Methods of assessing boron availability to kiwifruit plants growing on high boron soils

Abstract

Five soil boron (B) extraction methods were evaluated for their ability to predict available B to kiwifruit plants in soils with high B concentration. The methods were hot water soluble (Hws‐B), 0.05M mannitol in 0.01M calcium chloride (CaCl₂ extractable (Man‐B), 0.05M hydrochloride acid (HCl) soluble (HC1‐B), resin extractable (Resin‐B), and saturation extract (Sat‐B). The amounts of B recovered by the first four methods investigated were strongly correlated with each other, the highest correlation obtained being between Hws‐B and HC1‐B. Plant B was highly correlated to the B recovered by the first four extractants and poorly correlated to the B determined by the saturation method. Soil B concentrations corresponding with B toxicity in kiwifruit are 0.51, 0.80, 0.18, and 2.0 μg‐g^‐1 soil for Hws‐B, Man‐B, HC1‐B, and Res‐B, respectively. The coefficients of determination in some cases were improved when in the regression equations, soil pH and clay content were included.     

Fractionation of chromium in tannery sludge-amended soil and its availability to fenugreek plants

Purpose

Fenugreek (Trigonella foenum-graecum L.) is a medicinal plant with antidiabetic effects. Chromium has been related to better glucose tolerance in humans. The objective of this study was to determine whether tannery sludge could be used for Cr biofortification of fenugreek.

Materials and methods

Soil was mixed with tannery sludge containing 6.03 g Cr kg^?1. All Cr was in the form of Cr(III). Three treatments were disposed: control without sludge, and two treatments with 10 and 20 g sludge kg^?1, respectively. Control and the 10 g sludge kg^?1 treatments received NPK fertilizer to adjust the concentrations of major mineral nutrients to similar levels in all treatments. Soils were potted and planted with fenugreek. Plants harvested at the initial flowering stage were analysed for total Cr, Fe, Zn and Pb. Sequential soil extraction was applied to obtain operationally defined soil Cr fractions.

Results and discussion

Total Cr in all treatments was below or within the allowable range for agricultural soils (100–150 mg kg^?1). In control soils, most Cr was in the residual fraction (HF/HClO₄ digest). Tannery sludge-amended soils incorporated most Cr into the moderately reducible fraction (oxalic acid/ammonium oxalate extract). In fenugreek shoots, Cr concentrations reached 3.2 mg Cr kg^?1, a higher concentration than that reported for other leafy vegetables. Lead concentrations in plant shoots from this treatment were enhanced but hardly exceeded 1 mg Pb kg^?1.

Conclusions

Tannery sludge-amended soils containing Cr within the range of permissible concentrations can increase shoot Cr in fenugreek. Only sludge with low Pb concentrations should be used for Cr biofortification of fenugreek.     

土壤Se的分级与Se的植物有效性的关系

Nine soils with distinct properties and Se levels were selected to test a fractionation procedure of soil Se based on sequential extraction. Soil Se was fractionated into readily available Se (fraction Ⅰ, extracted by 0.5 M NaHCO₃), slowly available Se (fraction Ⅱ, extracted by 0.1 M NaOH-0.1 M Na₄P₂O₇), amorphous oxide-occluded Se (fraction Ⅲ, extracted by acid ammonium oxalate), free oxide-occluded Se (fraction Ⅵ, extracted by dithionite-citrate-bicarbonate buffer solution) and residual Se (fraction Ⅴ, determined by HNO₃-HClO₄ digestion of the final soil residue). The recovery of soil Se (the sum of all fractions over total soil Se determined independently) by this procedure was from 88.1% to 110.9%, mean 99.2%±6.4% for the test soils. The sum of fractions Ⅰ and Ⅱ, provided a good measure of available Se in soils and the percentage of fraction Ⅰ plus Ⅱ over the total soil Se, tentatively defined as Se availability index, could be used to indicate soil Se status and predict Se deficiency.     

