Weed Seed Bank Response to Soil Depth, Tillage and Weed Management in the Mid Hill Ecology

Abstract

The size and composition of weed seed bank was studied in the glass house based on the study initiated in the field under conventional and minimum tillage with five weed managements in wheat and dry direct seeded rice rotation at various soil depths such as 0-5 cm, 5-10 cm, 10-15 cm, and 15-20 cm. The experiments were conducted at Agronomy Farm, Khumaltar, Nepal during 2001-2003. The number of weed species was greater in weed seed bank than in the field. Eighty–one weed species belonging to 25 families were retrieved from the soil seed bank samples collected over three seasons. Dicot broadleaves ranked first in terms of number of species followed by grasses, sedges, monocot broadleaves and pteridophytes. Alopecuros aequalis, Digitaria sanguinalis, Echinochloa colona, Phalaris minor, Polypogon fugox, Cyperus difformis, C. dilutus, C. iria, C. sanguinolentus, Fimbristyllis littoralis, Chenopodium album, Coronopus didymus, Lindernia procumbens, Rumex crispus, Soliva anthemifolia, Stellaria media, S. aquatica, Commelina diffusa, Murdania sp. and Ceratopteri thalictroides were the common weeds. Vertical distribution of weed seed bank of grasses, sedges, and broadleaves showed in descending order from 5 cm to 20 cm in all season’s soil samples and the pressure of most weeds was at 5-10 cm soil depth. The total number of weeds in seed bank per square meter ranged from 6,800 to 9,500 in 0-5 cm depth. Tillage affected on grass weed seed bank but had no consistent effect on sedges and neither on broadleaves over seasons. Sulfosulfuron and fenoxaprop affected on annual grass weed seed bank but not on broadleaf by the later. Bispyribac–sodium and anilophos both suppressed grass and sedge weed seed bank. Weed seed bank was influenced by management as well as soil depths.