Charred organic carbon in German chernozemic soils

Burning vegetation produces partly charred plant material which subsequently could contribute to the highly refractory proportion of soil organic matter. The presence of charred organic carbon (COC) was investigated in 17 horizons originating from nine soils from Germany and the Netherlands using a suite of complementary methods (high-energy ultraviolet photo-oxidation, scanning electron microscopy, solid-state ¹³C nuclear magnetic resonance, lignin analysis by CuO oxidation). Charred organic carbon could not be detected in the A horizons of an Alisol and a Gleysol, but it contributed up to 45% of the organic carbon and up to about 8 g kg^–1 of the soil in a range of grey to black soils (Cambisol, Luvisol, Phaeozem, Chernozem and Greyzem). All these soils have chernozemic soil properties (dark colour, A–C profile, high base saturation, bioturbation). A 10-km colour sequence of four chernozemic soils, which were very similar in chemical and physical properties, showed a strong relation between colour and the content of COC. This suggests that the COC affects mainly soil colour in the sequence studied. Finely divided COC seems to be a major constituent of many chernozemic soils in Germany. These results suggest that besides climate, vegetation and bioturbation, fire has played an important role in the pedogenesis of chernozemic soils.     

Vertigenesis in soils of the central chernozemic region of Russia

On the basis of soil studies along routes and on key plots, 35 new areas of soils with definite features of vertigenesis have been identified in Belgorod and Voronezh oblasts and in the northern part of Volgograd oblast (in the Don River basin). Earlier, vertic soils were not noted for these areas. In the studied region, their portion in the soil cover is much less than 1%. All the delineated areas of vertic soils are confined to the outcrops of swelling clay materials of different origins (marine, lacustrine, glacial, and colluvial sediments) and ages (Quaternary or Tertiary) that may be found in four landscape positions: (1) in the deep closed depressions within vast flat watersheds; (2) in the bottoms of wide hollows on interfluvial slopes and, sometimes, on steeper slopes of local ravines; (3) in the hydromorphic solonetzic soil complexes, and (4) on step-like interfluvial surfaces with the outcrops of Tertiary clays. Within the studied areas, soils with different degrees of expression (six grades) of vertic properties are present. These soils belong to the type of dark vertic soils proper and to vertic subtypes of different soil types according to the Russian soil classification system; according to the WRB system, they belong to Vertisols proper and to reference soil units with a Vertic prefix in the groups of Chernozems, Phaeozems, and Solonetzes. Statistical data on the morphometric indices of the vertic properties (the depth and thickness of the soil horizons with slickensides, a wedge-shaped structure, and cracks filled with material from the upper horizons) and the depth and thickness of the Vertic horizon are analyzed.     

Effect of tillage and rotation on organic carbon forms of chernozemic soils in Saskatchewan

The effects of selected tillage and rotation systems on soil organic carbon and its fractions were studied on Chernozemic soils in south‐western and east‐central Saskatchewan. After practicing a no‐till fallow unfertilized‐wheat rotation for 7 years on an Orthic Brown Chernozem in south‐western Saskatchewan, total soil organic carbon (TOC) in the 0 – 5 cm and 5 – 10 cm layers was slightly lower than the tillage fallow‐unfertilized wheat comparable treatment. However, light fraction of organic carbon (LFOC) was similar in the two treatments. Comparison of the tillage fallow‐unfertilized wheat to a treatment involving conversion to a fertilized continuous cropping system for 10 years showed TOC increased slightly in the two depths and LFOC increased by 24 % and 29 % in the 0 – 5 cm and 5 – 10 cm layer, respectively, of the continuous cropping treatment. Microbial biomass carbon (MB‐C) was increased significantly at the 5 – 10 cm depth. After conversion of fallow‐wheat to alfalfa as perennial forage for 10 years, TOC increased by 80 % and 27 %, LFOC by 245 % and 286 %, and HFOC by 63 % and 20 % at 0 – 5 cm and 5 – 10 cm depths, respectively, compared to the tilled cereal‐fallow system. Meanwhile, water soluble organic carbon (WSOC) was not affected but MB‐C increased significantly. In an Orthic Black Chernozem in east‐central Saskatchewan, the depletion and restoration of organic carbon was observed when native sod was changed into cropland and then back to grassland. For example, the TOC of cropland under cereal‐fallow rotation for 62 years decreased by 42 % and 33 % at 0 – 5 cm and 5 – 10 cm depths, respectively, compared to native sod. The LFOC decreased by 79 % and 74 % in the layers, and reductions in WSOC and MB‐C were even greater. After cropland was re‐seeded to grassland for 12 years, the concentration of total organic carbon was increased by 16 % and 22 % while the mass of organic carbon was the same as the cropland in the two layers. The LFOC and MB‐C amounts in the grass seed‐down were double that of the cropped land, but the amounts of TOC, LFOC, and MB‐C in grass seed‐down were still significantly lower than the native sod.     