The relationship between boron soil test results and boron uptake by bean plants

Abstract

Boron sensitive crops, kidney beans and soybeans, were grown in pots containing soil collected from a beet field and a nearby pasture. Two soil extraction procedures were used to measure boron concentrations in the soils. Dilute acid was used to extract what is believed to be readily available boron. A modified‐Soxhlet apparatus, which employed continuous leaching with hot water, measured what is believed to be slowly available boron. Plant boron status was determined by analyzing the above ground portion of the plants grown in two soils. The amount of boron in the plant tops provides an indication of biologically available boron or that boron actually available to plants. Although kidney beans and soybeans extracted more boron from the beet soil, both soil extraction procedures indicated that the concentration of boron was higher in the pasture soil. Neither extraction procedure proved reliable in predicting plant response.     

冲积潮土镁的释放特征及相对植物有效性

Experiments including two in laboratory and one in greenhouse were carried out to study non-exchangeable magnesium release from fluvo-aquic soils sampled from Daxing and Changping counties located in the suburbs of Beijing and Mg relative availability of the two soils to plants.In a batch experiment in labortory the soils were incubated under wet conditions and alternation of dry and wet conditions and determined for amount of Mg relesed at the 4th,8th and 12th week,respectively,after extraction of exchangeable Mg with 1molL^-1 NH4Ac.The amount of Mg released from the soil of Daxing was higher than from the soil of Changping,which was in accordance with the fact that the soil of Daxing had higher contents of all forms of Mg than that of Changping.There was little difference in Mg release from soils between wet conditions and alternation of dry and wet conditions.About 1%-2% of the total non-exchangeable Mg might be released within 12 weeks of incubation.restoring about 30%-35% of the original soil exchangeable Mg.Results of the experiment on kinetics of Mg release from the soils through continuous extractions with 0.5molL^-1 NH4Ac(pH7.0) on a continuous flow apparatus in laboratory showed that Mg released rapidly in the beginning,decreased sharply with time and kept stable at 60 and 240 min for the soile of Changping and Daxing,respectively,Among the five mathematical models used to describe the kinetics of Mg release,the parabolic diffusion equation best fitted the cumulative Mg release,indicating that diffusion of Mg out of the soils might be the controlling processa.The experiment of exhaustive cropping with 1 crop of tomato(Lycopersicon esculentum Mill.) followed by six crops of corn(Zea mays L.)in greenhouse showed that soil exchangeable Mg decreased remarkably with cropping .After three crops,the percentage of the total plant Mg uptake that came from soil non-exchangeable Mg was 29.5% for the soil from Changping and 35% for the soil from Daxing,About 50% of the total Mg uptake by plants in the six crops was believed to come from the soil non-exchangeable Mg form.     

Extraction of soil phosphorus with calcium chloride solution for prediction of plant availability

Abstract

Soil and vegetative samples of ley and cereals were collected four times during the growing season from field and pot trials with different phosphorus (P) fertilisation levels. The soil samples, dried and of field moisture condition, respectively, were extracted by 0.01M calcium chloride (CaCl₂) at two different soil:extractant ratios (1:2 and 1:10), and analysed by inductively coupled plasma emission spectrometry (ICP) for content of P. The plant samples were digested in concentrated nitric acid (HNO₃) and the P content determined by ICP. Calcium chloride‐extractable P content was lowest in the middle of the growing season, while plant P was highest in the beginning of the season. Phosphorus extracted by CaCl₂ solution was higher at a soil:extractant ratio of 1:10 than at 1:2, and also when drying the soil before extraction. A soil:extractant ratio of 1:2 minimizes the risk of coming too near the limit of determination. However, if organic soils are also to be included, a ratio of 1:10 has to be used in order not to have all the solution absorbed by some types of soils. The solution of ammonium lactate/acetic acid (AL) extracted nearly two powers of ten more P than CaCl₂ solution. There was a good relationship between the methods. If calcareous or very acid soils had been included, a less good relation would have been expected. Plant P content varied more in straw than in grain between different treatments. Measuring CaCl₂‐extractable P with ICP might be able to predict plant uptake of P by plants. This would be a great advantage when using 0.01M CaCl₂ as a universal extradant.     

