Olsen Extractable Phosphorus Research Articles

Variability modeling and mapping of soil properties for improved management in Ethiopia

AbstractManaging soils for improved agricultural production requires information on soil fertility status. Our objective was to map for better soil management in Ethiopia and determine their spatial correlation at a separation distance of 29 m. We collected 82 soil samples (0–20 cm depth) at 560 ha of land and determined pH, Olsen extractable phosphorus (Olsen‐P), and organic carbon (OC). We then interpolated between sample points (ordinary kriging‐OK and distance weighting‐IDW [inverse distance weighting]) to evaluate spatial dependence. Olsen‐P ranged from 2.68–42 mg/kg and exhibited high variability with a coefficient of variation (CV) ≥35%. Conversely, soil pH showed low variability (CV ≤ 15%) and ranging from 4.84 to 6.81. Soil OC content varied from 0.81% to 3.17%. The IDW (R2 = 0.86; RMSE = 0.019) outperformed the OK. The semivariogram results indicate a strong dependence for pH and OC for spherical, exponential, and Gaussian models, while moderately spatially auto correlated for Olsen‐P for all models. The IDW and OK predict the spatial variability of the pH (moderately acidic), Olsen‐P (low), and OC (very low) contents. The soil maps may help to improve soil management alternatives, increase crop productivity, and secure environmental quality.

Impact of sewage sludge, nanoparticles, and clay minerals addition on cucumber growth, phosphorus uptake, soil phosphorus status, and potential risk of phosphorus loss

There is little information about the impact of sewage sludge, nanoparticles, and clay minerals on cucumber ( Cucumis sativus L.) growth and phosphorus content in different plant parts. In this study we treated a soil with different rates of sewage sludge (1%, 5%, and 10%), along with two nanoparticles (SiO 2 and nano-montmorillonite at 0 and 1%), and two clay minerals (zeolite and vermiculite at 0 and 3%). We aimed at investigating the impact of these amendments on cucumber growth, phosphorus content in root, shoot, and fruit, phosphorus content in rhizosphere and non-rhizosphere soils, and determining the impact of these amendments on the potential risk of phosphorus loss from soil. Plant growth in the soil treated with sewage sludge at 1% and 5% was higher than that at 10% sewage sludge, while the cucumber in the 10% sewage sludge plus 1% nano-montmorillonite-treated soil dried out. Phosphorus content in fruit was higher than in root and phosphorus in root was higher than that in shoot. Cucumber plant in the 10% sewage sludge treated soil had the highest amount of phosphorus compared to the other treatments, while plants in the nanoparticles and clay minerals treatments had lower content of phosphorus than the control. The highest phosphorus content was extracted from soil treated with 10% sewage sludge, while the lowest was extracted from the soil treated with nanoparticles and clay minerals. In average of all treatments, soil phosphorus extracted by water-extractable phosphorus in the rhizosphere soil was higher than phosphorus in the non-rhizosphere soil. The results indicated that calcium chloride-extractable phosphorus was more effective in predicting phosphorus uptake than water-extractable phosphorus and Olsen-extractable phosphorus. Also, the soil treated with sewage sludge at 5% and 10% would potentially increase the risk of phosphorus losses. We concluded that the soil treated with 1% sewage sludge, with or without nanoparticles or clay minerals, could provide the amount of phosphorus required for the growth of cucumber, while there was no obvious potential risk of phosphorus loss, making this treatment more beneficial for cucumber. • Cucumber growth increased in soil at 1% sewage sludge; no phosphorus loss occurred. • Highest plant phosphorus was observed in soil at 10% sewage sludge. • Correlation of root P and CaCl 2 -extracted P was highest.

