Effect Of Soil pH Research Articles

Microbial-Mediated Emissions of Greenhouse Gas from Farmland Soils: A Review

The greenhouse effect is one of the concerning environmental problems. Farmland soil is an important source of greenhouse gases (GHG), which is characterized by the wide range of ways to produce GHG, multiple influencing factors and complex regulatory measures. Therefore, reducing GHG emissions from farmland soil is a hot topic for relevant researchers. This review systematically expounds on the main pathways of soil CO2, CH4 and N2O; analyzes the effects of soil temperature, moisture, organic matter and pH on various GHG emissions from soil; and focuses on the microbial mechanisms of soil GHG emissions under soil remediation modes, such as biochar addition, organic fertilizer addition, straw return and microalgal biofertilizer application. Finally, the problems and environmental benefits of various soil remediation modes are discussed. This paper points out the important role of microalgae biofertilizer in the GHG emissions reduction in farmland soil, which provides theoretical support for realizing the goal of “carbon peaking and carbon neutrality” in agriculture.

The effect of soil type on yield and micronutrient content of pasture species.

The use of multispecies swards on livestock farms is growing due to the wide range of benefits they bring, such as improved biomass yield and animal performance. Preferential uptake of micronutrients by some plant species means the inclusion of legumes and forbs in grass-dominated pasture swards could improve micronutrient provision to livestock via careful species selection. However, although soil properties affect plant micronutrient concentrations, it is unknown whether choosing 'best-performing' species, in terms of their micronutrient content, needs to be soil-specific or whether the recommendations can be more generic. To address this question, we carried out an experiment with 15 common grass, forb and legume species grown on four soils for five weeks in a controlled environment. The soils were chosen to have contrasting properties such as texture, organic matter content and micronutrient concentrations. The effect of soil pH was tested on two soils (pH 5.4 and 7.4) chosen to minimise other confounding variables. Yield was significantly affected by soil properties and there was a significant interaction with botanical group but not species within a botanical group (grass, forb or legume). There were differences between botanical groups and between species in both their micronutrient concentrations and total uptake. Micronutrient herbage concentrations often, but not always, reflected soil micronutrient concentrations. There were soil-botanical group interactions for micronutrient concentration and uptake by plants, but the interaction between plant species (within a botanical group) and soil was significant only for forbs, and predominantly occurred when considering micronutrient uptake rather than concentration. Generally, plants had higher yields and micronutrient contents at pH 5.4 than 7.4. Forbs tended to have higher concentrations of micronutrients than other botanical groups and the effect of soil on micronutrient uptake was only significant for forbs.

Two decades of monitoring earthworms in translocated grasslands at Manchester Airport

Construction of a second runway at Manchester Airport included a mitigation package of habitat restoration with relocation of earthworms as prey items for protected vertebrates. Translocation of turf in blocks was the standard method used for four of five monitored sites with loose soil moved at the other. To assess earthworm communities at these translocated grassland sites, monitoring was undertaken each October (1998–2019) by digging and hand sorting of soil, followed by vermifuge application. Fourteen earthworm species were recorded, representing all ecological groups, but the majority were endogeic species, dominated by Aporrectodea caliginosa. Total earthworm numbers fluctuated during the monitoring period, with lowest density at 4 m−2 and highest more than a hundred times larger. The overall mean from all sites across the monitoring period was 151 ind. m−2. The differences between sites such as total earthworm numbers and species richness were clearly influenced by the translocation method and specific site topography. Created Hummocks to 3 m for hibernating amphibians proved successful with grassland soil establishing well. Lumbricus terrestris failed to establish due to translocation technique. Using non-metric multidimensional scaling, integration of environmental data with earthworm records showed effects of soil moisture content, pH and rainfall on abundance of ecological groupings and particular species. In general, earthworm community composition was dynamic over the monitoring period suggesting that this and population size needs to be appraised over realistic timescales, which may be best monitored in decades.

