Zinc toxicity symptom development and partitioning of biomass and zinc in peanut plants 1

High soil zinc (Zn) concentrations can cause Zn toxicity in peanuts (Arachis hypogaea L.), which decreases productivity and can be fatal to the plants. The objectives of this study were 1) to determine the optimal sampling time and plant part for diagnosis of Zn toxicity in peanuts, 2) to relate toxicity symptoms to plant Zn concentrations and calcium:zinc (Ca:Zn) ratios, and 3) to model the distribution of Zn and biomass into plant parts in relation to Zn concentration in the whole plant. A greenhouse study utilized four soils (Lakeland sand, Tifton loamy sand, Greenville sandy clay loam, and Greenville sandy clay) with Zn applications of 0, 10, 20, and 40 mg Zn/kg soil. Plants were sampled for analysis of nutrient concentrations, and Zn toxicity ratings were recorded biweekly. Toxicity symptoms became visible 4–8 weeks after planting, with stunting appearing at four weeks, horizontal leaf growth and leaflet folding at six weeks, and stem splitting at eight weeks. Optimal sampling time for diagnosis of Zn toxicity using plant Zn concentrations in peanuts was 6–10 weeks after planting. Zinc toxicity ratings were more highly correlated with plant Zn concentration in stems (r = 0.84) than leaves (r = 0.79). However, the Zn concentration in the total aboveground plant had a correlation coefficient (r = 0.83) almost as high as for the stems alone and is more convenient to measure. Zinc toxicity symptoms occurred with Zn concentration in plant shoots >240 mg/kg, and Ca:Zn ratios <35. Increases in total plant Zn concentration were partitioned into peanut stems more than into leaves. Zinc toxicity also reduced stem biomass accumulation to a greater degree than leaf biomass.     

Soil zinc and pH effects on zinc concentrations of corn plants

Abstract

Z1nc (Zn) deficiency of corn (Zea mays L.) has been detected in 20 or more states 1n the United States including Georgia. Since soil pH is a major factor in assessing the availability of soil Zn, this measurement has been included with acid extractable soil Zn in developing calibration Zn soil tests in North Carolina and Virginia. The objectives of this study were to develop a reliable soil test for Zn based on soil pH and Mehlich 1 soil Zn for corn gown on coarse‐textured soils and to compare our soil test values with those recently published from North Carolina where Mehlich 3 was the extractant. The study was conducted 1n 1979 to 1981 on a Tifton loamy sand (Plinthic Paleudult) site which had been used to study the influence of lime rates on micronutrient availability since 1970. Treatments consisted of four soil pH levels ranging from 5.3 to 6.6 and soil Zn levels ranging from 0.5 to 4.9 mg/kg. The Zn levels were established from the previous study where 5.6 kg Zn/ha had been applied annually for eight years (residual treatment) and by applying 3.36 or 6.72 kg Zn/ha during 1979, 1980 and 1981.

Soil Zn, corn shoot, and ear leaf Zn values were reflective of the amount of Zn applied except that the residual Zn treatment resulted in Zn concentrations > than the annual application of 3.36 kg Zn/ha. Zinc tended to accumulate in the soil and in corn leaf tissue more from the residual Zn than the recently applied Zn treatments, especially at the highest pH levels. Increasingly more soil Zn was required to increase corn shoot and ear leaf Zn one mg/kg as soil pH increased. In the initial year, each unit (kg/ha) of applied Zn increased corn shoot Zn approximately 4 units (mg/kg) at pH 5.3 and only 0.3 unit at pH 6.6. Zinc deficiency symptoms developed in corn shoots for the two highest soil pH levels in two of three years. Corn yields were increased by Zn only in 1980 and were increased by residual or applied Zn at pH levels of 6.2 and 6.6. Regression equations from these studies were utilized to develop predictive corn shoot and ear leaf Zn values over wide ranges in soil Zn and pH. Our field research data using Mehlich 1 extractant could possibly be used satisfactorily in North Carolina regression equations where Mehlich 3 was the extractant; however, certain limitations would need to be imposed in the North Carolina equations.     

