Evaluation of manganese inorganic fertilizer sources and Mehlich‐3 extractant for prediction of manganese deficiency in soybeans on a Sharkey silty clay

Abstract

A greenhouse experiment was conducted on two Sharkey silty clay (very fine, montmorillonitic, nonacid, thermic, Vertic Haplaquept) soils (SharkeyA and‐B) to compare MnSO₄ and two Mn‐oxysulfatc sources (oxysulfate‐A and‐B) and to evaluate the Mehlich‐3 extractant. Soils were collected from a soybean [Glycine max (L.) Merr.] field with (Sharkey‐A) and without (Sharkey‐B) a history of Mn deficiency symptoms. Treatments consisted of two lime treatments, O and 2000 mg kg^‐1, and three Mn rates, 0, 20, and 40 mg kg^‐1. Each source was broadcast in granular form. Manganese sulfate was also applied in solution. Soybean plants were grown for 40 days. Dry weight, whole‐plant Mn concentration, and total Mn uptake were measured. Extractable soil Mn was determined using the Mehlich‐3 extractant. Dry weight was increased by applied Mn only on the Sharkey‐A soil, especially for the limed treatment. The Mehlich‐3 extractant delineated between the responsive (2.3 mg Mn kg^‐1) and non‐responsive (6.0 mg Mn kg^‐1) Sharkey soils. On the limed Sharkey‐A soil, sulfate applied in the granular form was more effective than sulfate applied in solution. It was also more effective than the oxysulfate sources, and the oxysulfate‐A was superior to the oxysulfate‐B source. Whole‐plant Mn concentration and uptake followed trends similar to those observed with dry weight, particularly on the Sharkey‐A soil. Multiple regression analyses suggested that soil pH, along with Mehlich‐3 extractable Mn, may improve the Mn soil test interpretation.     

Identifying critical limit in soil and plant for determining response of groundnut (Arachis hypogea) to boron application in Madurai soils of Tamil Nadu,India

To establish critical limit in soils and plant, soil samples were collected from twenty; 12, 5 and 3 soil locations of low, medium and high boron (B) status from Madurai district of Tamil Nadu, India for pot culture experiment. Based on the results of pot culture experiment, the critical limit was determined to be 42.7 mg kg^?1 for groundnut plants and 0.39 mg kg^?1 in Madurai soils. Groundnut plants were highly responded to B application in soils below the critical limit whereas soils with B greater than 0.51 mg kg^?1 did not respond. For the confirmation of pot culture results, a field experiment was conducted with different B treatments comprised of soil and foliar applications and results revealed that the pod yield of groundnut increased with increasing levels of B and the soil application of 20 kg ha^?1 as borax has showed significantly higher pod yield in the district.     

Boron fertilization of Mediterranean aridisols improves lucerne (Medicago sativa L.) yields and quality

Abstract

Lucerne (Medicago sativa L.) is grown as a forage crop on many livestock farms. In calcareous soils in eastern Turkey, lucerne production requires boron (B) addition as the soils are naturally B deficient. Field experiments with four B-application rates (0, 1, 3, and 9 kg ha^?1 B) were conducted in 2005 and 2006 to determine the optimum economic B rate (OEBR), critical soil test and tissue B values for dry matter (DM) production for lucerne grown on B-deficient calcareous aridisols in eastern Turkey. Boron application increased yield at each site in both years of production. The OEBR and critical soil and tissue B content were not impacted by location. Averaged over the two years and three locations, the OEBR was 6.8 kg B ha^?1 with an average DM yield of 12.0 Mg ha^?1. The average soil B content at the OEBR was 0.89 mg kg^?1 while leaf and shoot tissue B content amounted to 51.8 and 35.5 mg kg^?1, respectively. Boron application decreased tissue calcium (Ca), zinc (Zn), and copper (Cu), and increased tissue nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), iron (Fe), and manganese (Mn). Tissue and soil B increased without impacting yield at B levels up to 9 kg ha^?1. We conclude that 7 kg ha^?1 B is sufficient to elevate soil test B levels from 0.11 to 0.89 mg kg^?1 and overcome B deficiency at each of the sites in the study. Similar studies with different soils and initial soil test B levels are needed to conclude if these critical soil and tissue values can be applied across the region.     