The forms and availability to plants of soil potassium as related to mineralogy for upland Oxisols and Ultisols from Thailand

Potassium (K) deficiency is widespread in crops on highly weathered upland soils under a tropical monsoonal climate. Critical assessment of the forms of K in soils and of the ability of soils to release K for plant uptake is important for the proper management of K in crop production. The relationships between different pools of K were investigated as a function of silt and clay mineralogy for 14 upland Oxisols and 26 upland Ultisols soils from Thailand. Most soils contained no K-minerals in the silt fraction. XRD showed that kaolinite is the dominant clay mineral with variously minor or moderate amounts of illite, hydroxy-Al interlayered vermiculite and smectite present in some soils. For some soils, both conventional and synchrotron XRD were unable to detect illite. Analytical TEM including EFTEM of individual clay crystals showed that clay in the apparently illite-free samples contained very small amounts of illite. Many kaolinite particles appear to contain K which may be present in illite interleaved with kaolinite crystals. A glasshouse K-depletion experiment was conducted to assess the K supply capacity and changes in chemical forms of K and K-minerals using exhaustive K depletion by Guinea grass (Panicum maximum). Potassium deficiency symptoms and mortality of plants occurred on light textured soils, whereas plants survived for six harvests for Oxisols with clay texture, relatively high CEC and higher NH₄OAc-K (exchangeable K plus water-soluble K). There is a strong linear relationship of unit slope between NH₄OAc-K and cumulative K uptake by plants indicating that NH₄OAc-K is a major form of K available to plants. Thus K-bearing minerals contributed little K to plants over the time scale of the experiment and XRD patterns of whole soil samples, silt and clay from soils after cropping mostly showed no change from those for the initial soil. An exception was for a single surface soil clay where a minor amount of smectite was formed from illite by K release to plants.     

Evaluation of extractants for predicting availability of sulphur to mustard in inceptisols

Abstract

Mustard (Brassica juncea) is an important oilseed crop of northern India, which is widely grown in Delhi and adjoining States. This crop has a relatively high requirement of sulphur (S), and is sensitive to S‐deficiency. For predicting response of mustard to S application, several extractants have been tried with variable results. Since selection of a promising extractant for a particular soil needs careful consideration, the present investigation was planned to select the most promising extractant to predict the availability of S to mustard grown on Inceptisols of Delhi. For this purpose, a greenhouse experiment was conducted with twenty soils (two from each often important soil series from the cultivated alluvial soil belt of Delhi. Nine extractants, commonly used for estimating the availability of S, were evaluated and S in soil extract and in plant digest was estimated using the turbiditimetric method. The results indicate that the phosphate salt methods extracted comparatively more S than other extractants. The amount of S extracted by these extractants was found in the following order: KH₂PO₄‐500 ppm P>Ca(H₂PO₄)₂‐500 ppm P>0.001 M HCl>NaOAc+HOAc>heat soluble S>0.15% CaCl₂>l% NaCl> water soluble S>NH₄OAc+HOAc. Simple correlation coefficients of the amounts of S extracted by different extractants and the forms of S with the plant parameters were worked out. To determine the combined effect of soil characteristics on S extraction by different extractants, stepwise multiple regression analysis was carried out. Based on this study, the suitability of the extractants for mustard crops in Inceptisols of Delhi may be arranged as follows: 0.15% CaCl₂>water soluble S>0.001 M HCl>Ca(H₂PO₄)₂‐500 ppm>1%NaCl>NH₄OAc+HOAc>NaOAc+HOAc>KH₂PO₄‐500 ppm P>heat soluble S.     

