Iron and Calcium Availability to Groundnut Plants as Affected by Calcium Carbonate and Water Levels...

Journal of Crop Improvement, Vol. 21(2) (#42) 2008Available online at http://jcrip.haworthpress.com

© 2008 by The Haworth Press, Inc. All rights reserved.doi:10.1080/15427520701885782 209

WCIM1542-75281542-7535Journal Of Crop Improvement, Vol. 21, No. 2, February 2008: pp. 1–22Journal of Crop Improvement

Iron and Calcium Availability to Groundnut Plants as Affected by Calcium Carbonate

and Water Levels in Calcareous SoilSarkar, Basavaraj, and KarJournal of Crop Improvement Reshmi Sarkar

B. BasavarajSandipta Kar

ABSTRACT. To assess possible causes of soil and plant iron defi-ciency and chlorosis in groundnut (Arachis hypogaea L.) on calcareousclay loam soils of Karnataka, India, a pot experiment was conducted toevaluate the availability of iron and calcium at varying levels of CaCO3and soil water and their influence on pod yield. The CaCO3 levels of thesoil achieved by liming were: 5% (C1), 7% (C2), 10% (C3), 15% (C4), and20% (C5) (on mass basis). Three soil water levels, i.e., 75% (M1), 150%(M2), and 200% (M3) of field capacity, were imposed for one week eachat flowering and pegging stages. Amorphous iron oxide-occluded iron,free iron oxide, and water-soluble calcium increased significantly withincreasing levels of soil water. The diethyl triamine pentaacetic acid salt(DTPA)-extractable Fe, however, decreased at higher levels of CaCO3and soil moisture. Conversely, the concentration of bicarbonate ionsincreased at higher levels of CaCO3 and soil water. The pod yield ofgroundnut, which was highest under M2C2, decreased at higher levels ofCaCO3. This decrease in groundnut yield at higher levels of CaCO3 was

Reshmi Sarkar and B. Basavaraj are affiliated with the Department of SoilScience and Agricultural Chemistry, University of Agricultural Sciences,Dharwad, Karnataka, 580 005, India.

Sandipta Kar is affiliated with Department of Agricultural and Food Engineer-ing, Indian Institute of Technology, Kharagpur, West Bengal, 721302 India.

Address correspondence to: Dr. Reshmi Sarkar, 301 Ball Street, Apt. 1079,College Station, TX 77840, USA. (E-mail: [email protected]).

210 JOURNAL OF CROP IMPROVEMENT

attributed to deficiency of available Fe, DTPA-Fe, as caused by theincreased concentration of bicarbonate ions.

KEYWORDS. Calcareous soil, water-soluble calcium, bicarbonate,DTPA-Fe, water-soluble iron, iron deficiency, iron oxides, pod yield ofgroundnut

INTRODUCTION

Iron is the fourth most abundant element, by weight, that makes up theearth crust and occurs mostly in the form of oxides. Though the blacksoils of India are a rich source of iron oxides, iron deficiency is a majorproduction constraint in these soils (Murti et al., 1977; Sharma et al.,2006). Black soils contain calcium carbonate nodules of different sizes;a condition that results in a widespread iron deficiency in this soil type(Yerriswamy et al., 1995).

Groundnut or peanut (Arachis hypogaea, L.) is an important cash cropgrown on calcareous, black soils of India. The production of groundnut oncalcareous soils, though favored by the availability of calcium, is oftenlimited by the deficiency of iron. High calcium carbonate in black soilsinterferes with iron uptake by plants (Franzen and Richardson, 2000).Iron in soils commonly is not readily available to plants because its avail-ability is controlled by factors such as soil pH, calcareousness, organicmatter content, and erosion (Hansen et al., 2003). In addition, high watercontent of the soil in the rainy season aggravates the problem (Hodgsonet al., 1992). Although several studies (Prasad and Sakal, 1991; Rao et al.,1993; Kulkarni et al., 1995; Samdur et al., 2000; Goos and Johnson, 2000;Heitholt et al., 2003) have evaluated the effects of iron deficiency onyield, the reason for iron deficiency and its occurrence in calcareous soilis not yet fully understood. Due to the unavailability of iron, a cropmanifests deficiency symptoms of iron most clearly through chlorosis(Morales et al., 1998; Nikolic and Romheld, 1999; Samdur et al., 2001;Wiersma, 2005). The importance of iron deficiency and the advantage ofits symptomatic analysis in groundnut led us to conduct a pot experimentto evaluate the influence of different forms of iron and water-solublecalcium present in calcareous soil, as induced by varying levels of CaCO3and soil moisture, on the uptake of calcium and iron and yield ofgroundnut.