Determination of Soil Feature Effects on Plant-Available Phosphorus Extraction using Response Surface and Cate–Nelson Methodology

In this study, four soil extraction methods (Olsen, Soltanpour, Mehlich 3, and water saturation) were used to identify optimal concentrations of phosphorus (P) required for plant growth. Olsen soil extraction for P was the most appropriate method for soil types of this study as the greatest correlation coefficient for soil-test P and with plant factors was achieved. The optimal amount of soil features (pH, organic carbon, lime, gypsum, and clay) determined by using response surface methodology (a new optimization method) were 7.49, 0.66, 41.82, 4.21, and 31.34, respectively. More soil P was extracted when the soil had optimal amounts of these features, showing each feature had a significant effect on extracted soil P. Furthermore, the graphical method of Cate–Nelson determined the optimal amounts of P using Olsen, Soltanpour, Mehlich 3, and saturation extract methods for wheat as 15, 6.5, 35, and 1.5 mg kg^?1 soil in nongypsic soils and 17, 3.5, 45, and 2.5 mg kg^?1 soil in gypsic soils.     

Critical Toxic Ranges of Chromium in Spinach Plants and in Soil

ABSTRACT

Long-term irrigation with untreated industrial sewage effluents causes accumulation of high concentrations of chromium (Cr) and other heavy metals in soil and subsequently in crop plants (especially leafy vegetables), which can be phytotoxic to plants and/or a health hazard to animals and humans. Greenhouse experiments were conducted to determine the effects of Cr application on the growth of spinach (Spinacia oleracia L.) and to develop critical toxic ranges of Cr in plants and in soil. The study involved growing of spinach variety ‘Punjab Green’ in a greenhouse on silty clay loam and sandy soils equilibrated with different levels of applied Cr (0, 1.25, 2.5, 5, 10, 20, 40, 80, 160, and 320 mg Cr kg^{? 1} soil). Plants were harvested at: three growth stages 45, 60, and 90 days after sowing (DAS). Critical toxic ranges were estimated by regressing and plotting data on ammoniumbicarbonate-diethylenetriaminepenta-acetic acid (AB-DTPA) extractable Cr in soil or Cr concentration in plants versus dry-matter yield (DMY) of spinach at the three growth stages. Toxic ranges, i.e., slightly toxic (80%–90%), moderately toxic (70%–80%), and extremely toxic (< 70%) in terms of DMY relative to the attainable maximum DMY, were established for both soils and for plants at all three growth stages. There was no germination of spinach with applied Cr at 320 mg Cr kg^{? 1} rate in silty clay loam soil and at 40 mg Cr kg^{? 1} rate in sandy soil due to Cr toxicity. Roots accumulated more Cr in comparison with shoots. Chromium concentrations of 0.47–1.93 mg Cr kg^{? 1} soil in silty clay loam soil, 0.13–0.94 mg Cr kg^{? 1} soil in sandy soil, 1.08–5.40 mg Cr kg^{? 1} plant DM in silty clay loam soil and 0.54–11.7 mg Cr kg^{? 1} plant DM in sandy soil were found to be toxic. The critical toxicity ranges of Cr thus established in this study could help in demarcating Cr toxicity in soils and in plants such as spinach and other leafy vegetables due to irrigation of soils with untreated sewage water contaminated with chromium.     

