bluuebunny/crossref_metadata_2025_split huggingface dataset:
A SIMPLE MODEL FOR PREDICTING THE EFFECTS OF LEACHING OF FERTILIZER NITRATE DURING THE GROWING SEASON ON THE NITROGEN FERTILIZER NEED OF CROPS
Authors: BURNS I. G. 
Published: July 2006

SummaryThe model is based on the concept that there is an effective rooting depth above which all the inorganic N in the soil is equally available and below which all N is totally unavailable. The extent to which nitrate is leached below this depth is calculated from the excess rainfall over evapotranspiration and the water holding capacity of the soil.The model was tested against the results of N fertilizer experiments with lettuce, French beans and overwintered onions which had been carried out in at least 2 years (and often more) on adjacent sites of the same field. The yields from all of the experiments with each crop were plotted against the level of fertilizer applied and against the difference between that applied and that lost by leaching. Comparison of these graphs showed that correcting for leaching in this way greatly reduced the variability between the response curves. The model was also tested against the results of similar experiments with Brussels sprouts grown on different sites with different combinations of base and top dressing. The results showed that the poor response to top dressing could be explained by the relatively small amounts of N in the base dressing which were leached from the rooting zone of this crop.It appears that the model will enable worthwhile adjustments in N fertilizer dressings to be made for differences in rainfall, provided that leaching occurs during the early stages of crop growth when uptake is small.
A SIMPLE MODEL FOR PREDICTING THE EFFECTS OF WINTER LEACHING OF RESIDUAL NITRATE ON THE NITROGEN FERTILIZER NEED OF SPRING CROPS
Authors: BURNS I. G. 
Published: July 2006

SummaryA model is described for predicting the amounts of nitrate residues remaining in the soil in the autumn and the extent to which these are lost by leaching during the winter. It is used to predict the effects of winter rainfall on the growth of spring crops. The model is based on the assumption that any nitrate which remains in the effective rooting zone of the spring crop after the winter will be equally available and any nitrate leached below it will be totally unavailable. The losses of nitrate were estimated from the excess rainfall and the water holding capacity of the soil.The model was tested against the results of published N response experiments in the Netherlands and the UK. It predicted the differential effects of winter rainfall with reasonable accuracy, but tended to overestimate the spring nitrate contents observed in the Dutch experiments and underestimate those for the English data. These deviations appeared to be associated with errors in the estimation of the amounts of nitrate remaining in the soil in the autumn.With certain reservations, the model would appear to provide helpful advice for adjusting spring fertilizer dressings for the effects of differences in winter rainfall.
THE WATER BALANCE OF AN AGRICULTURAL CATCHMENT II. CROP EVAPORATION : SEASONAL AND SOIL FACTORS
Authors: McGOWAN M. , WILLIAMS J. B. 
Published: July 2006

SummaryRates of evaporation, soil water deficits and extraction depths for spring cereals and grass were estimated from soil water measurements for a four year period. Estimates of evaporation were also compared with evaporation formulae and evaporimeter values.Evaporation and soil water deficit were highly dependent upon weather, particularly rainfall. Evaporation from grass was noticeably restricted whenever deficits exceed 50 millimeters. Cereals extracted water from a slightly greater depth of soil but developed deficits, up to harvest, very similar to those under grass. Deficits developed in sand and clay soils were also very similar, because water held in large dense clay aggregates is not readily accessible to roots.Although soil type had only minor influence on rates of evaporation, deficits and depths of drying, because of movement of water through fissures, slow drainage and delayed swelling effects soil type has a strong influence on stream behaviour.
ELECTRIC CHARGE CHARACTERISTICS OF ANDO A, AND BURIED A, HORIZON SOILS
Authors: WADA KOJI , OKAMURA YUTAKA 
Published: July 2006

