Tuber yield and allocation of nutrients and carbohydrates in potato plants as affected by limestone type and magnesium supply

Abstract

Magnesium (Mg) is a nutrient that affects the development of plants and is mainly supplied through liming performed to correct soil acidity. By acting on photosynthesis and influencing carbohydrate partitioning in the plant, supplementary Mg supplied through soil or foliar application can increase the yield and quality of potato (Solanum tuberosum L.) tubers. The aim of this study was to evaluate the effect of supplemental Mg fertilization by soil or foliar application on plant nutritional status, tuber yield, and carbohydrate partitioning in potato crops in soil corrected with calcitic and dolomitic limestones. The experiment was carried out in pots under greenhouse conditions with a randomized block design in a 2?×?3 factorial scheme with four replications. Dolomitic limestone application and supplemental Mg fertilization via soil increased the concentrations of this nutrient in potato leaves. Liming with dolomitic limestone reduced the uptake of Ca and K by plants, but supplemental Mg fertilization did not alter the uptake of Ca, Mg or K. Supplemental Mg fertilization did not increase plant growth and tuber yield, even when calcitic limestone was used to elevate the base saturation to 60%; the exchangeable Mg concentration in soil was 9?mmol_c dm^?3, and the Ca:Mg relationship was 3.7. Liming with dolomitic limestone or providing supplemental Mg fertilization did not increase sugar and starch partitioning to the tubers.     

Evaluation of the growth and quality of the “Ife Plum” tomato as affected by boron and calcium fertilization

A local variety of tomato (Lycopersicon esculentum, Ife plum cv. 51691) was grown in soil culture for 5 months and treated with B at concentrations of 0, 1, 2, 4, 8, and 16 ppm as H₃BO₃, and Ca at 0, 40, 80, and 160 ppm as Ca(OH)₂. A significantly positive correlation was established between organic matter and water ‐ soluble B (r = 0.970), while the relationship between pH and B was negative (r = ‐0.490). Application of B at 2 ppm improved all growth parameters studied. Boron application higher than 2 ppm, induced leaf chlorosis and later necrosis of nodes and roots. Fruit yield correlated positively with soil ‐ B, stem diameter and floral number (r = 0.597, r = 0.650 and r = 0.812, respectively). Soil‐ and plant‐B were positively correlated (r = 0.790). Calcium when applied singly at higher levels increased total chlorophyll content of the leaf. Tomato fruit yield was optimum at B:Ca treatment concentration of 2 ppm B (4.48 kg/ha B) and 160 ppm Ca (358.4 kg/ha Ca), corresponding to a B:Ca fertilizer ratio of 1.80.     

Nitrogen,calcium, and magnesium fertilization affects growth and leaf elemental content of ‘dormanred’ raspberry

’Dormanred’ raspberry (Rubus species) plants grown in sand culture were subjected to varying concentrations of N, Ca, and Mg over a two‐year period. Increasing nitrogen fertilization resulted in linear reductions of leaf Ca, K, Zn, Fe, and Mn but did not affect leaf Mg. Leaf Ca and K increased linearly with Ca fertilization, but applied Ca had an antagonistic influence on leaf Mg. Magnesium fertilization had a positive influence on leaf Mg but negatively affected leaf K, Ca, and Mn. Plant growth was negatively correlated with leaf Ca and leaf K, but had a positive correlation with leaf Mg and Mn. Nitrogen fertilization increased plant growth up to the mid‐level of applied N, but additional N reduced plant growth.     

Response to molybdenum and limestone on wheat and barley grown on podzol soils

Abstract

Molybdenum applications had no effect on the grain yield of wheat or barley. Application of limestone increased barley yield at one of the three locations and had no effect on wheat yield at any location. The Mo concentration of boot stage tissue increased with added Mo. In most cases, 0.56 kg Mo/ha applications increased the Mo concentration of boot stage tissue above 10 ppm. Increases in Mo concentration due to added Mo were generally greater at higher rates of limestone application but the Mo x limestone interaction was statistically significant only for barley at the location having the lowest pH and for wheat at the two locations with the lowest pH. Molybdenum applied as a foliar spray was found to be an effective means of increasing the Mo concentration of cereal tissues. In the case of suspected Mo deficiency in cereals, a foliar application of 0.28 kg Mo/ha should correct the problem without any ill effect from an animal nutrition standpoint.     

