1M NH4OAc Research Articles

Estimation of plant available potassium in loamy soils by extraction with magnesium sulfate solution

The aim of the study. To find a method to estimate plant available potassium for soil testing that does not require expensive flame photometry or atomic absorption spectrometry. Location and time of the study. Southern parts of West and Central Siberia, 2016-2019. Methodology. Comparison the potassium pool, extractable by 0,1M MgSO4 solution, with exchangeable potassium, extractable by 1M NH4OAc solution (according to GOST 26210-91) by regression analysis of the contents in 100 soil samples of arable soils (Luvic, Haplic and Calcic Chernozems, and Luvic Phaeozems) with different granulometric composition. Results. Exchangeable potassium showed the best correlation with the uptake of the element by plants and with yield in a variety of soil and climatic conditions. It was found that the relationship between potassium availability indices KAIAc (potassium extracted by 1M NH4OAc) and KAIMg (potassium extracted by 0,.1M MgSO4) was satisfactorily described (R2 = 0.88) by a simple linear function for soils with texture classes from sandy loam to sandy/silty clay and well described (R2 = 0.92) by a power function for silt loam, clay loam and sandy/silty clay. In 81% of the soils surveyed the difference between the calculated (according to the power equation) and actual KAIAc values was no more than 20%, and for 97% of the studied soils it did not exceed 30%. The cost of analytical equipment required for potassium analysis for soil testing is 7-60 times lower for KAIMg determination as compared with KAIAc. Conclusions. The KAIMg potassium availability index can be used alongside the standard KAIAc availability index for soils with soil texture classes from silt loam to sandy/silty clay. Conversion of KAIMg into KAIAc can be made by the following formula: KAIAc = 8,.108 • KAIMg0,793.

Assessment of Soil Zn Availability for Khao Dok Mali 105 Rice: a Case study in Thailand

Khao Dok Mali (KDML) 105 rice is one of the most popular fragrant rice in the world with very high demand in world market. There have been a number of studies on nutrient management, mainly focusing on major plant nutrients. There is none of zinc (Zn) with this rice, thus; a research on the effects of Zn on KDML 105 rice was undertaken in different soils using pot experiment in greenhouse, objectively to obtain preliminary results that can be further examined in the field. Comparisons were examined to assess the reliability of 9 chemical methods of Mehlich 1, Mehlich 3, 0.1M HCl, 1M NH4OAc at pH 4.8, 1M NH4OAc pH 7.0., AB-DTPA, DTPA, 1M MgCl2 and 0.01M CaCl2 for evaluating the availability of Zn in soils to KDML 105 rice and for calculating rates of Zn fertilizer for rice. KDML 105 rice showed a slightly negative response to Zn applied at the rate of 3–42 mg/kg, despite the soils having different Zn contents. Extractable Zn derived from all extractants had a positive correlation with water-soluble- and exchangeable Zn (r= 0.54*–0.92**) indicating that these solutions dissolved Zn were mostly in water-soluble and exchangeable forms. The indices from all extractant methods, except DTPA and Mehlich, were identically suitable for the assessment of soil Zn availability for growing rice (r= 0.57*–0.70**), with the NH4OAc pH 4.8 showing a slight superiority over the method. The equations for calculating Zn fertilizer for rice from these chemical soil Zn analyses gave a highly significant correlation between the actual yields and the predicted yields (r2 = 0.84**–0.95**). The equation of use NH4OAc pH 4.8 of log (100-y)=2-1.370b-0.042x; when y was yield estimated from the rate of Zn fertilizer applied (x) and Zn content in soil (b), was the most reliable, having 95% accuracy for rice yield assessment.

