Short communication
Eect of organic and urea amendments in soil on nematode
communities and plant growth
Mohammad Akhtar
Plant Protection Department, Institute of Agriculture, Aligarh Muslim University, Aligarh 202 002, India
Accepted 3 September 1998
Because of concerns about the consequences of the use of chemical pesticides on human health and the en-vironment, alternative methods to control pests and diseases are being sought (Akhtar, 1997). Reductions in populations of plant-parasitic nematodes in re-sponse to applications of organic amendments have been reported by Muller and Gooch (1982), Akhtar and Alam (1993b) and Akhtar and Mahmood (1996a). Additionally plants exhibit several biochemical mech-anisms to counteract parasitizing nematodes. Neem (Azadirachta indica A. Juss) products, including leaf, seed kernel, seed extracts, oil cakes and oil have been reported to be nematicidal by Egunjobi and Afolami (1976), Akhtar and Alam (1991, 1993a) and Akhtar and Mahmood (1996a,b). Besides neem, several other plant terpenoids are known to have nematicidal prop-erties (Akhtar and Mahmood, 1994). Known in Asia for centuries, the neem tree has only in the last 30 y become a topic of interest in USA and Europe (Schmutterer, 1990). One of the ®rst companies to make and sell neem based product was M/s W.R. Grace, a US company, encouraged by the success of this product they later came out with another product trade named `Bioneem'.
Free-living nematodes may accelerate the decompo-sition of soil organic matter (Abrams and Mitchell, 1980). Numbers of free-living microbivorous nema-todes increase rapidly in the soil following the addition of organic and inorganic fertilizers (Marshall, 1977), while there can be a corresponding decrease in the numbers of plant-parasitic nematodes (Heald and Burton, 1968; Tomerlin and Smart, 1969). In a ®eld study we have assessed the eects of dierent amounts of two neem-based products (`Achook' Godrej Agrovet Ltd. Mumbai, India and `Suneem G' Sunida Exports, Mumbai, India), urea and compost amend-ments on the nematode community and on the growth of chickpea in ®eld soil. Chickpea (Cicer arietinumL.), an important pulse crop, is grown in semi-arid tropical regions of the world for its high seed-protein content
and its ability to increase soil fertility through symbio-sis with Rhizobium, plant-parasitic nematodes particu-larly Meloidogyne spp. and Tylenchorhynchus brassicae
are major limiting factors for its productivity.
The experimental ®eld was at Aligarh Muslim University, Agricultural Research Farm at Qila Road, Aligarh, India. It was thoroughly ploughed to a depth of 10±15 cm and in small plots measuring 23 m sep-arated by 0.5 m wide alleys. The ®eld soil was an Alluvial soil of pH 8.3 with 1.0% organic matter. The plots were treated separately with urea or compost (mixture of cattle solid manure and leaves) at 110, 220 or 330 kg N haÿ1, respectively, or with `Achook'
gran-ules (azadirachtin 0.15 wt%) or Suneem G (Azadirachtin 0.18wt%) at 5, 10 and 15 kg haÿ1, both
separately or combined with urea at 110, 220, 330 kg N haÿ1. Untreated control plots that did not receive
soil amendments or fertilizers were also included. Compost materials were added to the plots 4 weeks before planting and other treatments were added at planting of chickpea (C. arietinumL.). The experimen-tal design was a randomized block with ®ve replica-tions of each treatment including untreated plots. Cultivation, control of insects, foliar diseases and weeds were done according to local use. The ®eld was irrigated as required.
Soil samples for nematode assay were collected from each plot before sowing and 1 d after harvest. A bulked soil sample of 30±40 cores from 30 cm depth was taken from each plot using a 2.5 cm diameter cylindrical corer. Soil cores were bulked and a 100 g subsample (wet weight) was used for nematode extrac-tion by Baermann funnel (Hooper, 1986) at 308C for 24 h. From every subsample, all nematodes in each subsample were counted separately and identi®ed as: free-living or plant-parasitic nematodes (Basirolaimus indicus (Sher) Shamasi, Helicotylenchulus indicus
Siddiqui, Rotylenchulus reniformis Linford and Oliveira, Filenchus ®liformis Meyl, Meloidogyne incog-nita (Kofoid and White) Chitwood), and following
Soil Biology & Biochemistry 32 (2000) 573±575
0038-0717/00/$ - see front matter#2000 Published by Elsevier Science Ltd. All rights reserved. PII: S 0 0 3 8 - 0 7 1 7 ( 9 8 ) 0 0 1 4 7 - 3
identi®cation nematode subsamples were preserved in a 5% formalin.
