The influence of relief on the humus content in chernozems

Data on the influence of relief on the humus formation in chemozems are given. The insolation coefficient is proposed for the assessment of the solar energy distribution over the ground surface depending on the slope gradient and aspect. Specific features of the humus accumulation in soils on parent rocks different in texture are estimated using the proposed calculated coefficients.     

Magnesium influence on plant uptake of phosphorus in a calcareous soil

A pot experiment was conducted to investigate the role of magnesium (Mg) in plant utilization of ³²phoshorus (P)‐labelled P in a calcareous soil (Typic Hapluquent). Results with two successive harvests of ryegrass shoots indicated that Mg had no obvious influence on plant uptake of the P applied. In a separate incubation study with the same soil, labelled P along with different levels of Mg was introduced to the soil at two time intervals and soil inorganic P was fractionated. The isotope data of P in various fractions indicated that Mg at the test levels had no obvious influence on P transformation either. It is suggested from the experiments that Mg is unlikely to be able to promote plant utilization of fertilizer P in calcareous soils.     

Effects of root morphology and Hg concentration in the soil on uptake by terrestrial vascular plants

Vascular plant tissues of various species growing on flood plain soils along the South River at Waynesboro, VA. have previously been shown to contain Hg. These soils characteristically contain 10–20μg Hg g^?1. In the field, root/rhizome Hg content inAsclepias syriaca andSolidago sp. ranged from undetectable amounts at low Hg control sites to 1.96μg Hg gdw^?1 at contaminated sites, with the association being inversely related to subterranean organ size. Within each size class, tissue Hg was directly related to soil Hg concentration. The relationship of subterranean organ size and enhanced Hg association was further substantiated by high levels of Hg in the fibrous root systems of grasses grown under greenhouse conditions.     

腐殖酸对汞的络合稳定特性及其环境学意义

对3种腐殖酸与Hg的络合稳定特性研究结果表明,腐殖酸与Hg的结合存在松结态与紧结态2种形态,其中富里酸主要以松结态为主,灰色胡敏酸与棕色胡敏酸则以紧结态占绝对优势。3种腐殖酸中富里酸对Hg的络合容量最高,但络合强度最低,其络合汞的环境活性将较高;灰色胡敏酸对Hg的络合容量最低,但络合稳定性最高,故所结合Hg的环境活性最弱。但受容量因素制约,灰色胡敏酸对Hg的络合稳定性将因Hg/灰色胡敏酸相对比例的升高而急剧下降。棕色胡敏酸对Hg络合特性介于富里酸与灰色胡敏酸之间。     

Effects of nitrogen-containing fertilizers on solubility and plant uptake of cadmium

In a pot experiment, three N-fertilizers, differing in NO^? ₃ and NH⁺ ₄; content, were compared in terms of their effects on the extractability of soil Cd in 1M ammonium acetate at pH 7 and on the uptake of native and added Cd by winter rape (Brassica napus L. var. oleifera Metzger). In another similar experiment the Cd-availability in soils receiving NPK-fertilizer applied in a concentrated, granulated form was compared to that in soils receiving a uniform application of dissolved NPK-fertilizer. Both loamy sand and clay soils were used. With the N-fertilizers levels of extractable soil Cd and plant Cd-contents were lowest in the nitrate of lime treatment, highest in the ammonium sulphate treatment and intermediate in the nitro-chalk treatment. The addition of 1 mg kg^?1 DW Cd to the soil increased Cd-levels but did not change the response pattern. There was a strong association between the effects of the various fertilizers on Cd availability and their effects on soil pH: the stronger the acidifying effect the higher the Cd availability. When applied at a low dose, granular NPK was more effective than dissolved NPK at enhancing plant uptake of Cd from both soils, but this was not the case when applied at a higher dose to the sand. The two forms of NPK differed little in their effect on extractable soil Cd. Plant uptake of Cd was greater from soils receiving granular NPK with a high Cd-content than from those receiving granular NPK low in Cd. In both experiments extractable Cd was taken up to a greater extent from the sand than from the clay. An increase in fertilizer dose generally resulted in an increase in levels of soil-Cd and in Cd concentrations in the plants.     

