Least limiting water range indicators of soil quality and corn production, eastern Ontario, Canada

The least limiting water range (LLWR) attempts to incorporate crop-limiting values of soil strength, aeration, and water supply to plant roots into one effective parameter (on the basis of soil water content). The LLWR can be a useful indicator of soil quality and soil physical constraints on crop production. This study focused on assessing dynamic cultivation zone LLWR parameters between different cropping/tillage/trafficked clay loam plots at Winchester, Ont., to identify potential management impact on surficial soil physical conditions for contrasting growing seasons. This study also evaluated dynamic cultivation layer LLWR variables as indicators of corn (Zea mays L.) plant establishment and corn yield. The results suggest that no-till soils had lower average air-filled porosities (AFP) and O₂ concentrations than respectively managed tilled plots for both years of study. Potential trafficking effects on aeration properties were most evident in no-till relative to till; preferentially trafficked no-tilled plots had lower AFP and O₂ concentrations than respective non-preferentially trafficked no-till plots for both years of study. Corn establishment and yield variability were principally explained by cumulative differences between daily AFP and aeration threshold values, and the cumulative number of days daily AFP was below an AFP aeration threshold for specific corn growth stage periods. Lower AFP was linked to lower yields and plant establishments. Soil strength, as measured by cone penetration resistance, was important over certain sites, but not as important globally as AFP in predicting crop properties. Overall, conventional tilled soils that were not preferentially trafficked had most favorable aeration properties, and subsequently, greatest corn populations and yields. No-till soils were at greater risk of aeration limiting conditions, especially those in continuous corn and preferentially trafficked.     

Frost heaving of soils at two locations in Southern Ontario,Canada

Frost-heave measurements conducted over two winters in frost-susceptible soil at two adjacent Canadian locations, one near Guelph, and the other near Elora, Ontario, are examined in the light of supporting environmental data. The trend in the penetrating frost line, and the total depths achieved in each season at the Guelph site were similar, but surface displacement during 1976–1977 was less than half that recorded in 1975–1976. This disparity is attributed to seasonal variations in the proximity of the water table with respect to the soil freezing level. When the former is deep, closed-system conditions prevail, and frost heave is severely curtailed. The importance of access to water is also demonstrated at the Elora site where frost heaving was sustained by a water table close to the surface despite the presence of a snow cover.     

The soil solution chemistry of some Oxfordshire soils: temporal and spatial variability

The immiscible liquid displacement method was used to displace soil solutions from a variety of Oxfordshire soils. These included grassland, arable, and woodland soils. The results of detailed chemical analyses demonstrated that for most solutes there were significant seasonal differences as well as differences both within and between soil series. The variation over time intervals of a few days or weeks appeared to be relatively small in relation to sampling errors. Median concentrations (in mmol m⁻³) for soil solutions derived from 21 grassland sites and six arable sites sampled six or seven times throughout 1 year were: _pH 7.7, alkalinity 1810, Na 465, K 390, Mg 135, Ca 2120, Sr 1.9, Ba 0.16, Mn 0.52, Fe 3.4, Cu 0.25, TON 860, Cl 1590, S 327, P 64, Si 220, B 5.1, and DOC 4250. For many solutes, the individual soil solution concentrations spanned a range from approximately five-times less than these median values to approximately five-times more.     

Adoption of soil conservation practices: An empirical analysis in Ontario,Canada

Soil degradation threatens environmental quality and sustainable food production. As a result of efforts to promote soil conservation, farmers in Canada are thought to be reasonably aware of both the importance of conservation and the existence of remedial and preventive practices. Despite this, the adoption of conservation practices has been less than overwhelming. Forces other than awareness and positive attitude seem to be constraining many land managers from employing available conservation methods. This paper presents the findings from an empirical investigation of the use of soil conservation practices and barriers to their adoption in the southwestern region of Ontario, Canada. The analysis is set in the context of literature on technology adoption. A scheme for measuring farm-level conservation effort is developed, and barriers to adoption are derived from an analysis of a range of independent physical, personal, and economic factors, and from the obstacles or constraints identified by producers themselves. Key barriers relate to economic pressures, the complexity and compatibility of practices, and perceptions regarding the actual need for practices. The findings have relevance for the design of public policies and programs, notably the importance of supplying information on farm-level implications of conservation methods and the need for a stable economic environment for agriculture to allow longer-term planning.     

