Sorption-desorption of indaziflam in selected agricultural soils

Indaziflam, a new alkylazine herbicide that inhibits cellulose biosynthesis, is under current development for soil applications in perennial crops and nonagricultural areas. Sorption and desorption of indaziflam in six soils from Brazil and three soils from the United States, with different physical chemical properties, were investigated using the batch equilibration method. Sorption kinetics demonstrated that soil-solution equilibrium was attained in <24 h. The Freundlich equation described the sorption behavior of the herbicide for all soils (R(2) > 0.99). K(f) values of the Brazilian oxisols ranged from 4.66 to 29.3, and 1/n values were ≥ 0.95. Sorption was positively correlated to %OC and clay contents. U.S. mollisol K(f) values ranged from 6.62 to 14.3; 1/n values for sorption were ≥ 0.92. K(f) values from mollisols were also positively correlated with %OC. These results suggest that indaziflam potential mobility, based solely on its sorption coefficients, would range from moderate to low in soil. Desorption was hysteretic on all soils, further decreasing its potential mobility for offsite transport.     

Sorption-desorption isotherms and biodegradation of glyphosate in two tropical soils aged with eucalyptus biochar

ABSTRACT

The objective of this study was to evaluate the sorption-desorption process and biodegradation of glyphosate in two tropical soils aged with biochar derived from eucalyptus. The biochar aging period was 30 d. There was little difference between the amounts of sorbed glyphosate in Ultisol (96.8, 96.8 and 96.4%) and Alfisol (97.1, 97.5 and 97.4%) soils that were unamended or amended with biochar aged for 0 or 30 d, respectively. Similar amounts of desorbed herbicide occurred in Ultisol (3.3, 3.3 and 3.4%) and Alfisol (4.1, 4.2 and 3.9%) soils, respectively. The degradation time half-life (DT50) of glyphosate in Ultisol unamended and initial amended were higher (38 and 36 d, respectively) than DT50 in the amended soil with 30 d of biochar aging (27 d); and in the Alfisol DT50 was higher in unamended soil (38 d), and similar in soil unamended at 0 and 30 d of biochar aging (21 and 26 d, respectively). The addition of biochar to two tropical soils or its aging did not have any effect on the sorption and desorption of glyphosate and its biodegradation in relation to the unamended soils, and it can did not affect the transport and persistence of this herbicide in soil.     

Sesquioxidic components of selected Taiwan soils

Twenty two surface soils, representing six parent materials and four soil groups, were sampled in Taiwan for the present study.Except in the soil derived from volcanic ash, the sesquioxidic components and relatively easily extractable Si were present only in small amounts in the NaOAc and H₂O₂- NaOAc extractable fractions. In addition to Fe, both Si and Al were present in the dithionite-citrate-bicarbonate extracts in considerable amounts, indicating that Si and Al were either present separately or in association with Fe in the sesquioxidic fractions of the soils. The amounts of Si, Al and Fe extracted by the dithionite-citrate-bicarbonate and boiling KOH treatments differed from sample to sample, indicating that they are important variables in the nature of the soils studied.The amounts of the ammonium oxalate-extractable Al and Fe, representing the noncrystalline sesquioxidic products of relatively recent weathering, also differed with parent materials and pedogenic processes. The statistical data indicate that the ammonium oxalate-extractable Al and Fe are related to the contents of organic matter but not to acidity and the contents of clay. The percentage distribution of the extractable Al in the > 2 μm fractions of the selected soil samples ranged from 22.0 to 52.5% and that of the extractable Fe from 11.1 to 38.1%, indicating that the active non-crystalline Al and Fe components in the non-clay fractions deserve close attention in the study of pedogenesis and other soil physicochemical reactions in relation to soil fertility and environmental protection.     

