Effect of Castor and Velvetbean Organic Amendments on ...

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Abstract: Effectiveness of castor (Ricinus communis) and velvetbean ... amendment rate until a level of about 4 g to 5 g of velvetbean or castor anaendment/pot.
S u p p l e m e n t to the J o u r n a l o f Nematology 30(4S):624-631. 1998. © T h e Society o f Nematologists 1998.

Effect of Castor and Velvetbean Organic Amendments on Meloidogyne arenaria in Greenhouse Experiments 1 C. H. S. P.

R I T Z I N G E R 2 AND

R. MCSORLEY3

Abstract: Effectiveness of castor (Ricinus communis) a n d velvetbean (Mucuna deeringiana) a m e n d m e n t s was tested for suppression o f the root-knot n e m a t o d e (Meloidogyne arenaria) a n d growth o f okra (Hibiscus esculentus) in three g r e e n h o u s e experiments. Regression analysis was u s e d to relate n e m a t o d e population data or p l a n t growth responses to various rates (0, 1, 2, 4, or 8 g / 5 6 0 c m s soil pot) o f each a m e n d m e n t in separate experiments. In general, p l a n t growth parameters r e s p o n d e d positively to the a m e n d m e n t rate until a level o f a b o u t 4 g to 5 g o f velvetbean or castor a n a e n d m e n t / p o t . Similar trends were observed for n e m a t o d e galls, egg masses, a n d second-stage juveniles extracted from root systems. In m o s t circumstances, quadratic equations best expressed the relationships between p l a n t or n e m a t o d e parameters a n d rates of velvetbean or castor a m e n d m e n t , leading to the a s s u m p t i o n that a best rate o f the a m e n d m e n t for plant growth or n e m a t o d e suppression can be predicted. In a third e x p e r i m e n t , in which both a m e n d m e n t s were c o m p a r e d directly, velvetbean a m e n d m e n t was m o r e efficient t h a n castor in s u p p r e s s i n g n e m a t o d e s as well as in improving p l a n t growth. Key words: Hibiscus esculentus, Meloido~ne arenaria, Mucuna deeringiana, n e m a t o d e , n e m a t o d e m a n a g e m e n t , okra, Ricinus communis, root-knot n e m a t o d e .

A variety o f organic a m e n d m e n t s has been used for management of nematodes. These amendments are associated either with reduced infection or survival of nematodes or with increases in microbial and animal species antagonistic to nematodes (Ichinohe, 1985; Linford et al., 1938; Mankau, 1968; Mankau and Minteer, 1962; Muller and Gooch, 1982; Rodriguez-KSbana, 1986; Sitaramaiah and Singh, 1978; Trivedi and Barker, 1986; Watson, 1945). Of the amendlnents tested by Ritzinger (1997), castor (Ricinus communis L.) and velvethean (Mucuna deeringiana [Bort.] Merr., M. pruriens DC) were the most effective in improving plant growth and reducing nematode population levels. There was insufficient evidence in these studies to conclude if nematode suppression was due to the release of toxic substances, to improved plant nutrition, or to the enhanced growth of antagonistic organisms. Effectiveness of nematode suppression by organic amendments generally depends on the amount of the amendment used, C /N ratio, and time of decomposition (McSorley and Gallaher, 1995a, 1995b).

Received for publication 9 March 1998. i A portion of a Ph.D. dissertation by the first author. Florida Agricultural Experiment Station Journal Series No. R-06190. 2 Centro de Pesquisa Agroflorestal do Acre, EMBRAPA, Caixa Postal 392, CEP 69900-000 Rio Branco, Acre, Brazil. 3 Professor, Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32611-0260.

