Amino sugars in soils of the North American cultivated prairie

Characterizing amino sugar dynamics in cultivated soils helps to further understand the influence of cultivation on soil organic matter turnover. This study was designed to evaluate accumulations and patterns of four amino sugars in 17 surface (0–10 cm) soil samples along a climosequence in the North American long-term cultivated prairie from Saskatoon, Candada, to Texas, USA. Mean annual temperature (MAT) ranged from 0.9 to 22.2°C and mean annual precipitation (MAP) from 300 to 1308 mm. Samples were analyzed for glucosamine, mannosamine, galactosamine, and muramic acid. Amino sugar contents (mg kg^?1 soil) varied markedly among the 17 sites and were controlled by mean annual temperature (MAT) and clay and silt contents, mainly. The relationship between amino sugar-N proportions to total N (%) and MAT followed parabolic regression models. Compared with native sites, amino sugars were depleted by 53% and the amino sugar-N by 18% of the total, on average, after long-term cropping. The intensity of amino sugar-N depletion correlated positively with MAT (r = 0.77^***). Bacterially-derived galactosamine and muramic acid declined preferentially to mainly chitin-derived glucosamine after long-term cropping. The glucosamine-to-galactosamine and glucosamine-to-muramic acid ratios can be used, therefore, as indicators for the identification of land use effects on microbially-derived SOM residues.     

Land use effects on amino sugar signature of chromic Luvisol in the semi-arid part of northern Tanzania

 Characterizing amino sugar signature in particle size separates of tropical soils is important for further understanding the fate of microbial-derived compounds during the decomposition of soil organic matter (SOM) in tropical agroecosystems. We investigated the impact of land-use changes on the nature, amount and dynamics of amino sugars in soil of the semi-arid northern Tanzania. Samples were collected from the uppermost 10 cm of native woodland, degraded woodland, fields cultivated for 3 and 15 years and homestead fields fertilized with animal manure. The amount of glucosamine, galactosamine, mannosamine and muramic acid were determined in bulk soil and size separates. Compared to the native woodland, a 68% and 72% reduction in total amino sugar contents were found in the 3- and 15-year cultivated fields, respectively. Moreover, 39% of the total amino sugar was lost from the degraded woodland. This may be attributed to accelerated decomposition of amino sugars and/or decreasing microbial biomass input under the semi-arid environment following clear-cutting and cultivation. In contrast, only a 20% decline was found from the fields where animal manure had been applied. Most of the amino sugar depletion occurred from the coarse and fine sand-associated SOM. The decline from the silt and clay-bound amino sugar was relatively small, indicating the importance of organo-mineral associations in the stabilization of microbial-derived sugars in this tropical soil. After 15 years of continuous cultivation, the ratio of glucosamine:galactosamine increased from 1.44 to 2.23, while the ratio of glucosamine:muramic acid increased from 14.5 to 26.5 (P<0.05). These results suggest that cultivation may have led to preferential depletion of bacterial-derived amino sugars (muramic acid and galactosamine) compared with fungal-derived glucosamine. Received: 22 June 2000     

Amino sugars and muramic acid—biomarkers for soil microbial community structure analysis

Characterizing functional and phylogenetic microbial community structure in soil is important for understanding the fate of microbially-derived compounds during the decomposition and turn-over of soil organic matter. This study was conducted to test whether amino sugars and muramic acid are suitable biomarkers to trace bacterial, fungal, and actinomycetal residues in soil. For this aim, we investigated the pattern, amounts, and dynamics of three amino sugars (glucosamine, mannosamine and galactosamine) and muramic acid in the total microbial biomass and selectively cultivated bacteria, fungi, and actinomycetes of five different soils amended with and without glucose. Our results revealed that total amino sugar and muramic acid concentrations in microbial biomass, extracted from soil after chloroform fumigation varied between 1 and 27 mg kg⁻¹ soil. In all soils investigated, glucose addition resulted in a 50-360% increase of these values. In reference to soil microbial biomass-C, the total amino sugar- and muramic acid-C concentrations ranged from 1-71 g C kg⁻¹ biomass-C. After an initial lag phase, the cultivated microbes revealed similar amino sugar concentrations of about 35, 27 and 17 g glucosamine-C kg⁻¹ TOC in bacteria, fungi, and actinomycetes, respectively. Mannosamine and galactosamine concentrations were lower than those for glucosamine. Mannosamine was not found in actinomycete cultures. The highest muramic acid concentrations were found in bacteria, but small amounts were also found in actinomycete cultures. The concentrations of the three amino sugars studied and muramic acid differed significantly between bacteria and the other phylogenetic microbial groups under investigation (fungi and actinomycetes). Comparison between the amino sugar and muramic acid concentrations in soil microbial biomass, extracted after chloroform fumigation, and total concentrations in the soil showed that living microbial biomass contributed negligible amounts to total amino sugar contents in the soil, being at least two orders of magnitude greater in the soils than in the soil inherent microbial biomass. Thus, amino sugars are significantly stabilized in soil.     

