Soil-water Ratio Research Articles

Minimizing Confounding Factors in Phosphorus Leaching Assessment for Dairy‐and Poultry‐Manure‐Amended Soils

Soil phosphorus (P) concentrations have increased over the years, increasing P losses to surface waters. Phosphorus saturation ratios (PSR), used as environmental soil tests, have different relationships with conventional water‐soluble‐P (WSP) determinations for dairy and poultry‐manure‐amended soils. Objective was to develop a WSP procedure to characterize P leaching from manure‐amended soils. Soil samples were collected from dairy and poultry sites. WSP was determined using 1∶10 and 5∶1 soil–water ratios. Soils in columns were leached using unsaturated flow. Results showed that relationships between PSR and WSP 5∶1 were consistent for all soils. The 5∶1 ratio, closer to field moisture conditions, could be a good indicator of P leaching. There was good correlation between the WSP 1∶10, 5∶1, and column leachate, and a paired t test showed no difference between the last two. Thus, a single 5:1 extraction could be as useful in P leaching assessments as laborious column studies.

Analysis of an Ion-Selective Electrode Based Methodology for Integrated On-The-Go Mapping of Soil pH, Potassium, and Nitrate Contents

Knowledge of the spatial variation of soil attributes is critical for precision agriculture. On-the-go soil sensors have been able to provide relatively high mapping density while assessing this variation. A new ion-selective electrode (ISE) based approach was developed and tested for simultaneous mapping of soil pH, residual nitrate (NO3-), and soluble potassium (K+) contents. In this article, results of laboratory experiments investigating the effects of key measurement factors on ISE performance are presented. In addition to four different soils, these factors included: soil/water ratio (SWR), quality of water used for electrode rinsing (QWR) and for ion extraction (QWE), presence of ionic strength adjuster (ISA), and solution agitation (stirring). After the targeted ion activity presented by different soils, SWR was the second most influential factor causing increased measurement variance, while the influence of QWE was only significant for pH measurements. Based on this study, the following measurement parameters were recommended: agitated purified water extraction without ISA, addition of a fixed amount of water (preferably 1:1 soil/water ratio), and use of regular (tap) water for electrode rinsing.

Influence of soil–water ratio on the performance of slurry phase bioreactor treating herbicide contaminated soil

The influence of soil–water ratio was studied on the performance of the slurry phase bioreactor operated in sequencing batch mode (anoxic–aerobic–anoxic microenvironments) during the bioremediation of soil contaminated with pendimethalin. The performance of the reactors was evaluated at different soil–water ratios (1:5–1:25; at soil loading rate (60 kg of soil/cum-day to 12 kg of soil/cum-day)) keeping the loading rate of pendimethalin constant (133.2 g/kg of soil-day) in six reactors and variable (66.6 g/kg of soil-day to 166.6 g/kg of soil-day) in other four reactors. At 1:20 soil–water ratio, the slurry phase system showed enhanced degradation of substrate (629 μg pendimethalin/g soil). The removal efficiency of pendimethalin in the reactors was dependent on the mass-transfer rates of the substrate from the soil to the aqueous phase. Soil–water ratio and substrate loading rates showed significant influence on the substrate portioning, substrate degradation efficiency and substrate desorption rate.

Phosphorus retention processes in shell sand filter systems treating municipal wastewater

The suitability of shell sand as a P sorbent has been tested both with laboratory batch experiments as well as in a sub-surface flow (SSF) meso-scale constructed sand filter treating municipal wastewater from a single household. The batch experiments suggest that retention of P in shell sand occurs both as sorption and precipitation. The soil–water ratio was found to be a crucial parameter when performing laboratory batch experiments. The maximum retention capacity was about 8000 and 800 mg P kg −1 sand, and the K d was 33.7 and 82.9 L kg −1 for soil–water ratios of 5 g–75 mL and 50 g–50 mL, respectively. The average total accumulated P concentration in samples from the SSF sand filter was 335 mg P kg −1. The K d value based on [PO 4 3−] and accumulated concentration of inorganic P in the SSF filter was 89.8 L kg −1. Thus the batch experiments overestimated the retention capacity of shell sand in real sand filter systems, however, a ratio of 50–50 gave a more reasonable estimate than a ratio of 5–75. The K d value from batch samples with a ratio of 50–50 also gave a good estimate of the K d value in the constructed sand filter. Ca–P was found to be the predominant form of P mineral in samples collected from the SSF sand filter. Some Al–P, loosely bounded P, and occluded P were also present in the sand.