Spatial patterns of structural diversity across the boreal forest-tundra ecotone in Churchill, Canada

Vegetation structural diversity, also called structural complexity, has great effects on biodiversity and ecological processes, with higher biodiversity often observed in areas with higher structural diversity. As for other ecological variables, structural diversity is spatially heterogeneous. Thus, quantifying its spatial heterogeneity may provide clues to the spatial variation in ecological processes. We studied the spatial patterns of structural diversity in two different environments, tundra and forest-tundra ecotone, near Churchill, MB, Canada. We sampled vegetation and quantified five types of structural diversity (ground cover, herbaceous plants, woody plants, all live plants, and deadwood) along five transects, with lengths of 81–227 m, and used wavelet analysis to assess the scales of spatial pattern. We also assessed the effects of soil pH, microtopography, elevation, and distance from lakes on structural diversity. In general, structural diversity was spatially structured on a variety of scales, from 2 to 55 m, with larger scales being observed in the tundra than in the ecotone transects. In addition, structural diversity in the tundra was generally higher near lakes and in areas with a higher pH, whereas in the ecotone it increased mostly with increasing pH and microtopographic variation. Spatial heterogeneity is an important characteristic of the forest-tundra ecotone and even tundra areas that appear homogeneous are structurally diverse at a variety of scales.

The influence of phosphorus application and varying soil pH on soil and herbage properties across a range of grassland soils with impeded drainage

AbstractOn soils dominated by high proportions of clay and organic matter, soil acidity and poor nutrient use efficiency have a major impact on output potential. Due to the inherent chemical properties of these soils, reducing soil acidity and the prevalence of undesirable metallic cations poses challenges. As a result, these soils have a large capacity for phosphorus (P) fixation, therefore reducing plant P availability. Limestone (CaCO3or MgCO3) is applied to agricultural soils to counteract soil acidity and reduce P fixation. The current study investigates the effects of four contrasting annual P application rates (0, 50, 100, 150 kg P/ha); split (50:50) between spring and summer, across soils with a range of soil pH values from a previous liming trial. The effect of soil pH ranges and P treatment rates on seasonal herbage growth and herbage P concentration was investigated over three years. Soil nutrient status was also investigated. Soil pH had a significant impact on the rate of mineralization and soil P concentration across each site. A soil pH of 6.2 caused a 1.8 mg/l increase in soil test P. An annual P application was necessary to maintain sufficient herbage P concentration for animal dietary requirements (0.35% DM), however there was no effect of P application or liming rate on herbage productivity across the three sites as all sites possessed sufficient soil P reserves. The current experiment has shown that despite optimal soil fertility status, ensuring sufficient plant available P is a problem on these particular soils.

The effect of soil pH on a carbohydrate level of tomato fruits (Lycopersicum esculentum Mill.) from bobo and Sidera villages

Soil pH has an effect not only on the growth and production of tomatoes but also has an influence on sugar metabolism. How the pH influences a production and the change of the sugar is still unknown. Therefore, this study aims to determine the effect of the soil pH on the carbohydrate content of tomatoes in Bobo and Sidera villages. The method used was quasi-experiment because the researchers did not randomly select tomatoes for the experimental group and the control group, but the researchers used tomato plants in the two villages that have the differences in the pH of the soil. The data obtained were analyzed using ANAVA assisted by XL STAT 2017 program. The results showed that the soil pH affected the carbohydrate content of tomato fruit found in Bobo and Sidera Villages. The pH of the soil in Sidera Village was lower than the pH found in the village of Bobo.

The effect of soil pH on a carbohydrate level of tomato fruits (Lycopersicum esculentum Mill.) from bobo and Sidera villages

The effect of soil pH on a carbohydrate level of tomato fruits (Lycopersicum esculentum Mill.) from bobo and Sidera villages

Analyzing Resilience in the Greater Yellowstone Ecosystem after the 1988 Wildfire in the Western U.S. Using Remote Sensing and Soil Database