Total and carboxyl acidity and methoxyl groups of humic acid preparations of chernozemic soils

Abstract

Alkaline‐soluble, acid‐precipitable organic matter from the Ah and Bm horizons of Chernozemic soils developed on four parent materials in each of three soil zones was analyzed for total and carboxyl acidity, and methoxyl groups. The values are expressed as meq/g dry ash‐free organic matter.

Total acidity generally was higher in the Black Chernozems than in the Brown Chernozems and higher in the Bm horizon than in the Ah horizon. The distribution of carboxyl acidity between the Ah and companion Bm horizons of individual soils appeared to be related to texture and rainfall.

The. methoxyl group content of the Brown Chernozems was larger than that of the .Dark Brown Chernozems, which in turn had a larger methoxyl group content than that of the Black Chernozems. It was concluded that the organic matter in the Ah horizons of the Brown Chernozems was not as humified as that of the Black Chernozems. The pH value and a minimum clay content are possible determining factors as to the amounts of methoxyl carbon present.     

Process studies of a chernozemic pedon,Alberta (Canada)

Soil-forming processes in a Gleyed Black Chernozemic (Aquic Cryoboroll) pedon in central Alberta, Canada, were investigated. Vegetation similar to the present Boreal Transition Forest seems to have occupied the region during the Late Holocene. The influence of this forest ecosystem appears compatible with observed pedon properties, notably a well-structured, base-saturated mull A horizon. Rapid soil moisture depletion during the growing season limits the potential for leaching. Readily decomposed, calciumrich litter, particularly from understorey shrubs, and cation leaching from the forest canopy maintain a high base status and mild weathering environment. Faunal and other processes promote rapid formation of characteristic A horizon fabrics. The suitability of some current Canadian soil taxonomic concepts is discussed.     

Fertilizer phosphorus placement studies on calcareous and non‐calcareous chernozemic soils: Growth,p‐uptake and yield of flax

Abstract

We examined soil potassium (K) supply capacity as related to wheat response to K fertilization, using a cation exchange membrane (CEM) burial technique to measure potential K supply rate. A growth chamber experiment was conducted to determine soil and plant response relationships. Canadian Prairie Spring wheat (Triticum aestivum ’Biggar') was grown on three soils of different initial K fertility with three rates of added K. Wheat response to K fertilization was well related to the amount of exchangeable K and K supply rate in the soil. Soils with high initial K supply rate demonstrated an adequate K release rate which was associated with low response to added K fertilizer. A soil K supply rate less than 5 μg cm² hr^‐1 represented soil K supply power that is less than optimal for wheat nutrition.     

液体培养研究不同土壤中硝化活性

A red soil, a fluvo-aquic soil and a permeable paddy soil were used in a long-term investigation to study changes in nitrification with treatments: 1) soil incubation, 2) liquid incubation inoculated with soil samples, and 3) liquid incubation inoculated with ammonia-oxidizing bacteria (AOB) from the soils. There were significant differences (P < 0.001) in nitrification rates among the three soils when measured for 28 days by adding (NH4)2SO4 at the rate of 154 mg N kg-1 dry soil to fresh soil. However, the amounts of nitrifying bacteria in the three soils were not related to soil nitrification capacity. When the soil samples or the isolates of AOB enriched from the corresponding soil were incubated in liquid with pH 5.8, 7.0 and 8.0 buffers and 10 mmol L-1 ammonium nitrogen, there were no significant nitrification differences in the same soil type at each pH. The ability to oxidize ammonia through AOB from different types of soils in a homogeneous culture medium was similar, and the soil nitrification capacity could reflect the inherent properties of a soil. Altering the culture medium pH of individual soil type also showed that acidification of an alkaline fluvo-aquic soil decreased nitrification capacity, whereas alkalinization of the acidic red soil and permeable paddy soil increased their nitrification. For a better insight into factors influencing soil nitrification processes, soil properties including texture and clay composition should be considered.     