Sarkar, Basavaraj, and Kar 211

MATERIALS AND METHODS

Pot Culture Experiment

A clay loam, which is grouped under the great group Calcareous TypicHaplustert, from the experimental farm of the University of AgriculturalSciences (UAS), Dharwad, was collected (0–15 cm). The collected soil wasdried, powdered, passed through a 2 mm sieve and utilized in the presentstudy. The experiment was conducted in a glasshouse at the experimentalfarm of UAS, Dharwad, Karnataka, India. The experiment included five lev-els of calcium carbonate: 5%, 7%, 10%, 15%, and 20% of the dry mass ofthe soil (designated as C1, C2, C3, C4, and C5) representing the prevalentlevels of CaCO3 in the soils of North Karnataka and three levels of watertreatment (75%, 150%, and 200% of field capacity moisture content bymass). The required amount for each level of calcium carbonate wasthoroughly mixed with the processed soil. The pots were filled with theprocessed soil and kept covered for two months to attain equilibrium. Thewater level was set to field capacity (FC) of the soil during this period of twomonths. Groundnut variety JL-24 was selected as the test crop. The seeds ofgroundnut were sown in January 2000, and the crop was raised at FCmoisture until the flowering stage using common cultural practices exceptfor the addition of gypsum (Sarkar, 2000; Prasad et al., 1999). The watertreatments, 75%, 150%, and 200% of FC, were imposed for one week atflowering and pegging. In these two crucial growth stages, required amountof water (less for 75% of FC and more for 150% and 200% of FC) wasadded to soil. The experimental site represented a hot, semi-arid eco-region.

Soil Analysis

The processed experimental soil was analyzed for pH, electrical conduc-tivity (EC), and organic carbon (Jackson, 1967). Water-soluble calcium(WS-Ca) present in the soil was extracted with double-distilled water(DDW, 1:1, w:v, soil:water) and determined by versenate method (Black,1965). Bicarbonate (HCO3

−) was estimated by titration of soil extract(1:2.5, soil: water) with 0.05 N sulfuric acid (Jackson, 1967). Oxalatereagent was used to extract amorphous iron oxide-occluded iron. A citrate-bicarbonate-dithionite (CBD) method was followed to extract free ironoxide, and both the forms of extracted iron were analyzed by atomicabsorption spectrophotometry (AAS; Mehra and Jackson, 1960; Milleret al., 1986). Diethyl triamine pentaacetic acid salt (DTPA) was used toextract available iron, which was estimated via AAS (Tandon, 1998).


Water-soluble Fe (WS-Fe) was extracted by shaking the soil for 16-h indouble-distilled water (1:40, soil: DDW) and estimated via AAS. (Miller etal., 1986). Initial concentrations of Ca, Fe, and HCO3

− as well as basicchemical properties of the soil are presented in Table 1.

Plant Analysis

Oven-dried (overnight at 70°C) plant samples were ground anddigested in diacid mixture (9:4, v:v, nitric acid:perchloric acid). Theextract was filtered and used for analysis of iron via AAS and for analysisof calcium using a versene-titration method (Tandon, 1998).

Statistical Analyses

The treatment combinations of five levels of CaCO3 and three levels ofsoil moisture regimes, three replications each, were applied in acompletely randomized design. The SAS software was used for analysisof variance and Windows Excel was adopted for a correlation–regressionanalysis (Hoshmand, 1994).