Varietal tolerance of zinc toxicity in peanuts

Peanuts (Arachishypogaea) are more susceptible to zinc (Zn) toxicity than other crops. However, there is potential for rapid evolution of Zn tolerance in many species. The objectives of this study were to test a nutrient solution screening procedure for identifying Zn tolerant cultivars and to identify plant characteristics and cultivars which have potential for Zn tolerance. Florunner was used as the test cultivar to determine the optimum Zn and pH levels for the nutrient solution cultivar screening test. The screening test showed that VA 81B and NC 6 (both virginia‐type peanuts) were more Zn sensitive than Florunner and that N. M. Valencia C and McRan (both valencia‐type peanuts) were more tolerant than Florunner. Field tests were carried out at three locations in Tift County, Georgia: Gibbs Farm (1986–87), Richards Farm (1991), and Stephens Farm (1992). Two out of four field tests did not have adequate soil Zn levels to test Zn tolerance; soil pH between 5.0 and 5.5 and Mehlich 1 soil Zn level ranging from 15–20 mg/kg should be adequate for cultivar screening in the field. Spanish‐type cultivars (Pronto, Spanco, and Starr) had the lowest toxicity ratings and highest yields (Gibbs, 1987), but yields were not economically viable for any cultivars. Aboveground plant Zn or calcium (Ca): Zn ratio were not good indicators of cultivar tolerance. However, low hull Zn concentration, high hull Ca: Zn ratio, and high plant Zn: root Zn ratio correlated well with high yield and low toxicity rating. Minimization of Zn uptake by the hulls would evidently be beneficial in aiding peanut plants in tolerating high soil Zn levels while producing economic yields.     

Comparison of soil zinc extractants for detection of applied zinc and prediction of leaf zinc concentration

Abstract

Many soil extractants have been developed for determination of zinc (Zn) availability to plants. The optimum soil Zn extractant should be useful not only for prediction of plant Zn concentration but also for detection of applied Zn levels. The objectives of this study were: i) to compare soil Zn extradants for detecting applied Zn and for predicting peanut leaf Zn over a range of soil pH levels, and ii) to correlate other soil‐extractable Zn levels with Mehlich‐1. Soil and peanut leaf samples were taken from a field study testing pH levels as the main plots and Zn application rates in the sub‐plots. Extractable Zn was determined on soil samples using Mehlich‐1, Mehlich‐3, DTPA, MgNO₃, and many dilute salt extradants of varied strength and pH. Correlation of extractable soil Zn to cumulative applied Zn levels revealed Mehlich‐1, Mehlich‐3, DTPA, and AlCl₃ extradants to be among the best indicators of applied Zn. Leaf Zn concentration was best correlated with soil Zn extracted by dilute salts, such as KCl, CaCl₂, NH₄Cl, CaSO₄, and MgCl₂. Including soil pH as an independent variable in the regression to predict leaf Zn considerably improved R‐square values. The DTPA‐extractable soil Zn levels were very well correlated with Mehlich‐1‐extractable Zn. Mehlich‐3 extracted about 20% more soil Zn than Mehlich‐1, but Mehlich‐3 soil Zn was not as well correlated to Mehlich‐1 soil Zn as DTPA soil Zn. Lower pH solutions extracted more of the applied Zn, but more neutral solutions extracted Zn amounts which were better correlated with Zn uptake. On the other hand, Mehlich‐1, which had a lower pH, had better correlations with both applied Zn and leaf Zn than did Mehlich‐3. Shortening the DTPA extraction time to 30 minutes resulted in better correlations than the standard two hour extraction time. Chloride (Cl) was the best anion tested in relation to soil applied Zn recovery in combination with potassium (K), calcium (Ca), and aluminum (Al), and Cl optimized leaf Zn correlations for ammonium (NH₄), K, Ca, and magnesium (Mg). The larger the valence of the cation, the better the correlation with applied Zn and the poorer the correlation with leaf Zn.     

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.     

