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Potential use of karanjin (3-methoxyfurano-2′,3′,7,8-flavone) as anitrification inhibitor in different soiltypesDeepanjan Majumdar Dr , Bhavesh Pandya , Anu Arora & SoniDharaa Department of Environmental Science , Institute of Scienceand Technology for Advanced Studies and Research , V.V. Nagar,Gujarat, 388120, IndiaPublished online: 06 Aug 2006.

To cite this article: Deepanjan Majumdar Dr , Bhavesh Pandya , Anu Arora & Soni Dhara(2004) Potential use of karanjin (3-methoxy furano-2′,3′,7,8-flavone) as a nitrificationinhibitor in different soil types, Archives of Agronomy and Soil Science, 50:4-5, 455-465, DOI:10.1080/03650340410001689406

To link to this article: http://dx.doi.org/10.1080/03650340410001689406

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POTENTIAL USE OF KARANJIN (3-METHOXYFURANO-2’,3’,7,8-FLAVONE) AS A NITRIFICATION

INHIBITOR IN DIFFERENT SOIL TYPES

MOGLICHE ANWENDUNG VON KARANJIN (3-METHOXYFURANO-2’,3’,7,8 FLAVONE) ALS NITRIFIKATIONSHEMMER IN

VERSCHIEDENEN BODEN

DEEPANJAN MAJUMDAR*, BHAVESH PANDYA, ANU ARORA and SONI DHARA

Department of Environmental Science, Institute of Science and Technology for Advanced Studies andResearch, V.V. Nagar, Gujarat-388120, India

(Received 30 January 2004)

Karanjin, a furanoflavonoid (3-methoxy furano – 2’, 3’, 7, 8-flavone), is obtained from the seeds of karanja tree(Pongamia glabra Vent.), which is reported to have nitrification inhibitory properties but has been tested in fewsoil types. Efficiency of karanjin as a nitrification inhibitor in seven different soils of India was tested in alaboratory incubation study. The soils (800 g) were adjusted to field capacity moisture content, fertilized withurea and urea combined with karanjin at a rate of 20% of applied urea-N (100 mg kg7 1 soil) and incubated at358C for a period of 7 weeks, during which urea [CO(NH2)2], ammonium (NH4

+), nitrite (NO27 ) and nitrate

(NO37 ) content in the soils was measured periodically and nitrification inhibition at different stages was

calculated. Urea hydrolysis was almost complete within 72 h of application in all the soils and was not affectedby karanjin. Karanjin had conserved ammonium in all the soils at all stages and nitrate formationwas effectivelyminimized. Nitrite in soils was short-lived and low. Nitrification inhibition by karanjin remained high for aperiod of approximately 6 weeks, decreased with time and ranged from 9– 76% for all the soils. The study showsthat this plant product can be an effective nitrification inhibitor in several types of soil.

Keywords: India; Karanjin; Nitrification inhibitor; Soil; Urea

1. INTRODUCTION

Nitrogen is the major nutrient controlling crop production in soils, and N fertilizershave made a major contribution towards improving agricultural productivity world-wide. However, fertilizer N-use efficiency needs to be improved further to attain betterproduction of crops and minimize fertilizer-related pollution of the environment(Sahrawat and Keeney, 1986).

*Corresponding author: Dr Deepanjan Majumdar, Department of Environmental Science, Institute ofScience and Technology for Advanced Studies and Research, V.V. Nagar, Gujarat-388120, India.Tel: (02692) 234955. Fax: (02692) 238355. E-mail: joy_ensc@yahoo.com/joy_ensc@rediffmail.com

Archives of Agronomy and Soil Science,August/October 2004, Vol. 50, pp. 455 – 465

ISSN 0365-0340 print; ISSN 1476-3567 online # 2004 Taylor & Francis LtdDOI: 10.1080/03650340410001689406