The influence of soil age and regional climate on clay mineralogy and cation exchange capacity of moist tropical soils: A case study from Late Quaternary chronosequences in Costa Rica

Tropical soils exhibit large differences across landscapes in many attributes, notably clay mineralogy (2:1 vs. 1:1 clays), bulk geochemistry (Ca, Al), pH, cation exchange capacity (CEC), organic matter and soil texture. In order to examine the factors controlling these variables, a series of three chronosequences (≤120ka) of tropical soils on uplifted terraces along the Pacific coast of Costa Rica were studied. The three study locations differ mainly as a function of soil moisture and leaching, with conditions ranging from 2700mm/yr mean annual precipitation (MAP) on the southern Nicoya Peninsula (4-month dry season), to 3200mm/yr in the Esterillos region (3-month dry season), and 4250mm/yr on the Osa Peninsula (no dry season). Analytical methods include X-ray diffraction (XRD), transmission-analytical electron microscopy (TEM-AEM), inductively coupled plasma optical emission and mass spectrometry (ICP-OES, ICP-MS), ammonium acetate extraction (1M NH4OAc, pH=7, for CEC) and C:N analysis.Soil weathering reactions and related decrease in CEC occur three-to-four times faster in a sequence of Inceptisol-to-Oxisol soils in the wettest climate (Osa) compared to the less-moist Esterillos area; in the even drier monsoon climate soils (Nicoya), this evolved, low-CEC (<10cmolc/kg) state does not occur, even after 120ka of soil formation, and rate of compositional alteration is approximately five to ten times slower than at Osa. The dominant exchangeable cation at all sites is Ca. Interlayer K and Al increase relative to Ca over time, resulting in interstratified K-S with smectite layers that become progressively more vermiculite-like and illite-like.The age-related evolution of tropical soils appears to be a predictable sequence in lowland tropical landscapes where periodic tectonism, erosion or volcanism produces unweathered parent material at the land surface. Empirical data from this project enables the extrapolation of simple equations applicable to tropical volcanic arc landscapes where presence of uplifted marine terrace soils facilitates determination of soil age. The two variables controlling soil composition can be combined into an effective age (ageeff) that takes into account soil age and weathering intensity (factoring in MAP and wet-dry months from climate data), and equations are of the form, e.g. ECEC=−18.1∗ln(ageeff)+77, with R2 values of 0.75 to 0.87. Greatest scatter occurs in the youngest soils. Given the apparent prevalence of this sequence and the systematic nature of its reaction progression, these results could be useful for modeling tropical soils.

Structural Characterization of a Thrombin-Aptamer Complex by High Resolution Native Top-Down Mass Spectrometry.

Native mass spectrometry (MS) with electrospray ionization (ESI) has evolved as an invaluable tool for the characterization of intact native proteins and non-covalently bound protein complexes. Here we report the structural characterization by high resolution native top-down MS of human thrombin and its complex with the Bock thrombin binding aptamer (TBA), a 15-nucleotide DNA with high specificity and affinity for thrombin. Accurate mass measurements revealed that the predominant form of native human α-thrombin contains a glycosylation mass of 2205Da, corresponding to a sialylated symmetric biantennary oligosaccharide structure without fucosylation. Native MS showed that thrombin and TBA predominantly form a 1:1 complex under near physiological conditions (pH6.8, 200mM NH4OAc), but the binding stoichiometry is influenced by the solution ionic strength. In 20mM ammonium acetate solution, up to two TBAs were bound to thrombin, whereas increasing the solution ionic strength destabilized the thrombin-TBA complex and 1M NH4OAc nearly completely dissociated the complex. This observation is consistent with the mediation of thrombin-aptamer binding through electrostatic interactions and it is further consistent with the human thrombin structure that contains two anion binding sites on the surface. Electron capture dissociation (ECD) top-down MS of the thrombin-TBA complex performed with a high resolution 15 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer showed the primary binding site to be at exosite I located near the N-terminal sequence of the heavy chain, consistent with crystallographic data. High resolution native top-down MS is complementary to traditional structural biology methods for structurally characterizing native proteins and protein-DNA complexes. Graphical Abstract ᅟ.