Crops were harvested and dry weight of shoot and root were recorded 60 d after sowing. Dry weights were determined after placing the plants in an oven for 12 h at 608C. Data were subjected to analysis of var-iance. Fischers' least signi®cant dierence (FLSD) was calculated for separation of means.
There was a signi®cant increase in dry shoot and root weight of chickpea in response to application of each treatment compared with the control plants (Table 1). The growth of shoots in plots treated with Achook or Suneem G at the largest dose in the pre-sence of urea was up to three times greater than in the control plots. Plant growth was even greater but not signi®cantly in plots treated with `Achook' or `Suneem G' together with urea. Plant growth increased with increase in dose of the neem material applied. The urea amendment was as eective as compost at single and double doses although urea was phytotoxic at 330 kg N y haÿ1 when given alone or combined with
neem-products. However, at the single and double dose treatments, plant growth was greater in the neem-products treated plots than in plots treated with the urea alone. The two combinations (urea plus neem products) signi®cantly (PR0.05) promoted even greater growth except for Suneem G at 2(Table 1).
Numbers of plant-parasitic nematodes diered greatly according to treatment. Number increased in
control plots because chickpea is a highly nematode-susceptible crop. The addition of the neem products (Achook and Suneem G) and two combinations (urea plus neem products) compost and urea signi®cantly (PR0.05) reduced the total number of plant-parasitic nematodes (Table 1). The greatest reduction in plant-parasitic nematode numbers was observed with Achook and Suneem G with urea amendments fol-lowed by Achook and Suneem G alone, urea and com-post. Moreover, reduction in nematode numbers was correlated with increasing doses of the treatments.
In unamended soil the numbers of free-living nema-todes between the time of sowing and harvesting the crop were not signi®cantly dierent. In all the treated plots, except those treated with compost manure, the numbers of free-living nematodes signi®cantly decreased (PR0.05) especially with neem products treatments (Table 1). In the case of compost treatment, numbers of free-living nematodes were signi®cantly (PR0.05) greater than control plots. There were sig-ni®cant dierences in numbers of free-living nematodes obtained at dierent doses of each treatment.
Neem contains triterpene that acts by delaying the rapid transformation of ammonium nitrogen into nitrate nitrogen (nitri®cation inhibitor). This ensures slow and continuously available nitrogen during plant growth. However. Rodriguez-Kabana (1986) pointed out that nitrogen fertilizers releasing ammonium N in the soil are very eective in suppressing nematode
Table 1
Eect of neem-products, urea and compost on nematode communities and growth of chickpeaCicer arietinum(n= 5) Treatment Ratea No. of nematodes per 100 g soil Dry weight per plant (g)b
Plant-parasitic Free-living Shoot Root Total Initial population 2600 2160
`Achook' 1 422 a 1205 a 20.8 10.5 31.3 a
2 314 b 1040 b 22.0 11.2 33.2 b 3 200 c 930 b 24.5 12.0 36.7 b
`Suneem G' 1 390 a 1120 a 20.0 10.0 30.0 a
2 288 b 1018 b 22.5 11.5 34.0 b
3 190 c 940 b 24.0 12.3 36.3 b
Urea 1 628 c 1240 a 13.5 8.4 21.9 c
2 430 a 1390 c 14.9 9.5 24.4 d
3 390 a 1520 d c c c
`Achook' + Urea 1 205 c 1290 a 22.0 12.0 34.0 b
2 115 d 1420 c 24.5 13.5 38.0 e
3 80 d 1575 d c c c
`Suneem' + Urea 1 220 c 1140 a 23.9 12.3 36.2 b
2 118 d 1475 c 25.0 13.9 38.9 e
3 85 d 1610 d c c c
Compost 1 675 e 2495 e 14.4 8.4 22.8 c
2 520 f 2775 f 15.3 9.3 24.6 d
3 318 b 3015 g 18.3 10.5 28.8 a
Control (untreated) ± 5982 g 2112 h 8.4 4.1 12.1 f
SE(m) 41.7 52.7 0.82 0.26 0.35
a 1
is single strength, 2double strength and 3 triple strength.bAverage plant weight from whole plot.cPlants died before measurements
were taken.Values within the same column followed by the same letter are not signi®cantly dierent (PR0.05).