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The poor efficiency of fertilizer N is largely due to loss of added N bynitrification, denitrification, leaching, immobilization, run-off and ammoniavolatilization. Denitrification and leaching losses are associated with nitrificationof ammonium to nitrate. Nitrification leads to formation and emissions of N2Oand NO while denitrification leads to formation and emission of N2O and N2

while leaching of NO3 (produced via nitrification) leads to groundwater pollution(Prasad and Power, 1995). Nitrification inhibitors, when added with nitrogenfertilizers to the soil, delay the transformation of ammonium to nitrite by slowingdown the enzymatic activity of the soil nitrifiers and thus indirectly delayconversion of NO2 to NO3 (Zacherl and Amberger, 1990). Ammonium is retainedon clay minerals by ion exchange while nitrate readily leaches down from soil.Therefore, addition of a nitrification inhibitor will reduce the amount of nitrateleached as well as denitrification losses of N as N2O and N2 (Sahrawat, 1989).Nitrification inhibitors also suppress methane (CH4) emissions (Lindau et al., 1993;Ghosh et al., 2003). These are highly important positive environmental aspects ofnitrification inhibitors. Reduced N loss not only protects the environment, but alsoincreases nitrogen use efficiency, resulting in higher yields (Prasad and Power,1995).Despite a great interest in nitrification inhibitors, only a few compounds have been

adopted for agricultural use. The main problems are high cost involved in thedevelopment and economics of field use coupled with the variable results obtainedunder field conditions. In addition to synthetic nitrification inhibitors nitrapyrin orDCD, natural products from Neem (Azardiracta indica Juss) are reported tohave nitrification inhibiting properties (Reddy and Prasad, 1975; Sahrawat andParmar, 1975) and have been widely evaluated in India. Karanjin, a furanoflavonoid (3-methoxy furano – 2’, 3’, 7, 8-flavone), obtained from the seeds of Karanja, hasnitrification inhibitory properties (Sahrawat, 1974, 1981; Sahrawat and Mukherjee,1977). It is suggested that the furan ring present in karanjin is responsible for inhibitingnitrification (Sahrawat, 1996).There are reports that the efficacy of nitrification inhibitors like nitrapyrin and

DCD had decreased with increasing organic matter content of soil, whichadsorbed nitrapyrin and DCD to reduce their activity (Goring, 1962; Reddy, 1964;Chancy and Kamprath, 1986; Tate, 1987). An inhibitor can be regarded successfulonly when it inhibits nitrification efficiently in many different soil types. Karanjinhas not been tested in many different soil types and so the present study was setup to evaluate the efficacy of karanjin as a nitrification inhibitor in different soilstypes.

2. MATERIALS AND METHODS

2.1. Soil collection

Seven soil samples were collected from 0 – 15 cm depth at different regions in India(Table I) and composite soil samples from each location were prepared. Samples wereair-dried, crushed and passed through a 2 mm sieve and were set aside fordetermination of chemical and physical properties (Table II). Soils (800 g each) werepre-incubated for 72 h at field capacity moisture content before addition of thetreatments.

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2.2. Preparation of karanjin

Karanja seeds were obtained from Neem Mission, Pune, India. Karanja seeds werecrushed and this seed powder (500 gm) was defatted by boiling in hexane (2 l) in asoxhlet apparatus for 24 h. Karanjin was precipitated out on cooling the hexane extractin a refrigerator. After 72 h, the precipitate was collected and crystallized in ethanol andits melting point was observed. It was recrystallized a number of times in ethanol toyield the final product (Singh, 1966).

TABLE I Type and location of the soil samples used in the study

Soil type Location District State Remarks

Gangetic Alluvium Kolkata 24 Parganas West Bengal Illitic, Entisol, clay loam, formed bysilting of riverGanges

Alluvium Vallabh Vidyanagar Anand Gujarat Illitic, Inceptisol, Sandy loamDeepBlack Bharuch Bharuch Gujarat Montmorillonitic, Vertisol, Clayey,

Black cotton orRegur soil, alsocalled as tropical Chernozem

MediumBlack Bhuj Bhuj Gujarat Montmorillonitic, Vertisol, clayeyloam, derived frombasaltic trap