Potassium bentonites reduce radiocaesium availability to plants

After the Chernobyl accident in 1986 the fate of radiocaesium from the fallout became of pressing concern. Specific soil amendments, as K fertilizer and specific clay minerals, promised to mitigate the worst effects. We therefore investigated the influence of bentonite and the K status of the soil on the radiocaesium equilibria in soil and on its availability to ryegrass. A sample of a sandy soil was contaminated with ¹³⁴Cs and amended with K and Ca salts (0–0.97 mmol kg^?1) and K bentonite (0–2%). After 4 weeks' incubation of the soil mixtures, ryegrass was grown for 18 weeks in a pot trial and harvested on seven occasions. No significant treatment effects on ¹³⁴Cs activity concentrations were found at the first and second harvest. From the third harvest onwards, however, ¹³⁴Cs activity concentrations in the grass were reduced up to twofold (P < 0.05) by increasing rates of K bentonite. Adsorption studies with ¹³⁷Cs revealed that the radiocaesium interception potential (RIP) of the soil–bentonite mixtures (> 1% bentonite) increased about 10‐fold during plant growth. The RIP of the K bentonite after plant growth was up to 10 times larger than that of pure illite. The formation of specific Cs sorption sites is ascribed to the in situ illitization of the K bentonite. The increase in RIP during plant growth is reflected in a decrease in exchangeable K⁺ at 2% K bentonite of about 18%. Radiocaesium concentrations in grass could be reliably predicted from the Cs⁺ and K⁺ concentrations in the soil solution. Adding K bentonite to a soil contaminated with radiocaesium is effective in fixing Cs in the soil.     

Cadmium occurrence in soil organic matter and its availability to wheat seedlings

Experiments were performed concerning the influence of soil organic matter on Cd availability to wheat seedlings. Cadmium added to soil was bound by alkali soluble humic substances through linkages so strong that it was not removable by seedlings under toxic limit. Cadmium linked by organic matter was principally found in fulvic acids, and after polyamide chromatography of the latter, all fulvic Cd was completely recovered in first fraction which contained the major part of aminoacid compounds. These findings suggest that interactions between Cd and proteic substances, frequently reported in studies on animal tissues, are active in soil too.     

The influence of earthworms on the mobility of microelements in soil and their availability for plants

The influence of earthworms (Aporrectodea caliginosa, Lumbricus rubellus, L. terrestris, and Eisenia fetida) on the mobility of microelements and their availability for plants was studied. The contents of water-soluble Fe and Mn compounds extracted from the coprolites were 5–10 times higher than that in the soil (enriched in calcium carbonate and dried) consumed by the earthworms. This digestion-induced effect became higher with the age of the coprolites (up to 9 days) and took place under their alkalization. In the excreta (surface + enteric) of earthworms, the Fe concentration exceeded those of Mn and Zn by many times. Iron and manganese were mostly concentrated (>80% and >60%, respectively) in the organic part of the excrements. In the tests with hydroponics, the excreta were found to be a source of iron compounds available for plants that were similar to Fe₂(SO₄)₃ or Fe-citrate by their physiological effect in the case when the Fe concentration in the excretions was above 0.7 μM. However, the single application of excreta of different earthworm species into the CaCO₃ enriched soil did not significantly affect the plant (cucumber) nutrition. The analysis of the transport of microelements with xylem sap showed that this fact appeared to be due to the absence of an Fe deficit in the cucumber plants because of their high capability for the absorption of weakly soluble iron compounds.     

Boron availability to plants from coal combustion by-products

Agronomic use of coal combustion by-products is often associated with boron (B) excess in amended soils and subsequently in plants. A greenhouse study with corn (Zea mays L.) as test plant was conducted to determine safe application rates of five fly ashes and one flue gas desulfurization gypsum (FDG). All by-products increased soil and corn tissue B concentration, in some cases above toxicity levels which are 5 mg hot water soluble B (hwsB) kg^?1 soil and 100 mg B kg^?1 in corn tissue. Acceptable application rates varied from 4 to 100 Mg ha^? for different by-products. Leaching and weathering of a high B fly ash under ponding conditions decreased its B content and that of corn grown in fly ash amended soil, while leaching of the same fly ash under laboratory conditions increased fly ash B availability to corn in comparison to the fresh fly ash. Hot water soluble B in fly ash or FDG amended soil correlated very well with corn tissue B. Hot water soluble B in fly ash amended soil could be predicted based on soil pH and B solubility in ash at different pH values but not so in the case of FDG. Another greenhouse study was conducted to compare the influence of FDG and Ca(OH)₂ on B concentration in spinach (Spinacia oleracea L.) leaves grown in soil amended with the high B fly ash. The Ca(OH)₂ significantly decreased tissue B content, while FDG did not affect B uptake from fly ash amended soil.     