长期定位施肥对土壤腐殖质结合形态的影响

长期施用有机肥或有机无机肥配施均能显著提高潮土、旱地红壤和红壤性水稻土耕层松结态腐殖质、稳结态腐殖质和紧结态腐殖质含量,但以有机无机肥配施的效果最好。有机无机肥配施能提高三种土壤耕层稳结态腐殖质和潮土耕层松结态腐殖质碳占重组有机碳的比例,降低三种土壤紧结态腐殖质碳占重组有机碳的比例。单施有机肥或化肥也能提高潮土耕层三种结合态腐殖质碳占重组有机碳的比例,降低旱地红壤和红壤性水稻土紧结态腐殖质碳占重组有机碳的比例。施肥还可以提高三种土壤耕层松结态腐殖质/紧结态腐殖质的比值。     

Earthworm feeding activity and development of the humus profile

Earthworm casts and digestive tract contents were simultaneously examined, using the same methods, in a recently formed humus profile in a mountain spruce forest. Earthworm species had distinct diets and an earthworm foodweb could be distinguished. Lumbricus terrestris and Aporrectodea icterica were distinct from the other species examined: the former to some extent as a litter consumer, and both species because they excavated mineral material which was deposited within new top layers of the mull humus. Aporrectodea nocturna and Aporrectodea caliginosa both had a non-specific soil feeding mode. Most of the species enriched the humus profile with amorphous organic matter finely incorporated within a mineral matrix. Besides different food selection, a network of burrows was produced as a consequence of the different burrowing behaviour of each earthworm species. Received: 2 January 1997     

生物炭对紫色土中腐植酸淋溶的影响

为了减少紫色土腐植酸的流失,提高龙川江流域紫色土肥力,采用土柱室内模拟方法,通过模拟降雨淋溶,研究了不同生物炭处理下(CK、1%、3%、5%和10%)对紫色土淋溶液p H值、电导率、体积以及胡敏酸和富里酸的影响。结果表明:在29 d试验过程中,淋溶液的p H值和电导率随着生物炭比例增加而增加;与CK相比,在1%、3%、5%和10%的生物炭处理条件下紫色土水分损失分别减少了6.33%、10.13%、16.46%和25.32%;胡敏酸浓度和累积淋失量随着生物炭比例增加而减小;除了1%和3%之外,富里酸浓度和累积淋失量也随着生物炭比例增加而减小;生物炭比例为10%的处理条件下对紫色土淋溶液中胡敏酸和富里酸浓度及累积淋失量最小,胡敏酸浓度和累积淋失量分别为1.46 mg/L、0.12 mg,富里酸浓度和累积淋失量分别为149.64 mg/L、29.60 mg,该处理有利于更大程度吸附胡敏酸和富里酸,减少其流失。     

Effects of plant-bacterial-amoebal interactions on plant uptake of nitrogen under field conditions

Summary Bacterial biomass and numbers of bacterivorous naked amoebae were estimated daily in soil associated with barley roots and, to avoid the influence of roots, in soil from a field in its fifth summer under bare fallow. The estimates were associated with two rainfall events and were started just before the first. Increases in bacteria were observed after each rainfall, and bacterial production was about the same size for both treatments. A peak in naked amoebae followed each burst of bacterial production in the root-associated soil, whereas in the fallowed soil protozoan production was low after the first rainfall and undetectable after the second. The bacterial populations in the fallowed soil had yet to decline by the end of the 12-day study, probably because grazing pressure by protozoa was low. Calculations based (1) on short-term decreases in bacterial biomass in soil close to roots or (2) on the amount of C added to the soil by plants over the growing season indicated that N released via bacterial-protozoan interactions contributed 10%–17% of the N taken up by the fertilized barley.     

Effects of plant age on nitrogen uptake and distribution by greenhouse plants

Water‐soluble nitrogen (N) fertilizer is intensively used in greenhouse crop production. Any N not used by a crop is subject to leaching as nitrate (NO₃‐N), which may pollute groundwater. A close correlation between N supply and N uptake by plants would increase the efficiency of N fertilization and minimize the possibility of NO₃‐N pollution. The objectives of this study were to measure N uptake by American marigold (Tagetes erecta L. ‘First Lady') and New Guinea Impatiens (NGI) (Impatiens hawkeri Bull. ‘Selenia') during growth, to determine the effect of plant age on N uptake, to determine if the two species have a preference for NO₃‐N or ammonium (NH₄‐N), and to determine the total N required for 70 days of growth.The plants were grown in solution culture using solutions supplying 120 mg each of NO₃‐N and NH₄‐N. At ten day intervals, six cultures were chosen at random for nutrient solution analysis and plant sampling for dry weight and tissue analysis. Nitrate‐N uptake was greater than NH₄‐N uptake throughout the experiment for both marigold and NGI. Total N uptake by marigold was greater during the first 50 days after transplanting with maximum N uptake during the period 30 to 50 days. In contrast, N uptake by NGI was greater during the period 40 to 70 days after transplanting. Maximum N uptake for NGI occurred during the period 60 to 70 days. Results of this study suggest that early N fertilization of marigold could be more important for their growth and quality than N applied later. For NGI, N fertilization later in the crop's development appears to be more important than early on. The total N absorbed by marigold during the experiment was 1.1 gm N plant^‐1; for NGI the quantity was 0.5 gm N plant‐¹.     