Evaluación de la calidad de suelo: generación e interpretación de indicadores

Las prácticas de manejo del suelo alteran sus propiedades, especialmente cuando las entradas de energía al sistema suelo-planta son menores que las salidas, o su resiliencia es incapaz de regresarlo al estado previo a la intervención. Cuando las alteraciones se acercan a los límites de tolerancia del sistema suelo aparecen factores que limitan la producción. Los cambios se pueden establecer mediante indicadores e índices de calidad. Éstos muestran la dirección del cambio con el tiempo. El objetivo de este trabajo fue evaluar la calidad de suelo actual en cuatro ejidos agrícolas de Tepeaca, Puebla, México, que tienen siglos de dedicación a la producción agrícola. Se investigó su historia, los patrones de cultivo más comunes y las clases de tierra dominantes, def inidas con la participación de los productores locales. Se analizaron propiedades físicas, químicas y biológicas de suelos sometidos a diferentes manejos y se def inieron los indicadores de calidad. Los criterios de selección para los sitios de muestreo, fueron los patrones de cultivo más frecuentes: (i) flor de corte, (ii) hortalizas continuas, y (iii) hortalizas con descanso durante temporada de ausencia de lluvias. Como referencia se tuvo los mismos suelos, pero sin manejo. Las propiedades seleccionadas como indicadores fueron pH, conductividad eléctrica materia orgánica del suelo, estabilidad de agregados en húmedo, fósforo extraíble Olsen, hierro extraíble con DTPA, densidad de lombrices. Las cuatro primeras fueron sensibles para diferenciar entre suelos sin alterar (no cultivados) y los suelos cultivados. Las cuatro últimas fueron escogidas por mostrar tasas de cambio en función de los patrones de cultivo, lo que indica la necesidad de promover estrategias de manejo agronómico. Con ellas se construyó un índice de calidad de suelo que permite establecer la dirección del cambio que experimentará la calidad del suelo al modif icar uno o más indicadores.

Evaluation of Coconut Wastes as an Amendment to Acidic Soils in Low-Input Agricultural System

The effectiveness of plantation wastes along with locally available organic materials in ameliorating acidic soil was studied by conducting an experiment with coconut husk, poultry manure, vermicompost, and compared with limestone. Application of organic amendments significantly increased the soil pH, and it was greatest in poultry manure–amended soils followed by vermicompost and coconut husk + poultry manure treatments. The relative liming efficiency was greatest for poultry manure through out the observation period of 180 days. The coconut husk alone showed the least liming effect and its liming efficiency had increased when applied in combination with poultry manure and or vermicompost. This increase in soil pH was mirrored by significant reductions in exchange acidity, exchangeable aluminum (Al3+), diethylenetriaminepentaacetic acid (DTPA)–extractable iron (Fe2+), and manganese (Mn2+) and increases in cation exchange capacity, exchangeable bases, especially calcium (Ca), and Olsen-extractable phosphorus (P) by addition of organic amendments and lime. This study indicated the potential of using coconut husk along with poultry manure for managing acidic soils in low-input agricultural systems, especially in tropical islands.

Grassland species composition and biogeochemistry in 153 sites along environmental gradients in Europe

This data set consists of vascular plant and bryophyte species composition and plant and soil biogeochemical data from 153 acid grasslands located in the Atlantic biogeographic region of Europe. Data were collected between 2002 and 2007. The grasslands all belong to the Violion caninae association and were managed by grazing or cutting but had not received fertilizer inputs. These data provide plant composition from five randomly located 2 × 2 m quadrats at each site with all vascular plants and bryophytes identified to species level with cover estimates for each species. Topsoil and subsoil were collected in each quadrat, and data are provided for pH, metal concentrations, nitrate and ammonium concentrations, total carbon and N, and Olsen extractable phosphorus. Aboveground plant tissues were collected for three species (Rhytidiadelphus squarrosus, Galium saxatile, and Agrostis capillaris), and data are provided for percentage N, carbon, and phosphorus. These data have already been used in a number of re...

