suggests that the litter has partly lost its barrier function.     

Estimation of soil weathering stage and acid neutralizing capacity in a toposequence Luvisol–Cambisol on loess under deciduous forest in Belgium

Soils derived from loess are extensive in Europe and are well suited for forestry. They are suspected to be poor acid buffers, however. We have estimated the weathering stage and acid neutralizing capacity of acid soils under forest in a toposequence on loess in the Belgian silt belt. The soils vary distinctly in morphology and physico‐chemical properties according to their topographic position. Dystric Cambisols have developed in colluvial deposits in the dry valley floors, whereas Dystric Luvisols have formed on the slopes in a rejuvenated material. The Cambisols are more acid and less saturated in bases than are Luvisols. They are strongly depleted of clay and contain less weatherable minerals. Easily weatherable minerals are concentrated mainly in the clay fraction of both soil types. Clay minerals of size < 2 μm therefore act as major sinks for protons in these soils. A simplified expression taking into account the total reserve in bases, total aluminium and iron occluded in silicates is used to estimate acid neutralizing capacity. Our estimates confirm that these acid loessic soils are indeed poor acid buffers. They show that the Dystric Cambisols depleted of clay are sensitive to potential acidification, whether natural or man‐made.     

秸秆不同还田方式对土壤入渗特性及持水能力的影响

通过入渗试验及对土壤水分特征曲线的测定,对比研究了秸秆在经过粉碎、氨化及与无机土壤改良剂混合3种措施处理后加入土壤中对土壤入渗特性及持水特征的影响。结果显示：长秸秆处理加入土壤后显著降低土壤入渗能力;粉碎氨化后的秸秆较对照处理及粉碎秸秆处理能显著增加土壤稳定入渗率、土壤累积入渗量,同时在经过30 d培养后土壤体积质量较对照低7.13%;无机土壤改良剂（氢氧化铁）能显著提高土壤稳定入渗率和累积入渗量,但在减小土壤体积质量、增加土壤孔隙度作用方面不如氨化秸秆处理显著,同时当秸秆与其混合加入土壤时未对土壤改良效果起到正交互作用;各种处理土壤持水能力差异不明显,但粉碎并氨化措施处理过的秸秆在中低吸力段均表现出较高的土壤持水能力,这对于提高旱区农田蓄水保墒抗旱能力有重要意义。     

Topographic variation in heterotrophic and autotrophic soil respiration in a tropical seasonal forest in Thailand

Soil respiration is a carbon flux that is indispensable for determining carbon balance despite variations over time and space in forest ecosystems. In Kanchanaburi, western Thailand, we measured the soil respiration rates at different slope positions—ridge (plot R), upper slope (plot U), and lower slope (plot L)—on a hill in a seasonal tropical forest [mixed deciduous forest (MDF)] to determine the seasonal and spatial variations in soil respiration on the slope. The heterotrophic (organic layer and soil) and autotrophic (root) respiration was differentiated by trenching. Soil respiration rates showed clear seasonal patterns: high and low rates in rainy and dry seasons respectively, at all plots, and tended to decrease up the slope. Soil respiration rates responded significantly to soil water content in the 0–30?cm layer, but the response patterns differed between the lower slope (plot L) and the upper slope (plots R and U): a linear model could be applied to the lower slope but exponential quadratic models to the upper slope. The annual carbon dioxide (CO₂) efflux from the forest floor was also associated with the slope position and ranged from 1908?gC?m^?2?year^?1 in plot L to 1199?gC?m^?2?year^?1 in plot R. With ascending position from plot L to R, the contribution of autotrophic respiration increased from 19.4 to 36.6% of total soil respiration, while that of the organic layer decreased from 26.2 to 9.4%. Mineral soil contributed to 46.3 to 54.4% of the total soil respiration. Soil water content was the key factor in controlling the soil respiration rate and the contribution of the respiration sources. However, the variable responses of soil respiration to soil water content create a complex distribution of soil respiration at the watershed scale.     

