An evaluation of methods for characterizing phosphate sorption in rice soils

Abstract

Two single value methods of indexing P sorption were compared to parameters derived from P adsorption isotherms in a range of waterlogged and dry rice soils. These measures of P sorption capacity correlated closely with one another. However, they did not correlate equally with several other soil properties (pH, extractable Fe and Al). Because relationships between P sorption and soil properties proved to be method dependent, results from different methods must be compared with caution.

It is suggested that the single value method of Bache and Williams² be adopted when the rapid analyses of many samples is required. It is suited to routine analysis of soils with markedly different P sorption capacities, from both waterlogged and dry conditions.

Close correlations between the single value methods and P sorbed at a standard supernatant concentration suggest they may be useful in testing soils for P fertilizer requirements.     

Relationship of soil properties to p‐fixing capacity of soils in northern Idaho

Abstract

Phosphorus sorption studies were conducted on volcanic ash influenced surface horizons of 29 northern Idaho soils. Results show that the amount of P sorbed was significantly correlated with citrate‐dithionite extractable aluminum (r = .64**), but not with Fe. Other significantly correlated soil properties were: percent base saturation (r = ‐.73**), percent clay (r = .42**), and exchangeable acidity (r = .39*).     

Prediction of phosphorus requirements of Desmodium intortum cv. greenleaf using a phosphorus sorption index and extractable phosphorus

Abstract

The rates of applied phosphorus required for 90% maximum yield of Desmodiim intortum cv. Greenleaf were calculated from pot experiments using 24 fertilized and unfertilized soils from the Atherton Tableland, Queensland, Australia.

Phosphorus required was highly correlated (r² = 0.94) with the phosphorus sorbed (P sorbed) by the soils at a supernatant solution P concentration of 0.08 ppm. P sorbed was found to be a function of phosphorus buffer capacity at 0.08 ppm ("PBC") and phosphorus extractable by acid (0.005 M H₂S0₄) or bicarbonate (0.5 M NaHCO₃). PBC was highly correlated (r² = O.84) with a phosphorus sorption index ("PSI") derived from one addition of 500 μg P g^‐1 soil.

Combining PSI with acid or bicarbonate extractable P in a multiple regression equation allowed the estimation of phosphorus required with multiple correlation coefficients of R² = 0.80 and R² = 0.83 respectively.     

Fractionation of phosphorus in soils with different geological and soil physicochemical properties in southern Tanzania

ABSTRACT

Soil phosphorus (P) forms have been practically defined as chemically fractionated pools. A knowledge of the abundance and diversity of P forms in soil, and the factors affecting them, will lead to better soil management. However, little is known about the differences in P forms among soils with different geological properties in tropical Africa. The aim of this study was to investigate the P forms in soils with different physicochemical properties formed under different geological conditions in southern Tanzania and to identify the factors affecting the P forms in these soils. In total, 37 surface soil samples were collected from three geological groups; the plutonic (mainly granite) rock (PL) group, the sedimentary and metamorphic rock (SM) group, and the volcanic ash (V) group. Soil P was sequentially extracted by NH₄Cl, NH₄F, NaHCO₃, NaOH + NaCl, and HCl, and inorganic (P_i) and organic P (P_o) in each fraction were determined. The lowest total P was in the PL group (average, 360 mg P kg^-1) because of the high sand content. Iron (Fe)-P (NaOH-P_i) was the major form in this group, accounting for 8.4% of total P. In the SM group (average total P, 860 mg P kg^-1), Fe-P was the major form in most, accounting for 7.8% of total P. Soils in the SM group occasionally had high calcium (Ca)-P due to application of chemical fertilizer at the collection site. The V group had the highest total P (average, 1600 mg P kg^-1) and its major P form was Ca-P, which was possibly derived from primary minerals (i.e., apatite), accounting for 14% of total P. In addition, the high oxalate-extractable Al possibly caused the accumulation of Al-P in the V group. Oxalate-extractable Fe generally increased with increasing Fe-P_i, while oxalate-extractable Al increased with increasing organic P and Al-P_i in soils in all three geological groups. These results demonstrate that the soil P forms differ greatly among sites in southern Tanzania with different geological conditions and associated soil properties.     

