Abiotic and Biotic Factors Controlling Grain Aroma along Value Chain of Fragrant Rice:A Review

The aroma of fragrant rice is one of the grain quality attributes that significantly influenceconsumer preferences and prices in world markets. The volatile compound 2-acetyl-1-pyrroline (2AP) isrecognized as a key component of the aroma in fragrant rice. The variation in grain 2AP content amongvarious fragrant rice varieties is associated with the expression of the badh2 gene, with 19 alleles havingbeen identified so far. The grain 2AP content is strongly influenced by environmental and managementfactors during cultivation as well as post-harvest conditions. This review pinpointed the major abiotic andbiotic factors that control grain 2AP content. Abiotic factors refer to water, temperature, light quality,fertilizer application (both macro- and micro-nutrients), and soil properties, including salinity, while bioticfactors include microorganisms that produce aromatic compounds, thus influencing the grain aroma infragrant rice. Post-harvest management, including storage and drying conditions, can significantly impactthe grain 2AP content, and proper post-harvest conditions can intensify the grain aroma. This reviewsuggests that there are rice varieties that can serve as potential sources of genetic material for breedingrice varieties with high grain aroma content. It offers an overview of recent research on the major factorsaffecting the aroma content in fragrant rice. This knowledge will facilitate further research on theproduction of high-quality rice to meet the demands of farmers and consumers.

Effect of Sulfur Fertilization on Productivity and Grain Zinc Yield of Rice Grown under Low and Adequate Soil Zinc Applications

This study aimed to investigate the responses in rice(Oryza sativa cv.Osmancik 97)production and grain zinc(Zn)accumulation to combined Zn and sulfur(S)fertilization.The experiment was designed as a factorial experiment with two Zn and three S concentrations applied to the soil in a completely randomized design with four replications.The plants were grown under greenhouse conditions at low(0.25 mg/kg)and adequate(5 mg/kg)Zn rates combined with S(CaSO_(4)·2H_(2)O)application(low,2.5 mg/kg;moderate,10 mg/kg,and adequate,50 mg/kg).The lowest rate of S at adequate soil Zn treatment increased grain yield by 68%compared with the same S rate at low Zn supply.Plants with the adequate S rate at low Zn and adequate Zn supply produced the highest grain yield,with increases of 247%and 143%compared with low S rate at low Zn and adequate Zn supply,respectively.The concentration of grain Zn and S responded differently to the applied S rates depending on the soil Zn condition.The highest grain Zn concentration,reaching 41.5 mg/kg,was observed when adequate Zn was supplied at the low S rate.Conversely,the adequate S rate at the low soil Zn conditions yielded the highest grain S concentration.The total grain Zn uptake per plant showed particular increases in grain Zn yield when adequate S rates were applied,showing increases of 208%and 111%compared with low S rate under low and adequate soil Zn conditions,respectively.The results indicated that the synergistic application of soil Zn and S improves grain production and grain Zn yield.These results highlight the importance of total grain Zn yield in addition to grain Zn concentration,especially under the growth conditions where grain yield shows particular increases as grain Zn is diluted due to increased grain yield by increasing S fertilization.

Response of nitrogen mineralization dynamics and biochemical properties to litter amendments to soils of a poplar plantation

Understanding the impact of plant litters on soil nitrogen （N） dynamics could facilitate development of management strategies that promote plantation ecosystem function. Our objective was to evaluate the effects of different litter types on N mineralization and availability, microbial biomass, and activities of L-asparaginase and odiphenol oxidase （o-DPO） in soils of a poplar （Populus deltoides） plantation through 24 weeks of incubation experiments. The tested litters included foliage （F）, branch （B）, or root （R） of poplar trees, and understory vegetation （U） or a mixture of F, B, and U （M）. Litter amendments led to rapid N immobilization during the first 4 weeks of incubation, while net N mineralization was detected in all tested soils from 6 to 24 weeks of incubation, with zero-order reaction rate constants （k） ranging from 7.7 to 9.6 mg N released kg-1 soil wk-1. Moreover, litter addition led to increased （C） 49-128% and increased microbial biomass carbon MBC：MBN ratio by 5-92%, strengthened activities of L-aspaxaginase and o-DPO by 14-74%; Up to about 37 kg N ha-1 net increase in mineralized N in litter added soils during 24 weeks of incubation suggests that adequate poplar and understory litter management could lead to reduced inputs while facilitate sustainable and economic viable plantation production.