SummaryThe electric charge characteristics of four Ando soils (A1 and μA1) and a Chernozemic soil (Ap) were studied by measuring retention of NH4+ and Cl– at different pH values and NH4Cl concentrations. No positive charge appeared in the Ando soils at pH values 5 to 8.5 except for one containing allophane and imogolite. The magnitude of their negative charge (CEC; meq/l00g soil) was dependent on pH and NH4Cl concentration (C; N) as represented by a regression equation: log CEC =a pH +b log C +c, where the values of a and b were 0.113–0.342 and 0.101–0.315, respectively. Unlike the Chernozemic soil, Ando soils containing allophane, imogolite, and/or 2:1–2:1:1 layer silicate intergrades and humus showed a marked reduction of cation retention as pH decreased from 7 to 5. This was attributed to the charge characteristics of the clay minerals and to the carboxyl groups in humus being blocked by Al and Fe.
WET AND DRY PORE SIZE DISTRIBUTION IN A KAOLINITIC SOIL BEFORE AND AFTER REMOVAL OF IRON AND QUARTZ
Authors: HOMSHAW L. G. , CAMBIER P. 
Published: July 2006

SummaryA kaolinitic soil was treated chemically to remove iron and quartz. Before and after treatment the properties of the soil were, respectively: iron content, 7 and 1%; quartz content, 21 and 0%: water content at saturation (water/kaolin content, g/g), 0.40 for both, of which 0.34 was in pores for which the Kelvin radius rj, was ≤35 nm. Porosity and pore size distribution (PSD) up to this pore size were studied using nitrogen sorption, mercury injection, pressure membrane equilibration and low temperature scanning microcalorimetry (DSC). These analyses justified interpretation in terms of kaolinite content alone. The PSD was unaffected by the removal of iron or quartz or the moisture content of this soil.New DSC techniques show that the pore spaces within the treated samples (rj≤ 35 nm) are largely unconstricted, and thus, an experimental curve relating temperature depression for melting to pore size is possible using only one sample.
WEATHERING IN TERTIARY GRAVELS IN N.E. SCOTLAND
Authors: KOPPI A. J. , FITZPATRICK E. A. 
Published: July 2006

SummaryThe weathering of highly quartzose flint‐containing gravels, believed to be the remnants of Tertiary beach deposits in N.E. Scotland, has been studied in detail. The deposits also contain infrequent boulders of granite, quartz schists and granulites which are largely kaolinised, but the kaolin varies in crystallinity between the two sites investigated. Quartz, alkali feldspars, muscovite and biotite‐like mica have been variously altered, and the weathering products include fine grained silica and leucoxene.
EFFECT OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI ON THE RELATIONS OF PLANT GROWTH, INTERNAL PHOSPHORUS CONCENTRATION AND SOIL PHOSPHATE ANALYSES
Authors: STRIBLEY D. P. , TINKER P. B. , SNELLGROVE R. C. 
Published: July 2006

SummaryThe effect of infection by vesicular‐arbuscular mycorrhiza on the predictive value of soil analysis for available P was tested in a glasshouse experiment. Leeks (Allium porrum) were grown on ten Rothamsted soils with a wide range of initial NaHCO3‐soluble P, each of which also received 5 levels of added P. Soils were partially sterilized with 1 Mrad of γ‐radiation, or left untreated; plants on sterilized soil were infected with yellow‐vacuolate endophyte (Glomus mosseae) or left non‐mycorrhizal. The NaHCO3‐soluble P in the soils was measured 5 days after phosphate addition.Yields from all P levels on all soils were plotted against soil NaHCO3‐soluble P content and separate smooth response curves were obtained for non‐infected and artificially‐infected plants. Infection increased yield only on soils with less than 100 mg P kg−1. In contrast, naturally‐infected plants gave no clearly defined response curve to P, and on three soils the yields were consistently low. These soils gave very low natural infections and had low spore densities probably due to the cropping history of the sites.Artificially‐infected plants had much higher shoot P concentrations than did uninfected plants of similar dry weight, over a large range of soil phosphate levels; this effect was also noted with the endophyte G. fasciculatus. Naturally‐infected plants showed a poor relationship between shoot P concentration and yield.
SOILS OF THE STATE OF BAHRAIN
Authors: BRIDGES E. M. , BURNHAM C. P. 
Published: July 2006