The 1988 Yellowstone fire altered the structure of the local forest ecosystem and left large non-recovery areas. This study assessed the pre-fire drivers and post-fire characteristics of the recovery and non-recovery areas and examined possible reasons driving non-recovery of the areas post-fire disturbance. Non-recovery and recovery areas were sampled with 44,629 points and 77,501 points, from which attribute values related to topography, climate, and subsequent soil conditions were extracted. We calculated the 1988 Yellowstone fire burn thresholds using the differenced Normalized Burn Ratio (dNBR) and official fire maps. We used a burn severity map from the US Forest Service to calculate the burn severity values. Spatial regressions and Chi-Square tests were applied to determine the statistically significant characteristics of a lack of recovery. The non-recovery areas were found to cover 1005.25 km2. Among 11 variables considered as potential factors driving recovery areas and 13 variables driving non-recovery areas, elevation and maximum temperature were found to have high Variance Inflation Factors (4.73 and 4.72). The results showed that non-recovery areas all experienced severe burns and were located at areas with steeper slopes (13.99°), more precipitation (871.73 mm), higher pre-fire vegetation density (NDVI = 0.38), higher bulk density (750.03 kg/m3), lower soil organic matter (165.61 g/kg), and lower total nitrogen (60.97 mg/L). Chi-square analyses revealed statistically different pre-fire forest species (p < 0.01) and soil order (p < 0.01) in the recovery and non-recovery areas. Although Inceptisols dominated in both recovery and non-recovery areas, however, the composition of Mollisols was higher in the non-recovery areas (14%) compared to the recovery areas (11%). This indicated the ecological memory of the non-recovery site reverting to grassland post-disturbance. Unlike conventional studies only focusing on recovery areas, this study analyzed the non-recovery areas and found the key characteristics that make a landscape not resilient to the 1988 Yellowstone fire. The significant effects of elevation, precipitation, and soil pH on recovery may be significant to the forest management and forest resilience in the post-fire period.

Allelopathic effects of soil pH on nitrogen uptake, its utilization efficiency and soil enzymes in tea bush soil

Allelopathic effects of soil pH on nitrogen uptake, its utilization efficiency and soil enzymes in tea bush soil

Effect of soil pH on the sorption capacity of soil organic matter for polycyclic aromatic hydrocarbons in unsaturated soils

Sorption by soil organic matter (SOM) is considered the most important process affecting the bioavailability of hydrophobic organic chemicals (HOCs) in soils. The sorption capacity of SOM for HOCs is affected by many environmental factors. In this study, we investigated the effects of soil pH on the sorption capacity of SOM using batch sorption experiments. The soil organic carbon-water partition coefficients ( K OC ) of six selected polycyclic aromatic hydrocarbons (PAHs) were measured in artificial soil under various soil pH and water saturation conditions. Passive sampling was used for measurement of K OC with polydimethylsiloxane as sampling material. Regardless of soil pH, K OC increased with increasing soil water saturation for low molecular weight PAHs. On the contrary, K OC decreased with increasing soil water saturation for high molecular weight PAHs. Despite some fluctuations, K OC tended to decrease with increasing soil pH at all water saturations. This indicates that earlier studies on the effects of soil pH on K OC in saturated conditions could be extended to unsaturated soils. These K OC tendencies were reproduced in three different natural soils, suggesting that the effects of water saturation and soil pH might be generalized, at least for PAHs. The sorption capacity of SOM was found to be resilient under dynamic soil pH conditions. The range of sorption capacity of SOM under dynamic soil pH conditions can be used for adjusting the effects of soil pH.

Effect of Phosphogypsum Amendment on Chemical Properties of Sodic Soils at Different Incubation Periods

The application of phosphogypsum (PG) on sodic soils provides nutrients to the soil, reduces the toxic effect of Na+, and improves soil properties. Laboratory experiments were performed to evaluate the effects of PG on the chemical properties of sodic soils. The treatments were arranged in a completely randomized design with five replications. The treatments included 0% GR (control), 50% GR (28.18 g·kg−1), 100% GR (56.37 g·kg−1), 150% GR (84.50 g·kg−1), and 200% GR (112.74 g·kg−1) rates that were thoroughly mixed with soil under incubation, whereas PG was mixed with topsoil before leaching at the same application rates under the leaching experiment. Soil and leachate samples from each pot were collected in 7, 14, 21, 28, and 35 days and subjected to spectrometric analysis. Results indicated that there was a highly significant ( p < 0.001 ) effect on soil pH, exchangeable sodium percentage (ESP), available P, exchangeable Na+, and Ca+2 under 35-day incubation compared with control. In a closed incubation system, most of the nutrients were released after 7 days of incubation and inconstantly released after 14 days of incubation. Furthermore, the removal of Na+ and SAR increased in initial leachate collection and decreased with the subsequent application of irrigation water (PV). Because of the high contents of Ca+2 released from PG and the residual effect of H2SO4, soil pH and ESP were rapidly reduced compared with control. Post leachate analysis also revealed that available P and extractable S-SO4−2 were significantly ( p < 0.001 ) increased in soil solutions. However, available P was decreased during incubations compared with the value of post leachate analysis. During a closed incubation, displaced Na+ replaces Ca+2 on exchange sites, resulting in increased Ca-P precipitation. Thus, the combined application of PG and irrigation water in 7 to 14 days would allow chemical reaction with the soils and reduce sodicity problems to crop planting.