Variation of soil and plant characteristics among old world bluestem species

Old world bluestems (Bothriochloa spp.) have been successfully introduced as grasses for livestock forage in the semiarid Texas High Plains. Questions remain, however, on effects of these grasses on soil resources. We tested the hypothesis that differences in grass species produce differences in soil properties important to crop growth and useful in selecting the optimum species for the Southern High Plains of Texas. Three old world bluestem (Bothriochloa) species [C.E. Hubbard ‘Caucasian’, B. caucasica (Trin.);‘WW Spar’, B. ischaemum (L.) Keng.var ischaemum (Hack.);and S.T. Blake ‘WW-B Dahl’, B. bladhii (Retz)] were grown in a randomized complete block design, with three replications, for nine years on a clay loam soil near Lubbock, Texas. Soil samples were collected in the ninth year to determine soil texture, wet aggregate stability, bulk density (BD), soil organic carbon (SOC), particulate organic carbon (POC), and soil strength as measured by the cone pentrometer. The grass species differed in their above-ground biomass and below- ground root production. In the ninth year of production, Bothriochloa caucasica and B. bladhii produced about twice the above-ground biomass with about 25% fewer roots than B. ischaemum. Soils where B. caucasica was grown had the highest BD (1.36 Mg m–3) and B. ischaemum had the lowest (1.31 Mg m–3). The soil in which B. ischaemum was growing had a lower BD, greatest root biomass, organic matter content, and aggregate stability suggesting superior soil quality for agricultural production. The species B. bladhii, however, often exhibited soil properties that were similar to both other species tested. Since Bothriochloa bladhii had superior or similar soil properties for plant growth among the species tested and has been shown to be higher in forage quality, animal performance, and carrying capacity than the other species, it appears to be the best choice among these three species to optimize both animal performance and desirable soil properties.

Antioxidant Activities and Characterization of Polyphenols from Selected Northern Thai Rice Husks: Relation with Seed Attributes

Rice production generates a significant amount of agricultural waste. This study aimed to give results related to the existence of antioxidant phenols in agricultural waste of selected Northern Thai rice varieties. The antioxidant activities, contents of total flavonoids and phenolic compounds in the ethanolic rice husk extract were evaluated. The highest antioxidant activities were found in the variety PES1CMU, with 2,2’-azinobis-3-ethyl-benzothiazoline-6-sulfonic acid and 2,2-diphenyl-1-picrylhydrazyl as 679.66 and 4.16 mmol/(L·g) trolox equivalent, respectively, ferric reducing antioxidant power as 0.87 mmol/(L·g) Fe2+, total phenolic content as 29.90 mmol/(L·g) gallic acid and total flavonoid content as 12.16 mg/g catechin equivalent. Polyphenol compounds were identified mainly by standard polyphenols using the liquid chromatography mass spectrometry, with the highest contents of phytic acid, o-coumaric acid, naringin and kaempferol. The non-glutenous and wetland ecotypes of rice husk samples were the richest in antioxidant activities and polyphenol contents characterized by using principal component analysis. The glutenous rice husk contained higher antioxidant activities than the rest. Interestingly, quercetin is a significant phenolic compound that positively correlated with the overall antioxidant activities of rice husk. This finding will be relevant for future application of rice husk antioxidant components in the production of functional ingredients as well as for the food and pharmaceutical industries.