麦根酸的分泌及其对土壤中铁的有效性的影响

Large amounts of phytosiderophore are detected from both the solution and the rhizosphere soil when cereal crops are under Fe deficiency stress.The extension of phytosiderophore in the rhizosphere soil is found only within 1 mm apart from the root surface.The rate of phytosiderophore secretion is negatively related to chlorophyll content in young leaves and positively related to the Fe-solubilizing capacity.Results from in vitro experiments whow 10 μmoles mugineic acid can dissolve 501 μg Fe from iron hydroxide and 146 ug from strengite.Thus,phytosiderophore can considerably enhance the soil iron availability by increasing the solubility of amorphous iron hydroxide and iron phosphate,and active Fe is consequently accumulated in the plant rhizosphere,43% higher than in the bulk soils There is evidence to support that mugineic acid chelates with Fe%3 at a rate of 1:1 in the acid condition.In addition,we observe mugineic acid has certain effects on mobilization of P as well as Fe by dissolving the insoluble iron phosphate,And phytosiderophore seems to be an effective remedy for the chlorosis of dicotyledonous plants.     

Microbial biomass phosphorus and its significance in predicting phosphorus availability in red soils

Abstract

Red soils are widespread in Southern China and other subtropical regions in the world. An improved management of phosphorus (P) is crucial for sustainable agriculture and environmental quality in red soil regions. Plant‐availability of P in red soils mainly depends on fertilization and biological cycling. Both laboratory analyses and greenhouse experiments were conducted to examine the relationships between plant P uptake, chemical index of P, and microbial biomass P in red soils with different fertility levels. Microbial biomass P ranged from 2.1 to 43 mg kg^‐1 in the red soils and was significantly correlated with total P (r=0.84*), organic P (r=0.87*), or Bray I extractable P (r=0.94**). Extractable P plus organic carbon accounted for >85% of the variation in microbial biomass P in the red soils. The significant relationship between microbial biomass P and extractable P suggests that microbial biomass P has a great potential in predicting P‐supply ability in soil. Greenhouse experiments showed that there were close relationships between ryegrass dry matter yield, plant P uptake or tissue P concentration and microbial biomass P in the red soils. The corresponding correlation coefficients were 0.79*, 0.90*, and 0.91*, respectively. These results imply that microbial biomass P plays an important role in the availability of P to plants, and is a potential biological index of P availability in the red soils.     

土壤微生物量氮的动态及其生物有效性研究

采用盆栽试验和15N示踪技术对玉米生长期间不同施肥处理黑土土壤微生物量氮的动态变化及其与土壤氮素组分、玉米吸氮量之间的关系进行研究。结果表明,在玉米生长期间,施肥并没有影响土壤微生物量氮的变化趋势,但不同施肥处理土壤微生物量氮的含量明显不同。玉米植株残体的加入,增加了土壤微生物量氮的数量,降低了土壤微生物对肥料15N的释放率。土壤微生物量氮与土壤全氮含量呈极显著的正相关(r=0.727**),与土壤碱解氮及玉米吸氮量之间均呈显著正相关(相关系数分别为0.528* 和0.536*)。土壤微生物量氮和土壤氮素组分对作物吸氮量的通径分析表明,土壤微生物量氮的有效性近于土壤矿质态氮、高于土壤酸解有机氮和非酸解氮。土壤微生物量氮是作物吸收氮素的有效来源。     

诊断油菜缺硼的土壤硼素临界范围

Relationships between seed yields of oilseed rape(Brassica napus L.) and extractable boron concen-trations in three soil layers(A,P and W) were investigated through ten experiments on three types of soils(Alluvic Entisols,Udic Ferrisols and Sagnic Anthrosols) in northern,Western and middle Zhejing Province.Among several mathematical models used to described the relationships,the polynomial equation,y=a bx cx^2 dx^3,where y is the yield of oilseed rape seed and x the extractable boron concentration in P layer of soil,was the best one.The critical range of the concentrations corresponding to 90% of the maximum oilseed rape yield was 0.40-0.52 mg kg^-1,The extractable boron concentration of the P layers of the soils was the most stable,The critical range determined was verified through the production practices of oilseed rape in Zhejiang and Anhui provinces.     