SummaryThe State of Bahrain lies in the arid zone on the southern side of the Arabian Gulf. The factors influencing soil formation on the Islands are examined and an account given of the soils. These can be placed in four groups: Solonchaks, Regosols, Yermosols and Fluvisols. The Solonchaks of the northern plain contain unprecedented amounts of gypsum which, in the absence of leaching, give rise to a variety of morphological features. The distribution of Regosols, Yermosols and Fluvisols can be related closely to physiographical location throughout the country.
DENITRIFICATION IN A VERY ACID TROPICAL SOIL
Authors: WICKRAMASINGHE K. N. , TALIBUDEEN O. 
Published: July 2006

SummaryIn a very acid upland clay surface soil and with glucose added to give initial C/N weight ratios (added glucose‐C: NO3‐N) in the soil of 0, 2 and 5, the rates of evolution of N2 and N2O were maximum at C/N = 2 but were significantly less at 0 and 5. The total N2 and N2O production was highest at C/N = 0, confirming that increasing amounts of glucose immobilised more nitrate into the biomass.As with added NO−3‐N, the time lag, preceding a maximum ‘steady state’ rate of N20 evolution, increased regularly with increasing glucose. Within this ‘steady state’ period, the gaseous CO2‐C/(N2+ N2O)‐N weight ratio in the effluent gas are between 1.0 and 1.3, which corresponds well with the stoichiometric ratios of 1.07 and 1.29 for the reduction of NO−3 to N2O and N2 respectively. Before and after this period, this gaseous C/N ratio was much higher.Denitrification was not observed in subsurface soil even after adding 100 mg kg−1glucose‐C although it contained 4 times as much indigenous nitrate as the surface soil. Inoculating this soil with increasing amounts of the surface soil, up to 15 per cent by weight, induced substantial increases in the rates and amounts of denitrification.The effects of increasing the soil pH. of introducing increasing oxygen concentrations in the influent gas. and the fate of added NH+4‐N, are briefly reported here. In these experiments. NO−2‐N did not accumulate in the incubated soil nor was there any NH3in the effluent gas. Evolution of N2 only occurred when N2O evolution was in its final stages.
TILTH MELLOWING
Authors: UTOMO W. H. , DEXTER A. R. 
Published: July 2006

SummaryEffects of weathering action, mainly wetting and drying cycles, on the strength of the clods produced by tillage are studied. Experiments were carried out on sandy loam soils at two sites in South Australia, and on silt loam and clay soils at Wye College, England.It is found that tillage increases the amplitude of soil water content fluctuations. These bigger soil water content fluctuations resulted in a decrease in the clod strength and this in turn modified the size distribution of the clods produced by tillage in the South Australian soils. The decrease in clod strength, as measured by the drop shatter test, was followed by an increase in the proportion of the smaller aggregate size fraction produced by a second implement pass.It is suggested that, for soils in which the increase in the soil water content fluctuations after the first tillage implement pass decreases clod strength, a further implement pass should be delayed for several days. By doing this, the soil can be tilled with minimum energy and cost to produce a good seed bed.
THE EFFECT OF SOIL TYPE, SLOPE, RAIN INTENSITY AND THEIR INTERACTIONS ON SPLASH DETACHMENT AND TRANSPORT
Authors: QUANSAH C. 
Published: July 2006

SummaryFrom a factorial experiment using a graded sand and three soils (sand, clay loam, and clay), five slopes (0.0, 3.5, 7.0, and 14.0 per cent) and four intensities (50, 80, 110, and 140 mm h−1), splash detachment and splash transport are described in terms of the direct effects and the first and second order interactions of these variables.The graded sand and three soils tested are significantly different in the mean weight of soil detached and transported. They can be placed in rank order of graded sand, sand, clay, and clay loam with increasing resistance to splash detachment. The amount of material transported is in the order of graded sand > clay > sand > clay loam. For each soil there are significant increases in splash detachment and splash transport with increasing rainfall intensity. Both splash parameters are significantly correlated with slope steepness.The most important interactions that influence splash detachment and splash transport are soil × intensity and slope × intensity respectively. Significant interactions show that the factors are not independent of each other; the simple effects of a factor differ, and the magnitude of any simple effect varies according to the level of the other factors of the interaction term. These interactions have not been explicitly studied in previous research on splash erosion.Power equations are established between splash activity and the above variables and reasonable working ranges for the exponents are suggested.
STRUCTURE FORMATION UPON MIXING Na‐MONTMORILLONITE WITH BI‐ AND TRIVALENT ION‐CLAYS1
Authors: FRENKEL H. , SHAINBERG I. 
Published: July 2006