A Method for Measuring Soil Solution Electrical Conductivity in the Field Using TDR

This paper describes a simple and easy method for estimating soil solution electrical conductivity (ECw) and electrical conductivity of saturation extracts (ECe) in the field from simultaneous measurements of volumetric water content (θ) and bulk soil electrical conductivity (ECa) made using TDR.A model that relates ECw to θ and ECa (Rhoades et al., 1976) and the EC of an aqueous extract from a soil paste of 1:1 soil-water ratio (EC1:1) form the basis of this method. The relationship of EC1:1 to the EC of the soil solution of the same soil of 1:x soil-water ratio (EC1:x) is assumed to be EC1:x=x-nEC1:1 where n is a parameter to be determined by experiment but is assumed to be one in this study. The parameters of Rhoades' model are determined based on the ECw estimated from the EC1:1 using the relationship assumed above.This method was applied to two irrigation experiments conducted in an irrigated cornfield in a semiarid region, China and in a grass-covered spot in a humid region, Japan. The results show that this method is effective in monitoring soil salinity in the field.

SELECTING RICE GENOTYPES TOLERANT TO ZINC DEFICIENCY AND SODICITY STRESSES. I. DIFFERENCES IN ZINC, IRON, MANGANESE, COPPER, PHOSPHORUS CONCENTRATIONS, AND PHOSPHORUS/ZINC RATIO IN THEIR LEAVES

Zinc (Zn) deficiency is often reported on rice crops growing in sodic soils. Thirty rice genotypes were tested for their tolerance to Zn deficiency and sodicty stresses by transplanting 35-days old seedlings in pots having sodic soil of pH2 (1 : 2 soil water ratio) 9.8, and DTPA-extractable Zn 1.8 ppm;. Ten genotypes (Group A) showed potential to tolerate both the stresses with better survival (73–100%), tillering and were free from any visible symptoms of either Zn deficiency or sodium (Na) toxicity on their leaves. Sixteen genotypes (Group B) including CSR10, a tolerant check to sodicity, were found sensitive to Zn deficiency with less survival (35–80%), poor tillering and with visible symptoms of Zn deficiency. However, some of the seedlings of these genotypes were free from visible symptoms of Zn deficiency. Four genotypes (Group C) were sensitive to sodicity (survival 3–13%) and exhibited symptoms of Na toxicity within a week of transplanting. Analysis of the top three leaves and their leaf sheaths at 33 days after transplanting showed that Zn deficiency affected plants of group B genotypes (CSR10, CSR23, CSR-89IR1, 89H1-931098, and IR47538-3B-9-3B-1) invariably had higher Zn concentration compared to those plants of the same genotype which were free from these symptoms and also of group A (CSR-88IR15, CSR-89IR14, IR4630-22-2-5-1-2 and Trichi). There was no effect of Zn deficiency on phosphorus (P) concentration, and P/Zn ratio was rather lower in affected plants. The concentrations of iron (Fe) and manganese (Mn) in the leaves and leaf sheaths were influenced differently. Manganese was more than Fe in Zn deficiency tolerant genotypes/ plants of group A and B respectively, but it was the reverse in those susceptible to it. Whether alteration in Fe and Mn concentrations is the cause or effect of Zn deficiency requires more study. This showed that Fe and Mn concentrations should also be considered while studying Zn deficiency problems in rice. The survival of rice seedlings was best, but negatively correlated (r) with the Fe/Mn ratio of any of the top three leaves and leaf sheaths. This was equally good with Mn/Zn and Fe + Mn/Zn ratios. Appearance of Zn deficiency symptoms in plants of group B genotypes in spite of having higher Zn concentration than group A is most likely due to differences in physiological availability of Zn at the cellular level. This needs to be confirmed with further study.