Effects of long-term amendment of organic manure and nitrogen fertilizer on nitrous oxide emission in a sandy loam soil

To understand the effects of long-term amendment of organic manure and N fertilizer on N2O emission in the North China Plain, a laboratory incubation at different temperatures and soil moistures were carried out using soils treated with organic manure （OM）, half organic manure plus half fertilizer N （HOM）, fertilizer NPK （NPK）, fertilizer NP （NP）, fertilizer NK （NK）, fertilizer PK （NK） and control （CK） since 1989. Cumulative N2O emission in OM soil during the 17 d incubation period was slightly higher than in NPK soil under optimum nitrification conditions （25℃ and 60% water-filled pore space, WFPS）, but more than twice under the optimum denitrification conditions （35℃ and 90% WFPS）. N2O produced by denitrification was 2.1-2.3 times greater than that by nitrification in OM and HOM soils, but only 1.5 times greater in NPK and NP soils. These results implied that the long-term amendment of organic manure could significantly increase the N2O emission via denitrification in OM soil as compared to NPK soil. This is quite different from field measurement between OM soil and NPK soil. Substantial inhibition of the formation of anaerobic environment for denitrification in field might result in no marked difference in N2O emission between OM and NPK soils. This is due in part to more rapid oxygen diffusion in coarse textured soils than consumption by aerobic microbes until WFPS was 75% and to low easily decomposed organic C of organic manure. This finding suggested that addition of organic manure in the tested sandy loam might be a good management option since it seldom caused a burst of N2O emission but sequestered atmospheric C and maintained efficiently applied N in soil.

Surveying the genomic landscape of silage-quality traits in maize(Zea mays L.)

Despite the longstanding importance of silage as a critical feed source for ruminants,its quality improvement has been largely overlooked.Although numerous quantitative trait loci(QTL)and genes affecting silage quality in maize have been reported,only a few have been effectively incorporated into breeding programs.Addressing this gap,the present study undertook a comprehensive meta-QTL(MQTL)analysis involving 523 QTL associated with silage-quality traits collected from 14 published studies.Of the 523 QTL,405 were projected onto a consensus map comprising 62,424 genetic markers,resulting in the identification of 60 MQTL and eight singletons.The average confidence interval(CI)of the MQTL was 3.9-fold smaller than that of the source QTL.Nine of the 60 identified MQTL were classified as breeder’s MQTL owing to their small CIs,involvement of more QTL,and large contribution to phenotypic variation.One-third of the MQTL co-localized with DNA marker-trait associations identified in previous genomewide association mapping studies.A set of 78 high-confidence candidate genes influencing silage quality were identified in the MQTL regions.These genes and associated markers may advance marker-assisted breeding for maize silage quality.

The Role of Cover Crops towards Sustainable Soil Health and Agriculture—A Review Paper

Cover crops are the plants which are grown to improve soil fertility, prevent soil erosion, enrichment and protection of soil, and enhance nutrient and water availability, and quality of soil. Cover crops provide several benefits to soils used for agriculture production. Cover crops are helpful in increasing and sustaining microbial biodiversity in soils. We summarized the effect of several cover crops in soil properties such as soil moisture content, soil microbial activities, soil carbon sequestration, nitrate leaching, soil water, and soil health. Selection of cover crops usually depends on the primary benefits which are provided by cover crops. Other factors may also include weather conditions, time of sowing, either legume or non-legume and timing and method of killing of a cover crop. In recent times, cover crops are also used for mitigating climate change, suppressing weeds in crops and increasing exchangeable nutrients such as Mg2+ and K+. Cover crops are also found to be economical in long-term experiment studies. Although some limitations always come with several benefits. Cover crops have some problems including the method of killing, host for pathogens, regeneration, and not immediate benefits of using them. Despite the few limitations, cover crops improve the overall health of the soil and provide a sustainable environment for the main crops.

Genetic architecture of quantitative trait loci(QTL)for FHB resistance and agronomic traits in a hard winter wheat population