RESULTS AND DISCUSSION

Availability of Ca

The concentration of WS-Ca increased significantly with increasedlevels of either soil water or CaCO3 (Table 2). The highest concentration

TABLE 1. Basic chemical properties and initial concentration of bicarbonate ion, calcium, and iron of the experimental soil

Basic Chemical Properties

pH (soil : water, 1:2.5) 7.34Electrical Conductivity (dSm−1) 0.61Organic Carbon (%) 0.63

Initial concentration of bicarbonate ions, Ca, and Fe

Water-soluble Ca (mg/kg) 370

Bicarbonate (mg/kg) 537Amorphous iron oxide-occluded iron (mg/kg) 1064Free iron oxide (mg/kg) 423DTPA-Fe (mg/kg) 8.49Water-soluble iron (mg/kg) 0.89


of WS-Ca in soil after the harvest of groundnut was observed under M3C5,where the applied levels of soil water and CaCO3 were at their maximum.The higher soil-water levels have been shown to increase dissolution of CO2produced from root respiration, and this action could ultimately lead togreater dissolution of CaCO3 (CaCO3 + CO2 + H2O = Ca2+ + 2 HCO3

−)(Mengel and Kirkby, 2001) and thus release more WS-Ca under M3 thanunder M1 or M2. The increasing trend for HCO3

− ion was similar to that ofWS-Ca, as the increased water in soil increased the HCO3

− concentration.Similar results were also reported by Boxma (1982) and Toselli et al. (2000).

Availability of Fe

The concentration of free Fe oxide and amorphous Fe oxide-occludedFe also increased significantly with increased water levels (Table 2). Theconcentration of Fe oxides, however, decreased with increasing levels ofCaCO3. Similarly, WS-Fe also increased with increase in soil water butdecreased with increasing CaCO3 (Table 2). The interaction effects of soilwater and CaCO3 showed that the WS-Fe was highest under M3C1. The

TABLE 2. Effect of different levels of soil water and CaCO3 on the concentration of water-soluble Ca, bicarbonate ion, and of different forms

of iron in calcareous soil (after harvest of groundnut)

Treatments Water- soluble Ca

(mg/kg)

Bicarbo-nate

(mg/kg)

Free iron oxides (mg/kg)

Amorphous Fe oxide-occluded

iron (mg/kg)

Water- soluble

iron (mg/kg)

DTPA-Fe (mg/kg)

C1 108.67 628.00 395.00 1018.67 1.67 4.56C2 130.00 678.33 378.33 926.33 1.46 3.51C3 159.33 725.33 370.00 800.33 0.95 2.79C4 189.00 771.00 363.00 665.67 Trace 2.60C5 239.00 796.33 354.67 434.00 Trace 2.31M1 84.40 641.40 365.00 655.20 0.64 3.70M2 148.60 740.20 370.00 765.00 0.92 3.34M3 262.60 777.80 381.60 886.80 1.03 2.42

LSD (at 5% level)

M 13.65 24.10 3.82 57.97 0.14 0.13C 21.15 37.36 5.92 89.86 0.21 0.18M x C NS NS NS NS NS NS

NS = Not significant.C1 = 5% CaCO3; C2 = 7% CaCO3; C3 = 10% CaCO3; C4 = 15% CaCO3 and C5 = 20% CaCO3M1, M2, and M3 are respectively 75%, 150%, and 200% of field capacity moisture content bymass.


lower concentration of WS-Fe at higher levels of CaCO3 might be due tohigher concentration of HCO−

3 ions, which increased the soil pH andreduced the solubility of iron (Thakur et al., 1995). On the other hand, anincrease in soil water intensified the reduced environment, whichincreased the solubility of Fe. A significant decrease in the concentrationof DTPA-extractable Fe was observed with increasing levels of soilmoisture and CaCO3, and the lowest concentration of DTPA-Fe wasdetected in soil under M3C5 (Table 2). This phenomenon was attributed tothe significant increase in HCO3

− ion concentration with increasing levelsof water and CaCO3. A significant negative correlation (r = −0.90) wasobserved between HCO3

− ion concentration and DTPA-Fe. Similarfindings were reported by Rao et al. (1993).