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Singh and Sitaramaiah (1994) reported that the decomposition rate of an amendment depends on the soil type and the climate. Since the rate of organic amendment decomposition is also related to the amount applied, nematode suppression is related to both the quantity and quality of the decomposition products (Singh and Sitaramaiah, 1994). Although many studies have shown that the amount of the organic amendment is i m p o r t a n t in n e m a t o d e suppressi on (Holtz and Vandecaveye, 1938; Linford et al., 1938; Mankau, 1968; Mankau and Minteer, 1962; McSorley and Gallaher, 1995b; Rodriguez-K,~bana, 1986; Sitaramaiah and Singh, 1978; Watson, 1945), f u r t h e r research on the quality and quantity of amendments still is needed to stimulate their widespread use (McSorley and Gallaher, 1995a, 1995b). Castor and velvetbean were chosen for greenhouse studies because they had been used in earlier tests as organic amendments, had suppressed Meloidogyne arena~a (Neal) Chitwood race 1, and had provided the best p l a n t growth r e s p o n s e a m o n g several amendments tested (Ritzinger, 1997). The objectives of these greenhouse experiments were to determine which amendment type was m o r e effective in i m p r o v i n g pl ant growth and suppressing M. arenaria race 1 on okra (Hibiscus esculentus L.) and to determine the effects of various application rates

Organic A m e n d m e n t s : Ritzinger, McSorley 625 specified below for each experiment. Plants w e r e m a i n t a i n e d in a g r e e n h o u s e a n d sprayed twice p e r week with a dilute soap solution to reduce infestations of whiteflies. MATERIALS AND M E T H O D S No o t h e r pesticides or fertilizers were apT h r e e e x p e r i m e n t s were carried out in a plied. g r e e n h o u s e d u r i n g s u m m e r a n d fall 1996 At harvest, o k r a plants were r e m o v e d o n the University o f F l o r i d a c a m p u s in f r o m the soil, a n d s t e m d i a m e t e r , p l a n t Gainesville, Florida. Castor a n d velvetbean height, a n d fresh top weight were recorded. plants to be used as dry organic a m e n d - Root galls a n d egg masses were rated accordments for all three e x p e r i m e n t s were grown ing to the root-knot index of Taylor a n d in 18-cm-diam. clay pots. A b o v e - g r o u n d Sasser (1978), w h e r e 0 = 0 galls or egg parts o f b o t h types of plants were harvested masses p e r r o o t system, 1 = 1-2, 2 = 3-10, 3 before the reproductive stage. Leaves a n d -- 11-30, 4 = 31-100, a n d 5 = m o r e than 100 stems o f e a c h were c h o p p e d separately, galls or egg masses p e r r o o t system. In the m i x e d well, a n d then air-dried until constant first a n d second experiments, eggs were exweight was reached. It r e q u i r e d 6.9 g a n d 4.4 tracted f r o m egg masses in the okra r o o t g o f fresh castor a n d velvetbean, respec- systems with 1.05% NaOC1 (Hussey a n d tively, to obtain 1.0 g of dry a m e n d m e n t . A Barker, 1973). T h e extracted eggs were then mineral analysis of each a m e n d m e n t , deter- incubated on B a e r m a n n trays (Rodriguezm i n e d according to m e t h o d o l o g y described K~bana a n d Pope, 1981) for 7 days, a n d the elsewhere (Ritzinger, 1997), is p r e s e n t e d in h a t c h e d J2 were counted. In the third exTable 1. p e r i m e n t , the same technique was used but For all experiments, 2-week-old seedlings with only 10 egg masses f r o m each root sysof ' C l e m s o n Spineless' okra (Hibiscus escul- tem. After those 10 egg masses were reentus L.) were used as test plants. Seedlings m o v e d f r o m the root system, the r e m a i n i n g were transplanted, one p e r pot, into plastic r o o t system was i m m e r s e d in a phloxine B pots filled with 560 cm 3 of steam-sterilized solution (0.15 g / 1 tap water) (Southey, field soil m i x e d with sand in a ratio o f 1:1 by 1982) f o r r a t i n g all the r e m a i n i n g e g g volume. T h e composition of the soil mixture masses and galls. At harvest, a soil sample for all e x p e r i m e n t s was 95% sand, 4% clay, was taken f r o m each p o t to d e t e r m i n e the and 1% silt. final p o p u l a t i o n of J2 in 100 cm 9 soil f r o m O n e day after transplanting, the pots re- the infested treatments by m e a n s o f the cenceived n e m a t o d e i n o c u l u m a n d a m e n d m e n t trifugal flotation technique (Jenkins, 1964). treatments according to the r e q u i r e m e n t s of T h e e x p e r i m e n t a l design differed someeach experiment. T h e inoculum t r e a t m e n t what for each e x p e r i m e n t ; however, data consisted o f 1,000 fresh second-stage juve- were statistically analyzed as a completely niles (J2) o f Meloidogyne arenaria race 1, r a n d o m i z e d factorial design in all cases. In which had b e e n increased on 'Rutgers' to- the first two experiments, which involved m a t o (Lycopersicon esculentum Mill.). Pots different rates of a m e n d m e n t s , regression with n o J 2 c o n s t i t u t e d the n o - i n o c u l u m analysis was used to d e t e r m i n e the pattern t r e a t m e n t . A m e n d m e n t t r e a t m e n t s a r e o f response o f each m e a s u r e d variable to the

of these a m e n d m e n t s on n e m a t o d e levels a n d plant growth.