Elevated CO2 does not favor a fungal decomposition pathway

We examined the effect of prolonged elevated CO₂ on the concentration of fungal- and bacterial-derived compounds by quantifying the soil contents of the amino sugars glucosamine, galactosamine and muramic acid. Soil samples were collected from three different terrestrial ecosystems (grassland, an aspen forest and a soybean/corn agroecosystem) that were exposed to elevated CO₂ under FACE conditions for 3-10 years. Amino sugars were extracted from bulk soil and analyzed by gas chromatography. Elevated CO₂ did not affect the size or composition of the amino sugar pool in any of the systems. However, high rates of fertilizer N applications decreased the amount of fungal-derived residues in the grassland system. We suggest that these results are caused by a decrease in saprophytic fungi following high N additions. Furthermore, our findings imply that the contribution of saprophytic fungi and bacteria to SOM in the studied ecosystems is largely unaffected by elevated CO₂.     

Net microbial amino sugar accumulation process in soil as influenced by different plant material inputs

Identifying the impact of plant material inputs on soil amino sugar synthesis may advance our knowledge of microbial transformation processes in soils. In a 12-week laboratory microcosm incubation, 1, 2, 4, and 6% (w/w) soybean leaf or maize stalk were initially added to soil, respectively, whereas soil without plant addition was used as a control. The results showed that adding organic materials to the soil led to a net accumulation of amino sugars, because of greater microbial synthesis. The ratios of glucosamine to galactosamine and of glucosamine to muramic acid, two indicators differentiating the relative contribution to soil organic matter of fungi and bacteria, showed substantial variance across the gradient of substrate addition. Our results suggest that the amount of nutrients in a given substrate is the primary attribute determining microbial net accumulation of soil amino sugars, especially in the relatively short term, whereas the composition of nutrients might be more important in the relatively long term when nutrients are not sufficient. The use of the two ratios (glucosamine to galactosamine and glucosamine to muramic acid) reflects different dynamics of galactosamine and muramic acid during the decomposition of organic substrates in soils. Muramic acid, compared with galactosamine, is more likely to accumulate in the soil active organic fraction under abundant nutrient conditions, whereas it would be decomposed along with active organic matter when the nutrients are scarce and remain in minor quantities in the clay fraction without being attacked by microbes.     

外源氮素和凋落物添加对温带森林土壤氨基糖转化特征的影响

【目的】温带森林土壤氨基糖的转化特征对外源氮素和凋落物加入的响应研究,对于温带森林土壤氮素管理和缓解氮沉降所带来的负面影响具有重要的意义。【方法】采用室内恒温恒湿模拟培养的方法,研究了外源氮素和凋落物添加条件下温带森林土壤有机层中3种微生物来源的氨基糖含量的变化特征,并利用真菌和细菌来源氨基糖的比值（氨基葡萄糖/胞壁酸）,分析了外源物质添加条件下真菌和细菌残留物对土壤氮素转化和积累的相对贡献。【结果】温带森林有机层土壤中不同微生物来源氨基糖对外源物质加入的响应不同。单施氮素以及氮素与凋落物同时添加均有利于细菌残留物胞壁酸的积累,但是单施氮素添加对真菌残留物氨基葡萄糖含量的积累没有影响,且氮素与凋落物同时添加不利于氨基葡萄糖含量的积累。氨基半乳糖对外源物质添加的响应较小。真菌残留物的稳定性高于细菌残留物,氮素与凋落同时加入时不利于土壤微生物残留物的稳定性。此外,土壤中真菌和细菌来源氨基糖的比值受到外源物质加入的影响,单施氮素以及氮素与凋落物添加降低了氨基葡萄糖/胞壁酸比值（分别降低28.3%和30.5%）,两种外源物质加入时细菌残留物对氮素转化的相对贡献大于真菌残留物。【结论】外源氮素和...     