Un método alterno para determinar cationes en solución de muestras pequeñas de suelo

Se evaluó una serie de ecuaciones basadas en la relación entre iones en solución y en la fase intercambiable del suelo para desarrollar un método que permitiese determinar cationes en solución en muestras de suelo bien pequeñas. Se evaluó uno serie de ecuaciones basadas en la relación entre iones en solución y en la fase intercambiable del suelo para desarrollar un método que permitiese determinar cationes en solución en muestras de suelo bien pequeñas.

Effect of Dilution on Calcium and Potassium Contents of Soil Solutions

AbstractThe effect of dilution on the composition of a soil solution of Magnolia sandy clay loam subsoil was investigated. Samples of a Ca‐ and K‐saturated soil as well as samples of a soil saturated with K and mixed with CaCl2 were equilibrated with water in various soil‐water ratios. Equilibrium solutions were separated and analyzed for Ca and K. Dilution increased the total amount of solution electrolytes with a concurrent change in the relative amount of each of the solution cations. The following equation was derived from Langmuir's isotherm to describe the desorption of neutral salts from soil surfaces: S = St V/(a + V) where S is the total meq of solution cations in volume V ml, and St and a are constants.The ratio‐law of Schofield was adequate to describe the change in the relative amount of each cation upon dilution of one soil system, but a correction term was added to the formulation of the ratio‐law in order to describe the data of the other soil system. This formulation of the ratio‐law is given as urn:x-wiley:03615995:saj2sssaj196703615995003100020010x:equation:saj2sssaj196703615995003100020010x-math-0001 where m is the number of solution mmoles, V is the solution volume in ml, and k and h are constants. The two foregoing equations provide the means for predicting the composition of a soil solution upon dilution.

SILICA IN SOIL SOLUTIONS: I. THE FORM AND CONCENTRATION OF DISSOLVED SILICA IN AQUEOUS EXTRACTS OF SOME SOILS

The effects of method of equilibration, soil-water ratio, pH, and temperature on the form and concentration of dissolved silica in soil-water mixtures were studied and some hypotheses concerning the role of soluble silica in soil development were evaluated in the light of the information obtained.Studies of methods of equilibrating soil-water mixtures showed that, with medium- and coarse-textured soils, shaking for a month resulted in increasing concentrations of dissolved silica with time. Concentrations of dissolved silica in similar mixtures that were allowed to stand were much lower and they changed very slowly with time after a few days. Shaking techniques are not suitable for obtaining equilibrium water-extracts of some soils.Concentrations of dissolved silica in water extracts of the soils studied increased with temperature and with soil-solution ratio, and decreased with increasing pH. The dissolved silica concentration of extracts of different soils ranged from less than 1 to more than 20 p.p.m. Monomeric silica, presumably Si(OH)4, was the form of dissolved silica in all of the extracts studied. This result discounts hypotheses of soil genesis involving silica sol.

Studies on soil reaction: III. The determination of the hydrogenion concentration of soil suspensions by means of the hydrogen electrode

A hydrogen electrode apparatus for soils is described. Similar or adjacent soils may show considerable differences inpH value, with no changes in their degrees of buffer action, as shown in titration curves with lime water. In such cases the conventional “lime requirements” are correlated with thepH values, but no such relation holds in dissimilar soils. ThepH value of a soil suspension is intimately connected with the nature and amount of the cations present. Neutral salts markedly increase the hydrogen ion concentration of both acid and slightly alkaline soils. Sodium salts, including the hydroxide, give lower hydrogenion concentrations than the corresponding potassium or calcium salts, and chlorides give lowerpH values than sulphates. The degree of buffer action (slope of titration curve) is unaffected by the addition of a neutral salt. Previous extraction of a soil with water causes a considerable increase i n thepH value of its suspensions. A number of soils showed a regular increase of about 0·1 inpH. value for twofold dilution. The “salt effect” and “dilution” effect appear to be of the same type. It is recommended that the soil-water ratio of 1:5 be generally adopted. The indicator methyl red gives erroneouspH values in turbid soil suspensions owing to the absorption of the red form, which is apparently a cation capable of undergoing “base exchange” with the soil.