环境因素对小麦根系非选择性阳离子通道(NSCCs)转运钾的影响

以石家庄8号小麦作为研究对象,通过添加钾载体抑制剂和钾专性通道抑制剂的方法,探讨了温度变化和重金属镉、铜对植物根系的非选择性阳离子通道(NSCCs)转运钾离子的影响。结果显示,NSCCs转运钾的最适温度在35℃左右,低温和高温都会使NSCCs的吸钾速率下降。较高的温度(40℃)对NSCCs转运钾的影响大于对专一性钾通道的影响;而较低温度(20℃)对专一性钾通道活性的抑制比对NSCCs的抑制更强。重金属镉和铜均对小麦的钾吸收速率产生影响,浓度越大,抑制作用越强。其中,根系NSCCs对镉的敏感度相对于专一性钾通道来说要低,而对铜的敏感度相对较高。说明不同重金属对两类通道蛋白的影响机制不一样。     

Effects of plant residues and environmental factors on phosphorus availability in soils

Abstract

Phosphorus availability is a major nutritional problem in several northern Idaho soils. Traditionally, fertilizers containing P have been applied to improve availability in soils; however, organic materials added to soils have the ability to provide large quantities of labile P via mineralization processes and to reduce sorption of P. Using this concept, plant residues applied to soils would increase P availability for future plant needs. This research evaluated the effect of plant residue, incorporated into a Northern Idaho soil, on P availability under controlled laboratory conditions. Alfalfa (Medicago sativa), pea (Pisum sativum) and wheat (Triticum aestivum) plant residues were incorporated into soil collected from the Ap horizon of a Latahco silt loam (fine‐silty, mixed, frigid Argiaquic Xeric Argialboll) at rates of 0, 1, 5 and 10% (w/w). The soils were incubated at soil water potentials of ‐0.05, ‐0.15 and ‐0.40 MPa, and temperatures of 10, 20 and 30°C over a 20 week period. Soils were sampled at 2, 4, 8, 12, 16 and 20 weeks for determination of NaOAc extractable P. Data were analyzed by SAS‐GLM and Omega squared (ω²) values were used to identify the impact of each main effect and interaction. A significant 4‐factor interaction of plant residue x amendment rate x water potential x incubation time, four 3‐factor interactions, six 2‐factor interactions and four main effects were observed at each of the three incubation temperatures. Since all interactions and main effects significantly affected P availability, ω² values were used to assess their relative importance. Amendment rate was the most important factor and plant residue material was the second most important factor observed affecting extractable P levels. In general, NaOAc extractable P increased with increasing amendment rates and incubation time‐period. Increasing incubation temperature and soil water potential also positively affected the extracted P level. The greatest amount of P was mineralized from alfalfa residue material while the smallest amount was released from wheat residue. Pea residue contributed an intermediate quantity of extractable P. This study demonstrated that residues applied to northern Idaho soils have the ability to enhance P availability in addition to providing a usable N source.     

Effects of prolonged irrigation on the humus of steppe soils in southwest Siberia

Changes in humus resulting from up to 20 years' irrigation with slightly saline water were studied in dry steppe soils in southwest Siberia. The amounts of brown humic acids and of the Pg fraction increased with the period of irrigation, and their maximum amounts occurred at greater depths in the profile. Other fractions of humus and humic acids fluctuated within the limits typical of dry steppe soils. The humus therefore remained essentially stable under irrigation for up to 20 years.     

Vesicular-arbuscular mycorrhiza: Influence on plant uptake of cesium and cobalt

A study was made to determine if infection with vesicular-arbuscular mycorrhizal (VAM) fungi would increase the uptake of ¹³⁷Cs and ⁶⁰Co by Yellow sweetclover [Melilolus officinalis (L.) Lam] and Sudan grass [Sorghum sudanense (Piper) Stapf.]. Plants were inoculated by germinating and growing plants in small volumes of soil containing one of three inoculum sources. Control plants were grown in steam-sterilized inoculum to which sieved (38 μm) inoculum washings had been added. Infected and control plants, with the accompanying soil volume, were subsequently transplanted into pots containing autoclaved field soil which 7 yr previously had been contaminated with ¹³⁷Cs and ⁶⁰Co. The clover was harvested at 65 and 93 days; Cs content was 2.0 and 1.7 times that of the control respectively, on these dates, while Co was not significantly different. The grass was harvested at 85 and 119 days; Cs content was greater in the treated than the control grass, but not significantly; however, Co content was increased 2.5 times that of the control at the first harvest data, but was not significant at the second.     

