Problem weeds and their management in the North-East Himalayas

The North East Himalayan region recognized as one of the seven biodiversity hotspots of the world where Indo-Malayan, Indo-Chinese, and Indian bio-geographical realms have converged. Based on the elevation, climate and soil conditions, water availability and socio-economic aspects, different agroecosystems are prevalent in the north eastern India. However, the agro-ecosystems of the region can be broadly classified as i) Jhum agro-ecosystem, ii) Terrace land agro-ecosystem, and iii) Valley land agroecosystem. The major production ecosystems of the region are: rice, jute, sugarcane, tea, horticultural crops and forest and wetland. Shifting cultivation is a primitive agricultural system still practiced in some of the hill areas which is characterized by uniqueness of weed problem and its weed flora is primarily governed by altitude, slope of the land, jhum-cycle and fallowing, burning, rainfall, run-off, crops and cropping geometry and many other relevant issues like biotic interference coupled with climatic factors. The nature and severity of weed menace in different crop ecosystems vary according to the agroecosystems in which the crop is grown. Weeds are one of the main production constraints in all crop ecosystems. The common agronomic factors contributing to weed problems in different crops are inadequate land preparation, seed contamination with weed seeds, use of poor quality seeds, broadcast seeding in lowlands, use of overage rice seedlings for transplanting, inadequate water management, inadequate fertilizer management, mono-cropping, labour shortages for weeding operations, delayed herbicide applications and other interventions. In this article, the distribution of weeds and their management practices are reviewed exhaustively.