Red Dungarpur Dungarpur Rajasthan Kaolinite+Illite, Alfisol, SandyLaterite Santiniketan Birbhum West Bengal Kaolinitic, Ultisol, Sandy loamHilly Soil Kota Kota Rajasthan Illitic, Alfisol, Sandy loam,Gravelly

TABLE II Physico-chemical properties of the soil samples

Soil Type

PropertyGangeticAlluvium Alluvium

DeepBlack

MediumBlack Red Laterite Hilly

pH 7.1 8.6 8.1 8.3 7.8 6.6 8.2Conductivity* (mmhos cm71) 68 84 22 12 37 26 49Organic Carbon (%) 0.41 0.50 0.44 0.68 0.15 0.26 1.17K* (mg kg71) 25 18 39 8 9 3 23P* (mg kg71) 12 57 7 59 42 31 22Sulphate* (mg kg7 1) 17 7 13 21 13 8 22Mineralizable N* (mg kg71) 111 189 35 91 138 147 28CEC* (me 100 g71) 27 32 92 84 18 12 55Ca* (me 100 g7 1) 13 11 38 11 54 14 20Mg* (me 100 g7 1) 14 15 24 3 46 4 9Particle density (g cc71) 1.56 2.47 2.45 2.49 1.66 2.48 2.38Bulk density (g cc7 1) 1.09 1.32 1.41 1.41 1.28 1.62 1.33Max.WHC* (%) 27 41 49 47 31 34 32Porosity* (%) 30 40 42 43 23 40 44NH4

+-N (mg kg7 1) 5.4 3.2 7.1 8.8 3.5 2.1 4.4NO3

7 -N (mg kg71) 2.1 1.8 2.7 2.5 2.2 1.9 3.1NO2

7 -N (mg kg71) ND ND ND 0.04 ND ND 0.5

*Values are rounded up to the next whole number.ND=Not detectable.

457KARANJIN AS A NITRIFICATION INHIBITOR

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2.3. Treatments

Preincubated soil (800 g) in plastic pots (1.5 l) was treated with an aqueous solution ofurea (2000 mg N l7 1) to supply 100 mg N kg7 1 soil. A 200 mg l7 1 solution ofkaranjin was prepared by dissolving crystals of karanjin in acetone and the solution wasadded to the soil containing urea-N (100 mg kg7 1 soil) at the rate of 20% of applied N.Each soil was treated with urea alone and urea+karanjin, to observe the effects ofkaranjin on nitrification of applied N, making 14 treatments in all. The same amount ofacetone was then added to all other treatments, to nullify the negative effect of acetone(if any) on soil microflora. Acetone and karanjin in acetone were added drop by drop tothe soil at room temperature and the beakers were constantly stirred to ensure propermixing and immediate evaporation of added acetone. Soon after this, soil was broughtto the moisture content at field capacity (18%, w/w) by adding distilled water. Moistureloss from the beakers during the experiment was determined by weighing the beakers onevery alternate day and distilled water was added to make up for the loss.

2.4. Incubation

Soil (800 g) was taken in triplicate in plastic pots and treated with urea and ureacombined with karanjin and was then incubated at 358C for a period of 7 weeks.Moisture loss was found to be appreciable from these vessels and distilled water wasadded daily to maintain the moisture content at field capacity.

2.5. Periodic analysis of soil urea, NH4+, NO2

7and NO3

7

Soil samples were collected intermittently from the beakers and analysed for theircontents of urea, NH4

+, NO27 and NO3

7 by Diacetyl Monoxime Method (Bremner,1982), Indophenol Blue Method (Keeney and Nelson, 1982), Modified Griess-IlosvayMethod (Keeney and Nelson, 1982) and Phenol Disulphonic Acid Method (Ghosh etal., 1983), respectively. Soil urea-N content was estimated on the 1st, 2nd and 3rd dayswhile soil NO2

7 was estimated on 3rd, 5th, 8th, 10th and 15th.days. Both soil NH4+

and NO3 contents were estimated on 5, 10, 15, 37, 42 and 49th days. Nitrificationinhibition (%) by nitrification inhibitors was calculated by the formulae proposed bySahrawat (1996):