Effects of lime and applied Mn on plant Mn,growth and chlorophyll concentration of ‘Tifway II’ bermudagrass

Abstract

A glasshouse study was conducted to determine effects of lime and Mn applied to three Florida soils on plant Mn, growth, and chlorophyll concentration of ‘Tifway II’ bermudagrass (Cynodon dactylon x Cynodon transvaalensis). Four replications of three lime rates (0, 1000, and 2000 mg CaCO₃/kg as dolomite and Ca(OH)₂ for Astatula fine sand (Typic Quartzipsamment, hyperthermic, uncoated) and Pompano fine sand (Typic Psammaquent, siliceous, hyperthermic); 0, 2000, and 4000 mg CaCO₃/kg as dolomite and Ca(OH)₂ for Myakka fine sand (Aeric Haplaquod, sandy siliceous, hyperthermic) and three Mn applications (none, 10 mg Mn/kg as MnSO₄, and 5 mg Mn/kg as MnEDTA) were used in a randomized, complete block, factorial design. A wide range of plant Mn concentrations existed across treatments for each soil. Differences in plant Mn concentration did not cause significant differences in growth or chlorophyll concentration. The critical plant Mn concentration was not reached, but it appeared to be below 20 mg Mn kg for bermudagrass. Models for prediction of plant Mn concentration using soil pH and extractable soil Mn (Mehlich I, Mehlich II, DTPA‐TEA) were obtained. The applications of MnSO, and MnEDTA each resulted in increased plant Mn under acidic soil conditions. Neither Mn application resulted in increased plant Mn concentration in grass grown on Pompano fine sand with soil pH values of 7.0 or above.     

Tillage,lime, and poultry litter effects on plant concentrations of zinc,manganese, and copper

Minimum tillage cropping systems and the use of animal manures on cropland are becoming more prevalent. An experiment was initiated to determine the effects of tillage and lime/gypsum variables on uptake of zinc (Zn), manganese (Mn), and copper (Cu) by corn (Zea mays L.) and to show correlations between plant uptake of these metals and soil pH and Mehlich 1‐extractable soil metals where poultry litter was used as a nitrogen (N) source. Surface soil samples were taken in the spring and fall for two years from a long‐term tillage experiment that had been in place for nine years. There were two tillage treatments [conventional (CT) and no‐tillage (NT)] and six lime/gypsum treatments (control, 8,960 kg gypsum ha^‐1 every fourth year, 4,480 kg lime ha^‐1 every fourth year, and three treatments of 8,960 kg lime ha^‐1 in a four‐year period divided by application times into 1, 2, and 4 treatments). Poultry litter was applied each year of the two‐year experiment at a rate of 8.96 Mg ha^‐1 on a dry weight basis. Soil samples were analyzed for pH and Mehlich 1‐extractable Zn, Mn, and Cu, and plant tissue (small plant, ear leaf, stalk, and grain) was analyzed for Zn, Mn, and Cu concentrations. Lime treatments resulted in lower Zn in the small plant and ear leaf for CT, but not for NT. Plant Mn was decreased by lime and gypsum rates for small plant, ear leaf, stalk and grain for both years for CT and NT. Correlations for plant Zn versus soil pH were generally non‐significant, except for one year for ear leaf Zn (R=‐0.413**). Correlations for soil pH and plant tissue Cu were all nonsignificant. Correlations for plant Mn and soil pH were strong with R values over 0.80. Plant Mn response to treatments was found at a pH range of 4.2 to 5.8 for ear leaf and pH 5.2 to 6.2 for stalks. Plant Mn and Zn versus Mehlich 1‐extractable soil Mn and Zn, respectively, were negative. This response was possibly due to oxidation‐reduction and non‐incorporation of the lime for Mn and non‐incorporation of the lime for Zn. Also, the poultry litter was high in Zn (447 mg kg^‐1), which could have masked pH effects. It was concluded that soil sampling for plant micronutrients for NT, especially where a waste material high in micronutrients is applied, can give erratic and even erroneous results. However, lime and tillage treatments had a predictable effect on micronutrient uptake as related to soil pH.     

Determining critical limit of boron in soil for wheat (Triticum aestivum L.)

