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1.
Abstract

Interpretation guidelines for the availability of calcium (Ca), magnesium (Mg), and potassium (K) in soilless media have been developed through plant growth studies and comparisons amongst extractants. The extractants used were 70% ethanol (EtOH), water, DTPA, ammonium acetate (NH4OAc) and silver thiourea (AgTu). Ethanol, which removes ions in pore water, extracted only 4.5, 13, and 26% of the Ca, Mg, and K, respectively, that could be extracted by AgTu from Pinus radiata bark of pH 5.66 and CEC of 11.2 cmol+/L. Acidification to pH 4.62 increased these proportions to 22, 40, and 38%. Correlations between water and DTPA for 39 media were excellent for both individual elements and the ratios Ca/Mg, K/Mg, and Ca, Mg, and K/(the sums of their concentrations in the extractants) (r2 = 0.88–0.98). Correlations between these extractants and AgTu and NH4OAc were poor for individual elements (r2 = 0.37–0.75) but high for ratios (r2 = 0.71–0.96). For Petunia ’Celebrity Salmon’ growing in peat media of similar pH but widely different Ca, Mg, and K proportions, the ratios of these elements in the shoots were highly correlated with their ratios in 2 mM DTPA extracts of the media. Similarly high correlations were obtained between the Ca/Mg ratios of the shoots of three Asplenium species growing in pinebark media and this ratio for DTPA, NH4OAc, and AgTu extracts of the media. The results indicate that the ratios of Ca, Mg, and K to one another in water and DTPA extracts of soilless media are good indicators of the availability of these elements to plants. Healthy specimens of the test plants grew in media whose DTPA extracts had a minimum Ca/Mg mole ratio of 1 or 2, depending on the Ca requirements of the species. The upper limit for good growth was deduced to be about 6. Limits for NH4OAc and AgTu extracts were similar to those found for crop plants in soils, at 1.6 or 3 to about 9. Minimum amounts of Ca, Mg, and K extracted by water and DTPA that were adequate for short‐term growth in the absence of further inputs were about 9,2.5, and 5 cmol+/L medium, respectively, at pH 6.0. The effect of pH on cations removed by water and DTPA raises the minima to about 19, 5, and 7.5 cmol+/L at pH 5.0.  相似文献   

2.
Abstract

Eighteen soils from northwestern Switzerland were used to study the value of seven universal extractants (CaCl2; DB‐DTPA; Mehlich 1, 2, and 3; Morgan‐Wolf; and NH4OAc‐EDTA) for predicting plant available potassium (K) as compared to a bioassay (a modified Neubauer test with winter rye). These extractants were evaluated on the basis of K uptake by the bioassay test and the soil K status. In order to create the sufficiency level of exchangeable K for plant growth, soils were treated with 0, 20, 40, 80, and 160 mg K/kg of soil. The range of K uptake by the bioassay tests was between 89.2 and 403.0 mg/kg of soil for the control pots, and 136.6 to 495.8 for the K treatments with optimal conditions for plant growth. The average amounts of K extracted by the seven universal extractants, in ascending order, were: CaCl2 < Morgan‐Wolf < Mehlich 1 < Mehlich 2 < NH4OAc‐EDTA < Mehlich 3 < DB‐DTPA. The highest simple correlation with K uptake versus the bioassay test was obtained with the DB‐DTPA (r = 0.89) extractant and the lowest with the Mehlich 1 (r = 0.53) extractant. The DP‐DTPA, NH4OAc‐EDTA and Mehlich 3‐K procedures showed an advantage over K procedures based on water soluble and exchangeable K pools in the investigated soils in order to predict the amount of plant‐available K. A simple regression and the Cate‐Nelson graphic method offer the possibility of assessing the soil‐K status using K values obtained by these universal extractants and to calibrate them against K forms as follows: exchangeable, water soluble, and non‐exchangeable.  相似文献   

3.
Abstract

The 1: 1.5 water extraction of horticultural substrate for K was evaluated using K uptake as the criterion. Two crops, chrysanthemum (2 trials) and verbena (2 trials) were grown in peat, peat + pumice (PP), pine bark and peat + sawdust + sand (PSS). The ammonium acetate (NH4OAc) extraction for K was evaluated in one trial. The number of K application rates varied from 9 to 23.

The relationship between both soil tests and plant uptake was very good for all substrates, although it was generally poorer in bark, particularly in the verbena trials. This was probably due to the relatively high level of native K in bark and the lower K requirement of verbena. The relationship between water extractable K and NH4OAc extractable K was linear and very good.