Inhibition of nitrification ð%Þ ¼ ðNU�NIÞNU

� 100

where NU ¼Nitrified N; i:e: ðNO3� þNO2

�Þ �N as per cent of total inorganic

N i:e: ðNO3� þNO2

� þNH4þÞ �N in soil fertilized with urea alone

NI ¼Nitrified N; i:e: ðNO3� þNO2

�Þ �N as per cent of total inorganic

N i:e: ðNO3� þNO2

� þNH4þÞ �N in soil fertilized with urea

combined with inhibitor

Nitrified N (%) was calculated at different stages of incubation by the followingformula:

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Nitrified N ¼ ðNO3� þNO2

�Þ �N

Total inorganic N i:e: ðNO3� þNO2

� þNH4þÞ �N

� 100

To calculate nitrified N by the above formula, initial soil NO2– -N, NO3

– -N andNH4

+7N have been subtracted from their respective content after treatment.

2.6. Statistical analyses

Duncan’s Multiple Range Test (DMRT) (Alder and Roesseler, 1977) was done todetermine significant differences between each pair of treatment means. All the datawere statistically analyzed by MSTAT-C (version 1.41), developed by Crop and SoilScience Division, Michigan State University, USA.

3. RESULTS AND DISCUSSION

3.1. Urea hydrolysis in soil

Urea was applied in soil through aqueous solution and so the time required for thedissolution of granular urea in soil was virtually removed and presumably theconversion of urea had started very early in soil. Urea estimation in soil was startedafter 24 h of its application, urea-N showed an appreciable reduction within 24 h andafter 72 h it was low in all the soils (Table III). In most of the soils (deep black, mediumblack, Gangetic alluvium, hilly, Tista alluvium), urea-N had come down to a level ofless than 50 mg kg7 1 soil while in laterite and red soils, urea-N was appreciable after24 h of application, decreasing appreciably to negligible levels after 72 h. The decrease

TABLE III Urea-N contents in soils treated with urea and urea combined with karanjin

Urea-N** (mg kg7 1 soil)

Soil+Treatment 1 DAI 2 DAI 3 DAI

Gangetic Alluvium (urea only) 42+ 15 cd 9+ 5 ab 2+ 1 aGangetic Alluvium (urea+karanjin) 52+ 24 d 4+ 1 a 0+ 0 aAlluvium (urea only) 36+ 21 bc 20+ 7 c 9+ 4 bAlluvium (urea+karanjin) 32+ 12 b 28+ 8 d 3+ 1 aDeep black (urea only 24+ 5 a 15+ 6 bc 10+ 4 bDeep black (urea+karanjin) 40+ 14 c 4+ 2 a 0+ 0 aMedium black (urea only) 40+ 9 c 20+ 8 c 3+ 1 aMedium black (urea+karanjin) 48+ 11 d 20+ 6 c 4+ 2 abRed (urea only) 95+ 42 e 82+ 22 ef 29+ 16 dRed (urea+karanjin) 91+ 31 e 75+ 25 e 38+ 14 eLaterite (urea only) 94+ 35 e 88+ 27 f 11+ 14 bLaterite (urea+karanjin) 97+ 41 e 24+ 11 cd 3+ 2 aHilly (urea only) 40+ 21 c 31+ 14 d 19+ 9 cHilly (urea+karanjin) 36+ 12 bc 15+ 8 bc 4+ 2 ab

DAI-Days of incubation.**All values are rounded up to the next whole number.Data represent mean+ SD, n=3.Values followed by the same letter are not different from each other statistically at 5% level of significance according toDuncan’s multiple range test (DMRT). DMRT has been done separately for different days of incubation.