Microbial residues as indicators of soil restoration in South African secondary pastures

Prolonged intensive arable cropping of semiarid grassland soils in the South African Highveld resulted in a significant loss of C, N and associated living and dead microbial biomass. To regenerate their soils, farmers converted degraded arable sites back into secondary pastures. The objective of this study was to clarify the contribution of microorganisms to the sequestration of C and N in soil during this regeneration phase. Composite samples were taken from the topsoils of former arable land, namely Plinthustalfs, which had been converted to pastures 1-31 years ago. Amino sugars were determined as markers for microbial residues in the bulk soil and in selected particle-size fractions. The results showed that when C and N contents increased during the secondary pasture usage, the amino sugar concentration in the bulk soil (0-5 cm) recovered at similar magnitude and reached a new steady-state level after approximately 90 years, which corresponded only to 90% of the amino sugar level in the primary grassland. The amino sugar concentration in the clay-sized fraction recovered to a higher end level than in the bulk soil, and also at a faster annual rate. This confirms that especially the finer particles contained a high amount of amino sugars and were responsible, thus, for the restoration of microbially derived C and N. The incomplete recovery of amino sugars in bulk soil can only in parts be attributed to a slightly coarser texture of secondary grassland that had lost silt through wind erosion. The soils particularly had also lost the ability to restore microbial residues below 5 cm soil depth. Overall, the ratios of glucosamine to muramic acid also increased with increasing duration of pasture usage, suggesting that fungi dominated the microbial sequestration of C and N whereas the re-accumulation of bacterial cell wall residues was less pronounced. However, the glucosamine-to-muramic acid ratios finally even exceeded those of the primary grassland, indicating that there remained some irreversible changes of the soil microbial community by former intensive crop management.     

Carbohydrate dynamics in particle-size fractions of sandy spodosols following forest conversion to maize cropping

In southwest France, much of the forested land on sandy spodosols has been converted to continuous maize cropping in the last few decades. To evaluate the impacts of this change on soil organic matter properties, we compared total organic C and neutral and amino sugars content in whole soil and particle size separates of two forested, and five related sites that had been either clear-cut for 12 and 18 mo, or cultivated to maize for 4-22 yr. Soil carbohydrates accounted for 4-7% of the total organic C across all sites. Soil organic C contents of clear-cut and cultivated sites were only 57-79% of the average value measured in forested sites. Accordingly, carbohydrate content of clear-cut and cultivated sites were only 35-66% of the value in forested sites. Ordering the sites in a chronosequence indicated that both total organic C and carbohydrate contents decreased with an increase in time elapsed since clear-cutting and maize cultivation. The only exception was a partial recovery of carbohydrate content in the site that had been under continuous maize for 22 yr. The clay+silt fraction (0-50 μm) was enriched in carbohydrates, mainly of microbial origin, whereas the sand size fractions (50-200 and 200-2000 μm) contained fewer carbohydrates which were mainly of plant origin. Monosaccharide analysis of particle size separates revealed significant differences in carbohydrate composition between sites. Relative to forested sites, the coarse and fine sand fractions in clear-cut and cultivated sites were depleted in carbohydrates and were relatively enriched in plant-derived carbohydrates. Carbohydrate content of the clay+silt fraction drastically decreased upon clear-cutting. Amino sugar content was consistently lower in clear-cut and cultivated sites than in forested sites, indicating that microbial populations were negatively affected by clear-cutting and cultivation. The fungal population appeared more sensitive than bacteria to these land-use changes as indicated by a greater decline in glucosamine than in muramic acid contents.     

外源氮添加对土壤微生物残体积累动态的影响－基于Meta分析

微生物残体是土壤有机碳库的重要贡献者。为明确外源氮添加对土壤微生物残体积累动态的影响,本文收集整理了1980—2020年已发表的文献,共选取122组试验观测数据,利用整合分析方法（Meta-analysis）,以微生物残体标识物－氨基糖为目标组分,定量分析了不同种类和数量的外源氮添加对土壤中微生物来源细胞残体积累数量和组成比例的影响,并系统解析其主要影响因素。结果表明:外源氮添加（0 ~ 6000 kg hm?1）对微生物细胞残体的积累有显著的促进作用,并能引起土壤中真菌和细菌来源细胞残体相对比例发生明显变化。与不加氮对照相比,氮添加使土壤氨基糖总量增加27%,其中氨基葡萄糖、氨基半乳糖和胞壁酸含量分别增加22.5%、29.8%和19.0%。同时,不同种类外源氮素添加对氨基糖积累特征的影响也有所不同,表现为有机氮（如动物厩肥）比无机氮添加对氨基糖积累的促进作用更大。此外,氮添加对氨基糖的影响程度还与土壤自身的碳氮比、土地利用类型和自然降雨量等环境因子密切相关。其中是否添加碳源对微生物残体的响应有较大影响,表现为:无碳源添加会降低土壤氨基糖葡萄糖和胞壁酸对氮添加的响应,削弱了微生物残体对土壤有机质的贡献比例;而氮源同时配合碳源添加条件下,土壤氨基糖积累量显著高于单一氮源添加的处理,说明氮添加对微生物残体积累的影响存在着碳氮耦合效应。     