Wheat resistance to Fusarium head blight(FHB)has often been associated with some undesirable agronomic traits.To study the relationship between wheat FHB resistance and agronomic traits,we constructed a linkage map of single nucleotide polymorphisms(SNPs)using an F6:8 population from G97252WG97380A.The two hard winter wheat parents showed contrasts in FHB resistance,plant height(HT),heading date(HD),spike length(SL),spike compactness(SC),kernel number per spike(KNS),spikelet number per spike(SNS),thousand-grain weight(TGW)and grain size(length and width).Quantitative trait locus(QTL)mapping identified one major QTL(QFhb.hwwg-2DS)on chromosome arm 2DS for the percentage of symptomatic spikelets(PSS)in the spike,deoxynivalenol(DON)content and Fusarium damaged kernel(FDK).This QTL explained up to 71.8%of the phenotypic variation for the three FHB-related traits and overlapped with the major QTL for HT,HD,SL,KNS,SNS,TGW,and grain size.QTL on chromosome arms 2AL,2DS,3AL and 4BS were significant for the spike and grain traits measured.G97252W contributed FHB resistance and high SNS alleles at QFhb.hwwg-2DS,high KNS alleles at the QTL on 2AL and 2DS,and high TGW and grain size alleles at QTL on 3AL;whereas G97380A contributed high TGW and grain size alleles at the QTL on 2AL and 2DS,respectively,and the high KNS allele at the 4BS QTL.Combining QFhb.hwwg-2DS with positive alleles for spike and grain traits from other chromosomes may simultaneously improve FHB resistance and grain yield in new cultivars.

Salicylic Acid Application Mitigates Oxidative Damage and Improves the Growth Performance of Barley under Drought Stress

Drought is a severe environmental constraint,causing a significant reduction in crop productivity across the world.Salicylic acid(SA)is an important plant growth regulator that helps plants cope with the adverse effects induced by various abiotic stresses.The current study investigated the potential effects of SA on drought tolerance efficacy in two barley(Hordeum vulgare)genotypes,namely BARI barley 5 and BARI barley 7.Ten-day-old barley seedlings were exposed to drought stress by maintaining 7.5%soil moisture content in the absence or presence of 0.5,1.0 and 1.5 mM SA.Drought exposure led to severe damage to both genotypes,as indicated by phenotypic aberrations and reduction of dry biomass.On the other hand,the application of SA to drought-stressed plants protected both barley genotypes from the adverse effects of drought,which was reflected in the improvement of phenotypes and biomass production.SA supplementation improved relative water content and proline levels in drought-stressed barley genotypes,indicating the osmotic adjustment functions of SA under water-deficit conditions.Drought stress induced the accumulation of reactive oxygen species(ROS),such as hydrogen peroxide(H2O2)and superoxide(O_(2)•^(−)),and the lipid peroxidation product malondialdehyde(MDA)in the leaves of barley plants.Exogenous supply of SA reduced oxidative damage by restricting the accumulation of ROS through the stimulation of the activities of key antioxidant enzymes,including superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),ascorbate peroxidase(APX)and glutathione peroxidase(GPX).Among the three-applied concentrations of SA,0.5 mM SA exhibited better mitigating effects against drought stress considering the phenotypic performance and biochemical data.Furthermore,BARI barley 5 showed better performance under drought stress than BARI barley 7 in the presence of SA application.Collectively,our results suggest that SA played a crucial role in improving water status and antioxidant defense strategy to protect barley plants from the deleterious effects of water deficiency.

Biochar-Induced Priming Effects in Young and Old Poplar Plantation Soils

The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil mass)produced from rice straw at 300℃(B300)and 500℃(B500)to young(Y)and old(O)poplar plantation soils,with the aim of studying the responses of biochar-induced PEs to poplar plantation ages.This incubation included six treatments:Y+CK(control),Y+B300,Y+B500,O+CK,O+B300,and O+B500.Carbon dioxide(CO_(2))emissions were significantly increased(p<0.05)in the B300 amended soils,while it was decreased in the B500 amended soils compared to the CK.The primed CO_(2) emissions were 2.35 times higher in the Y+B300 than the O+B300 treatments,which was measured to be 18.6 and 5.56 mg C·kg^(-1) with relative PEs of 12.4%and 3.35%,respectively.However,there was little difference between the primed CO_(2) emissions in Y+B500 and O+B500 treatments,which were measured to be-24.9 and-29.6 mg·C·kg^(-1) with relative PEs of-16.6%and-17.8%,respectively.Dissolved organic carbon(DOC)was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation,indicating greater C-limit of soil microorganisms in the young poplar plantation soil.Using ^(13)C isotope tracing,neither B300 nor B500 decreased native soil-derived DOC,which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C.In conclusion,the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biochar-induced PEs.Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs.