Proposal for advanced classification of brown forest soils in Japan with reference to the degree of volcanic ash additions

Abstract

The advanced classification of brown forest soils (BFS) is based on the specific properties of these soils, including the acid ammonium oxalate extractable aluminum (Al_ox) and lithic fragment contents, as well as their vertical distributions in the soil profile. In the present study, these properties were used to classify BFS, resulting in four types: (1) H-Al_ox-NGv BFS, (2) H-Al_ox-Gv BFS, (3) M-Al_ox BFS, (4) L-Al_ox BFS. H-Al_ox-NGv BFS is derived from volcanic ash characterized by a high Al_ox content and no lithic fragment, whereas L-Al_ox BFS is derived from weathered bedrock and has a low Al_ox content. H-Al_ox-Gv BFS and M-Al_ox BFS are derived from mixtures of volcanic ash and weathered bedrock. H-Al_ox-Gv BFS is characterized by high Al_ox content and many lithic fragments, whereas M-Al_ox BFS has moderate Al_ox content. H-Al_ox-NGv BFS and black soils (BLS) develop from accumulated volcanic ash, as indicated by declining Al_ox and clay content with decreasing depth in the surface horizons, as a result of successive additions of less-weathered volcanic ash to the soil surface.     

Phosphorus Forms in Overland Flow from Agricultural Soils Representative of Mediterranean Areas

Abstract

Phosphorus (P) losses through overland flow (surface runoff) may contribute to eutrophication of water bodies. The main purpose of this work was to study P forms in overland flow (dissolved and particulate) to identify which can be potentially used by algae. To this end, rainfall on 17 representative soils from Mediterranean areas was simulated, and P forms in overland flow studied by chemical and sink (resin, iron oxide–impregnated paper strip) extraction; sequential chemical fractionation of the suspended sediments was also used to establish “operational pools” with a differential capacity of P release. Total P (TP) in runoff ranged from 0.089 to 0.765 mg L^?1 and was mainly related to suspended sediment (particulate P, 86% of TP on average). Iron oxide strip P, which is taken to be an estimate of algal‐available P, accounted for 34% of TP on average in runoff samples; most of the P extracted by this sink was particulate P (68%). In most cases, FeO strip P was equivalent to dissolved reactive P (DRP) plus P extracted by NaOH and citrate‐bicarbonate in suspended sediment (the more labile P fractions) (Y=X, R²=0.82; P<0.001; n=15). One can thus assume that Fe oxide extracts DRP, adsorbed P on sediments, and P related to highly soluble precipitated Ca phosphates, but it does not extract releasable P through reduction of sorbent surfaces or the organic P that can be mineralized in the bottom of water reservoirs, which must be taken in account to estimate the long‐term algal‐available P in runoff.     

Developing an Environmental Manure Test for the Phosphorus Index

Abstract

Widespread implementation of the phosphorus (P) index has focused attention on environmental manure tests that can be used to estimate the relative availability of P in manure to runoff water. This article describes the development and use of a water extractable P (WEP) test to assess the capacity of land‐applied manure to enrich P in runoff water. WEP of surface‐applied manure has been shown to be strongly correlated to dissolved P concentrations in runoff from agricultural soils. WEP tests that have a defined water‐to‐manure‐solids ratio and involve extraction times of 30 to 120 min provide the best prediction of dissolved P in runoff across a wide range of manures. Consistent measurement of manure WEP can be achieved with manure sample storage times of up to 22 days (4°C), acidified extract holding times of 18 days, and solid separation by either centrifugation or paper filtration. Reproducibility of WEP tests is comparable to that of other common manure tests (e.g., total P), as verified by within‐laboratory and inter laboratory evaluations. A survey of 140 livestock manures revealed significant differences in mean WEP among different livestock manures, with swine greater than poultry (turkey, broiler and layer chickens) and dairy cattle greater than beef cattle. Such results support the use of WEP‐based coefficients to modify the source component of the P index.     