中国东南部某些水稻土的矿物学

Limited information is available concerning the mineralogy of paddy soils in the southeastern China. Using chemical methods in conjunction with X-ray diffractometry, we studied the mineral composition of three paddy soils: Jinghua (paddy soil on Quaternary red clay), Fuyang (Hapl-percogenic loamy paddy soil), and Shaoxing (gleyic clayey paddy soil). All the soils contained quartz, mica, vermiculite, chlorite and kaolinite, and the distribution of these minerals varied with soil particle size fractions. The clay fraction of the Fuyang and Shaoxing soils also contained smectite. Although X-ray data did not show the presence of smectite in the Jinghua soil, this mineral was identified by the chemical method, suggesting a transitional property of the mineral in the soil. Hydroxy-Al interlayered minerals were also present in the clay fraction. The amount of smectite in the soils was 31.6 (Shaoxing), 16.5 (Fuyang), and 21.4 (Jinghua) g kg^-1; for vermiculite it was 33.3 (Shaoxing), 16.5 (Fuyang), and 8.5 (Jinghua) g kg^-1. Smectite was only found in the clay fraction. In contrast, amounts of vermiculite in soil particle size fractions were 3.0~11.4 (sand), 2.1~6.0 (coarse silt), 4.6~18.9 (medium silt), 0.9~40.0 (fine silt), and 17.0~108 (clay) g kg^-1. The amount of noncrystalline aluminosilicates in the soils in g kg^-1 decreased in the order: Shaoxing (2.4) > Jinghua (1.9) > Fuyang (1.7). This study has provided useful mineralogical information that is fundamental in future development of management strategies of the soils.     

The distribution of zinc in selected soils in Louisiana

Abstract

The zinc (Zn) content of ten selected soils in Louisiana was partitioned into the following fractions: water‐soluble, exchangeable, chelated, organic and residual. In seven of the soils, water‐soluble > exchangeable < chelated < organic < residual Zn. In three of the soils, water‐soluble < exchangeable < chelated < organic < residual Zn.

The ten soils contained an average of 1.7, 0.9, 2.6, 4.4 and 86.4 per cent of the total in the water‐soluble, exchangeable, chelated, organic and residual mineral Zn fractions respectively.     

Lead sorption to selected Portuguese soils

We studied the interaction of lead with seven Portuguese soils with different physical and chemical properties in order to elucidate more fully the behaviour of Pb in soil. We studied these adsorption phenomena by voltammetric titrations with differential pulse polarography (DPP) at different pH (6.0–7.2) and ionic strengths, I (0.010–0.50 m ) in order to clarify some of the factors that might control soil sorption capacity for Pb. From the voltammetric data, average formation constants, , and binding capacity, C_c, have been estimated according to a surface complexation model based on Scatchard and van den Berg–R?zic methods. Linear Scatchard and van den Berg–R?zic plots (r≥ 0.99) indicated that the results can be interpreted according to the existence of just one predominant active site for Pb(II) adsorption. The values from both procedures () agreed in all cases (r= 0.938, n= 66, P < 0.001). The same happened with C_c values that were statistically equivalent (r= 0.9998; n= 66; P < 0.001). The C_c values were found to depend on the pH and I, as well as on the soil properties. Either Langmuir or Freundlich isotherms fitted the experimental data well (r > 0.90, P < 0.05). The lead binding capacities were strongly and significantly correlated (P < 0.05) with pH, cation exchange capacity, organic carbon, loss‐on‐ignition, total Al₂O₃ content, extractable forms of Al and pyrophosphate extractable Fe, [Fe_p]. From a forward, stepwise regression model we concluded that [Al₂O₃], [Pb′] (concentration of labile lead in solution), [Fe_p], pH and I are able to explain more than 99.7% of the variation in lead sorption in our soils. The soils’ surface groups with special affinity to Pb(II) are in the inorganic fraction associated with aluminium.     