Elemental leaf content and deficiency symptoms in rabbiteye blueberries: 2. Calcium and magnesium

In separate tests, rabbiteye blueberries (Vaccinium ashei Reade) grown in sand culture were subjected to varying levels of Ca (0–81 mg/liter) and Mg (0–24 mg/liter) applied at rates of 250 ml/plant daily. Other essential nutrients were kept constant. Leaf concentrations of N, P, K, Mg, Ca, Mn, Fe, Cu, B, Zn, Co, and Al were determined. The concentration of Ca in the leaves increased linearly but that of Cu decreased in response to increasing levels of Ca fertilization. Leaf concentrations of other elements were not significantly influenced by Ca fertilization. Leaf Mg and Al concentrations increased linearly in response to increasing levels of Mg fertilization. The P content in leaves followed a quadratic curve with increased Mg fertilization. Percent P increased from the 0 to 12 mg/liter levels and then decreased from the 12 to 24 mg/liter levels of Mg. High levels of Mg fertilization resulted in reduced Cu content of leaves.

Fertilization rates of Ca or Mg had little effect on shoot dry weight except at the 0 mg/liter levels. As leaf Ca decreased below 0.20% Ca, Ca deficiency symptoms became more prevalent. Magnesium deficiency symptoms increased as leaf Mg decreased below 0.15% Mg.     

Effets des engrais N,P et K sur le rendement et la qualite de l'ensilage ue mais

Abstract

Thirteen fertility trials were made throughout Quebec's corn growing region during 1972–74. These included eleven fertilizer combinations with corn silage as the test crop and were carried out on nine soils. Total dry matter and digestible nutrients (TDN) varied greatly from year to year, though, mean yields increased by 23 and 30 percent respectively with the 50 kg N/ha treatment, compared to control receiving no nitrogen fertilization. However, 150 kg N/ha was required to attain a maximum yield of 1250 kg/ha crude protein. Despite a 0.2 percent nitrate content found in the silage grown on the most northerly site, a 120 kg P/ha combined with 100 kg N and K gave the highest mean TDN production (9580 kg/ha).

Potassium fertilization affected plant K content of corn grown at the most northerly site only, where a 0.5 percent was found with the control on a suit containing low potassium levels. Further, striking increases in Ca and Mg concentrations were observed with corn grown on that soil. However, magnesium concentration ranging from 0.11 to 0.14 percent were found with nine field trials out of twelve. Also, low K:(Ca + Mg) ratios were found on three trials, which were increased with potassium fertilization levels of 150 kg K/ha. Accordingly, it is suggested that uptakes of 200, 48, 200, 30 and 30 kg/ha of N, P, K, Ca and Mg are required for good corn silage crops.     

Role of continuous nitrogen fertilization on nutrient composition of leaves sampled at various stages of growth and on yield of yam (Dioscorea rotundata)

Abstract

White yam (Dioscorea rotundata cv. Olonko) was grown consecutively for three growing seasons, i.e. from February to October of 1975, 1976 and 1977, and treated with six levels of nitrogen, viz: 0, 40, 60, 120, 160 and 200 kg N/ha in the field. Leaf samples were taken at four stages of growth as follows: vegetative, tuber formation, tuber development and tuber maturation, and analyzed for NO₃‐N, P, K, Ca and Mg.

Increasing nitrogen fertilization consistently increased leaf‐NO₃‐N, particularly at the vegetative stages of growth, while no consistent trend was established for leaf‐P. Leaf‐K was increased at low rate of nitrogen fertilization during tuber formation and maturation whereas leaf‐Ca increased only at tuber maturation in the presence of higher rates of nitrogen fertilization. There was a marked increase in leaf‐Mg at all stages of growth when N treatment was increased to 200 kg N/ha. A positive correlation (r = 0.84???) was obtained for leaf‐K at the vegetative growth stage with tuber yield, while leaf‐Mg was positively correlated with tuber yield at vegetative (r = 0.46?), tuber formation (r = 0.50?) and tuber development (r = 0.67??) stages. All other elements were negatively correlated with yield at all stages of growth. Tuber yield was highest at the 200 kg N/ha treatment.     

P ‐ Mo interactions on the yield and nodulation of white clover grown on limed‐lignite overburden materials

Abstract

A greenhouse study using lignite overburden surface soil from a lignite mine in northwest Louisiana was conducted to determine the yield response and nodulation of inoculated and non‐inoculated white clover (Trifolium repens L.) to P (0, 40, and 80 kg/ha) and Mo (0, 90, and 180 g/ha) fertilization. Results manifested a highly significant response of inoculated white clover to a single application of P and Mo. Application of P at the rate of 40 and 80 kg/ha increased the dry matter yield (DMY) of white clover by 164% and 154%, while Mo fertilization at the rate of 90 and 180 g/ha increased the dry matter yield (DMY) by 21% and 37%, respectively, over the control. The yield of white clover was also significantly affected by Rhizobium inoculation. Yield was increased from 2.1 to 2.5 Mg/ha which is equivalent to a 19% yield improvement over the non‐inoculated plants.