Diagnosis of zinc deficiency in canola by plant analysis

Abstract

Canola plants (Brassica napus cv. Eureka) were grown in soil culture with seven levels of zinc (Zn) supply (0, 67, 133, 200, 267, 533, and 1,067 μg Zn/kg soil) for 39 days. Critical Zn concentrations in young leaf blades and petioles were established for the diagnosis of Zn deficiency in canola plants during vegetative growth by assessing the relationship between the Zn concentration in the leaves and shoot dry matter on 22 and 39 days after sowing (DAS). Zinc concentrations in leaf blades and petioles increased with increasing Zn supply, but Zn concentrations were always 50% higher in the youngest open leaf (YOL) than in the youngest mature leaf (YML). The relationship between shoot dry matter and Zn concentrations in leaf petioles exhibited Piper‐Steenbjerg curvature, indicating their unsuitability for Zn‐deficiency diagnosis either alone or by inclusion with leaf blades. By contrast, inclusion of leaf mid‐ribs with leaf blades did not alter the relationship between shoot dry matter and Zn concentrations, nor the critical Zn concentration. Critical Zn concentrations in the YOL, YOL+1, and YOL+2 blade on 39 DAS, corresponding with the stem elongation stage, were 15–17, 9–10, and 7–8 mg Zn/kg dry matter, respectvely. In comparison, the critical Zn concentration in the YOL+2 leaf blades with mid‐ribs was 7–8 mg Zn/kg dry matter. In conclusion, during the vegetative stage up to stem elongation, YOL+2 leaf blades which are also the YML are recommended for the diagnosis of Zn deficiency in canola plants with the critical Zn concentration being 7–8 mg Zn/kg dry matter.     

Diagnosis of zinc deficiency in peanut (Arachis hypogaea L.) by plant analysis

Abstract

Critical values of zinc (Zn) concentration in young leaves Here established for the diagnosis of Zn deficiency in peanut by examining the relationship of Zn concentration in leaves to shoot dry matter (DM) at two growth stages of plants grown in pots of Zn deficient sand at seven levels of Zn supply (0, 67, 133, 200 267, 533, and 1067 μg Zn/kg soil). Zinc deficient peanut accumulated reddish pigments in stems, petioles and leaf veins in addition to the more common symptoms of Zn deficiency in plants. Zinc concentrations increased with increasing Zn supply in the blades of the youngest fully expanded leaf (YFEL) and in the blades of the leaves immediately older (YFEL+1) and younger (YFEL‐1) than it: they also increased with increasing Zn supply in the petioles of the YFEL+1 and YFEL and in the basal stem internode but their Zn concentrations Here always much lower than those in the blades. Critical Zn concentrations in the blades of the YFEL and YFEL+1 Here 8–10 mg Zn/kg DM at early pegging and mid pod filling: values for YFEL‐1 were similar but more variable. The blade of the YFEL is recommended for diagnosis of Zn deficiency in peanut and 8–10 mg Zn/kg DM as its critical value.     

Effect of soil zinc,pH, and cultivar on cadmium uptake in leaf lettuce (Lactuca sativa L. var. crispa)

Abstract

Six noncrisphead lettuce cultivars (Lactuca sativa L.) were grown in pots, using soil from field plots that had been amended annually with 90 MT/ha of an industrial sludge as part of a continuous study initiated in 1981. Two greenhouse experiments (each replicated 6 times) were completed—one in the spring and one in the fall. Variables included 6 cultivars, 2 soil pH levels and 2 soil Zn levels. All variables appeared to influence Cd accumulation in the leaf tissue. Uptake of Cd and Zn increased with decreasing soil pH for all cultivars. ‘Grand Rapids’ accumulated the least leaf Cd and ‘Summer Bibb’ the most. A positive correlation between leaf Zn and leaf Cd was observed, but the correlation between soil Zn and leaf Cd was variable.     