Effect of pH on the sorption of dissolved organic carbon derived from six tree species in forest soils

Dissolved organic carbon (DOC) is an important component of the total carbon (C) pool in temperate forest soils. The ability of forest soils to sorb DOC is an essential feature in the context of ecosystem changes (such as climate change) and the resulting changes in the C cycle. The aim of this study was to investigate the ability of forest soils with different pH levels to sorb DOC from litter of different forest tree species. To accomplish this, we conducted two laboratory experiments in which the soil differed in the depth from which they were sampled (topsoil vs. subsoil) and the initial DOC content. We modified the soil pH to obtain a range covering most soils in temperate forests (approximately 3.5–8). Soil samples were leached with extracts of similar DOC content obtained from the litter of six main forest-forming tree species in temperate zone. Increased DOC sorption was observed at approximate soil pH levels of 3.5 and 7.5, with the highest sorption capacity occurring at low pH. The DOC sorption capacity was decreasing with consecutive leaching with litter extract. The capacity of DOC sorption also depended on the litter species. In addition, the initial concentration of C in soil had no significant relationship with sorption capacity. Litter species were related to the sorption of released DOC, which was probably linked to the Al content in the litter. The increased DOC sorption at low pH was likely because of dissolved organic matter protonation (saturation of functional groups with H+ ions resulting in proton bridging and van der Waals forces), while Ca2+ ions causing cation bridging, flocculation or non-columbic interactions were likely responsible for the increased sorption at high pH. Our research shed light on the significant effects of soil pH on the stabilization of DOC, as well as the important role and positive influence of Al on DOC sorption by forest soils. Our findings provide new, significant insight by presenting that litter-derived DOC sorption is dependent both on soil pH and litter chemical composition.

Effects of Elemental Sulfur on Soil pH and Growth of Saskatoon Berry (Amelanchier alnifolia) and Beaked Hazelnut (Corylus cornuta) Seedlings

The land disturbed by open-pit oil sands mining must be restored to support the survival and growth of native boreal plants. Because tailings sand and sodic shale overburden are commonly used as an underlying parent substrate that is capped by boreal forest cover soils, the soil pH in reclamation sites is often higher compared with undisturbed boreal forest soil. Sulfur is a major byproduct of oil sands refining and could potentially be used as an amendment to lower the soil pH on reclamation sites. In this study, we examined the effects of soil pH and elemental sulfur on growth and physiological responses in Saskatoon berry and beaked hazelnut seedlings. We found that elemental sulfur was effective in lowering soil pH. However, addition of elemental sulfur to a forest soil of pH 5.7 lowered the soil pH to around 3, which impaired the growth and physiological performance of both plant species. The addition of 5 and 25 g kg−1 elemental sulfur to the pH 8.5 soil did not substantially improve the examined growth and physiological parameters in Saskatoon berry and beaked hazelnut seedlings. Further, excess addition of elemental sulfur in high pH soil could reduce the uptake of nitrogen, phosphorus, and calcium in Saskatoon berry. The results demonstrate that the amount of sulfur applied to the soil would need to be carefully determined for different soil types and pH levels to avoid potential toxicity effects.

Nematode diversity and community structure assessment in different vegetations of Jammu division of J & K, India

Nematodes are critical for soil processes, and changes in nematode community structure have the potential to have a significant impact on ecosystem functioning. As a result, fluctuations in nematode diversity and community structure can be used to ascertain the functional biodiversity of a soil. The aim of the present study was to evaluate the effect of different vegetation and soil pH and N on nematode structure and diversity from ten different sites (Jammu, Kathua, Samba, Udhampur, Reasi, Ramban, Rajouri, Poonch, Doda, Kishtwar) of the Jammu division. The highest absolute frequency of plant parasitic nematodes (91-100%) was observed in subtropical forests in Ramban, temperate forests in Doda, while the highest absolute frequency of bacterivorous nematodes (84-87%) was observed in crop soil in Reasi and Jammu. Soil pH had a detrimental effect on nematodes; bacteriovores were abundant at low pH, and plant parasitic at higher pH. The total nitrogen content also increased in all nematode trophic groups except omnivores. Ecological indices such as the enrichment index (EI), channel index (CI) and maturity index (MI) values indicated that crop soil with organic management is more nematode-friendly and has a better soil health status than other soil ecosystems. Nematode community structure indices may be helpful as soil monitoring tools and for assessing ecosystem sustainability and biodiversity.