Nodule formation (NF), likewise, was significantly favored by P and Mo fertilization. Results also revealed that Rhizobium inoculation had remarkably improved the nodule count of white clover. Nodule count was increased from 0.4 to 5.5 or 1375% improvement between the inoculated and non‐inoculated plants. The non‐inoculated white clover also responded significantly to P fertilization, but not to Mo addition. Nodule formation, however, was not observed from the non‐inoculated white clover except at the highest rate of P and Mo additions. Increasing P supply significantly increased the concentrations of P, S, Na, and Ca but decreased the concentration of K in the clover. Mo additions resulted in increased concentrations of P and Ca. No significant P‐Mo interaction effects were observed on the nutrient concentration of white clover.     

Effects of nitrogen,boron and potassium on boron deficiency,leaf mineral concentrations,and yield of table beets (Beta vulgaris L.)

Abstract

Application of 11.2 kg B/ha and/or of 224 kg N/ha reduced the number of table beet (Beta vulgarisL. cv Detroit Dark Red) roots with B deficiency compared to low rates or no N or B application in three field experiments. In two of the three experiments, the 224 kg/ha N rate decreased B concentration in leaves when no B was added yet B deficiency of roots was reduced compared to the 56 kg/ha N rate. B application increased B concentration in leaves. Calcium concentration in leaves was higher at 224 kg N/ha than for 56 kg N/ha. Nitrogen concentration in leaves was increased by increasing the rate of N while K concentration was decreased at the higher N rate. Average number of roots with B deficiency was significantly higher for the Morse strain than for the Harris strain of ‘Detroit Dark Red’ in one experiment where the two strains were compared. There were no differences between the two strains in leaf B concentration but Ca concentration was higher in the Morse strain than for the Harris strain. Yields were higher at the 224 kg/ha rate of N than at 56 kg N/ha but were not consistently affected by B and K applications. There was no clear relationship of leaf N, Ca and K concentrations to B deficiency of roots     

Tomato response to long‐term potassium and lime application on a sandy ultisol high in non‐exchangeable potassium

In a ten‐year study of potassium (K) and lime application to a Kalmia sandy loam (fine‐loamy, siliceous, thermic Typic Hapludult), a soil high in nonexchangeable K, corn (Zea mays L.) and soybean [Glycine max (L.) Herr.] have not responded to applied K. The objectives of this study were to determine if a high K‐requiring crop such as tomato (Lycocersicon esculentum Mill. cv. Redpak) would respond to KCl fertilizer rate or lime type (dolomitic, calcitic, and mixed) and rate on such a soil. Potassium was applied at 0, 56, and 112 kg K/ha every year for ten years. Lime was applied at 0, 2, and 9 Mg/ha in calcitic, mixed, and dolomitic forms twice in ten years (1970 and 1973). In 1980, the tenth year of the study, tomato fruit was harvested by hand once‐over to simulate machine harvest and divided into four maturity groups by color. Soil pH was higher with dolomitic than calcitic lime. Soil K saturation was not influenced by lime rate or type. Fruit yield and leaf phosphorus (P), calcium (Ca), and magnesium (Mg) concentrations increased with increasing lime rates. Leaf K, manganese (Mn), iron (Fe), boron (B), copper (Cu), zinc (Zn), barium (Ba), strontium (Sr), and aluminum (Al) concentrations decreased with increasing lime rate. Leaf Mn, Ba, and Sr concentrations were lower with dolomitic than with calcitic lime. Lime type had no effect on tomato yield. Wide ranges in basic cation saturation ratios had little effect on yield. Soil K saturation and leaf K, Zn, and Ba concentrations increased with increasing K rate. Soil Ca and leaf Ca, Mg, and Al concentrations decreased with increasing K rate. Applied K had no effect on total yield but onceover marketable yield increased linearly with increasing K rate. Marketable yield increased 14% with an increase in K rate from 0 to 56 kg/ha. Thus, fruit maturity was apparently hastened by K fertilization.     

