TABLE CONTENTS

Impact of Nutrient Supply Systems in Rice-wheat Cropping System on the
Dynamics of Nematode Community Structure in Sub-humid and Humid
Agro-ecosystems
Gaur, H.S. (1), I. Vadhera (2), A.K. Mukhopadhyaya (3), S.P. Tiwari (2), M.R. Khan (3) &
R.K. Jain (1)
(1) Division of Nematology, Indian Agricultural Research Institute, New Delhi-110012, India; (2) Department
of Plant Pathology, Jawaharlal Nehru Agricultural University, Jabalpur, India; (3) Department of Entomology,
Bidhan Chandra Krishi Vishwavidyalaya, Kalyani, WB, India
The rice-wheat cropping system has become popular in parts of India, but depletes soil
organic matter. Therefore, attempts are being made to devise nutrient supply systems
including organic sources. Dynamics of nematode community structure was studied over a
six year period (2001-07) in long term experiments in sub-humid (Indore, Madhya Pradesh)
and humid (Kalyani, West Bengal) agro-ecosystems in India. The nutrients were either
supplied at different doses entirely through mineral fertilizers (NPK) or substituted upto 25 or
50% equivalent of nitrogen through farm yard manure, crop residues or green manure. In
clayey soil at Indore, in all paddy plots where NPK alone was applied showed increase in the
population density of Hirschmanniella oryzae but when NPK was incorporated along with
FYM, crop residue, green manures and compost the population density decreased. The
equilibrium population density (EPD) of H. oryzae was significantly higher with 100% N
through NPK, than in plots where 25-50% NPK was supplied through manures. In nonfertilized
control EPD of H. oryzae was higher than in farmer’s practice. Similar trend was
observed in the EPD of Helicotylenchus spp. The EPD of saprozoic nematodes which belong
to cp-1 and cp-2 grades, increased when organic matter was applied. At Kalyani, the EPD of
Hirschmanniella spp. was 400-520 per 200 cm 3 soil in all the treatments. Tylenchorhynchus
mashhoodi had moderate EPD of 200-300, while the root-knot nematode, Meloidogyne
graminicola also prevailed at low–medium population densities (EPD 60-120) in all the
treatments. No significant variations could be related to the nutrient treatments. The
proportion of cp-1 and cp2 colonizers, hence, saprozoic nematode index (SNI), indicative of
very active organic matter decomposition process and active soil microbial community in
humid ecosystem. The contrasting observations on effects of similar nutrient supply systems
at the two locations could be correlated to differences in soil organic matter and agroecosystem
characteristics. The SNI emerged as a strong bioindicator of high organic matter
and microbial activity, indirectly soil health.
5 th International Congress of Nematology, 2008 81