Response of raspberries to soil nitrogen and boron applications

Abstract

Raspberry yield and size were increased by both nitrogen and boron application in field fertilizer studies including a N rate trial (0, 67, 134 and 268 kg N/ha) and a N x B interaction trial (0 and 67 kg N/ha, and 0 and 1 kg B/ha). Yield response to N (11% increase from 134 kg N/ha) was smaller than to B (23% increase from 1 kg B/ha). Both N and B increased berry size. Nitrogen application delayed berry ripening.     

Methods of assessing boron availability in potting media with special reference to toxicity

Abstract

Hot water, water and 2M DTPA (room temperature), all at 1:1.5 volume ratio, and saturation extracts with and without added DTPA, were compared for their ability to assess the availability of B in pottting media. In three experiments, B concentrations in the extractants were highly linearly correlated with one another, although medium components and pH affected the slopes of the relationships. Hot water extracted between 38 and 77% of the B in Pinus radiata‐based media and 58 to 97% of that in peat. The proportion was little affected by the pH of the medium. The solutions at room temperature extracted considerably less B than did hot water and the proportion extracted decreased with increasing pH. B in extracts at room temperature was more highly correlated ( r² = 0.90–0.97) with B uptake by a range of plants with widely differing tolerance of high concentrations of B than was hot water soluble B (r² = 0.79–0.94). No symptoms typical of B deficiency were observed at the lowest concentrations of extractable B attained in these experiments, which were 0.08 and 0.27 mg/L B in 2 mM DTPA (1:1.5 by volume) and saturation extracts containing DTPA respectively. Other evidence suggests that concentrations at the detection limit (about 0.03 mg/L) of the analytical technique used are adequate for normal flowering of Chrysanthemum morifolium cv. Yellow Mandalay. For absence of foliar toxicity symptoms in horticultural plants sensitive to B, 2 mM DTPA (1:1.5 by volume) and saturation extracts containing DTPA should not contain more than about 0.6 and 1 mg B/L, respectively. Tolerant species can remain symptom‐free in media giving up to about 5 and 8.3 mg B/L in the two extracts, respectively. These results will be particularly useful for checking for potential B toxicity in potting media containing composted waste materials.     

Evaluation of soil extractants for silicon availability for sugarcane

Adequate evaluation and interpretation of silicon (Si) phytoavailability in soil is a key to fertilizer recommendation. This study was conducted to determine the effect of soil texture on the choice of Si extractant, and provide baseline data on the relationship between extractable Si and sugarcane Si accumulation. The effects of soil texture and extractant solutions of Si were investigated on soil of nine areas of sugarcane cultivation. Si contents in clayey soils were higher than in sandy soils only in the extraction with standard calcium chloride, acetic acid, potassium chloride (KCl), and sodium acetate buffer. Other extractants failed to reveal differences in the Si availability among the three soil textures. The choice of the extractant should consider soil texture for the determination of adequate Si contents in soils planted with sugarcane, and the extractants that proved to be more efficient in the three soil textures was acetic acid and KCl.     

Improvement of boron soil test

Abstract

Boron soil tests often do not adequately reflect B plant uptake or deficiency levels in the Eastern United States. In an attempt to develop a better test, the following systems were studied: Silicic acid replacement of boron; B soil buffering power; and the addition of small quantities of boron (0.175 ugB/g‐soil) to each soil sample to overcome some of the stronger boron fixing sites prior to hot water extraction.

Boron extracted with B spiked hot water (r=0.80 for plant tissue B vs. extractable B, opposed to r=0.76 for nonspiked hot water) was the only new test that showed promise.

The results appear to explain why hot water extractable B correlates well with plant uptake for soils previously treated with boron fertilizer (e.g. alfalfa fields); but why, on the other hand, hot water extractable B fails to correlate well with plant boron uptake for soils not having a recent history of boron fertilization. . . in which some fixing sites apparently have to be satisfied before the hot water test will work well.