M. Akhtar / Soil Biology & Biochemistry 32 (2000) 573±575
populations and recommended that the rate required to obtain signi®cant suppression of nematode popu-lations is generally in excess of 150 kg N y haÿ1
which is supported by our results. Urea was phytotoxic at 330 kg N y haÿ1
when given alone or in combination with the neem-based products. On the other hand the two combinations (110 or 220 kg urea N haÿ1 plus
neem products) promoted greater plant growth. Thus, a combination of neem-based products and urea may have reduced plant-parasitic nematode numbers and increased plant growth.
Utilization of neem-based products in this way pro-vides an economical and feasible option for controlling plant-parasitic nematodes. Naturally occurring bio-chemicals and plant allelobio-chemicals can achieve eec-tive reductions in target phytopathogens while minimizing environmental risk but nontarget animals are often negatively aected, too. Further research on natural products is needed.
References
Abrams, B.I., Mitchell, M.J., 1980. Role of nematode-bacterial inter-actions in heterotrophic system with emphasis on sewage sludge decomposition. Oikos 35, 404±410.
Akhtar, M., 1997. Current options in integrated management of plant-parasitic nematodes. Integrated Pest Management Reviews 29, 187±197.
Akhtar, M., Alam, M.M., 1991. Integrated control of plant-parasitic nematodes on potato with organic amendments nematicide and mixed cropping with mustard. Nematological Meditteranea 19, 169±171.
Akhtar, M., Alam, M.M., 1993a. Control of plant-parasitic nema-todes by Nimin: an urea-coating agent and some plant oils.
Zeitstchrift fur P¯anzenkrankheiten and P¯anzenschutz 100, 337± 342.
Akhtar, M., Alam, M.M., 1993b. Utilization of waste materials in nematode control: a review. Bioresource Technology 45, 1±7. Akhtar, M., Mahmood, I., 1994. Potentiality of phytochemicals in
nematode control: a review. Bioresource Technology 47, 189±201. Akhtar, M., Mahmood, I., 1996a. Organic soil amendment in
re-lation to nematode management with particular reference to India. Integrated Pest Management Reviews 1 (4), 201±215.
Akhtar, M., Mahmood, I., 1996b. Control of plant-parasitic nema-todes with organic and inorganic amendments to agricultural soil. Applied Soil Ecology 4, 243±247.
Egunjobi, O.A., Afolami, S.O., 1976. Eect of neem (Azadirachta indica) leaf extracts on populations ofPratylenchus brachyurusand on the growth and yield of maize. Nematologica 22, 125±132. Heald, C.M., Burton, G.W., 1968. Eect of organic and inorganic
nitrogen on nematode populations on turf. Plant Disease Reporter 52, 46±48.
Hooper, D.J., 1986. Extraction of free-living stages from soil. In: Southey, J.F. (Ed.), Laboratory Methods for Work with Plant and Soil Nematodes. Ministry of Agriculture Fisheries and Food, HMSO, London, pp. 5±22.
Marshall, V.G., 1977. Eect of manures and fertilizers on soil fauna: a review, Special Bulletin No. 3. Commonwealth Bureau of Soils, Commonwealth Agricultural Bureaux, Wallingford.
Muller, R., Gooch, P.S., 1982. Organic amendments in nematode control: an examination of the literature. Nematropica 12, 319± 326.
Rodriguez-Kabana, R., 1986. Organic and inorganic amendments to soil as nematode suppressants. Journal of Nematology 189, 129± 135.
Schmutterer, H., 1990. Properties and potential of natural pesticides from the neem tree, Azadirachta indica. Annual Review of Entomology 35, 271±298.
Tomerlin, H.A., Smart, G.C., 1969. The in¯uence of organic soil amendments on nematode and other soil organisms. Journal of Nematology 1, 29±30.