草地土壤分离能力季节变化特征及其影响因素

土壤分离能力是土壤侵蚀机理模型的重要参数.受土壤性质、植被根系等因素影响,土壤分离能力呈现显著的季节变化.为研究草地土壤分离能力季节变化特征及其影响机制,以建植一年的柳枝稷、无芒雀麦草地及对照裸地为研究对象,以20 d为周期,测定土壤密度、黏结力和根系密度,并采集原状土样进行水槽实验(τ=6.5-23.4Pa),测量土壤分离能力,并运用相关分析、回归分析等方法,研究土壤性质及植被根系对土壤分离能力季节变化的影响.结果显示:柳枝稷和无芒雀麦草地具有类似的季节变化特征,而裸地与二者差异明显.4月中旬至6月下旬,草地土壤分离能力较大,此后土壤分离能力迅速下降;7月中旬直至10月上旬,草地土壤分离能力较低;10月下旬,土壤分离能力小幅回升;裸地土壤分离能力7、8月份较低,其余时间较高.裸地土壤分离能力试验期均值为柳枝稷草地的10.6倍,无芒雀麦草地的23.7倍.草地土壤分离能力的季节变化受根系密度和土壤黏结力的影响,随着根系密度与土壤黏结力增大,土壤分离能力呈指数形式降低,而土壤密度对土壤分离能力季节变化的影响并不显著.试验区内草地土壤分离能力可用水流剪切力、根系密度、根径和土壤黏结力等参数进行模拟(R2=0.636).研究结果可为土壤侵蚀机理模型的推广应用,以及小流域水土保持措施配置等工作提供科学依据.     

Temporary storage of soil organic matter and acid neutralizing capacity during the process of pedogenetic acidification of forest soils in Kinki District,Japan

Abstract

Pedogenetic acidification processes in forest soils derived from sedimentary rocks under mesic and thermic soil temperature regimes (MSTR and TSTR; corresponding to mean annual soil temperatures of 8–15°C and 15–22°C, respectively) in the Kinki District were investigated based on titratable alkalinity and acidity characteristics and soil solution composition. According to statistical analyses of the soil properties, the titratable alkalinity required to acidify soils to pH 3.0 was considered to be derived from reactions occurring at the surface of amorphous Al oxides, while titratable acidity at a pH ranging from 5.5 to 8.3 results from dissociation of acidic functional groups of soil humus and/or deprotonation of oxide surfaces. These reactions were generally more prevalent in MSTR soils. Based on the soil solution composition and titratable alkalinity and acidity in the soil profiles, two processes were postulated for pedogenetic acidification, that is, eluvi-illuviation of inorganic Al followed by subsequent adsorption of dissolved organic carbon (DOC) onto the precipitates of Al hydroxides and comigration of Al and DOC in the form of organo-mineral complexes. Both processes were conspicuous in MSTR soils and significantly contributed to soil organic matter storage in the subsoil layers. Pedogenetic acidification in forest soils with MSTR was characterized by an accumulation of acidity in the form of amorphous compounds and/or organo-mineral complexes in the B horizon. It seems, to some extent, similar to podzol formation, at least in terms of Al translocation. Amorphous Al hydroxides protect against further acidification through protonation and/or partial monomerization and can, thus, be regarded as a temporary storage of acid neutralizing capacity of the soil, which would be otherwise leached out directly from the soil profile. In contrast, the acid-buffering reactions of TSTR soils seemed to occur, if at all, mostly at or near the soil surface and the contribution of the B-horizon soils was limited.     

隔坡沟状梯田土壤水分变化规律探讨

采用定位观测与谐波分析方法研究了河北太行山低山片麻岩区坡地土壤水分变化规律及隔坡沟状梯田对土壤水分变化规律的影响，结果表明：土壤含水量的变化受降水和蒸散变化的影响，表现出明显的周期性变化规律，隔坡沟状梯田使土壤含水量序列增值增加，波幅减小，极值推迟，因而抗旱能力增强，此外，对隔坡沟状梯田改善土壤状况的机制进行了试验研究。     

黏粒质量分数对土壤水分蓄持能力影响的模拟试验

通过人工配制不同质地土壤,测定土壤水分特征参数,研究土壤中黏粒质量分数对其水分蓄持能力的定量影响。结果表明：1）黏粒质量分数对土壤水分蓄持能力有较大影响,土壤持水能力随黏粒质量分数增加而递增。2个水分特征曲线模型——Gardner模型及van Genuchten模型中,表征土壤持水能力的参数均随黏粒质量分数增加而增大。2）黏粒质量分数对土壤比水容量有较大影响,试验土壤在任一水吸力水平下的比水容量值均随其黏粒质量分数增大而增大。3）试验土壤饱和含水量、田间持水量分别与黏粒质量分数呈指数、对数正相关,凋萎系数与黏粒质量分数呈指数正相关。4）试验土壤有效水、迟效水含量随黏粒质量分数增加呈先升高后降低趋势,二者与黏粒质量分数均呈抛物线关系,最高点分别出现在黏粒质量分数为35.9%和35.8%处,易效水含量与黏粒质量分数相关性不显著。研究结果可为黄土区土壤水分蓄持机制进一步研究提供一定理论依据。     