Carbon sequestration in two Brazilian Cerrado soils under no-till

A considerable proportion of the 200 million hectares of the Brazilian Cerrado is suitable for annual crops but little is known about the effects of tillage on the C dynamics of Cerrado soils. We evaluated the role of two representative Cerrado Oxisols (350 and 650 g clay kg⁻¹) as sources or sinks of atmospheric C when managed under three tillage systems (conventional tillage (CT), reduced tillage (RT), and no-till (NT)) in 8- and 5-year long-term experiments. A literature review was also carried out and the mean C sequestration rates in no-till soils of tropical and subtropical regions of Brazil were calculated and compared with values for soils from temperate regions of the world. The original C stocks in 0–20 cm layer of soils under native Cerrado were higher in the clayey (54.0 Mg ha⁻¹) than in the sandy clay loam soil (35.4 Mg ha⁻¹), suggesting a higher physical stability of organic matter associated with variable clay minerals in the clayey Oxisol. The original C stocks of the native Cerrado soils appear not to have decreased after 23 years of conventional tillage in the sandy clay loam Oxisol, except when the soil had been subjected to erosion (15% loss of C), or after 25 years in the clayey Oxisol. Compared to conventionally tilled soil, the C stocks in no-till sandy clay loam Oxisol increased by 2.4 Mg ha⁻¹ (C sequestration rate = 0.30 Mg ha⁻¹ year⁻¹) and in the clayey Oxisol by 3.0 Mg ha⁻¹ (C sequestration rate = 0.60 Mg ha⁻¹ year⁻¹). The mean rate of C sequestration in the no-till Brazilian tropical soils was estimated to be 0.35 Mg ha⁻¹ year⁻¹, similar to the 0.34 Mg ha⁻¹ year⁻¹ reported for soils from temperate regions but lower than the 0.48 Mg ha⁻¹ year⁻¹ estimated for southern Brazilian subtropical soils. Considering the large area (about 70 million hectares) of the Cerrado which is currently used and potentially available for cropland, the adoption of no-till systems could turn the Cerrado soils into a significant sink for atmospheric C and contribute to the mitigation of global climate change.     

我国某些土壤中硫素的氧化

The status and activities of boron in soils were studied by the approach of electro-ultrafiltration(EUF).The samples of soils,including brown-red soil and calcareous alluvial soil,were collected from Hubei Province of China.The soil samples were incubated in saturated water and then their nutrients were ultrafiltrated with EUF equipment.Filtration and extraction were conducted in accordance with routine process,but fractions in anode and cathode were all collected.Analyses of B,K^ ,Mg^2 ,Ca^2 ,Cl^- and pH in fractions supposed that boron existed not only in a simple form of borate but also in ion -pair with cations partly in acidic soil,and borate was the primary form existing in the calcareous soil.In studying desorption kinetics with EUF,the boron content of Fractions 2-6 was accumulated.and the accumlative quantities were fit to time factors in three kinetic equations:the zero-order,first-order,and parabolic diffusion equations,Fit degree of the parabolic diffusion equation was the best,followed by the zero-order equation,and the first-order equation was the worst。     

Wear rate of animal-drawn ploughshares in selected Ghanaian soils

Rapid ploughshare wear was identified as a major constraint facing animal traction farmers in Ghana. The objectives of this study were to: (i) identify the types of animal-drawn ploughshare used by farmers and their production methods, (ii) develop and test a new cast steel share and compare its performance with existing ploughshares, and (iii) determine the factors responsible for the rapid wear and durability of ploughshares in selected soils in the country. To address this problem, new and used ploughshares were collected from farmers, blacksmiths and foundries and their microstructure, chemical composition and hardness were studied. Based on the above studies, new cast steel ploughshares were developed. On-farm tests were conducted on the new shares for wear and durability in the major animal traction soils in the country. On-station field trials with tractor-drawn shares were carried out to compare the performance of the new ploughshares with the imported and local blacksmith versions. Multivariate statistical methods were used to analyse the similarities among the shares with respect to producers, chemical composition, share hardness, soil physical factors (moisture content, bulk density, cone index and soil texture) and their relationship to wear rate. When pulled by tractor, the average wear rates of the imported, improved and blacksmith shares in soils containing 50%, 64% and 74% sand were 297, 362 and 562 g/ha, respectively. The average wear rates of the new share when pulled by animals in the major soil classifications were: Eutric Plinthosols, 146 g/ha; Plinthic Lixisols, 164 g/ha and Haplic Lixisols, 176 g/ha, respectively. This gave an average durability of 3–8 ha/share before the farmer declares the new ploughshare completely worn. This compares with 1–2 ha and 2–5 ha per share wear rates for the blacksmith-forged and the imported shares, respectively. The study concluded the new cast steel ploughshares have qualities of enhanced durability and toughness similar to the imported versions and more durable than the local blacksmith shares and have prospects for mass production.     