459KARANJIN AS A NITRIFICATION INHIBITOR

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TABLE IV NH4+7N contents in soils treated with urea and urea combined with karanjin

NH4+7N** (mg kg7 1 soil)

Soil +Treatment 5 DAI 10 DAI 15 DAI 25 DAI 37 DAI 42 DAI 49 DAI

Gangetic Alluvium (urea only) 51.2+ 8 bc 44+ 9 b 33.4+ 5 ab 31.2+ 8 bc 29.7+ 6 bc 26+ 8 cd 17.7+ 7 bGangetic Alluvium (urea+karanjin) 56.5+ 11 c 47.8+ 4 bc 42+ 8 bc 41.0+ 10 c 38+ 9 d 34+ 12 de 32+ 11 cAlluvium (urea only) 35.7+ 9 a 33.5+ 6 a 29.5+ 5 a 19.8+ 4 a 10.2+ 4 a 9.0+ 5 a 6.4+ 3 aAlluvium (urea+karanjin) 56.6+ 2 c 42.3+ 9 b 38.7+ 7 b 32.8+ 3 bc 27.0+ 3 b 26.0+ 5 cd 22.4+ 4 bcDeep black (urea only 74.3+ 7 de 52.6+ 8 c 42.9+ 8 bc 36.1+ 5 b 29.3+ 5 bc 23.1+ 3 bc 9.5+ 6 abDeep black (urea+karanjin) 77.6+ 11 e 60.6+ 5 d 48.3+ 6 cd 44.6+ 4 c 41.0+ 9 d 40.0+ 5 e 33.4+ 2 dMedium black (urea only) 50+ 15 b bc 44.1+ 7 b 39.1+ 8 b 36.6+ 14 bc 30.8+ 5 bc 22.5+ 8 bc 10.3+ 2 abMedium black (urea+karanjin) 54.3+ 18 bc 47+ 6 bc 42.3+ 13 bc 38.7+ 11 c 33.8+ 3 cd 25.4+ 7 cd 13.3+ 7 abRed (urea only) 46.0+ 6 b 36.7+ 6 ab 30.0+ 3 a 26.5+ 6 ab 23.1+ 8 b 20.0+ 8 bc 16.0+ 8 bRed (urea+karanjin) 54.0+ 5 bc 49.6+ 12 b 47.5+ 9 cd 41.1+ 10 c 34.8+ 8 cd 33.6+ 7 de 25.5+ 6 cLaterite (urea only) 69.7+ 8 d 61.3+ 4 de 51.4+ 4 d 40.3+ 5 c 35.3+ 4 cd 30.3+ 6 d 21.0+ 5 bcLaterite (urea+karanjin) 73.0+ 5 de 68.0+ 4 e 54.3+ 2 d 44.6+ 3 c 39.9+ 6 d 33.0+ 9 de 25.3+ 2 cHilly (urea only) 54+ 15 bc 48.5+ 10 bc 36+ 7 ab 27.5+ 7 ab 25+ 9 b 14+ 5 ab 8.7+ 4 abHilly (urea+karanjin) 57+ 12 c 54.1+ 7 c 44.2+ 4 bc 41.8+ 8 c 39.1+ 5 d 34+ 11 de 29.7+ 9 c

DAI=Days of incubation.Data represent mean+ SD, n=3 ** SD Values are rounded up to the next whole number.All values of soil NH4

+7N content have been reported after subtraction of initial soil NH4+7N.

Values followed by the same letter are not different from each other statistically at 5% level of significance according to Duncan’s multiple range test (DMRT). DMRT has been done separatelyfor different days of incubation.

460

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TABLE V NO377N contents in soils treated with urea and urea combined with karanjin

NO377N (mg kg7 1 soil)