Comparative yield and chemical composition of soybean and fababean grown on chernozemic soils on the Canadian prairies

Abstract

Soybean (Glycine max (L.) Merrill) and fababean (Vicar faba (L.)) were grown under field conditions on six Orthic Black Chernozemic soils over three years at two levels of fertility. At flowering, full pod and maturity the yield and N, P, K and S composition of harvested plant materials were compared. Application of fertilizer (P, K and S) increased dry matter and seed yields of both crops. At all, growth stages fababeans produced more dry matter than soybean, and at maturity produced higher yields of seed, hull and stalk. However, the ratio of seed: hull: stalk for both crops was similar and constant at 3.8: 1: 4.7 on all soils and at both levels of soil fertility. At the high level of soil fertility, at the flowering and full pod stages, the concentration of N, P, and K in fababean was higher than that in soybean, but both crops had a similar concentration of S. At low fertility both crops had similar concentrations of P, K and S. At maturity, soybean seed had the higher concentrations of the four nutrients. The concentration of P in the hull and stalk of both crops was similar, but fababean hull had a higher concentration of K and soybean stalk a higher concentration of S. Soybean seed also had a higher protein content and yielded more protein per hectare than fababean seed.     

Fertilizer placement studies on calcareous and non‐calcareous chernozemic soils: Growth,P‐UP‐take,oil content and yield of Canadian rape

Abstract

Field experiments were conducted on calcareous and non‐calcareous Orthic Black Chemozemic soils over a five year period to study the effect of rates and placements of P‐fertilizer on Canadian rape (Brassica napus L. cv Tower) production. Six rates of P as mono‐ammonium phosphate (MAP) were applied at seeding using four placement methods: i) broadcast and cultivated 10 cm into the soil (BC); ii) banded in the seed row with the seed (PWS); iii) banded 2.5 below and 2.5 cm to the side of the seed (PSS); iv) banded 2.5 cm directly below the seed (PBS). Soil type had no significant effect on rape growth, seed yield and P‐uptake. Rape responded best to P‐fertilizer banded with (PWS) or near (PSS, PBS) the seed. But, placing 15 kg/ha P or greater with the seed reduced seedling emergence; with 25 kg P/ha insufficient plants emerged to justify harvesting. The reduced seedling emergence resulted in reduced seed yield and P‐uptake. Maximum yields were obtained when the fertilizer was banded 2.5 cm away from the seed (PSS, PBS). The BC method produced the least growth, yield and P‐uptake responses of the four methods. Only when broadcast rates of P were in excess of 10 kg/ha did rape dry matter, seed and P‐uptake increase. Banding 10 kg/ha with or near to the seed was equivalent to broadcasting 25 kg/ha in terms of seed yield and P‐uptake. Application of P fertilizer also increased seed protein and oil concentrations.     

Distribution of applied cadmium in different size fractions of soils after incubation

The size fraction of soils is one of the important factors that influence the retention of heavy metals. The sorptive properties of soils for heavy metals are principally associated with clay and silt-size fractions. Phosphate fertilizers that are applied to highly weathered tropical soils contain a wide concentration range of cadmium (Cd) as an impurity. Tropical soils contain kaolinite and oxides of Al, Fe, and Mn, which have the ability to sorb Cd. However, the distribution of Cd in different size fractions and the chemical speciation of particulate-bound Cd in the clay size fractions when introduced to soil and allowed to incubate at field moisture capacity merits attention. Cadmium was, therefore, applied to selected surface Kenyan soils varying widely in physicochemical properties to investigate its distribution in different soil particle size fractions and the speciation of particulate-bound species in clay size fractions after incubation. The Cd content in different particle fractions was analyzed by graphite furnace atomic absorption technique after HF-HClO₄ digestion. The particulate-bound Cd species were investigated using chemical sequential extraction method. The study showed that clay size fraction of the natural and the Idaho monoammonium phosphate (MAP)-fertilizer or the Cd perchlorate-added MAP chemical reagent-treated soils contained the highest amount of the total Cd. However, silt and sand fractions of the treated soils also retained appreciable amounts of Cd. Speciation studies revealed that metal-organic complex-bound Cd was the most predominant compared to other particulate-bound Cd species in the clay size fractions of the soils treated with Idaho MAP fertilizer or the Cd perchlorate-added MAP chemical reagent. The distribution of total Cd in the different soil particle size fractions and the speciation of particulate-bound Cd in the clay size fractions varied with the soil type. The results indicate that clay size fractions can retain Cd making it less available; however, the influence of farming practices, which affect Cd mobility, should not be overlooked.     

Sulfur and nitrogen mineralization in soils compared using two incubation techniques

Net mineralization of sulfur and nitrogen was studied in three Canadian Prairie soils using two commonly used incubation methods. In the open system technique, where the soils were leached periodically II.3–11.8 μ g SO^2?₄ -S g^?1 soil was mineralized in 17 weeks. Little mineralization or a net immobilization of sulfur (from 1.4 to 1.3 μ g SO^2?₄-S g^?1 soil) was observed in a closed system where the soils were left undisturbed throughout incubation. Changes in the specific activity of ³⁵S-labelled soil solution sulfate during the closed incubation indicated that mineralization-immobilization processes were occurring simultaneously resulting in minimal net changes in CaCl₂-extractable SO_2?⁴ concentrations. The amounts of mineralized nitrogen (32.6–57.8 μg N g_?1 soil) were found to be independent of the incubation method employed.     