The influence of root hairs on the uptake of phosphate

Abstract

The uptake of phosphate from stirred solution by roots was not affected by root hairs. In contrast to this, root hairs appreciably increased the uptake of phosphate from a clay soil.     

Effect of placement of coated urea fertilizer on root growth and rubidium uptake activity in soybean plant

Abstract

We reported in the previous paper (Takahashi et al. 1991) that the deep placement of slow release N fertilizer (coated urea) contributed to a stable increase of soybean (Glycine max L. Merr.) yield. In the previous study we observed that the deep placement of coated urea did not depress appreciably the nitrogen fixation by root nodules although fertilizer N was efficiently utilized. We assumed that the N absorbed from the roots in the deep layers did not cause nodule senescence, contributed to the maintenance of the leaf activity during the maturation stage, and that the increase in the availability of carbohydrate and N improved seed production. In the current report the effects of placement of coated urea fertilizer on the root growth and activity were studied by measuring the root dry weight and Rb absorption activity.     

添加矿化垃圾腐殖土对绿化土壤物理特性的影响

矿化垃圾腐殖土作为绿化基质使用可以增加土壤中有机质及养分质量分数,但同时可能会对土壤物理及水分特性造成影响。运用土壤物理及水动力学方法,通过不同矿化垃圾质量添加比(0%、25%、50%、75%)进行田间、室内对比试验,比较不同配比对土壤物理性质和水分特性的影响。结果表明:1)添加矿化垃圾腐殖土质量比为25%时,土壤物理性质(密度、孔隙度等)和水分特性均无明显变化,仅土壤砂粒体积分数增加;添加比为50%时,土壤密度、毛管孔隙度和饱和含水率均无显著变化,但土壤总孔隙度明显降低,土壤砂粒体积分数及饱和导水率显著升高;添加比为75%时,土壤物理性质和水分特性均影响显著,其中土壤砂粒体积分数升高约217%,土壤饱和含水量降低11%,毛管含水量降低26%,土壤饱和导水率增加约93%,土壤有效水含量减少24.9%;2)Gardner模型能较好地拟合不同处理土壤水分特征曲线;3)添加矿化垃圾腐殖土在作为绿化基质使用过程中,质量添加比为25%~50%较适宜。     

The influence of use of different rates of mycorrhizal inoculum on root infection,plant growth,and phosphorus uptake

Abstract

Sorghum and leek plants were used as hosts in order to test the effectiveness and infectiveness of four mycorrhizal species on spore production, plant growth and phosphorus (P) uptake. When sorghum was used as a test plant, Glomus mosseae, Glomus etunicatum, and Glomus caledonium, respectively, gave the highest number of spores, while on leek, G. etunicatum, G. mosseae, and G. caledonium, respectively, resulted in higher spore production. Glomus intraradices produced the least amount of inoculum among the four species. Based on relative spore production and root infection, G. mosseae and G. etunicatum were determined to be the two best fungi as sources of inoculum for further use in the experiment. It is very important to know the minimum amount of inoculum in order to reach the maximum percentage of infection. Thus different amounts of inoculum were applied to determine optimum rates of inoculation. Sorghum and leek plants were infected with 0, 6, 12, 18, and 24 g G. mosseae and G. etunicatum of mycorrhizal inoculum per pot in a low P content and natural soil. As the inoculum rate increased, plant parameters and the percent of infection gradually increased with increasing rate to 18 g. Higher inoculum rates did not stimulate growth on infection percentage.     

Studies on the humus forms of forest soils

The results of humus composition analysis of each fraction separated physically from each horizon of the five forest soils used in the last paper (3) were presented.

Regular changes in humus composition were observed with the gradation of horizons and With the decrease in particle size. Most of the humic acids from plant residual fractions belonged to the Rp type; hurnic acids from the L layers showed a tannin-like character which disappeared with the progress of decomposition, and humic acids from the smaller particle fractions of the layers contained a Pg fraction.

As for humic acids from the A horizon, they all belonged to the P or B type and contained a Pg fraction. In addition, it was concluded that the humification process in the mineral layer Was clearly different from that in the organic layer.