Relation between soil P test values and mobilization of dissolved and particulate P from the plough layer of typical Danish soils from a long‐term field experiment with applied P fertilizers

Accumulation of phosphorus (P) in agricultural topsoils can contribute to leaching of P which may cause eutrophication of surface waters. An understanding of P mobilization processes in the plough layer is needed to improve agricultural management strategies. We compare leaching of total dissolved and particulate P through the plough layer of a typical Danish sandy loam soil subjected to three different P fertilizer regimes in a long‐term field experiment established in 1975. The leaching experiment used intact soil columns (20 cm diameter, 20 cm high) during unsaturated conditions. The three soils had small to moderate labile P contents, expressed by water‐extractable P (3.6–10.7 mg/kg), Olsen P (11–28 mg/kg) and degree of P saturation (DPS) (25–34%). Mobilization of total dissolved P (TDP) increased significantly (P < 0.05) from the intact soil columns with increasing labile P, whereas the increase in particulate P (PP) with increasing labile P content was modest and statistically insignificant. We found concentrations up to 1.5 mg TP/L for the plough layer of this typical Danish sandy loam soil. This highlights that even a moderate labile P content can be a potential source of TDP from the plough layer, and that a lower concentration margin of optimum agronomic P levels should be considered.     

Varietal traits limiting the grain yield of tropical maize III. Significance of tillers for productivity

Four highland tillering varieties were grown on a high plateau in Mexico with three plant densities to examine the contribution of tillers to the grain yield and the following results were obtained:

1) At low densities tillers were as efficient as the main culm in grain production, and grain yield attributed to the tillers was nearly 50 per cent of the total grain yield. However, at high densities tillers were less effective. The contribution of tillers to the total yield was only a few per cent.

2) The proposition was discussed that tillering ability was an important character for obtaining a reasonably high yield at low densities, but was not an important character in seeking a maximum grain yield with a high plant density.     

福建三个垂直带谱中土壤氧化铁的研究

应用穆斯堡尔谱分析、化学分析和光学显微镜分析，对福建三条最有代表性的土壤垂直带谱中的粗粒及粘粒氧化铁矿物进行研究。结果表明，赤铁矿从黄壤－黄红壤－红壤－赤红壤逐渐增多而针铁矿逐步减少，粗粒原生矿物组合类型从复杂趋向简单。铁的游离度及晶胶比从黄壤－黄红壤－红壤逐渐升高而活化度逐渐下降，但赤红壤例外，这可能与其成土年龄有关。本文还讨论了土壤分类的有关问题。     

Volcanic ash additions control soil carbon accumulation in brown forest soils in Japan

Abstract

The objective of the present study was to clarify the influence of volcanic ash addition on soil carbon stocks and the carbon accumulation process in brown forest soils (BFS) in Japan. The degree of volcanic ash addition to the soil was estimated according to the acid ammonium oxalate extractable aluminum (Al_ox) and lithic fragment contents, and their vertical distribution patterns. The BFS was classified in order of increasing volcanic ash influence on the soil into the following types: high Al_ox content with no gravel (H-Al_ox-NGv), high Al_ox with a high gravel content (H-Al_ox-Gv), moderate Al_ox (M-Al_ox), and low Al_ox (L-Al_ox), and then analyzed for carbon content, carbon amount, carbon stock, Al_ox amount and pyrophosphate extractable aluminum (Al_py) amount. The correlation between the carbon and Al_py amounts and the relationship between the Al_py and Al_ox amounts in the BFS samples indicated that the amount of carbon is determined by Al—humus complex formation, which is defined by the active Al generated from additional volcanic ash in BFS soil samples of BFS. Therefore, soils with thicker horizons and greater amounts of Al_ox had higher carbon levels in deeper horizons. For this reason, soil carbon stocks at depths of 0–30 cm and 0–100 cm, and in the effective soil depth of BFS, were larger and followed the order H-Al_ox-NGv = H-Al_ox-Gv > M-Al_ox > L-Al_ox. Furthermore, successive accumulations of volcanic ash on the soil surface promoted soil carbon accumulation as a result of the development of the surface horizon in H-Al_ox-NGv BFS. Our results suggest that volcanic ash additions control the soil carbon accumulation of forest soil in Japan.     