Soil +Treatment 5 DAI 10 DAI 15 DAI 25 DAI 37 DAI 42 DAI 49 DAI

Gangetic Alluvium (urea only) 6.1+ 2 ab 11.9+ 4 bc 6.1+ 3 ab 12.4+ 3 b 18.05+ 4 bc 30+12 bc 36.3+ 10 abGangetic Alluvium (urea+karanjin) 2.1+ 1 a 4.5+ 2 a 2.1+ 1 a 5.8+ 4 a 10.5+ 5 a 19+ 8 a 29.1+ 11 aAlluvium (urea only) 12.9+ 5 b 16.9+ 7 c 12.9+ 5 bc 29.4+ 8 d 46+ 14 d 53.6+ 14 d 58.9+ 11 cAlluvium (urea+karanjin) 4.1+ 2 a 8.4+ 4 ab 5.5+ 2 ab 12.7+ 4 b 20+ 8 bc 34.8+ 6 c 42+ 8 bDeep black (urea only 9.6+ 3 b 14+ 3 bc 9.6+ 5 bc 14.4+ 9 b 24.0+ 12 c 38.5+ 16 c 59.3+ 18 cDeep black (urea+karanjin) 2.8+ 1 a 4.5+ 1 a 2.8+ 2 a 7.6+ 4 ab 12.3+ 4 a 21.875+ 6 a 31.5+ 12 aMedium black (urea only) 10.5+ 4 b 14.5+ 4 b 18.8+ 8 c 21.8+ 6 c 24.9+ 11 c 28+ 10 b 42.5+ 15 bMedium black (urea+karanjin) 3.5+ 2 a 8.2+ 2 ab 7.4+ 4 bc 10.2+ 3 ab 12.5+ 7 a 17.7+ 5 a 32.7+ 10 aRed (urea only) 6.7+ 2 ab 8+ 3 ab 6.7+ 4 ab 9.9+ 2 ab 15.6+ 5 ab 24.5+ 8 ab 32.5+ 8 aRed (urea+karanjin) 2.2+ 1 a 4+ 1 a 2.2+ 1 a 5.7+ 2 a 11.0+ 4 a 19.9+ 6 a 28.5+ 7 aLaterite (urea only) 10.0+ 5 b 13.4+ 4 c 10+ 3 c 13.4+ 6 b 19.8+ 7 b 29.6+ 15 b 44.8+ 14 bLaterite (urea+karanjin) 3.1+ 2 a 8+ 3 ab 3.1+ 2 a 8.6+ 3 ab 11+ 6 a 18.9+ 9 a 31.5+ 8 aHilly (urea only) 8.2+ 3 b 10+ 5 bc 8.2+ 4 bc 12.4+ 5 b 19.1+ 7 bc 30+ 11 bc 37.6+ 15 abHilly (urea+karanjin) 2.9+ 1 a 3.4+ 2 a 2.9+ 1 a 9.6+ 4 ab 14.4+ 98 ab 26+ 5 ab 29.7+ 11 a

DAI-Days of incubation, SD values are rounded up to the next whole number.Data represent mean+ SD, n=3.All values of soil NO3

77N content have been reported after subtraction of initial soil NO377N.

Values followed by the same letter are not different from each other statistically at 5% level of significance according to Duncan’s multiple range test (DMRT). DMRT has been done separatelyfor different days of incubation.

461

KARANJIN

ASA

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NIN

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in soil urea-N was nonlinear during 72 h in all the soils. Karanjin apparently did nothave any negative influence on urea hydrolysis.

3.2. Dynamics of ammonium, nitrite and nitrate in soil

Ammonium estimation was started on the 5th day after application of urea-N, withinwhich urea starts to get hydrolyzed to ammonium in soil (Tisdale et al., 1995).Ammonium had a continuous decrease with time due to nitrification but the rate ofdecrease was not linear in any soil. Karanjin application led to more ammoniumconservation as compared to respective controls (urea without karanjin) at all stages ofincubation in all soils (Table IV).Nitrite is an intermediate product during the nitrification and is short-lived due to its

quick conversion to NO37 by nitrifiers (Paul and Clark, 1996). In all the soils, nitrite

was low during the first 15 days, never reaching more than 9.2 mg kg7 1 soil after whichit was negligible in most soils (data not shown). There was no specific trend in soilNO2

7 contents and it fluctuated widely in all the soils [average coefficient of variation(CV)=77 – 162%].Soil nitrate increased with time due to nitrification in all the soils (Table V). Where

karanjin was applied, nitrate formation was much lower than the respective controls(without karanjin) due to more ammonium conservation, while soils treated with ureawithout karanjin had a higher nitrate content due to faster nitrification. In soil, NH4

+

and NO37 share a known relationship during nitrification i.e. as NH4

+ decreases,

���� ���� � �

� �

� �� �� �� �� ��

���������

�� �

���

�

��

��

��

��

������� ���������

���� ���������

���� ��� !���

"��#�$��%� �����&'� �()*�

+��$�%���� �����&'� �()*�

, - ��.�� /�)�.(

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FIGURE 1 Nitrate accumulation on nitrification of ammonium in soils treated with urea and urea+karanjin.