Spatial variability of soil nutrients and GIS-based nutrient management in Yongji County, China

Integrated nutrient management is important for sustainable agricultural production and protecting environment quality and has been widely investigated around the world. In this article the spatial variability of soil nutrients was investigated and a regionalized nutrient management system was developed using geostatistics and geographic information system technologies. A total of 511 GPS-referenced soil samples were taken in Yongji County, Shanxi province, China, and analysed for major soil nutrients: soil total nitrogen (TN), Olsen extractable phosphorus (OLSENP) and extractable potassium (EXTK). Low concentrations of nitrogen (N) and phosphorus (P) were found and they are likely to be the main limiting nutrients for crop growth in this county. Within the county moderate spatial dependence was found for all three soil variables, but at different spatial scales. The spatial distributions of TN, OLSENP and EXTK were estimated by using kriging interpolation. The cropped areas of the county were divided into fertilizer management categories consisting of four classes of TN, three classes of OLSENP and two classes of EXTK. For the targeted crop yields, regionalized fertilization maps of N, P and K in the county were produced using geographic information system. In 3-year field verification trials in two villages the crop yields of the wheat–maize rotation system increased by 10–20%, and farmers' cash income increased by 1550–2610 RMB ha−1 year−1 where regional fertilization recommendations were implemented, in comparison with traditional farmers' practices. The regionalized maps are a practical alternative to site-specific soil nutrient management approaches in areas where it is not practical, because of small farm size or other constraints, to use intensive soil sampling and chemical analyses.

Determining the important environmental variables controlling plant species community composition in mesotrophic grasslands in Great Britain

AbstractQuestion: What is the relative importance of local site effects and selected important environmental variables in determining plant species composition? How do species respond to these environmental variables?Location: Ten mesotrophic grassland sites of high conservation value in southern England.Methods: Species cover was assessed in between 10 and 25 randomly selected 1‐m2 quadrats at each site. At each quadrat degree of waterlogging (W), soil Olsen extractable phosphorus (P) and soil pH were measured. Variation partitioning was used to separate site and soil effects, and HOF (Huisman, Olff & Fresco) modelling was used to produce response curves for the major species on soil gradients, based on coenoclines derived from partial canonical correspondence analysis (pCCA).Results: Variation partitioning identified Site as the most important environmental variable (34.6%). Only 18.7% was accounted for by the three soil variables together; W (degree of waterlogging), P and pH accounted for 11.1%, 5.7% and 4.3%, respectively in raw form with 2.4% shared. However, when Site and the other soil variables were removed the variation explained reduced to 2.3% for W, 1.1% for P and 1.0% for pH. The species responses to each of these soil environmental factors could be separated into four types on each gradient. Most species were abundant at low W, low soil P and intermediate pH.Conclusions: Site‐based factors were more important than the three soil variables, which were assumed to be directly or indirectly associated with productivity. This implies that each site has unique properties that are more important than the soil variables. The three soil factors were, however, significant and the groups of the most common species, based on significant response curves, can be used as a first approximation of indicators of environmental conditions in British mesotrophic grasslands for conservation. However, W accounted for most variation, and the current reliance on soil available P and soil pH for assessing conservation/restoration potential should be viewed with caution.