Phosphorus fractions in Brazilian Cerrado soils as affected by tillage

No-tillage systems lead to physical, chemical and biological changes in soil. Soil fertility is responsive to changes in tillage as it depends on nutrient status, soil water content and biological characteristics. This work aimed to determine long term changes in phosphorus forms and availability in the profile of two tropical soils under conventional and no-till systems, and to discuss the significance of these changes on plant growth and demand for P fertilizers. Undisturbed soil cores with 20 cm in diameter were collected to a depth of 40 cm, accommodated in PVC tubes and taken to a greenhouse, where the experiment was conducted. Two soils were collected in Central Brazil, in areas under Cerrado. Both soils had been cropped for at least 10 years under conventional tillage and no-till. In the greenhouse, pots received phosphorus fertilization or not at 43.7 kg ha⁻¹, and soybean was grown for 60 days, when soil P fractions were determined. Labile P fractions in the soil profile were not affected by management systems, and there was no accumulation of available P under no-till. A large amount of P added as fertilizer was adsorbed in soil and remained in moderately labile fractions, mainly on uppermost soil layers. Therefore, the phosphate fertilizer has promoted P accumulation on less available fractions in soil, remaining P on the soil after crop harvest. Eventually this phosphorus could migrate to more labile fractions and be available for crops grown in succession.     

Neutral sugars in melanins synthesized by actinomycetes from Brazilian soils

 Nine actinomycete melanins synthesized under various culture conditions, eight of them by actinomycete samples isolated from Brazilian topsoils under savanna (cerrado) vegetation and one from an ATCC sample, were subjected to a two-step hydrolysis procedure and the sugars released qualitatively and quantitatively determined by capillary gas-liquid chromatography (GLC). Humic acids (HAs) extracted from these soils, analysed previously, were used for comparison. The neutral sugars glucose, galactose, mannose, xylose, arabinose, ribose, rhamnose and fucose and the alcohol sugar inositol were present in varying amounts in most of the melanins analysed. The same sugars were present in the HAs used for comparison, except for ribose. Some qualitative and quantitative differences observed in the two types of macromolecules would be expected, considering their origins. The results indicate that the actinomycete melanins have a qualitative sugar distribution pattern similar to that of the HAs from Brazilian tropical soils and of HAs reported for soils from other climatic regions. The possible participation of actinomycete melanins in the formation of soil humic substances is discussed. Received: 4 April 1997     

华北某些旱地硫库的组成

Soil sulfur fractions,including monocalcium phosphate-extractable S,slowly soluble inorganic S,C-O-S,C-bonded S and unidentified organic S,were analyzed for 48 soils,as representatives of 6 major groups of upland soils,fluvisol,cinnamon soil,loessial soil,chestnut soil,black soil and brown soil,in North china,The contents of total S and monocalcium phosphate-extractalble S in the above 48 soils ranged from 234 to 860 and 5.1to 220.3mg kg^-1,respectively and each of 6 soil groups contained the samples with a low level of phosphate-extractable S.Great differences in the average contents of each fraction of S were observed among the above 6 soil groups.Expressed as average percentage of the total S in soils,fluvisols,cinnamon soils,loessial soils,chestnut soils,black soils and brown soils contained 6.1%,9.5%,5.7%,13.2%,3.5%and 6.8% monocalcium phosphate-extractable S,5.7%,3.0%,9.3%,10.4%,3.2%and 3.1% slowly soluble inorganic S,51.6%,26.7%,17.4%,31.2%,28.9%and 22.7% C-O-S,11.0%,9.1%,6.6%,6.8%,9.7%and 9.4% in C-bonded S,and 25.6%,51.7%,60.8%,38.4%,54.7%and 53.0% unidentifed organic S,respectively,FOr the above 6 groups of soils,the mean C/N ratios were remarkably similar,ranging from 9.7 to 10.7,while the mean N/S ratios ranged from 1.16 to 3.12,The highest ratios of C/N,C/C-O-S and C/C-bonded S were found in black soils.averaging 30.4,104.9and 314.7,respectively,while the lowest ratios arose in chestnut soil,averaging 12.4,39.7 and 183.3,respectively.     