Abstract

Critical values of boron (B) for wheat nutrition in soil and plant were determined through a pot experiment with twenty-one surface soils of Alluvial flood plain and Red-latertic belt comprising three major soil orders (Entisols, Alfisols, Inceptisols) with four levels of boron. Application of boron significantly increased the dry matter yield as well as uptake of B by plants. Critical concentration of hot calcium chloride (CaCl₂) extractable B in soil for wheat was found to be 0.53?mg?kg^?1. The critical plant B concentration varied with growth stages and values were 7.4?mg?kg^?1 at panicle initiation and 4.18?mg?kg^?1 at maturity, respectively. The findings of this investigation also recommend the application of 2?kg?B^?1?ha^?1 for ensuring B sufficiency to wheat in Indo-gangetic alluvial and Red-Lateritic soils.     

Evaluation of fly ash as a soil amendment for the Atlantic Coastal Plain: II. Soil chemical properties and crop growth

Crop yields in the Atlantic Coastal Plain of the U.S.A. are limited by the low moisture-holding capacities of the sandy soils common to the region. Corn was grown in a Hammonton loamy sand soil amended with fly ash (0, 5, 10, 20, 30, and 40%) to determine if the ash rates required to improve soil moisture holding capacity would adversely affect plant growth, or soil and plant levels of nutrients and heavy metals. Fly ash increased soil test levels of P, K, Ca, Mg, Mn, Cu, Zn, B, Cd, Cr, Ni, and Pb. Nutrient concentrations in plants grown in the ash-amended soils, except P, Mn, and B, remained within established sufficiency ranges. The 20 and 40% ash rates increased soil soluble salt (EC) levels from 0.2 to 1.1–1.5 and 1.7–2.1 mmho cm^?1, soil pH from 5.6 to 6.0–6.4 or 6.3–6.9, and extractable B from 0.2 to 2.2–5.9 and 2.2–9.0 mg kg^?1. Fly ash reduced corn germination, delayed seedling emergence, and reduced root and shoot dry weights. Plant B concentrations at the 40% ash rate were in the phytotoxic range (136–189 mg kg^?1). Management practices that allow for pre-leaching of B and soluble salts will likely be required to attain satisfactory corn growth in ash-amended soils.     

Beryllium phytotoxicity in soybeans

A greenhouse study was conducted to assess the effects of soil-applied beryllium (Be) on the growth and Be content of soybeans [Glycine max (L.) Merr.], grown on acid southeastern soils under limed and unlimed conditions. This study was conducted using a factorial design, with two soil types varying in clay content (Blanton sand, a loamy, siliceous, thermic Grossarenic Paleudult; and Orangeburg loamy sand, a loamy, siliceous, thermic Typic Paleudult), two soil treatments (limed and unlimed) and five Be concentrations (0, 25, 50, 100, and 150 mg Be kg^?1 t soil). Addition of Be to unlimed Blanton soil had the most toxic effects of all treatment combinations; at the 150 mg Be kg^?1 treatment plant biomass was reduced as much as 90% and plant Be concentration was as high as 226 mg Be kg^?1. Beryllium concentrations were greater in plants grown in a soil low in clay (Blanton soil). Liming of soils treated with Be resulted in lowered tissue Be concentrations in plants grown on either soil type.     

Agronomic Efficiency of Feldspar,Quartz Silica,and Zeolite as Silicon (Si) Fertilizers in Sandy Soil