VEGETATION RESPONSES TO 35 AND 55 YEARS OF NATIVE UNGULATE GRAZING IN SHRUBSTEPPE COMMUNITIES

Ungulate populations are managed in shrubsteppe ecosystems around the world, but relatively few long-term datasets are available that test the impacts of these grazers on shrubsteppe structure and function. This study evaluated 8 exclosures in 4 shrubsteppe communities to determine the effects of deer and elk over 35 or 55 years on (1) plant biomass and species composition, (2) soil nitrogen (N) mineralization and net nitrification rates, Olsen extractable phosphorus (P), and C:N ratios, and (3) arthropod diversity and abundance. The site with deer, the highest ungulate densities, and coldest climate (Sinlahekin Wildlife Area, WA) had greater vegetative biomass and cover inside the exclosures than outside. The sites with elk, moderate ungulate densities, and intermediate climatic conditions (Oak Creek and Wenas Wildlife Areas, WA) had no effects of exclosures on vegetative biomass or cover. The site with elk, the lowest ungulate densities, and driest climatic conditions (L.T. Murray Wildlife Area, WA) had greater shrub cover outside of the exclosures. Ungulates significantly increased net N mineralization and nitrification rates, providing a potential explanation for compensatory growth by grazed plants. Our data suggest that arthropod herbivory does not substitute for ungulate herbivory. To the contrary, arthropod diversity reflected ungulate-induced changes in plant biomass. In addition to effects on standing biomass, ungulates were associated with increased exotic plant species richness at all 4 sites. Our results suggest that there may be a balance between indirect positive and direct negative effects of herbivory on plants that varies with ungulate densities and site characteristics, and that arthropod herbivory does not functionally replace ungulate herbivory.

Comparison of soil test phosphorus methods in neutral to calcareous Manitoba soils

Increasing concern for the amount of P entering lakes in Manitoba may lead to regulation of P concentration in agricultural soils. A possible means for this regulation is the use of soil test P. This may require a means of comparing soil test P analyses as various laboratories in Manitoba employ different methods of soil test P determination. Thus, the objectives of this study were to (i) compare the methods of P determination in Manitoba soils, and (ii) develop equations for converting different soil test P methods from one to another. One hundred and fifteen archived surface soil samples representing major soils of Manitoba were used for the study. Soil test P was determined in these soils using the original Kelowna (K1) method and the two modified Kelowna methods (K2 and K3). Mehlich-3, Olsen- and water extractable-P were also determined for all soils. The results were analyzed statistically and were related using a simple regression analysis model. The amount of P extracted by the different extracting agents varied widely. Mehlich-3 extracted the largest amount of P (a range of 5.4–200 mg kg-1) while water extracted the smallest amount (a range of 0.2–70 mg kg-1). The P extracted by the Olsen and the three Kelowna methods were intermediate between Mehlich-3 and water-P. Our results also showed that the three Kelowna methods were not significantly different from one another. The Olsen method compared well with those of the modified Kelowna methods, but extracted less P than the original Kelowna and Mehlich-3 methods. Overall, the different agronomic soil test P methods were well correlated to each other with correlation coefficients (r) ranging between 0.95 and 0.98. However, the correlations between these soil test methods and water extractable P was not as high. Water extractable P and the agronomic soil test P methods were better related by a non-linear relationship than by a linear relationship. The coefficient of determination (R2) for all the regression equations relating the different agronomic soil test P methods ranged from 0.91 to 0.97. As such, the equations generated in this study can be used to convert the result from one soil test P method to another. Key words: Kelowna extractable phosphorus, Mehlich-3 extractable phosphorus, Olsen extractable phosphorus, water extractable phosphorus

Characterization of soil profiles in a landscape affected by long-term tillage

Soil movement by tillage redistributes soil within the profile and throughout the landscape, resulting in soil removal from convex slope positions and soil accumulation in concave slope positions. Previous investigations of the spatial variability in surface soil properties and crop yield in a glacial till landscape in west central Minnesota indicated that wheat ( Triticum aestivum) yields were decreased in upper hillslope positions affected by high soil erosion loss. In the present study, soil cores were collected and characterized to indicate the effects of long-term intensive tillage on soil properties as a function of depth and tillage erosion. This study provides quantitative measures of the chemical and physical properties of soil profiles in a landscape subject to prolonged tillage erosion, and compares the properties of soil profiles in areas of differing rates of tillage erosion and an uncultivated hillslope. These comparisons emphasize the influence of soil translocation within the landscape by tillage on soil profile characteristics. Soil profiles in areas subject to soil loss by tillage erosion >20 Mg ha −1 year −1 were characterized by truncated profiles, a shallow depth to the C horizon (mean upper boundary 75 cm from the soil surface), a calcic subsoil and a tilled layer containing ∼19 g kg −1 of inorganic carbon. In contrast, profiles in areas of soil accumulation by tillage >10 Mg ha −1 year −1 exhibited thick sola with low inorganic carbon content (mean 3 g kg −1) and a large depth to the C horizon (usually >1.5 m below the soil surface). When compared to areas of soil accumulation, organic carbon, total nitrogen and Olsen-extractable phosphorus contents measured lower, whereas inorganic carbon content, pH and soil strength measured higher throughout the profile in eroded landscape positions because of the reduced soil organic matter content and the influence of calcic subsoil material. The mean surface soil organic carbon and total nitrogen contents in cultivated areas (regardless of erosion status) were less than half that measured in an uncultivated area, indicating that intensive tillage and cropping has significantly depleted the surface soil organic matter in this landscape. Prolonged intensive tillage and cropping at this site has effectively removed at least 20 cm of soil from the upper hillslope positions.