Determining the optimum range of soil Olsen P for high P use efficiency, crop yield, and soil fertility in three typical cropland soils

Soil Olsen P level has a major influence on crop yield, efficient P utilization, and soil fertility. In this study, the optimum Olsen P range was determined from long-term (1990-2012) field experiments in three typical soil types of China under single cropping of maize or double cropping of maize and wheat. The critical soil Olsen P value for crop yield was evaluated using three different models, and the relationships among P use efficiency (PUE), Olsen P, and total P were analyzed. The agronomic critical soil Olsen P values obtained from the three models for the neutral soil of Gongzhuling and the calcareous soil of Zhengzhou were similar; however, the values from the linear-linear and linear-plateau models for both maize and wheat were substantially lower than those from the Mitscherlich model for the acidic soil of Qiyang. The PUE response change rates (linear equation slopes) under different soil Olsen P levels were small, indicating slight or no changes in the PUE as the soil Olsen P increased in all three soils. A comparison of the Olsen P levels that achieved the maximal PUE with the agronomic critical values derived from the three models indicated that the linear-plateau model exhibited the best performance. The regression equation coefficients of Olsen P response to total P decreased as follows:Zhengzhou (73 mg g^-1) > Qiyang (65 mg g^-1) > Gongzhuling (55 mg g^-1). The Olsen P level increased as the total P increased, which may result in a decrease in PUE. To achieve a relatively high crop yield, PUE, and soil fertility, the optimum Olsen P range should be 13-40, 10-40, and 29-40 mg kg^-1 at Gongzhuling, Zhengzhou, and Qiyang, respectively.     

Effect of land developmental process on soil solution chemistry in acid sulfate soils distributed in the Mekong Delta,Vietnam

Abstract

Water-soluble ionic substances in acid sulfate soils are likely to be strong controls for crop production and to have impacts on aquatic ecosystems. In dry seasons, in particular, oxidation of the soil surface followed by acidification probably produces lots of acids and soluble metals. To estimate acid and metal loads from acid sulfate soils to aquatic environments, we determined the composition of water-soluble ions from soils distributed in the Mekong Delta, Vietnam. At the end of the dry season, soils were taken from each soil horizon in two soil profiles on the delta under different land developmental processes. Water-soluble ions were extracted using both distilled water and artificially synthesized irrigation water (pH 6.3) adjusted to the same ionic strength and pH as the field canal water. The relationship between extracted basic cations in both extracts showed high linear correlation, indicating a similar extraction mechanism between both extractants. Higher ionic strength in the artificial irrigation water may not have any advantages for extraction by ion exchange and, thus, properties of extracts are likely to depend on the soil properties. The older the soil parent material, the larger the rates of soluble Al and Fe and the lower the pH. Progressive weathering of the soil on the older delta has already discharged greater amounts of bases, probably for compensation of acids, and the soil has started to release exchangeable Al sorbed onto negative-charge colloids and Fe from decomposed oxides. The soil profile of the older delta released relatively greater concentrations of Al with a lower content of base cations, where the annual averaged rice yield was half that of another site. Soluble metals and acids at both sites appear to accumulate in the upper horizons above the low permeable layer, which is probably widely distributed in the Mekong Delta.     