Percentage maximum dry weight and net growth rate were regressed against soil test values using a quadratic function and desirable values (DV) were estimated from the response curve. The initial DV for water extractable K For maximum dry weight in the chrysanthemum trials varied from about 45 ‐ 139 ppm and for NH4OAc extractable K in one chrysanthemum trial varied from 284 ‐ 469 ppm. The DV obtained from growth rate measurements were similar to those obtained using percent maximum dry weight. It was not possible to determine DV for plants growing in bark and in PSS in one trial.

The DV for verbena, which could be determined in peat in only one trial due to lack of response in the others was 10–11 ppm in the water extract.  相似文献   

4.
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 harvest with r=0.97 and r=0.95 (p<0.01) for subterranean clover and switchgrass respectively. The Mn extracted by 0.01M CaCl was also significantly correlated (p<0.01) with plant Mn concentrations and Mn uptake and proved to be better than the other extractants in estimating plant available Mn. Although Mn concentrations as high as 1769 mg/kg (shoots) and 8489 rag/kg (roots) were found in subterranean clover, Mn did not appear to be the major factor limiting growth. Measures of soil and soil solution Mn were not strongly correlated with yield. Both Al toxicities and Ca deficiencies seemed to be more important than Mn toxicities in limiting growth of subterranean clover and switchgrass in these horizons.  相似文献   

5.
Abstract

A trial was carried out with compost and compost/peat mixtures to test several extraction methods for the estimation of availability of phosphorus (P). The test plant was Dendranthema grandiflorum All composts had a high pH and salt content. Amounts of P extracted by different extraction methods decreased in the order: Formate < CAL < NH4‐acetate < CaCl2/DTPA < CaCl2. Dilution of compost with peat decreased pH and increased availability of P. The better availability of P caused by dilution with peat was not reflected by the Formate‐, CAL‐, and NH4‐acetate method. These acid and well‐buffered extraction solutions overestimate P, and are therefore not suited to estimate availability of P in composts and compost/peat mixtures. Weak extraction solutions, like CaCl2 and CaCl2/DTPA, gave results which showed a good correlation with P content of plants and P uptake. The advantage of the latter method compared with CaCl2 is the extraction of amounts of P comparable to amounts taken up by the plants. Therefore of all the extraction methods tested, the CaCl2/DTPA method showed the best suitability to estimate the availability of P in composts and compost/peat mixtures.  相似文献   

6.
Abstract

A study was conducted to calibrate and evaluate five buffers for the lime requirement (LR) determination of tropical peat soil. The buffers tested were the Shoemaker‐McLean‐Pratt (SMP); Mehlich; 0.1M ammonium acetate (NH4OAc); 0.1M barium acetate [(Ba(OAc)2]; and 0.1M calcium acetate [Ca(OAc)2]. Calibration was done by comparing the precision of linear regression equations adjusted to the relationships between the LR rates required to achieve pH 5.0 measured in a 1: 4 (soiltwater) ratio as determined by incubation and soil‐buffer pH values. Incubation LR using calcium carbonate (CaCO3) to achieve pH 5.0 by peat soil was utilized to calibrate each buffer. Evaluation was carried out by assessing the LR from the calibrated buffers which estimate the LR nearest to the target pH of 5.0. The calibration study showed that the SMP and Mehlich buffers were less precise than the Ba(OAc)2, NH4OAc, and Ca(OAc)2 buffers. The evaluation study indicated that the Ba(OAc)2 buffer is the most accurate, followed by NH4OAc and Ca(OAc)2 buffers. The Ba(OAc)2 buffer method is recommended for LR determination of tropical peat soil and NEUOAc or Ca(OAc)2 as an alternative method.  相似文献   

7.
Abstract

Sequential extraction of pine bark medium alone and after amendment with either manganese sulfate (MnSO4), composted rice hulls, or soil showed that at pH 5.5–7.0 most of the manganese (Mn) exists in a form that is extracted by acidic hydroxylamine hydrochloride, and which could therefore be in oxide or strongly‐bound forms. Acidification to pH 4.5–5.0 transferred large amounts of this ‘oxide’ Mn into ‘readily available’ and ‘weakly adsorbed’ fractions. Similar extractions of Sitka spruce bark showed that most of its Mn was extracted by weak cationic reagents ('readily available’ and ‘weakly adsorbed’ fractions). Growth of oats in pine bark, peat, and eucalypt sawdust media, with and without MnSO4 amendment, lowered the amounts of Mn in ‘readily soluble’ and ‘weakly adsorbed’ fractions and caused some loss of ‘oxide’ Mn. Comparison of data for Mn extracted by 2 mM DTPA (1:1.5 v/v) with Mn in sequential fractions showed that DTPA dissolves some ‘oxide’ Mn. The data further suggest that up to about 36 mg/L DTPA‐extractable Mn would not be toxic to most plants growing in media of pH 6.0, but 60 mg/L DTPA‐extractable Mn may be if the medium pH falls below 5.5.  相似文献   