Tillage,lime, and poultry litter effects on soil zinc,manganese, and copper

Abstract

Long‐term no‐tillage has profound effects on soil properties which can affect the availability of plant nutrient elements. The objectives were to study the effects of tillage and lime treatments on soil pH and extractable soil micronutrients 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 per year). 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. The crop was corn (Zea maize L.). Soil samples were analyzed for pH and Mehlich‐1 zinc (Zn), manganese (Mn), and copper (Cu). Soil pH was higher for NT than CT and was higher in the spring than in the fall. Lime rates resulted in soil pH increases, but showed less difference for CT than NT. The three 8,960 kg ha^‐1 per four yr treatments caused an interaction in that for CT the pH increased more for 2,240 kg ha^‐1each year than for 8,960 kg ha^‐1 every fourth year and the opposite was true for NT. Extractable Zn, Mn, and Cu all responded to this interaction being lower for the higher pH plots. Extractable Zn was higher for NT possibly due to high Zn from the poultry litter and non‐incorporation for NT. Extractable Cu was lower for NT as expected from the soil pH, whereas extractable Mn was not affected by tillage. Extractable Zn and Cu both increased over time due to inputs from the poultry litter. Neither extractable Zn nor Mn responded to increasing lime rates, however Cu decreased with increasing lime rate. Extractable Cu was influenced mainly by soil pH differences due to tillage and lime. Extractable Zn was influenced much more by tillage and from inputs by the poultry litter and not as much by pH differences. Extractable Mn was the least responsive to tillage and lime treatments of the three micronutrients studied.     

Use of routine soil tests in predicting corn leaf zinc

Abstract

Zinc of index corn leaves samples from 91 Minnesota sites on numerous soil types was correlated with soil Zn extracted by four routine procedures. The EDTA?(NH₄)₂CO₃ ‐ extractable soil Zn was more closely correlated with leaf Zn than soil zinc extracted by 0.1N HCl, EDTA‐NH₄OAc, or by NH₄OAc ‐ dithizone. Soil pH, CaCO₃ equivalent, extractable P, and organic matter of both acid and calcareous soils were negatively correlated with leaf Zn. When EDTA ? (NH₄)₂CO₃ ‐ extractable Zn was included with routine soil tests, a prediction equation for corn leaf Zn was formulated and compared with analytical values. However, the use of 1.4 ppm EDTA ? (NH₃)₂CO₃, ‐ extractable soil Zn alone as a critical value was equally effective in predicting leaf Zn.     

Creeping bentgrass response to zinc in modified soil

Abstract

Interpretations of soil zinc (Zn) tests for golf course greens vary among testing laboratories, with little information in the literature on which to base these interpretations. Our studies determined the effects of increasing fertilizer Zn on extractable soil Zn and tissue Zn levels for five creeping bentgrass (Agrostis palustris Huds.) cultivars, to investigate their potential for Zn toxicity. The effects of Zn concentrations up to 4000 mg/kg were investigated in three greenhouse studies on a potted soil mix of sand, Nicolett (fine‐loamy, mixed‐mesic, Aquic Hapludoll) soil, and Hypnum peat in an 8:1:1 ratio. ‘Penncross’ bentgrass was used in the first two studies, and ‘Penncross’, ‘Penneagle’, ‘Cobra’, ‘Emerald’, and ‘Prominent’ were compared in a third study. Mean DTPA‐extractable soil Zn concentrations increased from 0.6 mg/kg in the controls to 652 mg/kg in the pots treated with 4000‐mg Zn/kg soil. Tissue Zn concentrations increased from a low of 50 mg/kg for grass on the control pots to a high of 1500 mg/kg for plants grown in soil treated with 4000 mg/kg soil. No consistent deleterious effects were observed on the grass tissue of any of the varieties. Our study demonstrates that creeping bentgrass is capable of tolerating very high levels of Zn without tissue damage.     

Limestone and gypsum effects on calcium nutrition of ‘Florunner’ and ‘NC‐7’ Peanuts