尿素向氨基糖的转化以及对土壤氨基糖库动态的影响

采用13CO(NH2)2为底物进行黑土培养实验,利用气相色谱/质谱技术测定土壤中三种氨基糖含量以及同位素富集比例,根据其微生物标识物作用探讨土壤中不同微生物群落对于尿素碳的同化利用特征及黑土氨基糖库对于尿素添加的响应。研究结果表明,尿素碳可以被土壤微生物同化利用,但是可利用性显著低于葡萄糖。氨基葡萄糖中13C富集比例显著高于胞壁酸,表明真菌对尿素碳的同化能力高于细菌。尿素添加使土壤有机碳含量有所下降,同时土壤氨基糖总量及其与有机碳的相对比例也显著降低,说明在碳源严重受限条件下,氨基糖可被优先分解利用以补充碳源供给。胞壁酸含量虽低,但其调节并平衡碳氮元素供给与需求的能力较强;氨基葡萄糖稳定性高于胞壁酸,但在碳源缺乏时也可部分分解。土壤氨基糖的动态与土壤碳氮的可利用性及其耦合作用密切相关,在平衡土壤碳氮需求方面具有一定的调节作用。     

Optimisation of amino sugar quantification by HPLC in soil and plant hydrolysates

Amino sugars are increasingly used as indicators for the accumulation of microbial residues in soil and plant material. A reverse-phase high-performance liquid chromatography method was improved for the simultaneous determination of muramic acid, mannosamine, glucosamine and galactosamine in soil and plant hydrolysates via ortho-phthaldialdehyde (OPA) pre-column derivatisation and fluorescence detection. The retention time was reduced, and the separation of muramic acid and mannosamine was optimised by modifying the mobile phase. The effects of excitation wavelength, OPA reaction time, tetrahydrofuran concentration and pH value of the mobile phase on the amino sugar separation were tested. Quantification limits were in the range of 0.13 to 0.90 μg ml⁻¹. No interferences exist from amino acids or other primary amines, occurring in soil and plant hydrolysates.     

The automated determination of glucosamine,galactosamine, muramic acid,and mannosamine in soil and root hydrolysates by HPLC

Amino sugars make a significant contribution to soil organic N and are mainly of microbial origin. The most important amino sugars in soil are glucosamine, galactosamine, muramic acid, and mannosamine. A method was developed for the simultaneous determination of these four amino sugars by high‐performance reverse‐phase liquid chromatography in standard solutions, soil and root hydrolysates. Pre‐column derivatization with o‐phthaldialdehyde (OPA) was used in an automated sample injector with thermostatic regulation of the reagent at 4 °C. The separation of the four amino sugars was fully satisfactory and was not disturbed by other fluorescent components in the soil and root hydrolysates.     

Amino sugars as specific indices for fungal and bacterial residues in soil

Amino sugars are important indices for the contribution of soil microorganisms to soil organic matter. Consequently, the past decade has seen a great increase in the number of studies measuring amino sugars. However, some uncertainties remain in the interpretation of amino sugar data. The objective of the current opinion paper is to summarize current knowledge on amino sugars in soils, to give some advice for future research objectives, and to make a plea for the correct use of information. The study gives an overview on the origin of muramic acid (MurN), glucosamine (GlcN), galactosamine (GalN), and mannosamine (ManN). Information is also provided on measuring total amino sugars in soil but also on compound-specific δ¹³C and δ¹⁵N determination. Special attention is given to the turnover of microbial cell-wall residues, to the interpretation of the GlcN/GalN ratio, and to the reasons for converting fungal GlcN and MurN to microbial residue C. There is no evidence to suggest that the turnover of fungal residues generally differs from that of bacterial residues. On average, MurN contributes 7% to total amino sugars in soil, GlcN 60%, GalN 30%, and ManN 4%. MurN is highly specific for bacteria, GlcN for fungi if corrected for the contribution of bacterial GlcN, whereas GalN and ManN are unspecific microbial markers.     

