Crop Forage/ Soil Management/ Grassland Utilisation Agricultural Science Unit, Indian Statistical Institute, Kolkata, India Deferred Seeding of Blackgram (Phaseolus mungo L.) in Rice (Oryza sativa L.) Field on Yield Advantages and Smothering of Weeds A. Midya, K. Bhattacharjee, S. S. Ghose, and P. Banik AuthorsÕ address: Dr A. Midya, Dr K. Bhattacharjee, Dr S. S. Ghose and Dr P. Banik (corresponding author; e-mail: pbanik@isical.ac.in), Agricultural Science Unit, Indian Statistical Institute, 203, Barrackpore Trunk Road, Kolkata 700108, India With 6 tables Received January 30, 2004; accepted May 29, 2004 Abstract Field experiments were conducted at Agricultural Experi- mental Farm, Giridih, Jharkhand, during the kharif (wet) seasons of consecutive four years (1998–2001) to study the effect of staggered seeding of blackgram (Phaseolus mungo L.) in rice field as a cereal–legume intercropping system and to minimize the degree of competition between the crop species to avoid yield damage, and at the same time to create a high level of competition by the intercrops to suppress the weeds. Intercropping systems were assessed on the basis of land equivalent ratio, relative crowding coefficient, aggressivity, actual yield loss, monetary advant- age, etc. Intercropping reduced the yield of component crops when compared with respective pure stands. How- ever, deferred seeding of blackgram in rice (30 cm) after one weeding was most remunerative system and registered maximum rice-equivalent yield (2711 kg ha )1 ). Rice–black- gram (20 cm) intercropping system was very effective for weed smothering among unweeded intercropping treat- ments. In conclusion, deferred seeding of blackgram in rice field (30 cm) with one weeding may be recommended for better yield, weed suppression and better economics in the eastern plateau region of India. Key words: actual yield loss — blackgram — cereal–legume intercropping — deferred seeding — monetary advantage — weed suppression Introduction Cereal–legume intercropping is becoming an integ- ral part of cropping system where sustainable agriculture is emphasized. Legumes when inter- cropped with cereals fix considerable amount of atmospheric nitrogen, which is either available to the current companion crop or the succeeding crop (Ofori and Stern 1987). Legumes reduce external input requirement and improve the quality and quantity of the internal resources. In degraded soils of the eastern plateau, where crop failure due to erratic rainfall is a common feature, intercropping of cereals with legumes either simultaneously or as deferred seedings gives stability of production. Cereal–legume intercropping system in this tract has been recommended for maintaining soil fertil- ity and to augment yield (Banik and Bagchi 1993, Banik et al. 2000, Rauber et al. 2001, Singh and Rathi 2003). Upland rice is heavily infested with weeds, which causes drastic reduction in yield. It has been estimated globally that yield losses of rice were 24 % with sedges and broadleaf weeds, and 86 % with grassy weeds (De Dutta 1979). How- ever, almost similar grain yield may be obtained under upland rice when compared with transplan- ted lowland rice, provided that the weeds are effectively controlled. Weed management in inter- cropping system has hardly been studied to date (Moody and Shetty 1979, Altieri and Liebman 1986, Hong et al. 2004). Intercropping can sup- press the growth of weeds more than sole cropping (Yih 1982). Cost of manual weeding may be to some extent mitigated through sound crop hus- bandry considering intercropping as a component of integrated weed management. This experiment was conducted to study the suitability of deferred seeding of blackgram in rice field as a cereal– legume intercropping system in terms of advan- tages and economics in the sub-tropical uplands of the eastern plateau region of India. A secondary J. Agronomy & Crop Science 191, 195—201 (2005) Ó 2005 Blackwell Verlag, Berlin ISSN 0931-2250 U.S. Copyright Clearance Centre Code Statement: 0931–2250/2005/9103–0195 $15.00/0 www.blackwell-synergy.com