Corn forage yield and chemical composition as influenced by sulfur fertilization

Abstract

Soil sulfur (S) deficiency for plant growth has become an increasing problem in the United States. A field experiment was conducted to investigate effects of fertilization with 0 and 67 kg S/ha as a single or split application, in a Latin square design, on corn (Zea mays L.) forage yield and chemical composition. Sulfur fertilization by either method increased yield of whole plant and grain 7% and increased number of plants with two ears. Total S and sulfate‐S concentration in whole corn plants, leaf, stem, and grain were increased with S fertilization. The nitrogen (N):SO₄‐S ratio was a useful indicator of S deficiency.     

Influence of dolomitic limestone and N:P:K: Fertilization on the mineral composition of coastal bermudagrass grown under very acid soil conditions

Abstract

The influence of limestone and N:P:K fertilizer rates on elemental composition of Coastal bermudagrass forage was determined to evaluate causes for high yield responses to dolomitic limestone at high N:P:K rates, as well as severe stand loss, and chlorosis of bermudagrass in the unlimed treatments. Increasing N:P:K fertilization resulted in severe Mg deficiency. Maximum yields (when limed with dolomitic limestone) were associated with Mg concentrations of 1.0 g/kg plant tops. Magnesium lost to plant removal, Mg loss to enhanced leaching under N fertilization, and K interference associated with excess K accumulation at high rates of NK inputs all contributed to Mg deficiency. However, the accumulation of excess K, which interfered with Mg uptake when high rates of N and K were applied, was considered to be the primary cause of the observed Mg deficiency.     

Effects of saline nutrient solutions on the growth and accumulation of mineral elements in some tomato cultivars

Abstract

Tomato cultivars were grown in a saline nutrient culture system to investigate growth and fruiting responses in relation to the application of 3 mM potassium (K), 1.5 mM phosphorus (P), and 10 mM calcium (Ca). The deleterious effects of salinity on tomato stem growth and fruit yield were ameliorated following the addition of K, P, and Ca to the nutrient solution. Potassium levels in tomato leaves were increased 4‐fold compared to control plants in the presence of applied K. The use of K resulted in an increase in Na content, however, a comparatively low level of sodium (Na) was obtained in treatments receiving K, Ca, and P. Calcium content was greater than sufficiency levels in all treatments, whereas magnesium (Mg) declined with the increase in salinity. The amount of P in tomato leaves was increased 4–5 fold when the nutrient solution was supplemented with 1.5 mM P. Correlation of vegetative parameters, such as stem height and leaf growth to salinity, revealed no significant responses, however commercial parameters such as total soluble solids and fruit weight correlated significantly with the saline nutrient treatments.     

成都平原露地番茄施用钙、镁、锌、锰肥的效应

试验以成都平原露地番茄为研究对象,对中量元素肥料钙、镁及微量元素肥料锰、锌的施用效果进行了初步的研究。结果表明,Ca、Mg和Zn配合施用可使番茄产量增加10.0%以上;硝酸盐含量只有NPK处理的80.0%左右,Vc含量增加42.6%,糖酸比和固酸比增加;种植效益可增加10.0%以上。Mn对于增加番茄的产量、改善其品质的效果不明显。综合来看,Ca、Mg和Zn是成都平原露地番茄生长的营养障碍因子,且三者配合施用的效果优于单独施用。     

Effects of nitrogen carriers,nitrogen rates,and maturity on composition of smooth bromegrass

Abstract

Magnesium and Ca concentrations in smooth bromegrass (Bromus inermis L) were not affected by late‐winter applications of N. Magnesium concentrations were constant until rapid growth in mid‐May then they declined until early June harvest. Highest seasonal concentrations were found in the fall regrowth. Calcium concentrations declined as plants matured in spring. Highest seasonal Ca concentrations were found in the fall regrowth. Nitrogen, P, and K concentrations and K/(Ca+Mg) ratios were increased by N applications during early spring but did not differ significantly by early June harvest. Nitrogen and P concentrations decreased as plants matured in spring and fall. K concentrations and K/(Ca+Mg) ratios changed inconsistently from sampling date to sampling date. Forage yields were approximately doubled by 67 kg N/ha and tripled by 202 kg N/ha. Significant yield differences were related to different N carriers.     

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.     