ABSTRACT

Partial replacement of synthetic chemical fertilizers by naturally occurring alternatives is environmentally recommended. Feldspars (F), quartz silica (S), and zeolites (Z) are silicon (Si)-rich minerals that may be utilized as Si fertilizers. This study aims to assess the agronomic efficiency (AE) of the mentioned minerals as Si fertilizers and to estimate Si-use efficiency (Si-UE) in sandy soil. A field experiment was carried out (summer seasons of 2016 and 2017) in which F, S, and Z were mixed with surface soil in an application rate 500 mg kg^?1 soil with and without potassium humate (K-H, 2 mg kg^?1 soil). Treatments were distributed in a complete randomized block design (CRBD) with three replicates including control before cultivation of soybean (Glycine max L.). Yield (kg ha^?1) of soybean, available Si (mg kg^?1) in soil and uptake (mg kg^?1) of N, P, K, Cu, Fe, Mn, Zn, and Si by soybean seeds and straw were estimated. The most significant increase was by 67.87% followed by 38.69% was recorded for the S and S K-H treatments, compared to the control. Same treatments showed nonsignificant decrease in the available Si (mg kg^?1) that may refer to partial replenishment of plant available Si (PAS) in soil and avoid significant deficiency. Silica treatments resulted in the most significant increase in the uptake (mg kg^?1 soil) of Si, N, P, K, Cu, Fe, Mn, and Zn by seeds and almost by straw. Silica was more efficient agronomically than feldspar and zeolite. Absorption of more biocompatible Si-organo species may depend on Si source.     

Evaluation of Extractants for Boron under the Influence of Organic Matter and Applied Boron in Rhizosphere and Nonrhizosphere Soils Growing Rape (Brassica campestris L.)

Field experiments during 2006–07 and 2007–08 were conducted in an Aeric Endoaquept to evaluate extractants suitable for boron (B) under the influence of organic matter and B in both rhizosphere (R) and nonrhizosphere (NR) soils with rape (Brassica campestris L.) as a test crop. The results reveal that the average B content in Mehlich 3 (MH-3) B was greatest (0.791 mg kg^?1) in NR soil, while that of the same in R soil was greatest (0.785 mg kg^?1) with Mannitol–calcium chloride (CaCl₂) (MCC) followed by hot -CaCl₂ (HCC, 0.750 mg kg^?1) in the treatment T₄ where NPK (80:40:40), B at 0.5 kg ha^?1, and farmyard manure (FYM) at 5 t ha^?1 were applied together. Based on linear regressions and correlations between different extractants and yield responses, the MH-3 extractant gave the greatest value of co-efficient of determination (R² = 0.36**, r = 0.598**) and has proved to be a superior extracting solution for B in NR in an Aeric Endoaquept. The results further suggested that the extractability of B with these three extractants did not have any control over rhizosphere soil zone.     

Critical limit of boron for maize (Zea mays L.) in red and lateritic soil of Jharkhand,India

ABSTRACT

To establish a critical limit in soils and plant, an experiment was conducted in red and lateritic soil (Alfisols) of farmer’s field in tribal-dominated Panchayat Kurum, Palkot block, Gumla district, Jharkhand, India. Based on the results of the field experiment, the critical limits were determined as 0.48, 0.50, 0.47, and 0.42 mg kg^?1 in the soil, respectively, for hot water, hot calcium chloride, salicylic acid, and ammonium acetate-extractable B, while a critical limit of 12.00 mg kg^?1 was observed in maize tissue using the graphical method. In an analysis of variance method, the critical limits of B in soils were found as 0.45, 0.54, 0.49, and 0.43 mg kg^?1 using hot water, hot calcium chloride, salicylic acid, and ammonium acetate extractants, respectively. Maize plants were highly responsive to B application where soil B level was below the critical limit (0.50 mg kg^?1). In a field experiment, grain yield of maize increased with increasing levels of B application, while soil application at 1.0 kg ha^?1 + two foliar application (at the knee and pre-flowering stages) of borax at 0.2% were showed significantly higher grain yield of the maize crop. The hot water, hot calcium chloride, salicylic acid, and ammonium acetate-extractable B were significantly and positively correlated with organic carbon and negatively correlated with the electrical conductivity of soils.     