Sorption isotherms for predicting potassium requirements of some Iowa soils

Abstract

The sorption isotherm technique was used in predicting potassium requirements of some Iowa soils for growing tomatoes, potatoes, celery and beans. Based on previous comparisons, all of these soils would require additional amounts of K for optimum yields of celery, potatoes, tomatoes and beans. According to Woodruff's energy of exchange concept of K availability, all the soils used in this study are potassium deficient. Amounts of K needed to maintain a specific level of K in sorption equilibrium solution appeared to be largely a function of physicochemical characteristics of the soil. Predicted K requirements of these soils for optimum yields of these crops are reported.     

Short‐Term Effect of Lime,Phosphorus, and Iron Amendments on Water‐Extractable Lead and Arsenic in Orchard Soils

Abstract

Lead arsenate was extensively used to control insects in apple and plum orchards in the 1900s. Continuous use of lead arsenate resulted in elevated soil levels of lead (Pb) and arsenic (As). There are concerns that As and Pb will become solubilized upon a change in land use. In situ chemical stabilization practices, such as the use of phosphate‐phosphorus (P), have been investigated as a possible method for reducing the solubility, mobility, and potential toxicity of Pb and As in these soils. The objective of this study was to determine the effectiveness of calcium carbonate (lime), P, and iron (Fe) amendments in reducing the solubility of As and Pb in lead‐arsenate‐treated soils over time. Under controlled conditions, two orchard soils, Thurmont loam (Hapludults) and Burch loam (Haploxerolls), were amended with reagent‐grade calcium carbonate (CaCO₃), iron hydroxide [Fe(OH)₃], and potassium phosphate (KH₂PO₄) and incubated for 16 weeks at 26°C. The experimental results suggested that the inorganic P increased competitive sorption between H₂PO₄ ^? and dihydrogen arsenate (H₂AsO₄ ^?), resulting in greater desorption of As in both Thurmont and Burch soils. Therefore, addition of lime, potassium phosphate, and Fe to lead‐arsenate‐contaminated soils could increase the risk of loss of soluble As and Pb from surface soil and potentially increase these metal species in runoff and movement to groundwater.     

Aluminum concentrations in sclerotia from a buried humic horizon of volcanic ash soils in Mt. Myoko,Central Japan

The morphology and chemical composition of fungal sclerotium-like grains collected from the buried humic horizon of volcanic ash soil in Mt. Myoko were examined using a scanning electron microscope (SEM), energy dispersion xray micro-analyzer (EDX), and electron probe micro-analyzer (EPMA). A high C content, low level of Si and high concentration of Al characterized the grains considered to correspond to the sclerotia of Cenoccocum graniforme. The ²⁷Al MAS NMR spectrum of the sclerotia showed the existence of 6- and 4-coordinated Al. X-ray diffraction analyses supported the presence of amorphous Al (ex. Al-humus complex) in the sclerotia.     