Element contents in shoots of sunflower (Helianthus annuus): Prediction versus measuring

Sunflower (Helianthus annuus) is cultivated as food and feed crop as well as for bioenergy production. It is also investigated towards its ability to remove contaminants from soil and accumulate them in the shoots (phytoextraction). So the reliable prediction of element contents in shoots based on soil contents would be advantageous to easily decide whether plants grown on a certain area could be either used as food and feed or for phytoremediation in combination with bioenergy production. However, it is desirable to predict element contents in plants based on only a few numbers of predictors. This would mean on the one hand a reduced effort in time and costs for analysis and on the other hand existing data on soil quality could be than used for estimations of the element uptake of plants on larger scales. Samples of sunflowers were used, that were grown in plots situated at two different sites in Germany and treated with different amendments (NPK-fertilizer, Streptomyces+Mycorrhiza, Rendzina). One site (heavy metal polluted) was the test field “Gessenwiese”, which is situated on the area of the former uranium leaching heap “Gessenhalde”. The other site (non-contaminated) was the lysimeter station Falkenberg. Shoot contents of Ca, Cd, Co, Cu, K, Ni, Pb, and Zn were correctly predicted by the mobile soil fraction extracted with 1M NH4NO3 solution (simple regression), whereas for Mg, S, and U the specifically adsorbed soil fraction (extraction with 1M NH4OAc solution) needs to be added as predictor (PLS regression). Mn was the only element in the data set for which simple regression based on total soil contents (digestion with HF, HClO4, and HNO3) had to be used be used for correct prediction in the studied data set.

Comparison of cadmium extractability from soils by commonly used single extraction protocols

This study compares Cd extractability using 13 commonly used extraction procedures for 28 soils, varying in composition (0–88% sand; 0.9–12.8% organic matter; pH 5.2–8.2) and contamination level (0.2–41.4mg kg − 1 Cd). The procedures used were: soil solution extraction using rhizon soil moisture samplers, 0.01M CaCl 2, 0.1M Ca(NO 3) 2, 0.1M NaNO 3, 1M NH 4NO 3, 1M NH 4OAc, 1M MgCl 2, 0.11M HOAc, 0.1M HCl, 0.5M HNO 3, 0.02M EDTA + 0.5M NH 4OAc + 0.5M HOAc (pH 4.65), 0.005M DTPA + 0.01M CaCl 2 + 0.1M TEA (pH 7.3) and aqua regia digestion. Single extractions were compared and clustered based on Pearson correlation. Relative Cd extractability, expressed as percentages of pseudo-total content ( aqua regia), were compared between soils with pH below and above 7. Finally, multivariate regression functions for Cd extractability as a function of soil parameters were constructed. Distinctive subgroups of related extraction procedures could be distinguished using cluster analysis. A first major class of significantly related procedures consisted out of the weaker extractants and contained Rhizon extraction in addition to NaNO 3, CaCl 2, NH 4NO 3, Ca(NO 3) 2. The second major class contained the pseudo-total content ( aqua regia), more aggressive chelate based (DTPA, EDTA) and acid based (HOAc, HCl, HNO 3) procedures, and stronger extractions used to estimate exchangeable Cd in the soil (NH 4OAC, MgCl 2). Differences in extractability between acidic and alkaline soils were observed in the weaker extractants whereas no or little influence of soil pH on the extractability was observed when the more aggressive extractants were used. Cd extractability by the weaker extractants was found to be especially affected by soil pH, total Cd content and cation exchange capacity. Regression curves were constructed based on these three parameters. Finally, observed extraction values for the various procedures in 11 unpolluted control soils were included for future reference.