Yield and Grain Quality Response of Spring Wheat Varieties to Irrigation and Fertility Management

Experiments were conducted in 2020 and 2021 in North Dakota to determine the effects of foliar and soil applied fertilizers, variety and irrigation on yield and grain quality of spring wheat. Foliar application of N did not consistently increase yield and protein indicating the soil N levels were adequate to optimize yield. The variety Bolles had higher protein content than Faller. Zinc (Zn) content in the grain was greatest when applied at either flowering or post anthesis. It was also found to be correlated with grain protein content. Yield and grain protein content were negatively related. There was no consistent effect of phosphorous or Zn when applied to the soil on yield, protein, gluten, or Zn content in the grain. Zinc concentration in the grain was significantly correlated with the protein, gluten and P content of the grain. The timing of Zn application was critical to the success of translocating Zn to the grain. Grain Zn concentration increased with most late season foliar Zn applications to both varieties indicating potential for enriching spring wheat nutrient content through production management practices already common in areas that grow spring wheat.

Water Balance of Two Major Soil Types of the Texas High Plains: Implications for Dryland Crop Production

Crop production in the Texas High Plains is shifting from irrigated to dryland due to the increase of the depth to the water table from the Ogallala aquifer in regions where the saturated thickness of 9 m, the minimum to sustain irrigation, has been reached. Our objective was to use the mechanistic model ENWATBAL to evaluate the daily and annual water balance for three scenarios of rainfall in this region, a dry (189 mm), an average (449 mm) and a wet (669 mm) year. These three scenarios were applied to two major soil series of this region, Pullman and Amarillo. In all simulations, we used hourly input weather data for a location near Lubbock, Texas and used measured soil hydraulic properties to simulate the water balance for each soil series and the three rainfall scenarios. Results showed that in years with average and wet rain, storage of rainfall occurred in the Pullman but not in in the Amarillo soil series. However, storage of water could be enhanced by combining furrow dikes with minimum tillage along with crop covers that provide a surface residue. The implications of our results for dryland crop production in the semiarid climate of the THP suggest that for years with average and wetter rainfall soils in the Pullman series could store water that would be available for crop use. However, this was not the case for the Amarillo soil series and these soils represent a higher risk for dryland crop production.

Higher Grain-Filling Rate in Inferior Spikelets of Tolerant Rice Genotype Offset Grain Yield Loss under Post-Anthesis High Night Temperatures

Increased nighttime respiratory losses decrease the amount of photoassimilates available for plant growth and yield. We hypothesized that the increased respiratory carbon loss under high night temperatures(HNT) could be compensated for by increased photosynthesis during the day following HNT exposure. Two rice genotypes, Vandana(HNT-sensitive) and Nagina 22(HNT-tolerant), were exposed to HNT(4 ℃ above the control) from flowering to physiological maturity. They were assessed for alterations in the carbon balance of the source(flag leaf) and its subsequent impact on grain filling dynamics and the quality of spatially differentiated sinks(superior and inferior spikelets). Both genotypes exhibited significantly higher night respiration rates. However, only Nagina 22 compensated for the high respiration rates with an increased photosynthetic rate, resulting in a steady production of total dry matter under HNT. Nagina 22 also recorded a higher grain-filling rate, particularly at 5 and 10 d after flowering, with 1.5- and 4.0-fold increases in the translocation of ^(14)C sugars to the superior and inferior spikelets, respectively. The ratio of photosynthetic rate to respiratory rate on a leaf area basis was negatively correlated with spikelet sterility, resulting in a higher filled spikelet number and grain weight per plant, particularly for inferior grains in Nagina 22. Grain quality parameters such as head rice recovery, high-density grains, and gelatinization temperature were maintained in Nagina 22. An increase in the rheological properties of rice flour starch in Nagina 22 under HNT indicated the stability of starch and its ability to reorganize during the cooling process of product formation. Thus, our study showed that sink adjustments between superior and inferior spikelets favored the growth of inferior spikelets, which helped to offset the reduction in grain weight under HNT in the tolerant genotype Nagina 22.