Fate of microbial residues in sandy soils of the South African Highveld as influenced by prolonged arable cropping

Long‐term cultivation of former grassland soils results in a significant decline of both living and dead microbial biomass. We evaluated the effect of duration of cropping on the preservation of fungal and bacterial residues in the coarse‐textured soils of the South African Highveld. Composite samples were taken from the top 20 cm of soils (Plinthustalfs) that have been cropped for periods varying from 0 to 98 years in each of three different agro‐ecosystems in the Free State Province. Amino sugars were determined as markers for the microbial residues in bulk soil and its particle‐size fractions. Long‐term cultivation reduced N in the soil by 55% and the contents of amino sugars by 60%. Loss rates of amino sugars followed bi‐exponential functions, suggesting that they comprised both labile and stable fractions. With increased duration of cropping the amino sugars attached to silt dissipated faster than those associated with the clay. This dissipation was in part because silt was preferentially lost through erosion, while clay particles (and their associated microbial residues) remained. Erosion was not solely responsible for the reduction in amino sugar concentrations, however. Bacterial amino sugars were lost in preference to fungal ones as a result of cultivation, and this effect was evident in both silt‐ and clay‐sized separates. This shift from fungal to bacterial residues was most pronounced within the first 20 years after converting the native grassland to arable cropland, but continued after 98 years of cultivation.     

A novel GC/MS technique to assess N and C incorporation into soil amino sugars

Amino sugars have been used as biomarker to indicate microorganism contribution to soil organic matter turnover and sequestration. However, there is no direct gas chromatograph mass spectrometry (GC/MS) approach to assess microbial synthesis of amino sugars in soil. We developed a novel method which combines laboratory incubation of substrate containing ¹⁵N or ¹³C and a GC/MS technique to trace ¹⁵N or ¹³C isotope changes in three amino sugars, glucosamine, galactosamine, and muramic acid. Sample preparation followed the procedure of Zhang and Amelung (1996) [Zhang, X., Amelung, W., 1996. Gas chromatographic determination of muramic acid, glucosamine, galactosamine, and mannosamine in soils. Soil Biology and Biochemistry 28, 1201-1206.]. The GC/MS determination was conducted using a full scan mode with both electronic ionization (EI) and chemical ionization (CI) sources. The CI source was suitable for all of the three amino sugars, while the EI source was not applicable to muramic acid due to its low sensitivity in the determination as well as low concentration of muramic acid in soil. The enrichment of ¹⁵N or ¹³C in amino sugars during incubation was estimated by calculating the atom percentage excess (APE). ¹⁵N incorporation was evaluated according to fragment (F) abundance ratio of mass F+1 to F, whilst ¹³C incorporation was estimated according to the ratio of mass F+n to F (n is skeleton carbon number in the fragment). This novel method was assessed by using two soil samples (a Kandiudult and a Udoll) incubated with either ¹⁵N-amonium or U-¹³C-glucose. The results indicate that the GC/MS determination is reproducible, thus this technique is useful in detecting the microbial synthesis of amino sugars in soil, and especially it should be possible when looking at the position or how much labeled carbon and nitrogen atoms have been incorporated.     

Temporal responses of soil microorganisms to substrate addition as indicated by amino sugar differentiation

Amino sugars are one of the important microbial residue biomarkers which are associated with soil organic matter cycling. However, little is known about their transformation kinetics in response to available substrates because living biomass only contributes a negligible portion to the total mass of amino sugars. By using ¹⁵N tracing technique, the newly synthesized (labeled) amino sugars can be differentiated from the native portions in soil matrix, making it possible to evaluate, in quantitative manner, the transformation pattern of amino sugars and to interpret the past and ongoing changes of microbial communities during the assimilation of extraneous ¹⁵N. In this study, laboratory incubations of soil samples were conducted by using ¹⁵NH₄⁺ as nitrogen source with or without glucose addition. Both the ¹⁵N enrichment (expressed as atom percentage excess, APE) and the contents of amino sugars were determined by an isotope-based gas chromatography-mass spectrometry. The significant ¹⁵N incorporation into amino sugars was only observed in glucose plus ¹⁵NH₄⁺ amendment with the APE arranged as: muramic acid (MurN) > glucosamine (GlcN) > galactosamine (GalN). The dynamics of ¹⁵N enrichment in bacterial-derived MurN and fungal-derived GlcN were fitted to the hyperbolic equations and indicative for the temporal responses of different soil microorganisms. The APE plateau of MurN and fungal-derived GlcN represented the maximal extent of bacterial and fungal populations, respectively, becoming active in response to the available substrates. The different dynamics of the ¹⁵N enrichment between MurN and GlcN indicated that bacteria reacted faster than fungi to assimilate the labile substrates initially, but fungus growth was dominant afterward, leading to integrated microbial community structure over time. Furthermore, the dynamics of labeled and unlabeled portions of amino sugars were compound-specific and substrate-dependent, suggesting their different stability in soil. GlcN tended to accumulate in soil while MurN was more likely degraded as a carbon source when nitrogen supply was excessive.     