SummaryThe light transmittance of montmorillonite suspensions saturated with Na+, Mg++, Ca++, Al+++, Fe+++ or La+++ and with known mixtures of these ions was investigated. Also, the kinetics of bi‐ and trivalent ion montmorillonite tactoid formation and breakdown was followed by recording changes in light transmission as a function of time when M‐montmorillonite suspensions (M = Mg++, Ca++, Al+++, Pe+++ or La+++) were added to Na‐montmorillonite suspensions of the same concentration in a titrating vessel placed in the light path of a spectrophotometer. Introduction of a small fraction of Na+ onto the exchange complex of M‐clay had no effect on the size of the M‐tactoids. The breakdown of Mg++ and Ca++ tactoids occurred as the equivalent fraction of adsorbed Na+ increased from 0.2 to 0.5, with mixed Na‐M montmorillonite particles having an equivalent fraction of adsorbed Mg++and Ca++ less than 0.3 remaining as single platelets. Conversely, introducing even a small fraction (<10%) of trivalent onto the exchange complex of Na‐montmorillonite caused the formation of tactoids.Instantaneous formation of an intermediate unstable structure occurred upon mixing Na‐montmorillonite with M‐montmorillonite. It is proposed that edge‐to‐face association stabilizes this intermediate structure, whereas face‐to‐face association stabilizes the eventual tactoids.
A LABORATORY METHOD TO MEASURE GAS DIFFUSION AND FLOW IN SOIL AND OTHER POROUS MATERIALS
Authors: BALL B. C. , HARRIS W. , BURFORD J. R. 
Published: July 2006

SummaryAn apparatus was constructed to measure diffusivity of krypton‐85 and gas permeability in an enclosed core of soil of field structure or in other porous material. Sample enclosure decreased water loss by evaporation, reduced mass flow caused by changes in ambient temperature and pressure during diffusion measurement, and allowed subsequent measurement of gas permeability without further sample disturbance. When a bundle of tubes was used as a test sample to calibrate the apparatus, the resistances to diffusion and viscous flow agreed approximately with those calculated from the tube size and number. Gas movement was measured in dry sieved soil and in undisturbed cores of silty loam soil to illustrate the practical value of the method. In the dry cores, diffusivity relative to free air (DA/Do) was greater in ploughed soil, 0.18, than in direct drilled soil, 0.14, nearly in proportion to the greater air porosity in the ploughed soil, but air permeability in ploughed soil was four times greater than in direct drilled soil and was about 1 000 times greater than in compacted sieved soil.
A PARTIAL MODEL FOR THE RATE OF ADSORPTION AND DESORPTION OF PHOSPHATE BY GOETHITE
Authors: BARROW N. J. , MADRID L. , POSNER A. M. 
Published: July 2006

SummaryIt was assumed that the reaction between phosphate and goethite consisted of a second order forward reaction between phosphate molecules and adsorption sites, opposed by a first order desorption reaction. Because adsorption occurs at a charged surface, it was assumed that the rates were affected by the electrostatic potentials at the surface. A mixed analytic and numeric approach was used in which the rate equation was integrated over small time steps and a computer programme was used to generate the effect of many small steps.Comparison between the model and results for rate of adsorption suggested that the rate‐determining step preceded the electron transfer steps and did not, of itself, involve electron transfer. With this assumption, rate of adsorption could be modelled with the estimation of only one parameter beyond those needed to model the equilibrium values for adsorption. The model gave a good description of the rate of adsorption at three pH values for times up to one hour. It did not describe the slow adsorption over longer periods and this suggested that a different mechanism was involved. Although the main features were reproduced, description of desorption was less satisfactory. This deficiency of the model may occur because it was restricted to the reaction with phosphate and did not model the rate component for the other changes in charge that accompany adsorption.
SELECTIVE EXTRACTION OF AMORPHOUS IRON OXIDES BY EDTA FROM SOILS FROM DENMARK AND TANZANIA
Authors: BORGGAARD O. K. 
Published: July 2006