Phosphorus Intensity-Quantity Relationships in Soils Highly Contrasting in Phosphorus Adsorption Properties

Methods to evaluate the phosphorus (P) leaching potential of agricultural soils are of increasing importance to develop sound guidelines for P-based nutrient management strategies. Previous work showed that the dynamics of P solubility in 0.01 M CaCl2 closely resembled the dynamics of P solubility in drainage waters, with distinct change-points (concentrations of Olsen-P at which significant amounts of P begin to leach from soil to water) occurring in both conditions. In this study, we investigated the existence of a change point by evaluating the relationships between CaCl2-extractable P and Olsen-P test values in soils collected from two sites selected to have a similar wide range of soil extractable P (Olsen-P concentration was in the range of 4–171 mg P kg−1 for both soil groups), but very contrasting P adsorption properties (the P sorption index, a P sorption capacity related soil parameter, ranged from 335 to 669 mg P kg−1 in one group of soils, and from 1124 to 1482 mg P kg−1 in the other one). A close linear correlation between CaCl2-P and Olsen-P was verified in samples from both the sites studied. However, a change point of 88 mg kg−1 Olsen-P was evident for less P sorbing soils, whereas no change point could be determined in soils with the highest P retention, probably because the latter group of soils were not sufficiently saturated with P, even if having high content of Olsen extractable phosphorus.

Plant species richness, functional type and soil properties of grasslands and allied vegetation in English Environmentally Sensitive Areas

AbstractTo facilitate the maintenance and restoration of semi‐natural grasslands, it is important to understand their relationships with soil properties. Semi‐natural grasslands typically have a high incidence of stress‐tolerant species (measured here by high stress radius values), but not all have high species richness. Species richness and stress radius values were related to soil pH, Olsen extractable phosphorus (P), extractable potassium (K) and magnesium (Mg), total nitrogen (N) and organic matter (OM) at 571 sites representing a wide range oftemperate grasslands. Highest species richness (>30 m−2) occurred at pH > 6 and 4–15 mg l−1 P, but species richness was also highly variable at 4–15 mg l−1 P. At pH < 5, species richness was low (<20 m−2). Stress radius values were highest (mainly calcareous and heath grasslands and mires) at pH c. 8·0 and < 5·0, and at the lowest soil P levels (<5 mg l−1). A wide range of stress radius values occurred at low soil P levels because appropriate management is also needed to maintain semi‐natural grasslands. Reducing soil P is difficult in practice, so grassland restoration in the presence of elevated soil‐extractable P levels merits re‐assessment.