Melanogenic actinomycetes (Streptomyces spp.) from Brazilian soils

Summary Melanogenic actinomycetes were isolated from cerrado soils. Starch agar with a neutral pH was the best medium for selecting pigment-producing colonies. A pigmentation screening test selected 52% of these as possible melanin producers. Tests on liquid (organic and inorganic) and solid (peptone and tyrosine) media, and enzymatic tests, confirmed about 90% as melanin producers, 68% as dihydroxyphenylalanine (DOPA)-melanin and 32% as possible other kinds of melanin producers. Melanin production occurred mostly with an organic N, or an inorganic N with an additional organic N source. An exception was observed with three strains, which were able to produce melanins with an entirely inorganic N source in the medium. Instability of melanin production was a common feature in many strains. Further characterization of melanins produced by actinomycetes compared with soil humic acids may clarify the possible role of melanogenic actinomycetes in soil organic matter formation.     

中国某些水稻土中硝态氮向铵态氮的还原研究

Three paddy soils were examined for their capacities of dissimilatory reduction of nitrate to ammonium (DRNA). 15N-labelled KNO3 was added at the rate of 100 mg N/kg. Either glucose or rice straw powder was incorporated at the rate of 1.0 or 2.0 mg C/kg respectively. Three treatments were designed to keep the soil saturated with water: (1) a 2-cm water layer on soil surface (with beaker mouth open); (2) a 2-cm water layer and a 1-cm liquid paraffin layer (with beaker mouth open); and (3) water saturated under an O2-free Ar atmosphere. The soils were incubated at 28℃ for 5 days. There was almost no 15N-labelled NH4+-N detected in Treatment 1. However, there was 1.4 to 3.4 mg N/kg 15N-labelled NH4+-N in Treatment 2, and 2.1 to 13.8 mg N/kg in Treatment 3. Glucose was more effective than straw powder in ammonium production. Because there was sufficient amount of non-labelled NH4+-N in the original soils, 15N-labelled NH4+-N produced as such should be the result of dissimilatory reduction. Studies on microbial population showed that there were plenty of bacteria responsible for DRNA process (DRNA bacteria) in the soils examined, indicating that number of DRNA bacteria was not a limiting factor for ammonium production. However, DRNA bacteria were inferior in number to denitrifiers. The DRNA process in soil suspension started after 5 days of incubation. Glycerol and sodium succinate, though both are readily available carbon sources to organisms, did not facilitate DRNA process. DRNA occurred only when glucose was available and at a C:NO3--N ratio >12. Both availability and quality of the carbon sources affected DRNA.     

山西省几种典型土壤供钾能力评价

从山西省主要农田土壤中选取有代表性的耕层土壤样品 19个 ,应用生物耗竭法并结合化学方法对该省主要土壤的供钾能力进行综合评价。研究表明 ,供试的 19个土壤中无论不同形态钾含量还是耗竭后土壤钾素 (速效钾、缓效钾 )最低水平值的大小和出现前耗竭的茬数、作物吸钾量均存在较大差异 ,并因土壤类型、取土地区不同而异。最低水平值和作物吸钾量是土壤供钾的重要特征参数。供试山西土壤的长期供钾能力按取土地区有从南至北逐渐下降的趋势 ,在不同土壤类型上有红粘土、潮土 黄绵土、褐土 栗褐土、栗钙土的趋势。     

Parameters affecting extraction of selected fungicides from vineyard soils

This paper describes a sensitive method for the simultaneous quantification of eight commonly used grapevine fungicides in vineyard soils: cyprodinil, fludioxonil, metalaxyl, penconazole, pyrimethanil, procymidone, tebuconazole, and vinclozolin. The fungicides are extracted from the soil sample by sonication with water followed by shaking with ethyl acetate and are quantified by gas chromatography with mass spectrometry. Average extraction efficiencies in a sample of seven spiked, previously fungicide-free soils were > or =79% for all of the analytes, method precisions were > or =17%, and quantification limits were < or =50 microg/kg. However, because recoveries varied considerably from soil to soil, there is a need to control for soil matrix differences (mainly soil pH and exchangeable calcium content); as a consequence, soil fungicide contents must be quantified by the standard additions method. When the method was applied in this way to soil samples from vineyards belonging to the specified wine-growing region of Rias Baixas (Galicia, northwestern Spain) taken at the beginning of October (1 month after the crop's final treatment), levels of fludioxonil as high as 991 microg/kg were found, but at the start of the season (9 months after the previous crop's final treatment) only fludioxonil was detected at levels higher than its limit of quantification (45 and 52 microg/kg).     