Fourier transform infrared spectral features of plant biomass components during cotton organ development and their biological implications

Background:The majority of attenuated total reflection Fourier transform infrared(ATR FT-IR)investigations of cotton are focused on the fiber tissue for biological mechanisms and understanding of fiber development and maturity,but rarely on other cotton biomass comp on ents.This work examined in detail the ATR FT-IR spectral features of various cott on tissues/organs at reproductive and maturation stages,an a lyzed and discussed their biological implications.Results:The ATR FT-IR spectra of these tissues/organs were an a lyzed and compared with the focus on the lower wavenumber fingerprinting range.Six outstanding FT-IR bands at 1730,1620,1525,1235,1050 and 895 cm^(-1) represented the major C=O stretching,protein Amide I,Amide II,the O-H/N-H deformation,the total C-O-C stretching and the β-glycosidic linkage in celluloses,respectively,and impacted differently between these organs with the two growth stages.Furthermore,the band intensity at 1620,1525,1235,and 1050 cm^(-1) were exclusively and significantly correlated to the levels of protein(Amide I bond),protein(Amide II bond),cellulose,and hemicellulose,respectively,whereas the band at 1730 cm^(-1) was negatively correlated with ash content.Conclusions:The resulting observations indicated the capability of ATR FT-IR spectroscopy for monitoring changes,transportation,and accumulation of the major chemical components in these tissues over the cotton growth period.In other words,this spectral technology could be an effective tool for physiological,biochemical,and morphological research related to cotton biology and development.

Competitive Sorption Behavior of Arsenic, Selenium, Copper and Lead by Soil and Biosolid Nano- and Macro-Colloid Particles

Limited information exists on natural nanocolloid sorption behavior of As, Se, Cu and Pb in the environment. They are expected to have variable competitive sorption characteristics depending on size and composition and may transport elevated contaminant loads into surface and ground waters. A comprehensive characterization of their interactions with contaminants could provide a better understanding of the risks they pose to the environment. This study evaluated the sorption behavior of soil and biosolid nano- and macro-colloids with different mineralogical compositions for As, Se, Cu, and Pb contaminants. Single- and multi-contaminant Freundlich isotherms were us- ed to evaluate sorption affinity for the contaminants among the different colloid sizes and compositions. Sorption trends based on size indicated greater affinity for As and Cu by the smectitic and kaolinitic nanocolloids, greater affinity for Pb by the kaolinitic nanocolloids, and greater affinity for As, Se and Pb by bio-nanocolloids over corresponding macrocolloid fractions. Both, single- and multi-contaminant isotherms indicated sorption preferences for cation over anion contaminants, but with somewhat contrasting sequences depending on size and composition. Multi-contaminant isotherms generally predicted greater sorption affinities likely due to bridging effects, particularly for anionic contaminants. Surface properties such as zeta potentials, cation exchange capacity (CEC), surface area (SA), organic carbon (OC), and OC:SA significantly but variably affected sorption characteristics among the differing colloid sizes and compositions. Colloid zeta potential and pH shifts in the presence of different contaminant loads suggested prevalence of inner sphere bonding mechanisms for sorption of cation contaminants by mineral colloids and outer sphere sorption for cation and anion contaminants by bio-colloids.

Stability of Soil and Biosolid Nanocolloid and Macrocolloid Particles in the Absence and Presence of Arsenic, Selenium, Copper and Lead

Due to their enhanced stability and contaminant transport potential, environmental nanoparticles derived from soil and biosolid materials may pose a considerable risk to groundwater quality. Very little information exists on the stability and transportability of environmental or natural nanocolloids in the presence of As, Se, Pb and Cu contaminants, all of which are considered to represent substantial threats to human and animal populations through groundwater contamination. This study involved stability settling experiments of nanocolloids (NCs) (<100 nm) and macrocolloids (MCs) (100 - 2000 nm) fractionated from Bt horizons of three Kentucky soils and one biosolid waste material in water suspensions of 0, 2, and 10 mg·L-1 of As, Se, Pb and Cu. The results indicated greater stability in the mineral than the biosolid colloid fractions, and enhanced stability of NCs over corresponding MCs in the presence or absence of contaminants at low contaminant loads. At high contaminant loads nearly all colloids were unstable except for the bio-nanocolloids which still sustained considerable stability. At low contaminant loads, the MC fraction stability sequence was smectitic > mixed > kaolinitic > biosolid. Among the nano-fractions, the smectitic and kaolinitic colloids demonstrated lower stability than the MCs, but higher than those of the mixed and biosolid fractions. Physicochemical characterizations indicated that extensive organic carbon surface coatings and higher Al/Fe:Si ratios may have induced higher stability in the NC fractions, but their overall stability may also have been hindered in some cases by nano-aggregation phenomena.