Abstract

Minimum sufficiency levels of hull and seed Ca for maximum yield and grade of runner or Virginia type peanuts (Arachis hypogaea L.) have not been established and there is limited information on single and combined effects of limestone and gypsum on production and quality of peanuts. Field experiments were conducted on runner and Virginia type peanuts to study single and combined effects of limestone and gypsum on yield and grade, and to attempt to establish minimum sufficiency levels of hull and seed Ca for maximum yield and grade of each type. Gypsum treatments, O, low, medium, and high rates, were superimposed on residual limestone rates on three sites with ‘Florunner’ (runner type) and on one site with ‘NC‐7’ (Virginia type) peanuts. Yield and grade of Florunner peanuts were not increased by limestone or gypsum treatments on any site even though soil Ca concentrations (Mehlich 1) ranged from 152 to 200 mg/kg among the sites. These levels were lower than the Georgia recommended minimum sufficiency value of 250 mg/kg. However, yield and grade of ‘NC‐7’ peanuts were increased by limestone or gypsum, but maximum yield occurred only where gypsum was applied even with soil Ca levels of 682 mg/kg. The minimum hull Ca level of 1.2 g/kg and seed Ca of 0.42 g/kg were sufficient for Florunner peanuts since yields and quality were not increased by limestone or gypsum application. Maximim yield and grade were achieved with Florunner at leaf, hull, and seed Ca concentrations of 13.2, 1.2, and 0.42 g/kg as compared with 26.0, 1.9, and 0.58 g/kg for NC‐7, respectively. These data show that NC‐7 has a higher Ca requirement than Florunner.     

Potassium,magnesium, and irrigation effects on peanuts grown on two soils

Abstract

Research data are limited on K and Wg requirements of peanuts (Arachis hypogaea L.) grown on sandy soils either with or without irrigation. Purposes of this study were (1) to determine Mg, K, and irrigation effects on yield, sound mature kernels (SMK's), and diseases of ‘Florunner’ peanuts grown on two sandy soils and (2) to determine sufficient amounts of Mg and K in peanut leaves and soils. Field experiments were conducted for three years on a Lakeland sand (thermic, coated Typic Quartzipsainments) and a Fuquay loamy sand (siliceous, thermic, Arenic Plinthic Paleudults). Both soils initially tested low in Mehlich 1 extractable K and Mg, but Lakeland was lower than Fuquay in both K and Mg. Factorial treatments were 0, 67, 67 (split into three applications), and 134 kg Mg/ha as MgS0₄ and 0, 56, 112, and 224 kg K/ha as KC1.

Neither irrigation, K, nor Mg treatment affected number of diseased plants. (Sclerotium rolfsii) or pod rot on either soil. Also, yield and % SMK's were not affected by any treatment any year on Fuquay soil. On Lakeland soil, yields were increased by irrigation 60.3% in 1980 and 11.0% in 1982, by K rates of 56 kg/ha or more each year, and by Mg rates of 67 kg/ha or more in 1978 and 1982. Yields (3‐yr average) were increased 14.7% by Mg with K and 30.7% by K with Mg. Magnesium plus K increased yields 69.3% over the control. Treatments had no consistent effects on % SMK's. Concentrations of K and Mg in leaves and soils were increased by increased rates of application but were not affected by irrigation. Minimum sufficiency levels for maximum yield were 10 and 2.0 g/kg for leaf K and Mg and 20 and 11 ng/kg for soil K and Mg (0 to 30 cm depth), respectively.     

Effect of extractable zinc,phosphorus, and soil ph on zinc concentrations in leaves of field‐grown corn

Abstract

The variability in corn yield responses to applications of Zn fertilizer appears to be associated with several complex soil and climatic factors that affect the availability of endogenous soil Zn to the crop under specific conditions. Among the soil chemical properties that influence availability of endogenous Zn are soil pH, organic matter content, and extractable P. Over a period of several years, soil and plant analysis data were collected from 54 field experiments, field trials, and diagnostic visits to producer's fields. These data were subjected to multiple regression analysis, resulting in an equation: Zn_leaf = 37.14 + 1.513 Zn_st ‐4.04 pH_st ‐ 1.791 ln(P_st/100) where Zn_st, pH_st, and P_st were 0.1N HC1 extractable soil Zn (kg/ha), 1:1 soil‐water pH, and Bray's 1 extractable soil P (kg/ha), respectively. These factors accounted for 67% of variation in leaf Zn, which was a large portion of the variability in Zn_leaf considering that climatic conditions, management levels, and varietal differences were uncontrolled in most instances. Using the previously published critical level in the leaf opposite and below the ear as 17 μg Zn/g, these data can be used to set required soil test levels of Zn at different levels of extractable P and soil pH. Inadequate levels of extractable Zn would range from 2.5 (at pH 6.0, P = 70 kg/ha) to, 9.5 kg/ha (at pH 7.5, P = 420 kg/ha).     