Calcium and Iron Uptake and Iron Chlorosis

A concomitant increase in the concentration of WS-Ca with anincrease in the levels of water and CaCO3 in the soil was observed, andthe content of Ca in haulm and kernel of groundnut also increased signifi-cantly (Figure 1). The accumulation of Ca was highest under M3C5 inhaulm and M1C5 in kernel.

FIGURE 1. Accumulation of Ca by plant and water soluble Ca in soil atvarying levels of CaCO3 and soil moisture. C1 = 5% CaCo3; C2 = 7%CaCo3; C3 = 10% CaCo3; C4 = 15% CaCo3; and C5 = 20% CaCo3, M1, M2,and M3 are respectively 75%, and 150%, and 200% of field capacitymoisture content by mass.

0

5

10

15

20

25

30

35

40

45

M1C1M1C2M1C3M1C4M1C5 M2C1M2C2M2C3M2C4M2C5 M3C1M3C2M3C3M3C4M3C5Treatments

Ca

accu

mul

atio

n (m

g/pl

ant)

0

50

100

150

200

250

300

350

400

Wat

er S

olub

le C

a (m

g/kg

of s

oil)

Ca uptake bykernel

water soluble Ca


A significant increase in the content of iron in haulm was observed withincreases in levels of soil water and CaCO3, and the concentration was high-est under M3C5 (Table 3). The accumulation of Fe in kernels also followed anincreasing trend with increasing levels of soil-water and CaCO3 levels. Theaccumulation of Fe in kernels was highest at M2C2 (the interaction effects oftreatments were found to be statistically nonsignificant).

The changes in leaf color and iron chlorosis were prominent underdifferent CaCO3 and soil-water levels. The yellowness of leaves increasedwith increased level of CaCO3 under M1 (Plate 1) as well as soil waterunder C5 (Plate 2) although the Fe concentrations in haulm and pod werehigher than those under other regimes. Several other researchers made asimilar observation, and determining iron chlorosis by estimating ironconcentration in upper plant parts has been a debatable matter (Mengel,1994; Montanez and Sanz, 1994; Toselli et al., 2000).

Pod Yield and Iron Chlorosis

The pod yield of groundnut increased significantly with increase in soilwater but decreased with an increase in CaCO3 (Figure 2). The highest

TABLE 3. Accumulation of iron by groundnut plants at varying levels of water and calcium cCarbonate in soil

Treatments Iron uptake by plant (mg/plant)

Iron in haulm (mg/kg of haulm)

Iron in kernel (mg/kg of kernel)

C1 0.480 528.86 184.00C2 0.778 655.96 189.78C3 0.690 753.47 196.64C4 0.619 832.05 202.22C5 0.547 903.02 207.16M1 0.555 633.87 192.49M2 0.673 745.24 195.44M3 0.705 766.73 199.95

LSD (at 5% level)

M 0.031 47.17 2.53C 0.066 73.01 3.92M x C NS NS NS

NS = Not significant.C1 = 5% CaCO3; C2 = 7% CaCO3; C3 = 10% CaCO3; C4 = 15% CaCO3 and C5 = 20% CaCO3M1, M2, and M3 are respectively 75%, 150%, and 200% of field capacity moisture content bymass.


pod yield was obtained under M2C2, closely followed by that under M2C1.Nevertheless, the pod yield closely corresponded with Ca accumulation inkernels (Figure 1) as evidenced by a significant correlation between them(r = 0.79). Mengel and Kirkby (2001) also observed a similar relationshipbetween pod yield of groundnut and WS-Ca of soil. Multiple regressionanalysis (Equation 1), explaining 72% of pod yield, revealed a significanteffect (P = 0.05) of WS-Ca, HCO3

− ion concentration and free Fe-oxide

PLATE 1. Iron chlorosis at different CaCO3 levels.

5% CaCO3 7% CaCO3 10% CaCO3 15% CaCO3 20% CaCO3

(under soil moisture level of 75% of F.C.)

PLATE 2. Iron chlorosis at different water regimes.