Impact of Piers on Tidal Marshes： Accumulation of Wood Preservative Metals in Water and Soils

Wood treated with chromated copper arsenate （CCA） is a common material for pier pilings. Research on CCA impacts in estuarine systems indicates that the magnitude of the biological effect is variable and dependent on sediment and water characteristics. To assist environmental agencies in assessing pier impacts a project was conducted in the U.S.A. to investigate the spatial distribution and magnitude of As, Cr, and Cu accumulation in waters and soils near old and new piers. For new piers, soluble metal levels were highest within 2.9 m of the piers. Total As and Cu levels approached background levels at distances of 2.9 m and 1.4 m, respectively. For old piers, total As and Cu approached background levels at a distance of 9.0 m. Total Cr never exceeded background levels. Threshold effects concentrations were exceeded by sedimented As and Cu within 3.6 m of old piers and 2.1 m of new piers. Apparent effects thresholds were never reached. The only water chemistry variable impacted by piers was As with new piers. It was concluded that leachates accumulate only close to piers and at levels below critical biological thresholds, and would be expected to have negligible ecological effects in reasonably flushed areas.

Studying the Application and Advances of Diffusive Gradients in-Thin Films Techniques (DGTs) to Constrain Mobility and Bioavailability of Heavy Metals in Soils

The aim of this review is to investigate the application and latest developments of the Diffusive Gradients in-thin films (DGT) with a focus on the mobility and bioavailability of heavy metals in soil. Soil chemical extractions are extensively used to predict nutrients elements in the soil. However, these measurements have their weaknesses and shortcomings. Comparing DGT with conventional extraction methods, DGT is a sampling technique with significant advantages;including speciation capabilities, sensitivity, time-in- tegrated signal, low risk of contamination and time averaged concentrations. These findings have strengthened the usefulness of the DGT technique as a potential monitoring tool for soil with heavy metal contamination. Studies which have used the DGT technique to evaluate processes important to bioavailability have been booming in the last 13 years, especially its application in soils science. Some recent studies have shown a good relationship between the measurement of metals concentrations in soil and plant by DGT, and cohesive results have been obtained from these measurements when they are based on the DGT technique. DGT is a newly established procedure to assess the bioavailability of trace elements in sediments and soils, and its applications are still in the early stage of testing. Therefore, future application of DGT is likely to include the studies of HMs contamination in soil for risk assessment and transfer rates to the food chain, as some studies have indicated the potential of DGT in these areas.

Soil Temperature Dependent Growth of Cotton Seedlings Before Emergence

Soil temperature is an important variable governing plant growth and development. Studies were conducted under laboratory conditions to determine the effect of soil temperature on root and shoot growth of cotton during emergence. Cotton seedlings were grown for 192 h at 20, 32 and 38℃ in soil packed in 300 mm long and 50 mm diameter cylinders. The data indicated that the longest roots （173 ram） as well as shoots （152 mm） were recorded at 32℃ followed by 20 （130 mm root and 82 mm shoot） and 38℃ （86 mm root and 50 mm shoot）. Roots grown at 20 and 38 ℃ were 20% and 50% shorter, respectively, than those grown at 32℃ after 192 h. Roots and shoots exhibited the lowest length and dry biomass at 38 ℃. Shoot lengths grown at 20 （74 mm） and 38℃（51 mm） were 44% and 61% shorter than those grown at 32℃（131 mm） after 180 h growth period, respectively. Growth at all three temperatures followed a similar pattern. Initially there was a linear growth phase followed by the reduction or cessation of growth. Time to cessation of growth varied with temperature and decreased faster at higher temperatures. Sowing of cotton should be accomplished before seedbed reaches a soil temperature （≥ 38 ℃） detrimental for emergence. Further, the seedbeds should be capable of providing sufficient moisture and essential nutrients for emerging seedling before its seed reserves are exhausted to enhance seedling establishment in soil.