FLIES 304

Response of chickpea (Cicer arietinum ) to zinc fertilization and its critical level in soils of semi-arid tropics

KULDEEP SINGH and VK GUPTA

Department of Soils, Haryana Agricultural University, Hissar 125004, India

(Accepted." 06. 02.1985)

Key words: chickpea, zinc, DTPA extraction, critical level

Abstract. In a greenhouse experiment the response of chickpea (Cieer arietinum) to zinc fertilization was examined using 27 soils from the semi-arid tropics. The critical level of DTPA extractable soil Zn was evaluated. Zinc additions to the soil increased the dry matter yield of six weeks old plant shoot, grain and straw significantly at the 5 mgkg -1 level, but tended to decrease it at the 10 mg kg -1 level.

The DTPA extractable Zn of the soils ranged from 0.28 to 1.75 ppm and was nega- tively correlated at 1 per cent level with pH (r = - - 0.81) and positively with organic carbon (r = 0.79) and Olsen's P (r = 0.63). The per cent yield increase or decrease over zero zinc ranged from 67 to -- 16 in respect of gram yield and was positively correlated with available Zn (r = 0.86**). Zinc concentration in plants was greatly increased with the appfication of Zn and accumulation of Zn was higher in grain than straw. The critical level of available zinc in soil below which plant response to Zn fertihzation may be expected was 0.48 mg Zn kg -1 soil. Soils between 0.48 to 0.70 mg kg -1 of DTPA extract- able Zn appear boarderline and a negative response to applied Zn was observed in soils of high Zn category. The results show the suitability of DTPA soil test for demarcating soils on the basis of plant response to zinc fertilization.

Among the micronut r ien t disorders, zinc deficiency in field crops const i tutes

a major soil fer t i l i ty p rob lem in many areas o f the world. Therefore , a reliable

analyt ical me thod is needed to predict Zn ferti l izer needs o f various crops. In

recent years the DTPA has been repor ted [7] as being a useful ex t rac tan t for

zinc and three o ther micronutr ients (Fe, Mn and Cu) for near neutral and

calcareous soils. A high degree o f correlat ion be tween Zn ext rac ted by DTPA

and plant response by cereal crops to Zn applicat ion in different soils has

been repor ted by several workers [1,2, 5, 9 ] .

For a soil ex t rac t ion technique to be o f value in determining e lementa l

status o f soils and for predict ing the plant requirements , it is imperat ive to

calibrate the me thod based on yield responses to applicat ion o f fertilizers. As

critical values o f Zn as de termined by DTPA ext rac t ion varies f rom soil to soil

and f rom crop to crop [6], the present investigation was, therefore, under-

taken to s tudy the response o f chickpea (Cicer ar ie t inum L.) to Zn appli-

cat ion under greenhouse condi t ions and to evaluate critical level o f DTPA

extractable Zn for soils o f semiarid tropics.

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Fertilizer Research 8 (1986) 213-218 © Martinus Nifhoff/Dr W. Junk Publishers, Dordrecht - Printed in the Netherlands

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Materials and methods

Twenty seven surface soils were collected from Haryana state (India) to represent areas where chickpea is widely grown during rabi season as rainfed crop. Range and mean values o f some soil parameters of the soils used in the study are summarized in Table 1. These soils are typical of semi-arid regions, being low in organic matter and soluble salts and with pH values above 8.0 and with trace amounts of CaCO3. Olsen's P was low and ranged from 4 to 15 mg kg-1.

The soils were analysed for their initial available Zn content by extraction with DTPA solution (0.005M diethylenetriaminepentaacetic acid + 0.1 M triethanolamine + 0.01 M CaC12, with a pH of 7.3) using a soil x solution ratio of 1:2 and a shaking time of two hours [7]. Zinc was determined in the filtrates by atomic absorption spectrophotometry.

The greenhouse study was carried using 4 kg soil in polythene lined eathen- ware pots. Six chickpea (variety G-130) plants were grown in each pot. A basal dressing of N, P and K at the rate of 25, 50 and 50 mg kg -1, respectively was applied as analytical reagent grade urea, ammonium dihydrogen phosphate and potassium dihydrogen phosphate. The fertilizer treatments consisted of (i) zero Zn (Zno); (ii) 5 mgkg -1 o f Z n (Zns) and (iii) 10 mgkg -1 o f Z n (Znl0) as ZnSO4"7H20. The treatments were replicated thrice. The crop was irri- gated with deionized water when required.