Effects of a super-absorbent polymer derived from poly-γ-glutamic acid on water infiltration,field water capacity,soil evaporation,and soil water-stable aggregates

ABSTRACT

The poly-γ-glutamic acid super-absorbent polymer (γ-PGA SAP) is an environmentally friendly material. Five different γ-PGA SAPs contents based on weight, including 0% (CK), 0.05% (T1), 0.10% (T2), 0.15% (T3), and 0.20% (T4), were added to the soil in this study. The results showed that cumulative infiltration decreased by 32.4% (T1), 39.2% (T2), 51.0% (T3), and 52.0% (T4) at 90 min and the field capacity was increased by 18.7% (T1), 26.0% (T2), 37.8% (T3), and 58.3% (T4) compared with the CK. The cumulative evaporation of the different treatments with γ-PGA SAPs was 17.1% (T1), 23.5% (T2), 24.4% (T3), and 25.3% (T4) higher than that of the CK at the end of the evaporation experiment. The evaporation experiment lasted 96 h (CK), 132 h (T1), 144 h (T2), 180 h (T3), and 312 h (T4) to progress from field capacity to a soil water content of 10%. Adding γ-PGA SAPs to the soil significantly increase the water-stable aggregate content below 0.25 mm when the γ-PGA SAP addition exceeded 0.10%. So reasonable utilization of γ-PGA SAP can improve water use efficiency and improve soil structure in semi-arid areas.     

容重对土壤水分蓄持能力影响模拟试验研究

通过人工改变土壤颗粒级配,并设置不同容重水平,测定土壤水分特征参数,研究了容重对土壤水分蓄持能力的定量影响。结果表明:(1)容重对土壤水分特征曲线、比水容量有较大影响,试验土壤各吸力段水分蓄持能力均随容重增大递减,比水容量也随容重增大递减。(2)容重对试验土壤饱和含水量、田间持水量、凋萎系数有较大影响,此3个水分参数均随容重增大递减。饱和含水量与容重呈幂函数负相关关系,田间持水量及凋萎系数均与容重呈指数负相关关系。(3)容重对试验土壤有效水、易效水、迟效水含量有较大影响,此3水分参数均随容重增大递减,分别与容重呈指数、幂函数、对数负相关关系。     

The variation of soil water regime, oxygen status and rooting pattern with soil type under Sitka spruce

Soil water regime, oxygen status and rooting pattern under Sitka spruce were characterized in five soil types: a waterlogged peaty gley, a peaty gley, a flushed peaty gley, a surface water gley and a brown forest soil during 1982. The waterlogged peaty gley had a high water-table which only dropped below 30 cm depth for 46 d during the summer. Below the water-table the profile was anoxic and rooting was restricted to a depth of 12cm. The peaty gley experienced seasonal waterlogging with a winter water-table around 15cm depth. Roots that grew further down the profile during the summer as the topsoil dried to –100 kPa matric potential were later killed when the water-table rose. The top 30 cm of the flushed peaty gley remained oxygenated even below the water-table. Roots survived below the winter water-table. The top 30 cm of the surface water gley and brown forest soil were freely draining and remained aerated throughout the year. The platinum electrode polarographic method demonstrated that there was a sharp transition to anoxic conditions just above the water-table at the first two sites.     