SummarySoils from Denmark and Tanzania were extracted with EDTA solutions of different concentrations and pH. After extraction for 3 months there was no significant (95% level) further increase in amounts of iron (and aluminium, calcium, and magnesium) during longer extraction periods. X‐ray diffraction showed no change of the crystalline minerals caused by the extraction, which is believed to be specific for amorphous iron oxides. The EDTA method may thus serve as a reference method for the determination of amorphous iron oxides in soils.Although the difference between EDTA‐extractable iron and that extracted during 2 h by ammonium oxalate at pH 3.0 in the dark may be high, the ammonium oxalate method is considered to give a fast and often fair estimate of amorphous iron oxides.
MODELLING OF SOIL PORES AS TUBES USING GAS PERMEABILITIES, GAS DIFFUSIVITIES AND WATER RELEASE
Authors: BALL B. C. 
Published: July 2006

SummaryTwo models are presented describing the air‐filled continuous pores in soil and how they change with soil water potential. In the first model (A), the pores are represented by tortuous tubes of uniform radius. The radius, length and number are calculated from air permeability, relative diffusivity and air‐filled porosity measured at each soil water potential. In the second model (B), the pores are represented by tortuous tubes of three radii joined at random in series. The radii and total lengths of the tube sections are estimated by comparison of air permeability, diffusion coefficient and air‐filled porosity at each water potential with values calculated for a large number of theoretical systems.The models were applied to the results from undisturbed cores of a silt loam taken from 30 to 80 mm depth. For both models, the sequences of continuous pores were estimated to be 2 to 7 times as long as the sample but shortened as the sample dried. From the second model the average pore radius in direct drilled soil, 0.3 mm, was half that in ploughed soil and the minimum radius, 0.1 mm, was one‐quarter that in ploughed soil.
MOISTURE RELEASE CHARACTERISTICS AND POROSITY OF TWELVE SCOTTISH SOIL SERIES AND THEIR VARIABILITY
Authors: BACHE B. W. , FROST C. A. , INKSON R. H. E. 
Published: July 2006

SummaryMoisture release characteristics were measured in triplicate at nine sites for each of twelve soil series. Water content was linearly related to log suction for loamy soils, but a strongly curved relationship was found for dominantly sandy or clayey soils. Some series were highly variable, due mainly to textural variations within series, but texturally uniform series were less variable. The largest significant differences between series were given by the drainable pore space of B horizons, a useful property for drainage design advice; for some series drainable pore space indicated a different permeability than might have been expected from natural profile morphology.
PHOSPHATE ADSORPTION IN ALLOPHANIC SOILS
Authors: IMAI H. , GOULDING K. W. T. , TALIBUDEEN O. 
Published: July 2006

SummaryThe kinetics and heats of phosphate adsorption were measured on the <2 μm Na‐saturated fractions of three allophanc‐rich soils from Japan. Between 50 and 2250 μmol P g−1 as sodium phosphate were added to the soil fractions at pH 5 and pH 7, and at initial concentrations of 5 and 25 × 10−4m to avoid aluminium phosphate precipitation.An initial ‘instantaneous’ adsorption associated with exposed sites and, simultaneously, two inverse exponential rates of adsorption on internal and freshly forming external sites were observed. These rates are attributed to changes in the microstructure of allophane and to the desorption of organic matter held on allophanic surfaces. This interpretation is strongly supported by corresponding changes in the heats of adsorption with time. Calorimetry clearly indicates that when very large amounts of phosphate are added, new and very reactive surfaces are progressively exposed.More phosphate was adsorbed when the soil was acid and when the soil contained less organic matter.
COPPER ADSORPTION BY ALKALINE SOILS
Authors: DHILLON S. K. , SIDHU P. S. , SINHA M. K. 
Published: July 2006

SummaryThe adsorption of copper by four alkaline soils of northwest India was investigated using 0.05m CaCI2 as supporting electrolyte. The adsorption data conformed to the competitive Langmuir adsorption equation although there was possibliity of copper hydroxide or carbonate precipitation at higher concentrations of added copper. The adsorption capacities of soils were related to CEC, clay content and CaCO3 equivalent of soil. The free energy changes for adsorption and for interaction were negative and positive respectively.