Chemical extractability of copper added to soils at two different concentrations in a batch experiment

The bioavailability of Cu in soil is dependent on the desorption into the soil solution of Cu from the surfaces of soil colloid materials (viz. organic matter, the clay fraction, Fe and Mn oxides). Six samples of natural soils of the Typic Eutrochrepts type were used in this work to determine Cu extraction by using 0.1M Na2EDTA and 1M NH4OAc solutions. The soil samples were spiked with 3 or 1.5 g Cu kg-1 soil and analysed in batch tests. Most of the Cu added was sorbed within 24 h. Both single-step extractions with 0.5M Na2EDTA, 0.5M Ca(NO3)2 and 1M NH4OAc solutions, and sequential extractions, were performed. The proportions of copper extracted by the NH4OAc solution were found to be higher than those extracted by the Na2EDTA and Ca(NO3)2 solutions. The amount of Cu EDTA formed exhibited a high, negative correlation with OC, Fed and Mnd at an added copper concentration of 3 g kg-1. There were no significant differences between the mean percentage of copper extracted by the Na2EDTA solution from spiked and natural soils. There were, however, significant differences between the amount of copper extracted by the NH4OAc solution at both added Cu concentrations and that extracted from natural soils. Sequential extraction was highly efficient at both Cu concentrations. Copper was found to be primarily associated to carbonates. The correlations between non-extractable Cu (residual fraction) and organic carbon, Fed and Mnd (crystalline oxides) were highly significant at the higher Cu added concentration (3 g kg-1). On the other hand, that between residual Cu (non-extractable Cu) and pH was negative and highly significant at the lower Cu added concentration (1.5 g kg-1). There were no significant differences between the mean percentages of copper sequentially extracted and copper extracted by the Na2EDTA, NH4OAc, Ca(NO3)2 solutions at the two added Cu concentrations (3 g kg-1 and 1.5 g kg-1).

Association of cadmium, zinc, copper, and nickel with components in naturally heavy metal‐rich soils studied by parallel and sequential extractions

In this study, a new parallel and sequential extraction procedure was proposed to investigate the solubility of metals [cadmium (Cd), zinc (Zn), copper (Cu), and nickel (Ni)] and their association with soil components in naturally metal‐rich soils of Norway. Two different soils, alum shale (clay loam) and moraine (loam), developed on alum shale minerals were used. Each soil had two pH levels. For parallel and successive extractions, H2O, 0.1M NH4OAc (soil pH), 0.3M NH4OAc (soil pH), 1M NH4OAc (soil pH), and 1M NH4OAc (pH 5.0) were used. A significant amount of Cd was extracted by NH4O Ac related to concentration of NH4OAc in the extracting solution. The amounts of Zn, Cu, and Ni extracted by these reagents were almost negligible except with 1M NH4OAc (pH 5.0). Thus these metals were strongly bound to soil components. A seven step sequential extraction procedure was applied to evaluate the association of metals with soil constituents. The extractions were performed sequentially by extracting the soil with reagents having an increasing dissolution strength: 1M NH4OAc (soil pH), 1M NH4OAc (pH 5.0), 1M NH2OH.HCl (in 25% HOAc), 1M NH2OH.HCl (in 0.1M HNO3), 30% H2O2 (in 0.1M HNO3), 30% H2O2 (1M HNO3), and aqua regia. In both soils at both pH levels investigated, appreciable percentages of total Cd (20–50%) were found associated with the NH4OAc extractable fraction (mobile fraction). For Zn, Cu, and Ni, the percentage of total metal extracted with NH4OAc was low (<4%), but it increased significantly by introducing a reducing agent (NH2OH.HCl). The NH2OH.HCl‐extractable fraction was the greatest fraction (>60%) for all four metals examined. These results suggest that among the metals studied, only Cd was easily desorbed from soil and should be considered mobile and potentially bioavailable. Other metals (Zn, Cu, and Ni) were strongly associated with the soil components and should be considered less available to plants. Using the sequential fractionation technique as a measure of availability, mobility and potential bioavailability of these four metals in the alum shale soils were: Cd>Zn>Ni>Cu.