Peatland water chemistry in Central Ontario in relation to acid deposition

Thirty-one peatlands from two areas of central Ontario were sampled to assess the influence of acid deposition on peatland water chemistry. Factor analysis differentiated peatland water chemistry along three major axes of chemical variation, interpreted as axes of organic concentration, mineral concentration, and deposition influence. Water from the surface mats had a higher organic concentration than water from open pools. Mineral influence in peatland waters was reflected by higher concentrations of Ca, Mg, Na, and silica in fen pools compared to bog pools. The influence of high acid deposition in the Wanapitei study area was indicated by high concentrations of sulphate, Ni, Mn, and Cu, and lower pH compared to an area that has received less acidic deposition (Ranger). Regression analyses indicated that H⁺ variation in bogs could be largely explained by organic C concentration, but that sulphate concentration was also positively associated with acidity, while Ca was negatively associated with acidity.     

Characteristics of soil profiles affected by smelting of nickel and copper at Coniston,Ontario, Canada

Soil profiles were examined, described and sampled by horizons in various geomorphic positions along a transect originating at the Coniston smelter and extending in a southeasterly direction for approximately 12 km. The samples were then analyzed to determine particle-size distribution, pH, organic carbon and five heavy metals.Within the study area, elevated levels of nickel, copper and iron were found with maximum total concentrations of 1.2, 0.97 and 20.0%, respectively. Manganese and zinc did not occur in above-normal concentrations. The pH values of the soils were depressed with levels as low as 2.4.Near the smelter, erosion from soils on slopes has transferred materials into lower lying areas, thereby rearranging the areal distribution of nickel, copper and iron. Although the surface soil horizons along the entire transect have above-normal concentrations of these elements, only within the eroded area is there marked variability in their vertical distribution.     

Rice-soil interactions in Vietnamese acid sulphate soils: impacts of submergence depth on soil solution chemistry and yields

Abstract. The aim of this study was to investigate the effects of water submergence depth on radial oxygen loss (ROL), soil solution chemistry and rice growth performance in acid sulphate soils in southern Vietnam. ROL was measured in a solution culture. In a separate pot experiment the impact of water submergence depth on rice growth and soil solution chemistry was studied. Three submergence depths were used in the two experiments (5, 10 and 15 cm). ROL declined with submergence depth and was significantly greater in young roots (with no root hairs) than in older roots. In the pot experiment rice growth and soil solution chemistry were clearly affected by the submergence depth. During the first crop at 5 cm submergence, there was a significantly higher yield and a higher oxidation state (pe+pH) compared to 10 or 15 cm submergence. The Fe concentration was significantly greater at the 5 cm depth compared to the 10 or 15 cm depth. SO₄^2– reduction was delayed at the 5 cm depth. Rice yield was c. 25% less at the 15 cm than at the 5 cm depth. During a second crop, there was a substantial SO₄^2- reduction and H₂S formation and almost no significant effects of submergence depth on either soil solution chemistry or crop yield. In a field experiment with a dry-season rice crop, yield and Fe, Al and SO₄^2– concentrations were higher at a shallow submergence depth than at greater depths in the same field, showing similar depth trends to those found during the first crop in the pot experiment. Farmers should be advised to use a shallow submergence depth and, if possible, avoid deep-rooted rice varieties. A conceptual model is suggested, which summarizes the relationships between ROL and soil solution chemistry.     

The properties,genesis and geomorphological relationships of a sequence of soils on a limestone plain in Southeast Ontario,Canada

A sequence of soils was studied on a cross-section transverse to a drumlin continuing across lacustrine and alluvial deposits and terminating on a ridge. A calcareous till was deposited on a scoured, flat limestone plain during the last advance of the Wisconsin ice sheet and locally formed drumlins. After this local readvance, lacustrine sediments were deposited in a body of water ponded between the drumlin and the dead ice remaining in the valley floor. After the ice melted completely, alluvium was deposited in the valley.     