Zinc and copper toxicity in peanut,soybean, rice,and corn in soil mixtures

Abstract

Applications of zinc (Zn) and copper (Cu) at excessive rates may result in phytotoxicity. Experiments were conducted with mixtures of soils that were similar except for their Zn and Cu levels. The critical toxicity levels (CTL) in the soils and plants for these elements were determined. Peanut (Arachis hypogaea L.), soybean [Glycine max (L.) Merr.], corn (Zea mays L.), and rice (Oryza sativa L.) were the crops grown. One soil mixture had Mehlich 3‐extractable Zn concentrations up to 300 mg dm^‐3 with no corresponding increase in soil Cu; two soil mixtures had soil Zn concentrations up to 400 and 800 mg dm^‐3 with a corresponding increase in soil Cu up to 20 and 25 mg dm^‐3, respectively; and four soil mixtures had no increase in soil Zn, but had Mehlich 1‐extractable Cu concentrations from 6 to 286 mg kg^‐1. Under a given set of greenhouse conditions, the estimated Mehlich 3‐extractable Zn CTL was 36 mg dm^‐3 for peanut, 70 mg dm^‐3 for soybean, between 160 and 320 mg dm^‐3 for rice, and >300 mg dm^‐3 for corn. No soil Cu CTL was apparent for peanut or soybean, but for corn it was 17 mg dm^‐3 and for rice 13 mg dm^‐3. With different greenhouse procedures and the Mehlich 1 extractant, the soil CTL for rice was only 4.4 mg kg^‐1. Therefore, peanut and soybean were more sensitive to Zn toxicity, whereas corn and rice were more sensitive to Cu toxicity. Plant Zn CTL for peanut was 230 mg kg^‐1, while that for soybean was 140 mg kg^‐1. Copper appeared to be toxic to corn and rice at plant concentrations exceeding 20 mg kg^‐1.     

Effects of zinc fungicides and different zinc fertilizer application methods on soluble and total zinc in potato plant shoots

Abstract

The experiment was carried out to evaluate the effects of fungicides [with or without zinc (Zn)] and different Zn fertilizer application methods (no fertilizer; soil application; shoot application; soil plus shoot application) on the soluble and total Zn in the dry matter of potato shoots. Zinc fertilizer was applied to the shoots at 20 and 45 days after plant emergence (DAE), immediately before plant sampling. At 25 DAE, Zn fungicide increased soluble and total Zn in the fourth leaf. The same occurred, at 45 DAE, with the Zn fertilizer applied to the shoots. It were not observed significant increases on both soluble and total Zn contents in the fourth leaf of plants that received soil Zn fertilization. Even in the leaves with 262 mg Zn kg^‐1, there was no phytotoxicity symptoms. The total Zn concentration at 20 DAE was the best index correlated to potato tuber yield reaching 50.9 mg Zn kg^‐1 in the fourth leaf of plants at the highest marketable tuber yield treatment. Plant nutrient element contents [phosphorus (P), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), and manganese (Mn)] were not affected by the treatments.     

The relationship of soil and leaf nutrients to rice leaf oranging

A symptom called leaf‐oranging, indicating a deficiency of many nutrients, occurs in paddy rice (Oryzasativa L.) when production expands into some upland soils. Rice (Gui Chou cv.) was grown in culture pots in a flooded, weathered, upland soil (Nacogdoches) and compared to rice growth in a flooded soil currently used for paddy rice production (Dacosta) in Texas to understand the soil and plant factors involved in leaf‐oranging. Fertilizer rates of 0, 10, and 100 mg N/kg as (NH₄)₂SO₄ were applied to each soil along with phosphorus (P) and potassium (K) fertilizer. The orange Leaf Index (OLI), a measure of leaf‐oranging, was determined weekly and increased to 60–70% for plants grown in the upland soil but its progression was delayed by higher N treatments. No leaf‐oranging was observed in the paddy soil. The soil evoking leaf‐oranging was low in silicon (Si) and high in iron (Fe). In addition, analysis of leaves from these plants showed 19–25% higher leaf ammonium‐nitrogen (NH₄‐N), 9–137% higher manganese (Mn) levels and lower total N:NH₄ concentration compared to normal rice leaves four weeks after transplanting. This inferred that leaf‐oranging probably was associated with some degree of NH₄‐N toxicity and antagonism with K. Leaf‐oranging was also associated with low calcium (Ca) assimilation or Ca uptake inhibition because of the heavy Fe‐oxide coating of the roots of the affected rice plants. In this experiment, leaf‐oranging was not associated with toxic levels of Fe or Mn.     