Relationships between the Mehlich‐III soil test extraction procedure and standard soil test methods in North Dakota

One hundred surface soil samples were randomly selected from actual fanner samples submitted to the North Dakota State University Soil Testing Laboratory for comparing the usefulness of the Mehlich‐III extractant with results from currently used methods for extracting phosphorus (P), potassium (K), zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu) from neutral to alkaline pH soils from the northern Great Plains. Soil pH's were distributed across a range from pH 7.0 to 8.3. The Mehlich‐III extractant correlated well with P, K, and Zn values obtained by the Olsen, neutral normal ammonium acetate (1M NH4OAc, pH 7.0) or DTPA (diethylenetriamenepentaacetic acid) extraction procedures, respectively. The Mehlich‐III extractant was somewhat correlated with Cu by the DTPA method but poorly correlated with DTPA‐extractable Fe and Mn. The Mehlich‐III extractant appears to be adequate for extraction of P, K, and Zn across concentration ranges normally found in most agricultural soils in North Dakota.

A comparison of buffered and unbuffered ammonium salts to determine exchangeable base cations in acid soils

In soil samples from two study sites in southern Norway, exchangeable cations were determined using two different ammonium (NH4)‐salts as extractant. As expected, the cation exchange capacity (CEC) determined in 1M ammonium acetate (NH4OAc), buffered at pH 7.0 was higher than the CEC measured in ammonium nitrate (NH4NO3). By contrast, the amount of exchangeable calcium (Ca), magnesium (Mg), and barium (Ba) was lowest in the NH4OAc extract, in particular in the upper soil horizons high in organic matter (O‐ and E‐horizon). This suggests that NH4 in 1M NH4OAc does not compete effectively with multivalent base cations. The relatively high levels of exchangeable base cations in NH4NO3 could not be explained by increased weathering. An increase in selectivity of especially divalent cations may explain the relatively low amount of exchangeable base cations extracted by NH4OAc, as this involves increased deprotonation and thus a higher negative charge.

Manganese dynamic in acid soil and uptake by maize seedlings

Abstract Reports on manganese (Mn) soil tests in Brazil are not correlated either with total uptake of Mn by plants or plant growth response to added Mn salts. We have investigated the factors influencing Mn release in an acid soil and to better understand the Mn dynamic and uptake by maize seedlings. Soil preparation processes (air‐dry, oven‐dry, storage, etc.) significantly influenced Mn availability. Soil Mn extracted by 1M NH4OAc pH 7.0 was highly correlated with plant Mn. The use of a soil sample without drying seems promising for evaluting soil‐available Mn but the procedure still needs widespread evaluation.

Predicting value of diagnostic soil properties on actual and potential cation exchange capacity (CEC) in andisols and andic soils

Abstract Relationships between charge variation and diagnostic soil properties were studied in Andisols and andic subgroups of Inceptisols and Ultisols. Charge variation was calculated as the difference between “field” or actual cation exchange capacity (CECa), and potential CEC (1M NH4OAc, pH 7). Methods used to estimate CECa (effective CEC, silver thiourea) were higly correlated. The relative charge variation was greater than 70% in Andisols with very low content of layer silicates. Active Al (Alo) was positively correlated with CEC‐NH4 and negatively correlated with CECa. This result contributed to the explanation of the negative trend correlation observed between actual and potential CEC. The ratio CECa/Alo showed low values (<8) in Andisols. This parameter was also tested in 25 samples of Andisols described elsewhere. The predicting value of both Alo and CECa for a rough estimation of variable charge seemed apparent from the results obtained.

Effects of soil properties on the extraction of zinc

A study has been made of the extractable Zn in a selection of Scottish soils. The extractants' ability to remove Zn followed the order: 0.1M HCl > EDTA-(NH 4) 2CO 3, pH 8.6 > DTPA, pH 7.3 ≈ 1M NH 4OAc, set at soil pH > NH 4OAc, pH 4.8 > water. Possible reasons for variations in the amount of Zn extracted are discussed. The influence of soil pH was much more evident in low organic matter soils (⩽ 6.5%) than in soils with high organic matter contents (> 6.5%). For soils with high organic matter contents, the amounts of Zn extracted by HCl, EDTA or DTPA were positively correlated with soil CEC, whereas the correlations were negative or insignificant for soils with low organic matter contents. DTPA and NH 4OAc both appear to extract labile Zn from the soil solid phase with comparable efficiency when soil pH is < 5.5.