Three plants from each pot were harvested 6 weeks after planting and

Table 1. Range and mean values of DTPA extractable soil zinc and some soil character- istics

Low Zn soil Medium Zn soil High Zn soil (L0.48 mg kg -1 ) (0.48-0.70 mgkg -1 ) (70.70 mg kg -1 )

11 5 No. o f Soils 11

DTPA extr. Zn (mgkg -1) Range 0.28-0.45 Mean 0.40

Textural class Sand to sandy loam

pH Range 8.6-8.9 Mean 8.8

E.C (mmhosem-lJ Range 0.14-1.19 Mean 0.30

Org. Carbon (%) Range 0.03 -0.35 Mean 0.11

Olsen's P (mg kg - 1) Range 4-9 Mean 7

0.49 -0.70 0.60

Sand to sandy loam

8.2-8.8 8.7

0.19-1.52 0.35

0.10-0.26 0.17

6-10 8

0.72-1.75 0.95

Sandy loam to silty loam

8.0-8.8 8.5

0.25 -1.28 0.48

0.12-0.55 0.32

8-15 12

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remainder at maturi ty. The plant samples were thoroughly washed, dried at 70 °C and the dry matter yield recorded. The plant materials were processed taking care to avoid any external contamination. Following digestion with nitric and perchloric acids the zinc content was determined by AAS. The critical limit of Zn in soil needed for proper growth o f chickpeak was deter- mined by plotting the per cent yield of increase or decrease of grain and straw against available Zn [3].

Results and discussion

The DTPA extractable Zn in soils ranged from 0.28 to 1.75 mgkg -1 and was negatively correlated with pH (r = - - 0 . 8 1 ' * ) and positively with organic carbon (r = 0.79**) and Olsen's P (r = 0.63**). The positive relationship of DTPA-Zn with organic carbon o f soils suggests that DTPA extracted organic complexed Zn. Likewise, the positive influence of available Zn on P was

possibly due to the presence of insoluble zinc phosphate which released Zn slowly with less possibility of fixation.

Responses of Zn application

The average yield data indicate that chickpea response to Zn fertilization was significant. A significant response of dry matter yield o f 6 weeks old shoot, grain and straw yields at matur i ty was obtained to increasing levels of Zn treatments over no zinc treatment. The averages for chickpea grain yields for all locations were: 5.21, 5.91, 5.63 g per pot for Zno, Zns and Znlo, respect- ively. However, no significant difference in yield was noted between the Zn treatments. Soils also showed significant difference in yield. Similarly inter- action between soil and Zn levels was significant. The results in Table 2 show that significant responses to supplemental Zn were obtained in only the soils

Table 2. Response of chickpea to the application of zinc

Zinc status No. of Parameter Average yield Yield increase (%) of soils soils (g pot -1) at Zn s

(mgkg-l) Zn 0 Zn s Zn~o Range Mean

/0.48 11 Six weeks old 1.7 1.8 1.8 2 to 30 1 0 (low) shoot

Grain 3.4 5.9 5.5 10 to 67 34 Straw 6.7 9.0 8.5 13 to 43 34

0.48 to 0.70 11 Six weeks old 1.5 1.7 1.6 --10 to 24 8 (medium) shoot

Grain 5.3 5.8 5.6 --9 to 27 9 Straw 8.1 8.3 8.3 --19 to 27 4

70.70 5 Six weeks old 1.8 1.8 1.7 --6 to 7 --1 (high) shoot

Grain 6.6 6.3 5.9 --16 to 6 --4 Straw 9.6 8.6 8.9 --21 to 1 - -9

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with DTPA extractable values Zn below 0.70 mgkg -1 . With soils rated low or medium in available Zn, the application of 5 mgkg -1 Zn increased the yield o f chickpea as compared with control. The soils of higher Zn status gave a reduction in yield, it was, therefore, concluded that no useful purpose was served in applying more than 5 mgkg -1 Zn to these soils.

The response to 5 mgkg -1 Zn over the control in shoot at six-weeks o f growth and in grain and straw at. maturity of low zinc soil category ranged from 2 to 30, 10 to 67 and 13 to 43%, respectively (Table 2). The per cent yield response to applied Zn decreased considerably as DTPA extractable soil Zn increased. The per cent mean yield increase at Zns over control in soils of the medium zinc group was 8, 9 and 4 for six weeks old shoot, grain and straw respectively (Table 2). All the soils of high zinc group gave negative response at the Zns level. A similar negative response with clusterbean to applied Zn was noted by Singh and Gupta [8].

The per cent yield values for the low Zn soils indicate yield responses of 9 to 40 per cent for grain, and 12 to 29 per cent for straw and can be attributed to zinc application. The magnitude o f Zn response was more pronounced for grain as compared to straw indicating thereby the role of zinc in grain forma- tion. The results obtained in the present study for the response of Zn ferti- lization to chickpea growth and production clearly show the need for inclusion of Zn in fertilizer schedule for soils o f low and marginal zinc status.