8.
Abstract

Twenty‐six garden soils from Aspen, Colorado, contaminated with old silver mine dumps, were extracted with diethylenetriamine pentaacetic acid (DTPA) and NH4HCO3‐DTPA (AB‐DTPA). Total soil digests (HNO3‐HClO4‐HF) were carried out on 21 highly contaminated soils. All soil extracts and digests were analyzed for Pb, Cd, and Zn using inductively‐coupled plasma atomic emission spectrometry (ICPS). Linear regression equations for DTPA versus AB‐DTPA values gave 0.96, 0.99 and 0.99 “r”; values for Pb, Cd, and Zn, respectively. Linear regression equations for total Pb, Cd, and Zn levels versus their respective AB‐DTPA extractable levels were developed with “r”; values of 0.92, 0.93, and 0.89, respectively. It was concluded that AB‐DTPA test can be used to screen soils contaminated with the above‐mentioned elements.  相似文献   

9.
Mixtures of peat and substrate clays are commonly used as growth media for horticultural plant production. A quality protocol for substrate clays defines a threshold value of active manganese (Mnact = sum of exchangeable and easily reducible Mn) in substrate clays of < 500 mg kg–1 to prevent toxic reactions of plants. This threshold value was tested in experiments with peat‐clay blends under various growth conditions, and nutrient solution experiments were additionally conducted to investigate the effects of silicic acid and dissolved organic matter on the occurrence of Mn toxicity. Common bean (Phaseolus vulgaris L.) and hydrangea (Hydrangea macrophylla) plants were cultivated in different peat‐clay substrates and in peat under different moisture and pH levels. The clays varied in their Mnact content from 4–2354 mg kg–1. The results of the substrate experiments reveal that a threshold value for Mn in substrate clays is not justified, as plants grown in all peat‐clay substrates did not develop any Mn toxicity even at high substrate moisture or low pH conditions which are known to increase the Mn availability. The extraction of active Mn did not well reflect the Mn concentrations in plant dry matter and substrate solution. As plants tolerated high Mn concentrations in the substrate solution compared to the nutrient solution without toxicity symptoms, the influence of silicic acid and dissolved organic matter (DOM) on Mn toxicity was characterized in a nutrient‐solution experiment. Manganese toxicity was clearly diminished by silicic acid application, but not by DOM. The former effect probably explains the tolerance of bean plants in peat substrates where high silicon concentrations in the substrate solution were observed. Peat‐clay blends even provided up to five times more silicon to plants than pure peat.  相似文献   

10.
This study has been taken up to generate information on potassium status in maize rhizosphere soils differing in their clay content at different levels of added potassium. Soils with larger amounts of clay showed greater amounts of water soluble and ammonium acetate extractable K (NH4OAc K) in both the rhizosphere as well as non-rhizosphere. In the absence of added K (control), non-rhizosphere samples showed higher water soluble and NH4OAc K ranging from 8.0 to 28.9 mg kg?1 and from 132.5 to 294.0 mg kg?1, respectively compared to rhizosphere samples where water soluble K varied between 6.0 and 26.5 mg kg?1 and NH4OAc K from 125.0 to 262.5 mg kg?1. The difference in K content between rhizosphere and non-rhizosphere which could have been resulted from plant K uptake was significantly related with clay content (r = 0.98**) in control whereas at 150 mg kg?1 K addition this relationship was found to be non significant (r = 0.64NS). Electro ultra filtration (EUF) fractions also showed similar differences in K contents in soil between rhizosphere and non-rhizosphere.  相似文献   