玉米不同残体添加对棕壤团聚体中氨基糖分配的影响

[目的]秸秆残体还田能引起土壤微生物残留物氨基糖的变化,然而不同部位秸秆残体因含碳氮化学组分差异,还田到不同肥力土壤后对氨基糖在团聚体中分配的影响尚不明析.因此,研究添加玉米不同残体对不同肥力棕壤团聚体中氨基糖分配的影响,并利用微生物标识物氨基葡萄糖与胞壁酸比值变化指示棕壤团聚体真菌和细菌群落组成动态变化,对深入阐明秸...     

Kinetics of amino sugar formation from organic residues of different quality

Amino sugars are key compounds of microbial cell walls, which have been widely used as biomarker of microbial residues to investigate soil microbial communities and organic residue cycling processes. However, the formation dynamics of amino sugar is not well understood. In this study, two agricultural Luvisols under distinct tillage managements were amended with uniformly ¹³C-labeled wheat residues of different quality (grain, leaf and root). The isotopic composition of individual amino sugars and CO₂ emission were measured over a 21-day incubation period using liquid chromatography–isotope ratio mass spectrometry (LC–IRMS) and trace gas IRMS. Results showed that, the amount of residue derived amino sugars increased exponentially and reached a maximum within days after residue addition. Glucosamine and galactosamine followed different formation kinetics. The maxima of residue derived amino sugars formation ranged from 14 nmol g⁻¹ dry soil for galactosamine (0.8% of the original concentration) to 319 nmol g⁻¹ dry soil for glucosamine (11% of the original concentration). Mean production times of residue derived amino sugars ranged from 2.1 to 9.3 days for glucosamine and galactosamine, respectively. In general, larger amounts of amino sugars were formed at a higher rate with increasing plant residue quality. The microbial community of the no-till soil was better adapted to assimilate low quality plant residues (i.e. leaf and root). All together, the formation dynamics of microbial cell wall components was component-specific and determined by residue quality and soil microbial community.     

无机氮素加入量对玉米秸秆分解过程中棕壤氨基糖含量的影响

作物秸秆还田作为一种调控土壤养分循环、减少氮肥损失、维持和提高土壤有机质水平的有力措施,越来越受到人们的重视[1-2]。还田的秸秆是微生物的碳源和能源,常导致土壤微生物量迅速增加,相应的微生物死亡率和微生物残体积累量也提高[3-4]。根据Appuhn等[5]对微生物细胞壁组分的     

The effect of cultivation on sediment composition and deposition in prairie pothole wetlands

Texture, major nutrient content, and deposition rate of sediments were compared for five prairie pothole wetlands surrounded by native grassland and seven otherwise similar wetlands surrounded by row crop and small grain farmland. Specific differences in the nature of the sedimentation cycle of cultivated and noncultivated watersheds were indicated. Flux of total inorganic material into sediments averaged 80 and 43 mg cm^?2 yr^?1 in cultivated and grassland wetlands, respectively. Cultivated sediments contained significantly higher clay percentages, but lower percentages of silt and sand than grassland sediments. Deposition rates of clay at cultivated sites averaged five times that of grassland locations. Enrichment ratios (the quotient of sediment concentration divided by upland soil concentrations) suggested that sand was selectively retained in equal proportions on uplands in both types of watersheds, that silt was selectively removed (although in different proportions) from uplands in both types of watersheds, and that clay was selectively retained only on grasslands. Total N and organic matter concentrations were significantly higher in both the soils and sediments of grassland watersheds, but there were no differences in total P concentrations with respect to land use. Sediment flux rates for total N and organic matter were similar in the two land use types; however, P was transported at nearly twice the rate to cultivated wetlands. Enrichment ratios indicated that N and P were selectively removed in similar proportions from upland soils in both types of watersheds.