An evaluation of Colwell‐P as a measure of plant‐available phosphorus in soils of volcanic and non‐volcanic origins in the highlands of Papua New Guinea

Various soil test methods including Olsen, Colwell, Bray and Truog have been used to assess the levels of plant‐available P (PAP) in soils situated in the highlands of Papua New Guinea (PNG). Up until now, though, there has been no guarantee that these tests provide valid assessments of PAP in these somewhat atypical organic matter‐rich tropical soils. Furthermore, the critical soil‐P concentrations associated with the tests have been based on studies conducted elsewhere in sub‐tropical and temperate latitudes and as such may or may not be valid for soils or cropping situations in PNG. Soil (Colwell)‐P and leaf‐P data collected during a recent survey of sweet potato gardens in the highlands of PNG were therefore used to determine if useful relationships existed between these variables for different groups of soils, and if they do, to use these relationships to evaluate critical soil Colwell‐P concentrations corresponding to a known critical concentration of P in sweet potato index leaf tissue. Separate, highly significant linear relationships were obtained between leaf‐P and Colwell‐P for soils of volcanic and non‐volcanic origins. Based on these relationships, the critical Colwell‐P concentration for volcanic soils was found to be four times greater than that for non‐volcanic soils, presumably because much of the P extracted from the former soils with alkaline sodium bicarbonate had been chemically ‘fixed’ via sorption and precipitation reactions with sesquioxides and rendered unavailable to plants at ambient soil pH. These critical Colwell‐P concentrations if adopted as benchmark values for the soil groups in question should ensure that the results of future soil fertility surveys involving Colwell‐P assessments are correctly interpreted.     

Comparative Evaluation of Inductively Coupled Plasma–Optical Emission Spectroscopy and Atomic Absorption Spectrophotometry for Determining DTPA-Extractable Micronutrients in Soils

A study was conducted for comparative evaluation of atomic absorption spectrophotometry (AAS) and inductively coupled plasma–optical emission spectroscopy (ICP-OES) for determining extractable zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe) in sixty diverse soil samples having a wide range in pH and organic carbon (C). The results were significantly affected by the method of analysis and soil type but generally did not follow a definite trend. Results for extractable Fe in Alfisol samples were significantly greater when using ICP-OES than AAS; and the results for Zn, Cu, and Mn were not significantly different for the two methods. For Vertisol samples, the results for extractable Cu were significantly greater by ICP-OES than by AAS, whereas extractable Fe and Zn were significantly greater by AAS than by ICP-OES, and the results for Mn were not significantly different for the two methods. The results are discussed relative to soil type and differences in soil organic carbon and pH of the samples used in the study.     

Predicting environmental soil phosphorus limits for dissolved reactive phosphorus loss

The dependence of runoff dissolved reactive phosphorus (DRP) loss on soil test P or rapid estimations of degree of P saturation (DPS) often varies with soil types. It is not clear whether the soil‐specific nature of runoff DRP versus DPS is due to the different sorption characteristics of individual soils or the inability of these rapid DPS estimates to accurately reflect the actual soil P saturation status. This study aimed to assess environmental measures of soil P that could serve as reliable predictors of runoff DRP concentration by using soils collected from Ontario, Canada, that cover a range of chemical and physical properties. A P sorption study was conducted using the Langmuir equation  to describe amount of P sorbed or desorbed by the soil (Q_s, mg/kg) versus equilibrium P concentration (C, mg/L) in solution, where Q_max is P sorption maximum (mg/kg), k represents P sorption strength (L/mg), and Q₀ (mg/kg) is the P sorbed to soil prior to analysis. Runoff DRP concentration increased linearly with increasing DPS_sorp (i.e. the ratio of (Q₀ + Q_D)/Q_max) following a common slope value amongst soil types, while the P buffering capacity (PBC₀) at C = C₀ yielded a common change point, below which runoff DRP concentration decreased greatly with increasing PBC₀ compared to that above the change point, where C₀ and Q_D represent the equilibrium P concentration and amount of P desorbed, respectively. Both DPS_sorp and PBC₀ showed great promises as indicators of runoff DRP concentration.     