11.
Abstract

Individual soil tests are used to assess plant nutrient element needs. Separate soil tests, however, are time consuming and costly. Our objective was to develop a 0.5M sodium bicarbonate (NaHCO3) soil phosphorus (P) test in combination with 0.005M diethylenetriaminepentaacetic acid (DTPA) so macronutrient dements: ammonium‐nitrogen (NH4‐N), nitrate‐nitrogen (NO3‐N), P, potassium (K), calcium (Ca), and magnesium (Mg); and micronutrients: iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) could be quantified in one extraction. The NaHCO3‐DTPA extracting solution is a combination of 0.5M NaHCO3 and 0.005M DTPA and has a pH of 7.60±0.05. Sodium in the solution enhances the NH4, K, Ca, and Mg extraction; bicarbonate (HCO3) is for P extraction; DTPA chelates Ca, Mg, and micronutrients; and the water is for NO3 extraction. Soil samples (0–15 cm depth) came from two sources. The first set was from 12 N x P dryland proso millet (Panicum miliaceum L.) experiments, conducted from 1985 through 1987 in eastern Colorado. These soils were extracted with potassium chloride (KCl), NaHCO3, ammonium acetate (CH3‐COONH4), DTPA, ammonium bicarbonate DTPA (AB‐DTPA), and with the NaHCO3‐DTPA solutions. The second set included 25 soils from Alabama, Georgia, North Carolina, and South Carolina and were analyzed only for available P with the NaHCO3 and NaHCO3‐DTPA methods. Simple linear correlations for macronutrient elements and micronutrients were highly significant. Critical levels for the macronutrient elements: NO3‐N, P, and K were 27, 11, and 144 mg kg‐1, respectively; and the critical levels for the micronutrients: Fe, Mn, Zn, and Cu were 3.9, 0.35, 0.97, and 0.24 mg kg‐1, respectively.  相似文献   

12.
Abstract

Twenty surface soil samples were collected from Nainital Tarai (foothills of Himalya) where “Khaira”; disease (Zn deficiency of rice) is prevalent. Rice (Oryza sativa L. variety IR‐8) was grown in pots for 8 weeks after transplanting. Experiments were conducted to determine the suitability of five soil Zn extractants: dilute acid (HCl + H2SO4) mixture; DTPA‐(NH4) 2CO3, pH 7.3; dithizone; NH4OAc, pH 4.6; and 2N MgCl2 to predict Zn deficiency. Critical values for soil available Zn were established for rice by the old and new Cate and Nelson procedures1.

Zinc extracted from the soils with dithizone; NH4OAc, pH 4.6; 0.2N MgCl2. and DTPA‐(NH4) 2CO3 pH 7.3 was significantly correlated with the uptake of Zn by the rice plants. The correlation between Zn extracted with the dilute acid (HCl + H2SO4) mixture and plant Zn was not statistically significant. The ex‐tractants which extracted greater quantities of Zn gave higher critical values and vice versa. It is concluded that all extracting solutions except the dilute acid (HCl + H2SO4) mixture were found to he suitable for predicting available Zn in rice soils of Tarai.  相似文献   

13.
Abstract

Four extractants for soil Mn were compared for their sensitivity to changes in Mn availability caused by rates and sources of added soil Mn and soil pH variations. Their ability to extract amounts of Mn correlated with plant Mn concentrations was also determined. Two field experiments were conducted on a sandy, high water table soil (Ultic Haplaquod‐Arenic Plinthaquic Paleudult) which included 5 Mn rates, 4 Mn sources and 3 soil pH levels. Soybeans [Glycine max (L.) Merr. cultivar Ransom] were grown and leaf tissue and soils sampled at the late pod‐fill stage. All four extractants separated the high‐ Mn rates, but the small exchange method did not separate the low Mn rates. Few differences were observed among extractants due to Ma sources. The DTPA method was the only procedure to correctly distinguish soil pH levels by showing decreasing extractable Ma with increasing soil pH. Including pH in multiple regressions significantly increased the plant Mn‐soil Mn correlation coefficients. The DTPA method and the 0.1N H3PO4 method had the highest correlation coefficients and the double acid method the lowest. The small exchange method was intermediate. Considering all the results, the DTPA was the most promising method for extracting Mn from this sandy, southern Coastal Plain soil.  相似文献   

14.
Abstract

Three methods for soil potassium extraction (M NH4OAc pH 7, 0.01 M AgTU and 30 % hot H2SO4) were compared for a variety of kaolinitic soils of the tropics. The AgTU‐extractable K was much higher than the M NH4OAc‐extractable K when vermiculite clay was present in the soil. The correlation between both was given by an R value of 0.937. The amounts of K extracted by 0.01 M AgTU and by hot H2SO4 were approximately the same. The R value for these two methods was 0.843.