462 D. MAJUMDAR et al.

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TABLE VI Nitrification inhibition (%) by karanjin in different soils (values followed by same letter are not significantly different from each other at 5% level of significance)

Days of incubation

Soil name 5 10 15 25 37 42 49Mean Nitrification inhibition

(treatment wise)

Gangetic Alluvium 63 a 60 b 58 b 48 b 36 b 29 a 20 c 45Alluvium 76 b 69 c 66 b 57 c 48 c 33 b 28 d 54Deep black 70 ab 69 c 67 bc 54 c 39 b 33 b 19 c 50Medium black 68 ab 58 b 52 bc 47b 27 a 26 a 14 b 42Red 69 ab 58 b 56 b 46 b 29 a 23 a 18 c 43Laterite 68 ab 41 a 36 a 34 a 31 b 24 b 9 a 35Hilly 63 a 51 b 49 c 44 c 38 b 36 b 20 c 43Mean nitrificationinhibition (daysof incubation wise)

68 58 55 47 35 29 18

All values are rounded up to the next whole number.Data represent mean (n=3).Values followed by same letters are not significantly different from each other, according to Duncan’s multiple range test (DMRT). DMRT was performed separately for different days ofincubation.

463

KARANJIN

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NO37 increases although this change may not be proportionate to each other, since

NH4+ also gets reduced via ammonia volatilization and N2O and NO emission. A

curve fitting was done with NH4+ and NO3

7 to understand how closely they wererelated mathematically and it was found that they regressed with a high regressioncoefficient (R2) value (Figure 1).

3.3. Nitrification inhibition

In general, the amount of nitrified N was found to have increased in the later stages ofincubation and was high in all the soils at the end of 7th week. Nitrification inhibitionwas calculated to find out the efficiency of karanjin in nitrification inhibition. In general,nitrification inhibition was pronounced at the initial stages of incubation and decreasedwith time (Table VI). This may happen when a nitrification inhibitor remains effectiveonly up to a certain period of time in soil and becomes degraded in soil with time.During the incubation period, nitrification inhibition ranged from 9 to 76% in differentsoils. Average nitrification inhibition (%) did not have any significant correlation withorganic carbon content of the soils i.e. apparently organic matter content did notinfluence the activity of karanjin. In contrast, in some other studies (Goring, 1962;Reddy, 1964; Chancy and Kamprath, 1986; Tate, 1987) the efficacy of inhibitors likenitrapyrin and DCD was influenced by organic matter content of soils. Moreover,average nitrification inhibition did not correlate significantly with any of the other soilproperties.

4. CONCLUSION

Efficiency of karanjin in seven different soils types of India indicates that it is worthworking on this inhibitor, which holds the promise to be efficient in many soils. But ithas to be explored how it can be applied with fertilizers under field conditions on a largescale. It will also be interesting to watch its performance under field conditions, whichmay be largely different from its laboratory performance. The cost of its mass scaleproduction may not be too high since the trees are available in the wild and itsextraction and purification are not too expensive. But, only a little amount of purekaranjin can be procured from a large amount of karanja seeds, which may make massproduction time-consuming.

References

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Analysis, part 2 – Chemical and Microbiological Properties. American Society of Agronomy, Soil ScienceSociety of America, Inc., Madison, WI, USA, pp. 658– 664.

Chaney, H. and Kamprath, E. (1986) Effect of nitrapyrin in soils having different organic matter contents. SoilSci., 144, 211 – 218.

Ghosh,A.B., Bajaj, J.C., Hasan, R. and Singh,D. (1983) Soil andWater TestingMethods. Division of Soil Scienceand Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi.

Ghosh, S., Majumdar, D. and Jain, M.C. (2003) Methane and nitrous oxide emissions from an irrigated uplandrice of North India. Chemosphere: The Global Change Science, 51(3), 181 – 195.

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