Carbon sequestration in agricultural soils in the Cerrado region of the Brazilian Amazon

The introduction of crop management practices after conversion of Amazon Cerrado into cropland influences soil C stocks and has direct and indirect consequences on greenhouse gases (GHG) emissions. The aim of this study was to quantify soil C sequestration, through the evaluation of the changes in C stocks, as well as the GHG fluxes (N₂O and CH₄) during the process of conversion of Cerrado into agricultural land in the southwestern Amazon region, comparing no-tillage (NT) and conventional tillage (CT) systems. We collected samples from soils and made gas flux measurements in July 2004 (the dry season) and in January 2005 (the wet season) at six areas: Cerrado, CT cultivated with rice for 1 year (1CT) and 2 years (2CT), and NT cultivated with soybean for 1 year (1NT), 2 years (2NT) and 3 years (3NT), in each case after a 2-year period of rice under CT. Soil samples were analyzed in both seasons for total organic C and bulk density. The soil C stocks, corrected for a mass of soil equivalent to the 0–30-cm layer under Cerrado, indicated that soils under NT had generally higher C storage compared to native Cerrado and CT soils. The annual C accumulation rate in the conversion of rice under CT into soybean under NT was 0.38 Mg ha⁻¹ year⁻¹. Although CO₂ emissions were not used in the C sequestration estimates to avoid double counting, we did include the fluxes of this gas in our discussion. In the wet season, CO₂ emissions were twice as high as in the dry season and the highest N₂O emissions occurred under the NT system. There were no CH₄ emissions to the atmosphere (negative fluxes) and there were no significant seasonal variations. When N₂O and CH₄ emissions in C-equivalent were subtracted (assuming that the measurements made on 4 days were representative of the whole year), the soil C sequestration rate of the conversion of rice under CT into soybean under NT was 0.23 Mg ha⁻¹ year⁻¹. Although there were positive soil C sequestration rates, our results do not present data regarding the full C balance in soil management changes in the Amazon Cerrado.     

Sorption-desorption of "aged" sulfonylaminocarbonyltriazolinone herbicides in soil

Sorption-desorption interactions of pesticides with soil determine the availability of pesticides in soil for transport, plant uptake, and microbial degradation. These interactions are affected by the physical and chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. The objective of this study was to characterize sorption-desorption of two sulfonylaminocarbonyltriazolinone herbicides incubated in soils at different soil moisture potentials. The chemicals were incubated in clay loam and loamy sand soils for up to 12 wks at -33 kPa and at water contents equivalent to 50 and 75% of that at -33 kPa. Chemicals were extracted sequentially with 0.01 N CaCl(2) and aqueous acetonitrile, and sorption coefficients were calculated. Sufficient sulfonylaminocarbonyltriazolinone herbicides remained (>40% of that applied) during incubation to allow calculation of sorption coefficients. Aging significantly increased sorption as indicated by increased sorption coefficients. For instance, for sulfonylaminocarbonyltriazolinone remaining after a 12-wk incubation at -33 kPa, K(d) increased by a factor of 4.5 in the clay loam soils and by 6.6 in the loamy sand as compared to freshly treated soils. There was no effect of moisture potential on sorption K(d) values. These data show the importance of characterization of sorption-desorption in aged herbicide residues in soil, particularly in the case of prediction of herbicide transport in soil. In this case, potential transport of sulfonylaminocarbonyltriazolinone herbicides would be over-predicted if freshly treated soil K(d) values were used to predict transport.     

A study of potassium dynamics and mineralogy in soils from subtropical Brazilian lowlands

Purpose  

The dynamics and availability of potassium (K) in soils depend on many factors, including the mineralogy of fractions and the soil geochemical conditions. The objective of this work is to quantify K in distinct lowland soil compartments in the south of Brazil, relating them to particle size fractions and mineralogical constitution.