Soil water 200% of FC Soil water 75% of FCSoil water 150% of FC(under 20% CaCO3 in soil)


on pod yield of groundnut plants. The effect of WS-Ca, HCO−3 ion con-

centration and free Fe-oxide on pod yield was significant, as determinedvia the t-statistics.

The pod yield decreased with increasing levels of CaCO3 beyond C2under either M2 or M3. A decrease in the concentration of WS-Fe andDTPA-Fe at high CaCO3 or water levels might be the reason for thedecrease in pod yield and development of leaf chlorosis (Figures 1 and 2).As Ws-Fe was in a trace amount, correlation of DTPA-Fe with other ionconcentration was determined. This action revealed highly significantnegative correlations of DTPA-Fe with WS-Ca (r2 = −0.85) and withHCO−

3 ion (r2 = −0.90). The multiple regression relationship (Equation 2)

Pod Yield 129.559 0.075 WS-Ca 0.048 HCO 0.384

Free ir

3= − − + +−

oon oxide 0.015 Amorphous Fe oxide-occluded

Fe 2.905 WS-

−+ FFe 4.363 DTPA-Fe−

(1)

FIGURE 2. Effect of soil water and Ca on yield of groundnut. C1 = 5%CaCo3; C2 = 7% CaCo3; C3 = 10% CaCo3; C4 = 15% CaCo3; and C5 =20% CaCo3, M1, M2, and M3 are respectively 75%, and 150%, and 200%of field capacity moisture content by mass.

0

5

10

15

20

25

30

C1 C2 C3 C4 C5 C1 C2 C3 C4 C5 C1 C2 C3 C4 C5

M1 M2 M3

Treatments

Yie

ld (g

/pot

)

C = Ca levelsM = Moisture levels

Yield of haulm (g/pot)

Yield of pods (g/pot)


of DTPA-Fe with WS-Ca and HCO3− ion explained 83% of DTPA-Fe in

soil and, as demonstrated by the coefficients, showed greater effect ofHCO3

− ion than WS-Ca on DTPA-Fe. The multiple regression relation-ship (Equation 3) of pod yield with WS-Ca and HCO3

− ion also revealedhigher influence of HCO3

− ion in modifying yield than WS-Ca.

The results of multiple regression relationships clarified that HCO3−

ions had prominent effects on availability of Fe and in limiting pod yield.High concentrations of HCO3

- ions at high levels of CaCO3 and soil wateralso resulted in development of leaf chlorosis. The greater concentrationof HCO3

− ions in soil might have restricted iron translocation to upperportion of branches. A high concentration of Fe in chlorotic plantsoccurred in veins and in the apoplast, but Fe could not be translocatedacross the plasma membrane to intercostal cells in the presence of highHCO3

− concentration in apoplast (Rutland, 1971). The hypothesis alsowas well supported by the significant correlation between HCO3

− concen-tration and Fe content of haulm (r = 0.78). Other researchers havereported that a high level of HCO3

− ions in the soil affected metabolic pro-cesses in roots and leaves, thereby decreasing Fe availability in the soil andplant, which leads to the condition called “lime-induced Fe chlorosis”(Mengel, 1995; Tagliavini and Rombola, 2001; Ksouri et al., 2005).

CONCLUSIONS

Highest pod yield of groundnut was obtained when soil moisture wasat 150% of field capacity, along with the presence of 7% CaCO3. Levelsof CaCO3 above 7% decreased yield of groundnut on a calcareous clayloam. The presence of 7% CaCO3 level can be taken as the optimum levelfor healthy plant growth and appropriate accumulation of Fe and Ca. Thedeficiency symptoms of iron occurring in young leaves of groundnut werenot only due to lower concentration of available iron (DTPA-Fe andwater-soluble Fe) in calcareous soil but also due to higher concentration

DTPA-Fe = 9.150 0.003 WS-Ca 0.008 HCO3− − − (2)

Pod yield = Ws-Ca + 0.025 HCO3− −1 410 0 019. . − (3)


of bicarbonate ion, which restricted the translocation of iron to the inter-veinal cells of the upper part of branches, resulting in bicarbonate-inducediron chlorosis.

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