Twelve‐year tillage and crop rotation effects on yields and soil chemical properties in northeast Iowa

Abstract Long‐term tillage and crop management studies may be useful for determining crop production practices that are conducive to securing a sustainable agriculture. Objectives of this field study were to evaluate the combined effects of crop rotation and tillage practices on yield and changes in soil chemical properties after 12 years of research on the Clyde‐Kenyon‐Floyd soil association in northeastern Iowa. Continuous corn (Zea mays L.) and a corn‐soybean [Glycine max L. (Herr.)] rotation were grown using moldboard plowing, chisel plowing, ridge‐tillage, or no‐tillage methods. Tillage and crop rotation effects on soil pH, Bray P1, 1M NH4OAc exchangeable K, Ca, and Mg, total C, and total N in the top 200 mm were evaluated. Profile NO3‐N concentrations were also measured in spring and autumn of 1988. Crop yields and N use efficiencies were used to assess sustainability. Bray P1 levels increased, but exchangeable K decreased for all cropping and tillage methods. Nutrient stratification was evident for...

Potassium retention characteristics of a typic hydrandept from the Island of Hawaii

Abstract Potassium‐retention characteristics of the topsoil and subsoil of a medial over thixotropic, isomesic, Typic Hydrandept (Puaulu series) was investigated under moist conditions. This soil occurs in high rainfall areas where important losses of K are likely. Exchangeable cations were extracted with 1M NH4OAc pH 7 and Potassium Retention (Kr) was calculated by the difference between initial K (exchangeable, soluble, and added K) and final K. The results indicated that for any given K solution concentration, the amount of K held by the subsoil was twice that retained by the topsoil. The relationship between Kr and Potassium Adsorption Ratio (PAR) was nonlinear. The Gapon selectivity coefficient (KG) sharply decreased with increasing Potassium Saturation (Ep) and then leveled off to an almost constant value at Ep values of 0.25 for the topsoil and 0.15 (mmol‐1L)½ for the subsoil. This constant value of =KG was reached when 5 and 10% of the initial exchange sites were occupied by K retained in the tops...

STUDIES ON THE POTASSIUM-SUPPLYING CAPACITIES OF SOUTHERN ONTARIO SOILS. III. MEASUREMENT OF AVAILABLE K

This study was conducted to determine which of eight different extractants best described the K-supplying capacities of nine southern Ontario soils. The total amount of K extracted by eight crops of alfalfa grown in the greenhouse was related to soil K by regression techniques. The following procedures extracted increasingly higher average amounts of soil K: water; electro-ultrafiltration (EUF) at 20 °C (EUF-K-20) (37 μg K g−1); EUF at 80 °C (EUF-K-80) (83 μg K g−1); 2M NaCl (89 μg K g−1); 1M NH4OAc (131 μg K g−1); 0.1 M HNO3 (163 μg K g−1); seven sequential 7-min extractions with boiling 1 M HNO3 (Mactotal) (940 μg K g−1); and 0.2 M sodium tetra-phenyl boron (NaTPhB) (3248 μg K g−1). Of the eight extractants tested, the amount of K removed by EUF was the most closely associated to total K uptake; a multiple regression model with the logarithm of EUF-K-20 and the logarithm of EUF-K-80 as independent variables explained 97% of the total variation in K uptake. The K extracted by 2 M NaCl and by 0.1 M HNO3 also explained more variation in total K uptake (r2 = 0.86, and 0.92, respectively) than did 1 M NH4OAc (r2 = 0.61), which is currently used in the Ontario soil test program. The other extractants did not offer an improvement over NH4OAc, with the exception of the most soluble fraction of Mactotal (StepK). Extraction of soil K with electro-ultrafiltration may offer a more precise estimation of the K supplying capacities of southern Ontario soils than the currently used extractant. Key words: Electro-ultrafiltration, nonexchangeable K, ammonium acetate, soil test