Forests of the ultramafic mount Giting-Giting, Sibuyan Island, the Philippines

Mount Giting-Giting is an ultramafic mountain on Sibuyan Island, Romblon Province, Republic of the Philippines. It was studied along the Mayo's Peak Ridge which had rainforest from about 200m up to c. 1550m. The grassland and scrub vegetation from 1550m to the summit (2050m) of Giting-Giting was not explored. The mean annual rainfall at the base of the mountain was c.2100mm which included a dry season around February and March. There was a notable increase in wind speed with altitude and there was about one hurricane (called a cyclone in the Philippines) per year. Analyses showed that the soils are acid ( 4.4–5.5), and have relatively low concentrations of Olsen extractable phosphorus (0.22–2.07μg g−1), low exchangeable potassium (0.04–0.41mEq 100g−1), and relatively low (for ultramafic soils) Mg/Ca quotients (0.31–2.87) and exchangeable nickel (1.0-23.8μg g−1). Coupled plots (of 0.25 or 0.04ha) were studied at altitudes from 325m to 1540m. All trees ≥ 10cm dbh were enumerated and structural features of the trees and smaller plants were quantified. The forests were all of fairly small stature (maximum tree height 24m) but dense (up to 2180 trees ha−1 in Lower Montane Forest (LMF) and up to 880 ha−1 in Upper Montane Forest (UMF)). While different taxa could be readily recognized, specific determinations were often impossible from the mainly sterile specimens. The LMF was species rich with up to at least 111 species of tree (≥ 10cm dbh) per 0.25-ha plot. There was no family clearly dominant in the two lower plots at 325m and 385m (where the Dipterocarpaceae were probably reduced by logging). At 770m and 860m the Dipterocarpaceae accounted for 12.9% and 14.7% of the basal area respectively. There was a surprisingly high representation of the Sapotaceae (25.9% of the basal area) at 1240m. At 1540m, the Araucariaceae (Agathis sp.) dominated one plot (37.1% of the basal area) and the Myrtaceae the other (72.4%).

The interpretation of Olsen extractable P values in relation to recommendations for the fertilizer requirements of crops

A greenhouse experiment, with Okra (Abelmoschus esculentus L.) as the test crop, was conducted on twenty-one soils ranging in Olsen's extractable phosphorus from 1.8 to 15.5µg Pg−1 soil. The experiment was conducted at Punjab Agricultural University, Ludhiana, India. The soils were nonsaline with pH ranging from 7.7 to 8.6. A critical level of 2.55µg Pg−1 soil was predicted by Cate and Nelson's (1971) statistical procedure. Because of a wide range in relative yields, this value did not accurately predict response to applied P. An approach to compute minimum response to applied fertilizer, which is likely to be obtained at a particular Olsen P level, has been presented. It involves calculation of lower 60 percent confidence limits for relative yield and fitting loge-linear regression to the transformed data. The regression was tested on a published data set and was found to hold well.

DYNAMICS OF PHOSPHORUS DURING RECLAMATION OF SODIC SOILS

This study describes the phosphorus status of sodic soils formed under the influence of sodium carbonate, aquic natrustalf, and its possible leaching during their reclamation. Uncultivated, barren sodic soils contained high amounts of Olsen's extractable phosphorus, which decreased with depth, and the amounts were highly correlated with the electrical conductivity of the soil. The incubation studies conducted at saturated moisture content with differential amounts of gypsum at 0, 25, 50, 100, and 200 percent of laboratory-determined gypsum requirement (GR) showed that Olsen's P decreased with increases in the rate of gypsum applied. The leaching studies conducted in the field showed that phosphorus in sodic soils moved down, along with other soluble salts, though the peak P concentration lagged behind the other salts. Leaching studies conducted in plexiglass columns in the laboratory brought out that substantial leaching of P, up to 60 ppm P, could occur when sodic soils are leached as such or after surface application of gypsum. It seems that under natural conditions, Na2CO3, which is the predominant salt in sodic soils, reacts with native calcium phosphate to form highly soluble sodium phosphates, which are leached during reclamation. Gypsum, mixed with soil at a rate of 100 percent GR and above, decreases the leaching of phosphorus. It seems due to (1) immobilization of soluble P by CaSO4 through the formation of less soluble Ca-P compounds; (2) common ion effect to decrease solubility of Ca-P compound; and (3) lowering of soil pH, which in turn decreases the soluble P in the pH range of 8.3 to 10.