Phosphate,aluminium and iron in the soil solution of three different soils in relation to varying concentrations of citric acid

Several plant species excrete di- and tricarboxylic acids as a reaction to P and Fe deficiency. Therefore, the effect of citric acid on P, Al, and Fe soil solution concentrations of three soils was investigated in an incubation experiment. Citric acid additions of 10–50 μmole/g soil increased P, Al, and Fe solubility. The effect was strongly pronounced in the podzol with humic-P complexes as the main P fraction. The maximum increase was about 80 μmole P/L in the luvisol, 500 μmole P/L oxisol, and 3000 μmole P/L in the podzol. The Fe and Al solubility increased parallel to that of P with a ratio of Fe+Al_solubized/P_solubized of 10 or more. The solubization effect by citric acid was strong even after 90 days. Possible solubization reactions are discussed.     

Changes in chemistry and mineralogy of forest soils by acid rain

The goal of the present study was a qualitative and quantitative determination of chemical and mineralogical changes in forest soils due to acid atmospheric depositions. In the NE/SE Vienna Woods soil samples were taken at 4 depths (0 to 5 cm, 5 to 10 cm, 10 to 20 cm, 20 to 30 cm) in the contaminated infiltration zone of stemflow (S) of 8 beech trees (Fagus sylvatica), strongly influenced by acid atmospheric depositions (soil-pH 2.8 to 3.0) and in their non contaminated reference areas (R) between trees, where acid imput is much smaller (soil-pH 5.0 to 6.0). The results show that intensive weathering processes took place in the contaminated soil areas, which show higher clay and silt contents and smaller aggregates, as well as clay illuviation. Moreover, in the top of the contaminated soil areas higher contents of C_t and S_t and of the heavy metals Pb, Zn and Cu could be observed, accompanied by extreme low base saturation (expecially of Ca and Mg) and high Al-saturation (50 to 80% of the CEC). These data were confirmed by analysis of the water saturation extract. Moreover, in the contaminated top soils high amounts of Fe-oxides were found, whereas no “secondary” Al-chlorite (due to its instability at pH-values <4.0) could be traced. The desilification process which took place at the same time could be shown through total element analysis. In the clay-fraction strong weathering led to a loss of layer charge and to the genesis of highly expandable three-layer-silicates which could be determined by X-ray diffraction using n-alkylammonium-chloride technics and other chemical treatments.     

Effects of sorbed orthophosphate on zinc status in three soils of eastern Canada

P-Zn interactions can affect fertilizer use and produce Zn deficiencies with certain crops. Phosphorus-Zn sorption-desorption reactions were studied in topsoil and subsoil samples from three Quebec soils. Soils were equilibrated with P solutions, then with Zn solutions, and finally with solutions containing no P or Zn. The first equilibration evaluated P sorption (P_s), the second evaluated Zn sorption (Zn_s) after P sorption (P_s), and the third evaluated Zn desorption (Zn_D) as related to added P. Subsequently, Zn fractions were extracted sequentially with KNO₃ (Zn _{kno 3}), NaOH (Zn_NaOH) solutions and concentrated HN0₃+ H₂0₂(Zn_HNO,).
One mmole sorbed P resulted in increases of 0.5 to 1.0 meq (mean = 0.72) increases in cation exchange capacity (CEC). Increased Zn_s with added P was equivalent to 4 to 5% of the increase in CEC induced by P_s in the Uplands (sand) and St. Bernard (loam) soils, and 0.4 to 0.9% in the Dalhousie (clay) soils, while one meq increase in CEC resulted in 1.5-3.5% decrease in Zn_D. There existed positive correlations between P_s and extractable soil Fe materials. Phosphate sorption enhanced associations between Zn_s, Zn_D or Zn fractions and soil organic or crystalline Fe contents, confirming that P addition increased specific sorption of Zn on Fe components. Other mechanisms including precipitation, P-induced negative charge and 'bridge' effects are also discussed.     