The effect of nitrogen and boron soil applications on raspberry leaf N,B and Mn concentrations and on selected soil analyses

Abstract

Four years after yearly applications of N (0, 67, 134 and 268 kg/ha in a N rate trial) soil pH and soil extractable K, Ca and Mg were reduced. Boron application (1 kg/ha in a N x B interaction trial) increased hot water extractable soil B and soil extractable Mg. Old and new cane leaf N concentration was increased by N application but B application resulted in only a very small effect. Both N and B applications increased leaf B concentrations. Leaf Mn was increased by N application, probably because of the reduced soil pH. Boron had little effect on leaf Mn. It was concluded that leaf tissue is not suitable for determining the requirements of N and B fertilizer because of the instability of B concentrations in the leaves within and between seasons. Sampling of new cane leaves in July showed promise for diagnosing Mn requirements since the concentration during that month was relatively stable in three separate years of sampling.     

Elemental leaf content and deficiency symptoms in rabbiteye blueberries: 1. Nitrogen

Rabbiteye blueberries grown in sand culture were subjected to varying levels of N fertilization (0 ‐ 81 mg N/liter) applied in aqueous solution at the rate of 250 ml/plant daily. Essential elements other than N were kept constant. Shoot growth and leaf concentration of N, P, K, Mg, Ca, Mn, Fe, Cu, B, Zn, Co, and Al were determined. Shoot growth and percent leaf N increased with increased N levels. Shoot growth increased little at N fertilization levels of 0 ‐ 9 mg/ liter but increased rapidly at higher rates. N content in leaves followed a quadratic curve, with % N in leaves increasing more rapidly from 0 to 27 mg N/liter than from 27 to 81 mg N/liter fertilization levels. Leaf concentration of K, Ca, Mg, Mn, B, and Ca decreased linearly as N levels increased. Total content of all elements increased as N fertilization increased. Visual N deficiency became increasingly evident as % N content decreased below 1.4% N.

Nitrogen, the most utilized element in plants, is usually the first to become deficient in sandy soils low in nutrient content (1). Rabbiteye blueberries (Vaccinium ashei Reade) are often grown on acidic, sandy, upland coastal plains soils that are low in cation exchange capacity, organic matter content, and available nutrients. In these acidic soils, NH₄N is more available than in neutral soils (2). The NH₄N source appears to be more suitable for blueberry growth, resulting in greater nutrient uptake, plant growth, and % N of leaf tissue than did the NO₃N sources (5,6).

Nitrogen deficiency symptoms in rabbiteye blueberries are characterized by small, yellow and/or red leaves and stunted plants (3). Since young rabbiteye plants are very sensitive to fertilizer, similar chlorosis symptoms (yellowing or reddening of leaves) can be associated with over‐fertilization, possibly due to root damage (7). Cain (2) found that leaves from healthy container‐grown highbush (V. corymbosum L.) blueberry plants contained about 2% N and higher levels of K and Ca than field‐grown plants. Greenhouse and Field studies indicate that leaf N content in rabbiteye blueberries is usually lower, ranging from about 1.5 to 1.8 (3,7,8). Increased N fertilization decreased the nutrient uptake of other essential elements (Ca and Mg) in rabbiteye blueberries (6). In highbush, Popenoe (4) indicated that a depression of P and K might occur under conditions of high N levels.

This study was initiated to ascertain the effect of NH₄N fertilization levels on uptake patterns of essential elements and to determine the relationships of N fertilization, leaf N content, plant growth, and visible deficiency symptoms.     

Increasing root and leaf growth and yield in Mg‐deficient faba beans (Vicia faba) by MgSO4 foliar fertilization

Magnesium (Mg) deficiency reduces yield and quality of crops as Mg is involved in carbohydrate and protein anabolism. Foliar application of MgSO₄ represents a means of ameliorating the nutritional status of crops growing under conditions of deficiency. Foliar Mg application has been demonstrated to increase the chlorophyll concentration and vegetative yield of plants. However, in crop plants used for seed production, the limited number of available studies provides only conflicting results in terms of the efficiency of Mg leaf application on yield and quality. We have examined the effect of increasing Mg foliar application rates on differentially developed leaves and leaf stages with regards to Mg concentration, chlorophyll concentration and biomass formation. Our data reveal that in order to obtain significant effects MgSO₄ concentrations in the spraying solution should be higher than 50 mM, as lower concentrations did not lead to significant changes in the vegetative or generative material. Positive effects of the foliar application on chlorophyll concentration and leaf area were only measured in leaves treated with 200 mM foliar MgSO₄. The application of Mg did not affect the parameters chlorophyll, ion concentration and leaf area in the newly developing leaves, but it had an important influence with regard to yield traits, especially on the formation of pods. The quality of the seeds with regard to the protein concentration was reduced in response to the magnesium deficiency treatment, but the application of foliar magnesium prevented a significant loss of protein.     

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.