Chemical fractions and response of cauliflower (Brassica oleracea var. botrytis) to soil applied boron

The present study was conducted with an objective to estimate the distribution of boron (B) application in various soil fractions and their plant response for assessing the availability in the soil. Two soils (alluvial and red soil) and five levels of B (0, 0.5, 1, 2 and 3?mg B kg^?1 soil) were applied in the pot experiment, and pots were sown with cauliflower (Sabour Agrim) arranged in a completely randomized block design (CRD) with three replications. Result showed that the curd yield of cauliflower increased significantly upto 2?mg B kg^?1 soil irrespective of soils. The percent yield increase was 14.78 and 15.01 in alluvial and red soil over the control, respectively. The initial total B content was 35.88 (alluvial soil) and 15.51 (red soil) mg·kg^?1. The mean content of Fraction I, II, III, IV and V in alluvial soil was 1.11, 1.54, 0.65, 1.49, and 95.18% and in red soil was 2.68, 4.47, 6.62, 2.50, and 83.59% of the total soil B, respectively. For changes in amount of B fractions due to B applications there was significant effect on all the fractions except Fraction II. The increase in apparent B uptake was 0.43?mg B kg^?1 in alluvial soil and 0.25?mg B kg^?1 in red soil over the control (0?mg B kg^?1 soil). Regression equation of yield and B fractions showed the relationship between first four fractions to the yield. Residual fraction was found to be collinear during calculation. Overall the study predicted the bioavailability and dynamics of B in the two distinct soils.     

印度酸性耕作土中总锰、铁以及可提取态锰、铁的水平、分布及其与土壤性质的关系研究

A total of 400 surface soil(0–15 cm) samples were collected from cultivated soils representing four soil series,namely,Hariharapur,Debatoli,Rajpora and Neeleswaram in Orissa,Jharkhand,Himachal Pradesh and Kerala states of India,respectively,and were analyzed to measure the contents of total and extractable Mn and Fe,to establish the relationship among total and extractable Mn and Fe and soil properties,and to characterize the spatial distribution pattern of Mn and Fe in some cultivated acid soils of India. The contents of total as well as extractable Mn and Fe varied widely with extractants and soil series. However,the amounts of Mn or Fe extracted by diethylene triamine penta-acetic acid(DTPA),Mehlich 1,Mehlich 3,0.1 mol L-1 HCl and ammonium bicarbonate DTPA(ABDTPA) were significantly correlated with each other(P 0.01). Based on the DTPA-extractable contents and the critical limits(2 mg Mn kg-1soil and 4.5 mg Fe kg-1 soil) published in the literature,Mn and Fe deficiencies were observed in 7%–23% and 1%–3% of the soil samples,respectively. The content of soil organic carbon(SOC) had greater influence on total and DTPA-extractable Fe than did soil pH. Geostatistical analysis revealed that total and DTPA-extractable Mn and Fe contents in the acid soils were influenced by soil pH,SOC content,and exchangeable cations like potassium,calcium and magnesium. Spatial distribution maps of total and DTPA-extractable Mn and Fe in soil indicated different distribution patterns.     