Assessing biological recovery of acid-sensitive lakes in Ontario,Canada

Information on breeding waterfowl, habitat and food chains, gathered from acid-sensitive lakes in Ontario, was used to develop a model of effects of acid deposition on waterfowl and their response to predicted sulphur dioxide (SO₂ emission reductions in eastern North America. The Waterfowl Acidification Response Modelling System (WARMS) is composed of an acidification model linked to fish and waterfowl models. WARMS uses pH, area, dissolved organic carbon, total phosphorus, and presence of fish to calculate estimates of pre-acidification, present and eventual steady-state values for pH, fish presence and waterfowl breeding parameters under proposed SO₂ emission scenarios. We used WARMS to estimate chemical and biotic responses to scenarios simulated in three regions of Ontario where biomonitoring studies are underway. For pH and fish presence, WARMS predicts the greatest improvements in the highly damaged Sudbury region, slight improvements in Algoma, and that the strongest proposed emission reductions will be required to maintain current conditions in Muskoka. For waterfowl, species-specific differences are evident among regions. We discuss implications of these assessments of biological recovery for watersheds in eastern Canada.     

Modelling cations in three acid soils with differing acid input in Germany

Prediction of concentration changes of cations in soil solutions is complex, and chemical models are necessary for the purpose. The objective of this study was to determine whether the reactions considered in a coupled equilibrium model were appropriate to predict cation concentrations when the initial equilibrium was disturbed by adding small amounts of electrolytes. Multi-ion sorption in three acid soils (two Cambisols and a Podzol) was studied by sequentially adding small amounts of electrolytes to samples of the soils in batch experiments. A chemical equilibrium model that included inorganic complexation and multiple cation exchange was used to interpret the results. For the subsoils, the solubility of jurbanite was also included in the model. Model results for the two Cambisol surface soils agreed well or satisfactorily with the measured pH and sorption values of Na, K, Mg, Ca, Mn, Al and Fe, with a few exceptions. Linear correlation coefficients were generally between 0.97 and 1, and the regressin coefficients for cations (modelled against measured) lay between 0.6 and 1.3. For the subsoils sorption of sulphate was described satisfactorily for the spodic dystric Cambisol and to some extent for the spodic Cambisol. Correlation coefficients for subsoils lay between 0.63 and 1, and the regression coefficients (modelled against measured) were between 0.9 and 1.6 for the Cambisols. The model did not predict pH and sorption data in surface and subsurface soils with very small amounts of exchange capacities, pointing to the significance of cation buffering resulting from exchange sites. This study showed the usefulness and limitations of equilibrium models to predict the composition of the soil solution.     

Relationship of soil properties to pyroxasulfone bioactivity in a range of prairie soils

The relationship between pyroxasulfone bioactivity and soil properties has not been investigated in a wide range of soils typical of western Canada. In this study, 47 soils from Saskatchewan, Manitoba and Alberta, with varying organic matter content (1.5%–22.1%), pH (5.0–7.9), and clay content (6.8%–59.4%) were used to evaluate the effect of soil properties on pyroxasulfone bioactivity and its relevance to field application rates. Bioactivity was assessed by measuring the reduction of sugar beet shoot length after 7 days in response to 0, 92, 184, and 368 µg?ai?kg^?1 pyroxasulfone concentration in soil. Multiple regression analysis showed that pyroxasulfone bioactivity was related to soil organic matter content, pH and clay content. Grouping the soils according to these properties allowed for a summarization of pyroxasulfone field application rates required to achieve bioactivity based on the magnitude of sugar beet shoot length inhibition (%). The estimated field application rates ranged from less than 120–480 g?ai?ha^?1.     