Soil organic matter fractionation as a tool for predicting nitrogen mineralization in silty arable soils

After decades of searching for a practical method to estimate the N mineralization capacity of soil, there is still no consistent methodology. Indeed it is important to have practical methods to estimate soil nitrogen release for plant uptake and that should be appropriate, less time consuming, and cost effective for farmers. We fractionated soil organic matter (SOM) to assess different fractions of SOM as predictors for net N mineralization measured from repacked (disturbed) and intact (undisturbed) soil cores in 14 weeks of laboratory incubations. A soil set consisting of surface soil from 18 cereal and root‐cropped arable fields was physically fractionated into coarse and fine free particulate OM (coarse fPOM and fine fPOM), intra‐microaggregate particulate OM (iPOM) and silt and clay sized OM. The silt and clay sized OM was further chemically fractionated by oxidation with 6% NaOCl to isolate an oxidation‐resistant OM fraction, followed by extraction of mineral bound OM with 10% HF (HF‐res OM). Stepwise multiple linear regression yielded a significant relationship between the annual N mineralization (kg N/ha) from undisturbed soil and coarse fPOM N (kg N/ha), silt and clay N (kg N/ha) and its C:N ratio (R² = 0.80; P < 0.01). The relative annual N mineralization (% of soil N) from disturbed soils was related to coarse fPOM N, HF‐res OC (% of soil organic carbon) and its C:N ratio (R² = 0.83; P < 0.01). Physical fractions of SOM were thus found to be the most useful predictors for estimating the annual N mineralization rate of undisturbed soils. However, the bioavailability of physical fractions was changed due to the disturbance of soil. For disturbed soils, a presumed stable chemical SOM fraction was found to be a relevant predictor indicating that this fraction still contains bio‐available N. The latter prompted a revision in our reasoning behind selective oxidation and extraction as tools for characterizing soil organic N quality with respect to N availability. Nonetheless, the present study also underscores the potential of a combined physical and chemical fractionation procedure for isolating and quantifying N fractions which preferentially contribute to bulk soil N mineralization. The N content or C:N ratio of such fractions may be used to predict N mineralization in arable soils.     

玉米鲜样氮磷联合诊断方法和测定部位研究

采用“3414” 氮磷二元二次肥料试验方案设计田间小区试验,应用便携式高强度光度计对玉米鲜样第三、第六位叶肉和叶鞘硝态氮、铵态氮及可提取磷进行田间现场快速联合测定。结果表明,同一叶位叶肉与叶鞘之间硝态氮、铵态氮及可提取磷含量差异很大,经 t 检验,差异均达极显著水平。不同叶位相同部分氮、磷元素含量也有一定差异,经 t 检验,第三位与第六位叶肉硝态氮、铵态氮和叶鞘铵态氮的含量差异不显著,而叶肉和叶鞘可提取磷、叶鞘硝态氮的含量差异均达极显著水平;不同叶位各部分对应的硝态氮、铵态氮与施氮量和全氮呈正相关;可提取磷与施磷量和全磷也呈正相关关系,且第三位叶鞘相关性最好,均达极显著水平,该部位具有作为氮、磷营养状况诊断部位的可能性。硝态氮从反映土壤氮素水平和试剂成本上比铵态氮更适合作为诊断玉米植株氮营养状况的指标。     

土壤磷向地表径流迁移的提取系数研究

农田土壤磷随降雨径流进入地表水体是水环境富营养化的主要污染源。通过天然降雨径流小区,动态监测溶解态磷在降雨径流-土壤系统中的迁移,研究坡耕地表层土壤水浸提磷(WEP)和降雨径流溶解态磷(DTP)之间的关系。应用SPSS统计软件线性回归土壤WEP和径流DTP关系,拟合方程,y=0.281x-0.179(R=0.943)。方程斜率表示降雨径流溶解态总磷浓度对土壤不稳定磷浓度的提取系数。经最小二乘法线性回归检验,该模型拟合优度较高,整体性显著。土壤磷提取系数方程可实现磷素从农业营养元素向水环境污染因子内涵的转换,为农业非点源污染防治和水环境保护规划提供了一种估算农业非点源磷素污染潜在负荷的简单有效工具。