Lowland Rice Response to Thermophosphate Fertilization

Abstract

Use of adequate rates of phosphorus (P) in crop production on high‐P‐fixing acid soils is essential because of high crop response to P fertilization and the high cost of P fertilizers. Information on lowland rice response to thermophosphate fertilization grown on Inceptisols is limited, and data are also lacking for soil‐test‐based P fertilization recommendations for this crop. The objective of this study was to evaluate response of lowland rice to added thermophosphate and to calibrate P soil testing for making P fertilizer recommendations. A field experiment was conducted for two consecutive years in central Brazil on a Haplaquept Inceptisol. The broadcast P rates used were 0, 131, 262, 393, 524, and 655 kg P ha^?1, applied as thermophosphate Yoorin. Rice yield and yield components were significantly increased with the application of P fertilizer. Average maximum grain yield was obtained with the application of 509 kg P ha^?1. Uptake of macro‐ and micronutrients had significant quadratic responses with increasing P rates. Application of thermophosphate significantly decreased soil acidity and created favorable macro‐ and micronutrient environment for lowland rice growth. Across 2 years, soil‐test levels of Mehlich 1–extractable P were categorized, based on relative grain yield, as very low (0–17 mg P kg^?1 soil), low (17–32 mg P kg^?1 soil), medium (32–45 mg P kg^?1 soil), or high (>45 mg P kg^?1 soil). Similarly, soil‐test levels of Bray 1–extractable P across 2 years were very low (0–17 mg P kg^?1 soil), low (17–28 mg P kg^?1 soil), medium (28–35 mg P kg^?1 soil), or high (>35 mg P kg^?1 soil). Soil P availability indices for Mehlich 1 extractant were slightly higher at higher P rates. However, both the extracting solutions had highly significant association with grain yield.     

Laboratory Assessment of Nostoc 9v (Cyanobacteria) Effects on N2 Fixation and Chemical Fertility of Degraded African Soils

The potential of Nostoc 9v for improving the nitrogen (N)₂–fixing capacity and nutrient status of semi‐arid soils from Tanzania, Zimbabwe, and South Africa was studied in a laboratory experiment. Nostoc 9v was inoculated on nonsterilized and sterilized soils. Inoculum rates were 2.5 mg dry biomass g^?1 soil and 5 mg dry biomass g^?1 soil. The soils were incubated for 3 months at 27 °C under 22 W m² illumination with a photoperiod of 16 h light and 8 h dark. The moisture was maintained at 60% of field capacity. In all soils, Nostoc 9v proliferated and colonized the soil surfaces very quickly and was tolerant to acidity and low nutrient availability. Cyanobacteria promoted soil N₂ fixation and had a pronounced effect on total soil organic carbon (SOC), which increased by 30–100%. Total N also increased, but the enrichment was, in most soils, comparatively lower than for carbon (C). Nitrate and ammonium concentrations, in contrast, decreased in all the soils studied. Increases in the concentration of available macronutrients were produced in most soils and treatments, ranging from 3 to 20 mg phosphorus (P) kg^?1 soil, from 5 to 58 mg potassium (K) kg^?1 soil, from 4 to 285 mg calcium (Ca) kg^?1, and from 12 to 90 mg magnesium (Mg) kg^?1 soil. Positive effects on the levels of available manganese (Mn) and zinc (Zn) were also observed.     

Integration of Soil pH with Soil‐Test Values of Zinc for Prediction of Yield Response in Rice Grown in Mollisols

Seventeen Mollisols having pH_(1:2) in the range of 6.00 to 8.42 were analyzed with five extractants, and the extractable zinc (Zn) ranges were 0.84 to 2.75 mg Zn kg^?1 soil for diethylenetriaminepentaacetic acid (DTPA) (pH 7.3), 0.91 to 2.72 mg Zn kg^?1 soil for DTPA + ammonium bicarbonate (pH 7.6), 1.82 to 7.18 mg Zn kg^?1 soil for Mehlich 3, 1.22 to 3.83 mg Zn kg^?1 soil for ethylenediaminetetraacetic acid (EDTA) + ammonium carbonate, and 0.88 to 1.18 mg Zn kg^?1 soil for 1 mol L^?1 magnesium chloride (MgCl₂) (pH 6.0). Zinc extracted by DTPA (pH 7.3) and Mehlich 3 showed significant positive correlation with sand content, whereas only Mehlich 3 showed negative correlation with soil pH. All extractants showed significant positive correlation with each other except for 1 mol L^?1 MgCl₂‐extractable Zn, which had significant positive correlation with only Mehlich 3– and EDTA + ammonium carbonate–extractable Zn. A greenhouse experiment showed that Bray's percentage yield of rice was poorly correlated to extractable soil Zn but had a significant and negative linear correlation with soil pH (r = ?0.662, significant at p = 0.01). Total Zn uptake by rice had a significant positive correlation with 1 mol L^?1 MgCl₂– and Mehlich 3–extractable Zn. A proposed parameter (p extractable Zn + p OH^?) involving both soil extractable Zn and pH terms together showed significant and positive correlation with Bray's percentage yield and total Zn uptake of rice. The calculated values of critical limits of soil Zn in terms of the proposed parameter were 14.1699 for DTPA (pH 7.3), 13.9587 for DTPA + ammonium bicarbonate, 13.7016 for Mehlich 3, 13.9402 for EDTA + ammonium carbonate, and 14.1810 for 1 mol L^?1 MgCl₂ (pH 6.0). The critical limits of Zn in rice grain and straw were 17.32 and 22.95 mg Zn kg^?1 plant tissue, respectively.     