Soil pH-increase strongly mitigated N2O emissions following ploughing of grass and clover swards in autumn: A winter field study

Emissions from crop residues contribute largely to the total estimated N2O emissions from agriculture. Since low soil pH increases N2O production by impairing the last denitrification step, liming has been suggested as a mitigation strategy; however, it may also increase N2O emissions by enhancing mineralization and nitrification. To gain field-based empirical knowledge, we measured N2O fluxes with an autonomous field-flux robot in limed and control plots before and after autumn ploughing of 3-year-old grass, clover grass or red clover swards under different N fertilization regimes. Dolomite applied before establishing the swards raised soil pHCaCl2 from ~4.8 to ~5.8 in limed plots.Higher pH halved emissions from ploughed leys despite higher soil mineral N contents. It also reduced emissions before ploughing. We observed substantial N2O fluxes after ploughing, with peaks during a relatively warm wet period after freezing and higher peaks during diurnal snow melt over frozen soil. Average N2O fluxes were strongly positively correlated with high herbage yields in the preceding growing seasons rather than with the presence of clover. The yield-scaled average N2O fluxes were strongest in low pH soils at all yield levels; this was a true effect of soil pH on N2O, as herbage yields were not increased by liming. Here, yield-scaled flux was defined as the average N2O flux after ploughing divided by the dry matter. Fluxes in red clover plots were similar to those in grass plots, despite the lower C/N ratio and higher total amount of N in clover residues. However, clover in mixtures with grass increased yields and N2O emissions. This suggests that higher ley production enhanced microbial activity, including nitrifiers and denitrifiers, and that the pH effect on facilitating complete denitrification to N2 overrode any effect on mineralization and nitrification, thus resulting in N2O mitigation.

Acidic amelioration of soil amendments improves soil health by impacting rhizosphere microbial assemblies

Intensive cultivation with accompanying nitrogen fertilization leads to soil acidification in croplands of southern China, which in turn, imperils soil health, restricting the sustainability of agricultural production. Application of soil amendments is considered as a potential method for maintaining soil health; however, the underlying soil-health-promoting mechanisms are poorly understood. In the present study, we used lime, organic manure, and straw biochar, or their combinations, to treat severely acidified field plots (5 previous seasons of peanut monocropping). We analyzed the rhizosphere microbial communities, soil physicochemical properties, plant disease resistance, and plant physiological parameters at pod-bearing and pod-maturing stages of peanut. The effect of soil pH, regulated by the amendments, on the root-associated microbiome was more pronounced than the effects of other physicochemical properties. Specifically, Actinobacteria and Proteobacteria became more abundant in the rhizosphere upon the application of organic materials with lime. In vitro co-cultures of rhizosphere bacterial suspensions with a fungal pathogen revealed their enhanced disease suppression ability following treatment. Physiologically, application of organic amendments with lime promoted disease-resistance of plant roots, as determined by phenylalanine ammonia lyase and superoxide dismutase activities. The optimization of bacterial community composition in the rhizosphere played a key role in enhancing plant disease resistance, as inferred by structural equation model and network analyses. These findings suggest that the application of soil amendments reinforces disease suppression and plant physiological parameters in acidified soils by impacting microbial community assembly in the rhizosphere.

Phosphorus Limitation of Trees Influences Forest Soil Fungal Diversity in China

Fungal-biogeography studies have shown global patterns of biotic interactions on microbial biogeography. However, the mechanisms underlying these patterns remain relatively unexplored. To determine the dominant factors affecting forest soil fungal diversity in China, soil and leaves from 33 mountain forest reserves were sampled, and their properties were measured. We tested three hypotheses and established the most realistic one for China. The results showed that the soil fungal diversity (Shannon index) varied unimodally with latitude. The relative abundance of ectomycorrhizae was significantly positively correlated with the leaf nitrogen/phosphorus. The effects of soil available phosphorus and pH on fungal diversity depended on the ectomycorrhizal fungi, and the fungal diversity shifted by 93% due to available phosphorus, potassium, and pH. Therefore, we concluded that latitudinal changes in temperature and the variations in interactions between different fungal guilds (ectomycorrhizal, saprotrophic, and plant pathogenic fungi) did not have a major influence. Forest soil fungal diversity was affected by soil pH, available phosphorus, and potassium, which are driven by the phosphorus limitation of trees.