溶液培养条件下腐殖酸对铁异化还原的影响

腐殖酸对土壤和水体环境中铁(Fe)的还原过程有重要影响。本文采用从山西大同风化煤、河南巩县褐煤、云南昆明滇池底泥中提取制备的腐殖酸,通过布置培育试验并接种土壤悬液,研究了不同来源的腐殖酸对无定形氧化铁异化还原的影响。结果表明:单独添加腐殖酸对氧化铁的还原几乎没有影响;而当同时添加腐殖酸与葡萄糖时,培养基质中氧化铁的还原过程显著加强;腐殖酸浓度越高对氧化铁还原的促进作用越明显。不同来源的腐殖酸因其复杂程度和结构不同,对氧化铁还原的促进作用有明显差异,其中山西大同风化煤提取的腐殖酸促进作用最大,云南昆明滇池底泥和河南巩县褐煤提取的腐殖酸之间则无显著差异。     

长期试验的水稻土上藻类培养生长状况的研究

利用25年定位试验获得的具有不同肥力的水稻土,进行藻类生长的室内培养试验。结果表明：不施肥的条件下,在不同肥力的水稻土上,藻类生长的生物量,以叶绿素a含量表征,有着明显的差异,在长期施用NPK+OM处理的水稻土上,藻类的生长状况最好,其藻类平均叶绿素含量为1.08 μg/g,而在长期不施肥的对照水稻土上,藻类的生长状况最差,其藻类平均叶绿素含量仅为0.12 μg/g。试验显示,藻类的生物量与所试土壤的碱解N、速效P与全P等养分含量呈正相关关系。这为稻田生态系统中藻类生长及其环境效应的研究等提供了试验依据。     

A simplified incubation method using chip‐trays as incubation vessels to identify sulphidic materials in acid sulphate soils

Acid sulphate soils (ASS) can pose a significant hazard to natural ecosystems and developed areas situated within ASS landscapes. Management techniques used to minimize these hazards rely on methods that can classify ASS materials. These methods have traditionally required complex and time‐consuming techniques. A new simplified incubation method, modified from existing ones, was therefore developed to classify ASS materials in a timely manner. The simplified incubation method was found to be a viable alternative where samples cannot be incubated to a stable pH because of logistical or time constraints, but where there is still a need to classify slowly acidifying sulphidic materials. The use of chip‐trays as incubation vessels was also examined. Chip‐trays offer many advantages in terms of transport, storage and analysis of soil samples compared with soil‐slabs. This study establishes an acceptable level of precision ( ± 0.1 pH units with 95% confidence) for pH measurements in the incubation method and confirms that an acceptable level of precision is obtainable when using chip‐trays in the pH incubation method.     

Pyrogenic transformation of tundra soils: Laboratory simulation

Pyrogenic losses of carbon and nitrogen from the surface horizons of soils in shrub ecosystems of mountain tundra, which are the most affected by fires in natural environments, have been estimated in laboratory simulation tests. The specific features of pyrogenic transformation of the physical and chemical properties and microbiological processes after exposure to high temperatures simulating the effect of fires of different intensity have been identified. Pyrogenic nature of the impact depends not only on the intensity of a fire, but also on the soil type. Its impact on tundra soils leads only to short-term increases in CO₂ emissions due to the destruction of pyrogenic organic compounds. A high level of fire impact leads to a significant reduction in microbiological processes in soils and shows no trend toward recovery in the long term, even under optimal conditions.     

Environmental studies of agricultural soils in Poland

Journal of Soils and Sediments -     

The effect of inorganic nitrogen on the added nitrogen interaction of soils in incubation experiments

A laboratory incubation experiment was conducted to study the effect of indigenous inorganic N on the immobilization of applied N and on the occurrence of an added N interaction (ANI). Samples of six Mollisols from Illinois were incubated with ¹⁵N-labelled (NH₄)₂SO₄ (100 or 200 mg N kg^-1 soil), with or without the use of 0.01 M CaCl₂ to extract inorganic N (mainly NO _inf3 ^sup- ) before incubation. From 6 to 49% of the N applied was immobilized, higher percentages being obtained with unextracted soils than with the extracted soils and with the higher rate of N addition. Net mineralization of native N occurred in both the unextracted and extracted soils, but was more extensive in the unextracted soil and increased with the addition of N. The increases were accompanied by a positive ANI, which usually exceeded the amount of applied N immobilized and increased with the rate of addition. The ANI values observed with extracted soils were attributed to increased mineralization of native organic N.