澳洲东部三种沿海漫滩酸性硫酸盐土壤中铁一硫化物的分布

The distribution of iron monosulifde (quantified as acid volatile sulfur:SAV) was compared with geochemical properties that are known to affect its formation and accumulation in three coastal Holocene acid sulfate soils (ASS) at Tuckean Swamp,Mc Leods Creek and Bungawalbyn Swamp respectively,These properties included pH,reactive iron(FeR),pore-water sulfate(SO4^2-) and organic carbon(OC).Iron monosulfide was concentrated at the oxic/anoxic boundary,the Tuckean Swamp and McLeods Creek sites are Holocene sediments,whereas the Bungawalbyn Swamp is a Holocene peat.The concentration of SAV averaged 0.2 g kg^-1 in a 0.5m thick soil layer at the Tuckean Swamp,but was an order of magnitude lower in the oxic/anoxic transition layers at McLeods Creek and Bungawalbyn Swamp,The SAV mineral greigite(Fe3S4) was identified in the Tuckean Swamp by X-ray diffraction and scanning electron microscopy with quantitative energy dispersive X-ray analysis(SEM-EDX),Very small concentrations of greigite were also observed in the McLeods Creek,based on crystal morphology and elemental composition.The concentration of SAV was a small fraction of the total reduced sulfur,representing at most 3% of the pyrite sulfur,However,the presence of this highly reactive sulfide mineral,distributed within pores where oxygen diffusion is most rapid,has important implications to the potential rate of acid production from these sediments.     

Intersite characterization and variability of soil respiration in different arable and forest soils

Summary Soil respiration was investigated in three loamy Orthic Luvisols (two arable, one forest soil), three sandy Haplic Podzols (also two arable, one forest soil) with a modified intersite method according to Lundegardh (1924). The method allows characterization of the CO₂-flux from the soil and interpretation of the different levels with regard to temperature, nutrient and air supply. The method is sensitive to tillage and fertilization effects. In the two arable Luvisols the mean cumulative respiration rate was not uniform compared with the forest soil; in one case it was much higher and in another much lower. CO₂ evolution in the Podzol under spruce was much lower than in the two arable Podzols. In the sandy Podzols 5 replicate measurements gave adequate results, with an error probability of 10%, but in the loamy Luvisols it was necessary to use 10 replicates to specify the same degree of difference. If soil respiration is very high, immediately after fertilization with cattle slurry or dung on arable land, or after litterfall in a deciduous forest, more replicates are necessary.     

The effect of biochar loading rates on soil fertility,soil biomass,potential nitrification,and soil community metabolic profiles in three different soils

Purpose

Biochar is increasingly being used as a soil amendment to both increase soil carbon storage and improve soil chemical and biological properties. To better understand the shorter-term (10 months) impacts of biochar on selected soil parameters and biological process in three different textured soils, a wide range of loading rates was applied.

Materials and methods

Biochar derived from eucalypt green waste was mixed at 0, 2.5, 5, 10 % (wt/wt) with a reactive black clay loam (BCL), a non-reactive red loam (RL) and a brown sandy loam (BSL) and placed in pots exposed to the natural elements. After 10 months of incubation, analysis was performed to determine the impacts of the biochar rates on the different soil types. Also, microbial biomass was estimated by the total viable counts (TVC) and DNA extraction. Moreover, potential nitrification rate and community metabolic profiles were assayed to evaluate microbial function and biological process in biochar-amended soils.

Results and discussion

The results showed that biochar additions had a significant impact on NH₄ and NO₃, total C and N, pH, EC, and soil moisture content in both a soil type and loading-dependent manner. In the heavier and reactive BCL, no significant impact was observed on the available P and K levels, or the total exchangeable base cations (TEB) and CEC. However, in the other lighter soils, biochar addition had a significant effect on the exchangeable Al, Ca, Mg, and Na levels and CEC. There was a relatively limited effect on microbial biomass in amended soils; however, biochar additions and its interactions with different soils reduced the potential nitrification at the higher biochar rate in the two lighter soils. Community metabolic profile results showed that the effect of biochar on carbon substrate utilization was both soil type and loading dependent. The BCL and BSL showed reduced rates of substrate utilization as biochar loading levels increased while the opposite occurred for the RL.

Conclusions

This research shows that biochar can improve soil carbon levels and raise pH but varies with soil type. High biochar loading rates may also influence nitrification and the function and activity of microbial community in lighter soils.