Dissolution of phosphate rocks in soils. 1. Evaluation of extraction methods for the measurement of phosphate rock dissolution

The dissolution of phosphate rock (PR) in soil was determined by measuring the amount of either the dissolved inorganic phosphate (Pi) and Ca or the residual P and Ca remaining as undissolved PR in the soil. The dissolved Pi was extracted by either 0.5M NaOH or 0.5M NaHCO3 and the dissolved Ca was extracted using either 0.5M BaCl2/triethanolamine (TEA) or 1M NH4OAc. Undissolved PR was extracted by 1M HCl following the extraction with either 0.5M NaOH or 0.5M BaCl2/TEA.

Estimation of plant available manganese in acidic subsoil horizons

Abstract General agreement does not exist as to the most appropriate method to estimate plant available Mn in soils. In the current investigation soil and soil solution Mn were measured in limed and unlimed treatments of 11 acidic subsoil horizons and related to plant Mn concentrations, Mn uptake and growth of subterranean clover (Trifolium subterraneum L. cv. Mt. Barker) and switchgrass (Panicum virgatum cv. Cave‐in‐Rock). Manganese measurements were taken at planting and harvest and included: Mn extracted by 1M NH4OAc (pH 7), 0.01M CaCl2, 0.05M CaCl2, 0.033M H3PO4, 0.005M DTPA, 0.2% hydroquinone in 1M NH4OAc (pH 7), 0.01M NH2 OH.HCl 4 2 in 0.01M HNO3, total soil solution Mn and concentrations and 2+ activities of Mn2+ calculated from the GEOCHEM program. Measured and calculated values of soil solution Mn generally gave the best correlations with subterranean clover and switchgrass Mn concentrations and Mn uptake. Root Mn concentrations were highly correlated with soil solution Mn measurements taken at h...

Soil acidity and aluminium and manganese toxicity in the Te Kauwhata area, North Island, New Zealand

Abstract Soils within the Te Kauwhata Irrigation Scheme were sampled to determine the extent of soil acidity and aluminium (A1) and manganese (Mn) toxicity. Most soils belonged to yellow-brown earth or brown granular loam soil groups. Forty-one soil profiles were sampled at 20 cm intervals to 80 cm. Samples were analysed for pH, and A1 and Mn extracted by 1M KC1 and 0.02M CaCl2. Mn was also extracted using 1M NH4OAc, and 0.2% hydroquinone in 1M NH4OAc (easily reducible Mn). The results show that the soils have strongly acid subsoils. Toxic levels of extracted Al were common in most subsoils and some topsoils. The toxic levels of Mn are likely in many topsoils and soil horizons with Mn concretions. Incorporation of lime into the subsoil to increase soil pH and reduce Al toxicity and potential Mn toxicity may be necessary for some crops.

Extraction of phosphorus, potassium, calcium, and magnesium from soils by an ion‐exchange resin procedure

Abstract A procedure for the simultaneous extraction of phosphorus, potassium, calcium and magnesium from soils, by an ion‐exchange resin procedure applicable to large‐scale advisory soil testing, is described. The important steps are the disaggregation of soil by shaking in water during 15 minutes with a glass marble, the transference of the elements from the soil to a sodium bicarbonate treated mixture of anion and cation exchange resins during a 16‐hour shaking period, the separation of the resin from the soil by sieving and extraction of the elements from the resin. The results of resin extractable calcium, magnesium and potassium were comparable to the results of these elements extracted with 1M NH4OAc, to calcium and magnesium extracted with 1M KCl, and to potassium extracted with 0.025M H2SO4. For phosphorus the resin extractable values were not comparable to the results obtained by the former routine method, based on the extraction with 0.025M H2SO4. The results of resin extractable P presented cl...