DYNAMICS OF BURIED SEED POPULATION AND SEEDLING COHORTS OF 2 DOMINANTWEEDS IN A HILL AGROECOSYSTEM OF THE HUMID SUBTROPICS OF INDIA

Dynamics of the buried seeds and plant population of two dominant weed s, viz., Emilia sonchifolia (Linn.) DC. and Richardsonia pilosa HBK we re studied in the crop fields of Meghalaya, north-east India during ra dish and maize cropping and intervening fallow periods. The total buri ed seed population of R. pilosa was always larger than that of E. sonc hifolia, but the germinable fraction was invariably greater in the lat ter. A major portion (39-41%) of the viable (germinable + dormant) see d population in both weeds was confined to the surface soil layer (0-5 cm). The viable seed population of E. sonchifolia peaked during April , while that of R. pilosa showed two peaks (during August and December ). The survival pattern and half-lives of seedling cohorts showed some differences in the two weed species, but both being summer annuals, t heir populations behaved in a similar manner by showing higher seedlin g recruitment (K) and survivorship (p) rates in the summer crop (maize ) than in the winter crop (radish). However, the density of plants tha t could attain adulthood was significantly higher in E. sonchifolia th an R. pilosa which might have resulted in greater seed input of the fo rmer to the soil leading to its greater abundance in the crop fields.