不同水分状况下施锌对玉米生长和锌吸收的影响

选择潮土(砂壤)和土(粘壤)两种质地不同的土壤,进行盆栽试验,研究不同土壤水分条件下施锌对玉米生长和锌吸收的影响。结果表明,施锌显著增加了玉米植株根、茎、叶以及整株干物质重;缺锌条件下玉米植株根冠比、根叶比和根茎比趋向增大。施锌显著提高了玉米植株各器官中锌的浓度和吸收量,并明显促进锌向地上部运移。干旱胁迫抑制了玉米植株生长,根冠比、根茎比、根叶比增大;随着土壤水分供应增加,植株生长加快,各器官生物量以茎和叶增加大于根。水分胁迫下,在潮土上玉米叶片中锌浓度上升;在土上叶片中锌浓度下降。但增施锌后,根和茎锌浓度增加幅度较大,叶片增加幅度较小;施锌和水分胁迫对根和茎锌浓度的交互作用极显著。水分胁迫下,玉米植株对锌的吸收总量减少。水分胁迫和锌肥施用对玉米叶片、茎锌吸收量的交互作用十分显著,但对根锌吸收量的交互影响不显著。     

Soil pH and magnesium effects on manganese toxicity in peanuts

Manganese (Mn) toxicity can develop in peanuts grown on low pH soils. The objectives of this study were to quantify the impact of soil pH and magnesium (Mg) on the uptake of Mn and the development of Mn toxicity symptoms in peanut plants and to evaluate the use of the Mg:Mn ratio as a diagnostic tool for Mn toxicity in peanuts. Three greenhouse tests were utilized to meet these objectives: a study to determine dolomitic limestone effects, an experiment comparing rate effects of calcium (Ca), Mg, and potassium (K) on Mn toxicity, and a test to separate the effects of pH, Mn, and Mg on Mn toxicity. Soil, leaf, and stem samples were taken for analysis, and toxicity ratings were made. Increasing pH diminished the toxicity rating and leaf Mn concentration and increased the leaf Mg:Mn ratio. The toxicity rating was significantly correlated with both leaf Mn and Mg:Mn ratio, but leaf Mn generally had stronger correlations and was more useful in diagnosis. Magnesium application resulted in a marked reduction in the Mn toxicity rating and leaf and stem Mn concentrations in the second experiment; however, this result was not repeated in the final test. Using Mg to prevent Mn toxicity would require large Mg applications, which could have the serious detrimental effect of interfering with Ca uptake by the peanut fruit. Liming is the more practical method for avoidance of Mn toxicity in peanuts.     

Effect of pH on the uptake of cadmium,copper, and zinc from soilless media containing sewage sludge

Abstract

Swiss chard (Beta vulgaris cicla ’Fordhook Giant'), bean (Phaseolus vulgaris ’Hawksbury Wonder'), and Agrostis capillaris ’Parys’ were grown in soilless media composed of Pinus radiata bark and 0–41% by volume of dried sewage sludge containing [in mg/kg] cadmium (Cd) [22], copper (Cu) [1,116], and zinc (Zn) [1,121]. Sublots of all mixtures were adjusted to pH 4.5, 5.5, or 6.5. Shoot weights were not reduced by sludge addition but those of Swiss chard and bean shoots declined with pH. Shoot contents of Cu, Cd, and Zn increased with decreasing pH. Shoot Cu concentrations were always sub‐toxic, and in Swiss chard toxicity symptoms were not observed until shoot Zn content reached 1,300 mg/kg. Cadmium in Swiss chard shoots reached 22 mg/kg. Metal concentrations in the shoots were well correlated with total and extractable metals in the media only if pH was included in the regression equations.