Boron availability and uptake in huanglongbing-affected citrus trees on a Florida entisol

Abstract

Florida sandy soils, particularly, Entisols are low in boron (B) and occasionally have B deficiency for citrus. A study was set-up at Citrus Research and Education Center, Lake Alfred, Florida, on a Candler fine sand to determine the availability and uptake of B in a high-density citrus planting of Huanglongbing (HLB)-affected trees. Boron was applied at 1.12?kg ha^?1 in three splits, at University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) recommended rate (1×), and at 2× the recommended rate using foliar and soil application methods. Soil samples were taken from soil surface to 60?cm depth in 15-cm increments within the irrigated and non-irrigated zones. Soil and leaf samples were analyzed for B using Mehlich III extraction method and acid digestion, respectively. Results showed the leaf B concentration for soil applied rate 1× was significantly higher (P?<?0.001) than that of foliar applied either at single or double rate but both were in the optimum range recommended by UF/IFAS. The sorption study revealed that there was no sorption (K_D < 0.2?L kg^?1) but K_D at 0–15-cm depth was 3× greater than that at 15–60?cm depths. The concentration of B in the leaf tissue remained in the recommended optimum critical range. Sorption coefficients showed negligible B sorption which means most applied B would be prone to leaching under heavy rains or saturated soil conditions on Florida sandy soils thus requiring judicious management for optimizing tree performance and sustaining environmental quality.     

Wheat response to combined application of nitrogen and phosphorus in a saline sandy loam soil

Fertilization with nitrogen (N) or phosphorus (P) can improve plant growth in saline soils. This study was undertaken to determine wheat (Triticum aestivum L; cv Krichauff) response to the combined application of N and P fertilizers in the sandy loam under saline conditions. Salinity was induced using sodium (Na⁺) and calcium (Ca²⁺) salts to achieve four levels of electrical conductivity in the extract of the saturated soil paste (EC_e), 2.2, 6.7, 9.2 and 11.8?dS?m^?1, while maintaining a low sodium adsorption ratio (SAR; ≤1). Nitrogen was applied as Ca(NO₃)₂?·?4H₂O at 50 (N50), 100 (N100) and 200 (N200)?mg?N?kg^?1 soil. Phosphorus was applied at 0 (P0), 30 (P30) and 60 (P60)?mg?kg^?1?soil in the form of KH₂PO₄. Results showed that increasing soil salinity had no effect on shoot N or P concentrations, but increased shoot Na⁺ and chlorine ion (Cl^?) concentrations and reduced dry weights of shoot and root in all treatments of N and P. At each salinity and P level, increasing application of N reduced dry weight of shoot. At each salinity and N level P fertilization increased dry weights of shoot and root and shoot P concentration. Addition of greater than N50 contributed to the soil salinity limiting plant growth, but increasing P addition up to 60?mg?P?kg^?1 soil reduced Cl^? absorption and enhanced the plant salt tolerance and thus plant growth. The positive effect of the combined addition of N and P on wheat growth in the saline sandy loam is noticeable, but only to a certain level of soil salinity beyond which salinity effect is dominant.