Introduced earthworms (Lumbricidae) in restored and remnant tallgrass prairies of southern Ontario

Introduced earthworms alter the trajectory and composition of plant communities, for example, through their feeding, burrowing behaviour, and interactions with seeds. High densities of several earthworm species may decrease native biodiversity and disrupt restoration efforts in tallgrass prairies. This affects efforts to conserve and restore such habitat, which is of high conservation and restoration priority in eastern North America and typically restored through seeding events. To date, Lumbricus terrestris (Lumbricidae) and other species have remained largely undocumented in tallgrass prairies. We surveyed 22 tallgrass prairie sites in southern Ontario, Canada, to document earthworm density and species. Lumbricus terrestris was found at all sites. The average density was 66 ± 91 (SD) earthworms/m2 across our sampling plots, mostly juveniles (~94%). The number of all earthworms per plot significantly increased with the number of earthworm middens in each plot (χ21 = 4.50, P = 0.034). Prairies with a large number of middens had high earthworm density, but middens alone appear to explain little variation in our data (linear mixed-effects model, marginal R2 = 0.12) meaning there are other biologically important factors that affect their density. However, we found no effects of soil pH, organic matter content, or texture on the number earthworms per plot suggesting that earthworms can invade a range of tallgrass prairie soils with pH values between 5.27 and 7.67.

The effects of pH, salinity, age of leaves, post-harvest storage duration, and psyllid infestation on nutritional qualities of giant leucaena fodder

Giant leucaena (Leucaena leucocephala subsp. glabrata) can be managed as a profusely branched bushy plant by repeated harvest of its foliage for use as fodder. The objective of this research was to determine the effects of soil pH and salinity, age of the leaves, post-harvest storage duration, and psyllid infection on the nutritional qualities of leucaena fodder. To determine the effects of soil pH and salinity on fodder quality, giant leucaena K636 plants were grown in large pots containing soils adjusted to different pH and salinity levels. The effects of age of the leaves, post-harvest storage duration and psyllid infection on fodder quality were studied using leucaena samples collected from Waimanalo Research Station. Among five pH levels tested, pH 6.0 was found to produce the highest amounts of protein and structural fibers in the foliage. Mimosine contents were highest at pH 6 and 7 and lowest at pH 5.0. The growth of giant leucaena was retarded and the nutritional quality were adversely affected under salinity conditions. Compared to young leaves, old leaves contained 18.5% less protein, 95% less mimosine, 30% less tannin and 40% more structural fibers. Post-harvest storage duration up to 72 h, at room temperature did not seem to affect protein, tannin and structural fiber contents of the foliage; however, mimosine content was reduced by 25%. These results will help to identify ideal soil pH, age of foliage, and post-harvest storage duration for obtaining high forage yield and nutritional quality for giant leucaena.

The Mapping of Irrigated Paddy Fields which were Polluted by Detergent Waste in Kolam Village, Percut Sei Tuan Sub-district, Deli Serdang District

Rice is the staple food of the Indonesian people and in some places polluted by waste. This research aim was to provide a survey and map on the effects of detergent waste (phosphate available), electrical conductivity and soil pH in Kolam Village, Percut Sei Tuan Subdistrict of Deli Serdang District and analysis of sample points to P available, electrical conductivity and soil pH. This research started in September 2017 until January 2018. The method used was Grid Free and P available analysis used Bray II method, analysis of Electrical Conductivity with conductivity meter and analysis of soil pH with a pH meter. The results showed that the P available distribution consisted of very low (18%), low (52%) and moderate (30%). The distribution of soil electrical conductivity was low and the pH of the soil was acidic. Based on the analysis of sample points on P available, Electrical Conductivity and soil pH showed that the farther the distances from the irrigation pollutant channel, the availability of P decreased (0.088 ppm / meter) but did not affect the pH and electrical conductivity.