TABLE 1.

Mineral analysis and C / N ratio of the organic a m e n d m e n t treatments. Macronutrients (percent)

Micronutrients (ppm)

Amendment

C/N ratio

N

P

K

Ca

Mg

Mn

Zn

Cu

Fe

Castor Velvetbean

7.91 8.68

2.26 2.20

0.34 0.23

3.20 1.39

1.64 1.40

0.53 0.39

280 460

105 1,070

34.25 12.00

61.50 60.75

Data are means of five replications from the aerial plant parts harvested before the reproductive stage.

626 Supplement to the Journal o f Nematolog), Volume 30, No. 4S, December 1998 a m e n d m e n t rate at e a c h i n o c u l u m level. Since a quadratic regression resulted in a better fit (higher r 2) for all cases, it was chosen to r e p r e s e n t the trend r a t h e r than a linear regression. Analysis of variance was applied to the factorial designs and, when a main effect was significant with no interactions, a separate analysis was carried out a n d m e a n s were separated with Tukey's test (SAS Institute, Cary, NC). Experiment 1 - velvetbean amendment: O n 27 May 1996, 2-week-old okra seedlings were transplanted individually into each p o t receiving i n o c u l u m a n d a m e n d m e n t r a t e treatments. T h e i n o c u l u m t r e a t m e n t consisted of 0 or 1 , 0 0 0 J 2 / p o t . T h e a m e n d m e n t was applied as a m u l c h at the top o f the p o t at rates of 0, 1, 2, 4, or 8 g o f dry velvetbean p e r pot. T h e e x p e r i m e n t a l design was a 5 x 2 factorial with 10 replications (5 for each harvest date). O n 1 July, 35 days after inoculation, half o f the e x p e r i m e n t was harvested and plant pm-ameters and n e m a t o d e data were recorded. O n 23 July, 57 days after inoculation, the r e m a i n d e r of the e x p e r i m e n t was harvested a n d the same plant and nematode p a r a m e t e r s were recorded. At this time, J2 were extracted f r o m 100 cm 3 soil a n d counted. Experiment 2 - castor amendment: Two-weekold o k r a seedlings were transplanted a n d inoculated on 18 J u n e 1996. T h e i n o c u l u m consisted of 0 or 1,000 J 2 / p o t . T h e a m e n d m e n t consisted o f dry castor applied as a m u l c h at rates o f 0, 1, 2, 4, or 8 g / p o t . T h e e x p e r i m e n t was a 5 x 2 factorial with 10 rep-

lications. O n 25 July, 37 days after inoculation, half o f the e x p e r i m e n t was harvested following the same p r o c e d u r e as in the first experiment. On 17 August, 60 days after inoculation, the r e m a i n i n g pots of the experim e n t were harvested. Experiment 3 - combined amendments, velvetbean, and castor: O n 24 S e p t e m b e r 1996,

2-week-old okra seedlings were inoculated with 0 or 1,000 J 2 / p o t . T h e a m e n d m e n t treatments were castor or velvetbean, b o t h applied at rates o f 2 or 8 g / p o t . T h e experimental design was a 2 x 2 x 2 factorial with 12 replications, i n c l u d i n g two i n o c u l u m densities, two a m e n d m e n t s , and two amendm e n t rates. Thirty days after inoculation, on 24 October, half o f the e x p e r i m e n t was harvested a n d all the plant a n d n e m a t o d e data were recorded, except J2 were not extracted f r o m soil. T h e r e m a i n d e r o f the e x p e r i m e n t was harvested on 7 November, 45 days after inoculation. RESULTS AND D I S C U S S I O N

Experiment 1 - velvetbean amendment: T h e r e were significant (P