Concentration of zinc

Mean values of all soil treatments indicate that Zn concentration in six weeks old shoot, grain and straw ~increased significantly by zinc additions at both the levels o f Zn. The differences amongst various soils were also significant. The Zn concentration of the control in shoot at 6 weeks o f growth, and in grain and straw at maturity ranged from 12 to 75, 11 to 31, and 5 to 16mgkg -1, respectively (Table 3). The differences between zinc concen- tration at Zns and Znw levels were less than those between control and Zns level.

Table 3. Effect of Zn application on zinc concentration (mg kg -~ DM) of chickpea

Zn status No. of of soft soils (rag kg-1)

Parameter Zn concentration (mg kg -1 DM)

Zn o Zn s Znlo

Range Mean Range Mean Range Mean

/_0.48 11 Shoots 12-75 39 25-89 56 39-103 68 (low) Grain 11-25 15 23-39 32 34-48 42

Straw 5-12 8 8-16 13 12-22 16 0.48-0.70 11 Shoots 18-73 52 25-104 72 43-120 90 (medium) Grain 12-27 19 27-46 34 33-51 42

Straw 7-16 i0 9-19 12 11-21 16 70.70 5 Shoots 29-43 37 37-103 67 41-115 80

Grain 12-31 19 25-44 33 26-51 40 Straw 7-11 9 9-14 12 11-17 14

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Critical level of available soil zinc

The critical level of available Zn was obtained by plotting per cent yield increase or decrease in comparison to the treatment without Zn against DTPA extractable Zn values in accordance with Cate and Nelson (3) graphical method. The value thus established was 0.48 mgkg -1 below which economic response to zinc fertifization may be expected (Figure 1). Considering that a soil which gives more than 20% yield increase, 82% of the soil containing 0.48 mgkg -1 DTPA extractable Zn or less, recorded significant reponse to Zn treatment. The critical values of soil zinc were essentially the same as deter- mined on the basis of either grain or straw yields (Figure 1). In earlier studies

I+ < 6 0 LU n ,

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Figure 1. Scatter diagrams of % yield increase or decrease in chickpea grain and straw vs DIPA-Zn in various soils

critical levels of about 0.56, 0.60 and 0 .68mgkg -1 have been reported for pearl-millet, maize and wheat crops, respectively [4, 1, 5]. However, the critical levels of DTPA extractable Zn, in the present study was estimated as 0.48 mg kg -1 reflecting a lower sensitivity o f chickpea to zinc deficiency as compared to wheat and maize. Softs between 0.48 to 0 .70mgkg -~ of DTPA extractable Zn appear boarderline and chickpea may or may not show significant yield increases from Zn fertilization. Correlation coefficients relating soil extractable Zn with yield response of various crops to added Zn are often used as a criterion by which Zn soil extraction methods are evalu- ated. The correlation coefficient obtained in this study between DTPA extractable Zn and per cent yield increase was significant at 1% level (r = 0.86) for grain and (r = 0.94) for straw. The results clearly reveal that the DTPA soil extraction technique for Zn was quite effective in separating soils on the basis of plant response to Zn fertilization.

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Refe rences

1. Bansal RL, Takkar PN, Sahota NS and Mann MS (1980) Evaluation of soil procedures for predicting zinc availability to wheat under calcareous alkaline field conditions. Field Crops Res 3, 43 -51

2. Brown AL, Quirk J and Eddings JL (1971) A comparison of analyticalmethods for soil zinc. Soil Sci Soc Amer Proc 35 ,105-107

3. Catc RB and Nelson LA (1965) A rapid method of correlation of soil test analysis with plant response data. Inter Soil Testing Tech Bull 1, pp. 15

4. Gupta VK, Raj H and Singh K (1981) Pearlmillet response to zinc and its critical level in south-western soils of Haryana. J Indian 8oc Soil Sci 29 ,134-136

5. Gupta VK, Raj H and Singh M (1981) Evaluation of critical limit of DTPA extract- able soil zinc for predicting wheat response to applied zinc. Haryana agric Univ J Res 11 ,512-516

6. Katyal JC (1973) Twelfth annual report of all India coordinated scheme of micro- nutrients in soils and plants, ICAR, New Delhi. pp. 101

7. Lindsay WL and Norvell WA (1978) Development of a DTPA soil test for zinc, iron, manganese and copper. Soil Sci Soc Amer J 4 2 , 4 2 1 - 4 2 8

8. Singh K and Gupta VK (1984) The critical level of zinc in soil and plant for predict- ing response of clusterbean to zinc application. Plant and Soil (Submitted)

9. Takkar PN and Mann MS (1975). Evaluation of analytical methods for estimating available zinc and response of maize to applied zinc in major soil series of Ludhiana, Punjab (India). Agrochimica 19, 420-429