It is suggested that the AgTU extractant could be used for determination of plant‐available K in soil and for testing for the presence or absence of vermiculite clay in soils.  相似文献   

15.
Abstract

Eighty four soil samples collected from southeastern Norway were analyzed for Cd by extraction with NH4OAc, DTPA, NH4OAc-EDTA, NH4NO3, HCl and CaCl2. The total Cd, pH, exchangeable K and Ca, dithionite-extractable Mn, available P and fine sand (0.2–0.02 mm) contents were the principal factors related to the extractable Cd, with some inter-extractant variations. Cadmium extracted by NH4NO3, NH4OAc, HCl and CaCl2 decreased with increasing soil pH, but the Cd extracted by all the extractants increased with increasing total Cd, exchangeable K and Ca, available P, and Mn-oxide contents in the soils. The Cd concentrations in plants were significantly related to the extractable Cd, exchangeable Ca and Mg, pH, Mn-oxides and organic matter content.  相似文献   

16.
Abstract

A new soil extractant (H3A) with the ability to extract NH4, NO3, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H3A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH4 and NO2/NO3. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH4 or NO2/NO3. H3A was highly correlated with soil‐extractable inorganic N (NH4, NO2/NO3) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P.  相似文献   

17.
石灰性土壤中锰素营养的研究——Ⅱ.土壤有效锰的测定   总被引：2，自引：0，他引：2  
张维理  张乃凤 《土壤学报》1984,21(3):268-276
自从Leeper[5]首先提出用对苯二酚提取土壤易还原态锰评价土壤供锰状况以来,四十多年间各国的土壤农化工作者陆续设计并使用了种类繁多的土壤有效锰的提取剂。将其归纳大致可分为五类。  相似文献   

18.
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.  相似文献   

19.
Abstract

The objective was to find an uncomplicated test giving the best correlation between calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), zinc (Zn), and lead (Pb) extracted from humic forest soil and the total concentration of the element in some understorey forest plants using well‐known extractants. The elements were selected because Ca, Mg, Mn, Cu, and Zn are essential nutrients to plants and Zn and Pb are potentially harmful heavy metals received over the years in the southern parts of Norway by long‐range atmospheric transport. Extraction of organic podzolic surface soil (Oe and Oa horizon) from 17 different pine forests in central and southern Norway was carried out with four different reagents to evaluate uptake of Ca, Mg, Mn, Cu, Zn, and Pb in the understorey plants Deschampsia flexuosa, Vaccinium myrtillus (leaves and stems), and Vaccinium vitis‐idaea (leaves and stems). The NH4OAc, NH4NO3, HCl, and EDTA solutions used to extract the soil in addition to concentrated HNO3, demonstrated variability in capacity to extract the different elements from the soil. The extractants yielded significant relations between concentrations of Ca, Mn, and Pb in the Oe or Oa horizon and some of the plants or plant compartments, even though distinct correlation was more dependent on species and plant part than the actual extractant used. In the case of Zn, Cu, and Mg only a few sporadic correlations were observed between the different plant/plant compartments and the element concentrations in the soil extracts. Altogether none of the extractants was shown to be superior to the others in providing the best correlation with the elements concentrations in selected plant/plant compartments. In the case of Ca, Mn, and Pb all the extractants including concentrated HNO3 provided significant correlations with at least some of the selected plant/plant compartments.  相似文献   

20.
Abstract

The NH4HCO3‐DTPA (AB‐DTPA), 1 MNH4HCO3, 0.005 M DTPA, pH=7.6, was proposed as a multi‐element extractant, for evaluating macro and micronutrients availability to plants. AB‐DTPA was also evaluated as a soil test, for assessing boron availability and toxicity to alfalfa. In a pot experiment, ten soils of Northern Greece were used to assess AB‐DTPA as an extractant of available boron to wheat (Triticum aestivum L., cv. Yecora), in comparison with hot water and saturation extract. Boron (B) was added as borax (Na2B4O7*10H2O) to the ten soils, at rates equal to 0, 3, and 5 mg B kg‐1. Wheat was grown in pots containing the boron amended soils to the stage of tillering, and dry aboveground biomass, B concentration and B uptake by wheat were determined. AB‐DTPA extractable B was significantly greater than saturation extract and similar to hot water at each B application rate, and was correlated significantly with hot water (r=0.84), or with saturation extract (r=0.48). Extractable boron by all extractants, boron concentration in wheat and boron uptake were significantly affected by the soil x B application rate interaction. In assessing B availability to wheat using AB‐DTPA as a soil test, CEC should be included in the regression equation for B concentration, or pH for B uptake. However, the corresponding adjusted coefficients of determination for B concentration (adjusted R2=0.46) and B uptake (adjusted R2=0.48) were similar or lower to those of hot water (adjusted R2=0.45 and 0.60, respectively) and the saturation extract (adjusted R2=0.70 and 0.49, respectively), when the latter two soil tests were used in the regression equations without the inclusion of any soil property.  相似文献   

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