Factors affecting seasonal variation of methane concentration in water in a freshwater marsh vegetated with Carex lasiocarpa

To understand the underlying factors affecting the seasonal variation of the methane concentration in a cool temperate freshwater marsh vegetated with Carex lasiocarpa in the Sanjiang Plain of northeast China, we measured methane emission from, and the concentrations of methane, dissolved organic carbon (DOC) and acetate in, water samples taken from the standing water surface to the top of the gley soil layer in the C. laisocarpa marsh, before and after plants were covered with a black cloth at the three growing stages of June, July and August 2002. The methane oxidation rate was also measured in situ by applying acetylene, a methane oxidation inhibitor, to whole plants, and the methane production rate in water sampled in June and July was measured via the anaerobic incubation in the laboratory. The methane production rate in water samples was significantly correlated with acetate concentration rather than DOC concentration, whereas the mean acetate concentration in water samples was higher in June than in July and August. Hence, the low methane concentration in June did not result from a lack of acetate for methane production. The mean methane and DOC concentrations in water samples were enhanced by 22.3 and 31.1% in June, 2.1 and 5.0% in July, and 3.4 and 15.2% in August, respectively, after plants were covered with a black cloth. The methane oxidation rate and redox potential in the freshwater marsh decreased from June to July or August. These results suggest that there was more oxygen in the rhizome and rhizosphere in June than in July and August, which not only accentuated methane oxidation but also reduced methane production. Therefore, the high methane concentration in water in July and August could be ascribed to both an increase in temperature and a decrease in redox potential or oxygen concentration in the rhizosphere.     

Effect of magnetized water on infiltration capacity of different soil textures

The infiltration process is important in the planning and management of irrigation systems. This study was performed in Mazandaran province, Iran, to compare the effect of magnetized and non‐magnetized irrigation water on cumulative infiltration and final infiltration rate of three soil textures. Magnetized water was obtained by passing the water through a strong permanent magnet installed on a feed pipeline. The results showed that the effects of soil texture and magnetized irrigation water on cumulative water infiltration and final infiltration rate was significant (P < 0.01). Cumulative water infiltration and final infiltration rates with magnetized water were greater than that of non‐magnetized water. The cumulative water infiltration rate after 4 h for magnetized and non‐magnetized water was 26.4 and 12.7 cm in clay soil, 37.6 and 20 cm in silty loam soil and 40.8 and 29.3 cm in sandy loam soil, respectively. The final infiltration rates after 4 h for magnetized and non‐magnetized water were 0.05 and 0.023 cm/min in clay soil, 0.063 and 0.036 cm/min in silty loam soil and 0.076 and 0.046 cm/min in sandy loam soil, respectively. Therefore, magnetized irrigation water had most effect on the infiltration capacity of clay soil.     

Effects of acid deposition on acidity and exchangeable cations in podzols of the Kola Peninsula

Response of soil and soil water of podzols in the Kola Peninsula to acid deposition was estimated under both field and laboratory conditions. A significant increasing trend of exchangeable acidity in organic (O) horizons and exchangeable Al in podzolic (E) horizons of podzols with distance from the nickel smelter was observed. The simulated rain at pH 4.5 did not alter chemical properties of soils and soil solutions. As much as 95–99% of the applied H⁺ ions were retained by soils and appeared in the percolates after a treatment period that depended on acid load and soil thickness. Ca and Mg in soil solutions were highly sensitive to acid loading. Simulated acid rain enhanced the leaching of exchangeable base cations out of root zone. Acid inputs resulted in decreased pH, amount of exchangeable base cations and base saturation, in elevated exchangeable acidity and it's Al fraction in soil solid phase. The most significant changes occurred in O and E horizons. Substantial amounts of both Ca and Mg can be lost from the root zone of podzols in the north-western Kola, subjected to acid deposition, thus leading to forest productivity damage.     

延安市农业水土资源匹配及承载力

为客观分析延安市农业水土资源空间匹配状况,根据耕地、水资源量等数据,在分析延安市水土资源空间分布格局的基础上,通过构建洛伦兹曲线以及农业水土资源匹配计算模型,对延安市及其13个区县农业水土资源的匹配程度进行评价。结果表明:延安市农业水土资源匹配系数0.26×104 m3/hm2,匹配程度较差,低于全国同期平均水平0.54×104 m3/hm2,并且空间匹配程度存在明显的差异,总体上呈现出南优北差的匹配格局。在全面分析影响农业水土资源承载力多种因素的基础上,建立延安市农业水土资源承载力评价体系,将粒子群优化算法与投影寻踪模型结合在一起,对延安市各区县农业水土资源承载力进行了评价。结果表明,子长县和延长县农业水土资源承载力最低,承载力IV级;黄龙县农业水土资源承载力最高(II级),其他大部分区县农业水土资源承载力处于中等偏低水平(III级),研究可为提高粮食生产效益及区域农业水土资源可持续利用提供依据。