Some aspects of the phenology of rice-field weeds

Abstract

On the basis of their life-span, rice-field weeds may be classified as annuals and perennials; the latter forms a low percentage (24.7) and the former a high one (75.3). The largest number of perennials, however, are contributed by the Gramineae. The maximum flowering of weeds (40.4 per cent) takes place in the period ranging from the monsoon, to the post-monsoon. Though not as high as this value, significant proportions of flowering occur in the season from the pre-monsoon to monsoon (11.8 per cent), from the monsoon to the winter via the post-monsoon (9.9 per cent) and monsoon alone (9.3 per cent). In the seasonal category of flowering, the Gramineae also constitutes a great bulk of the weeds. The highest fruiting percentage of weeds (31.0) is found in the seasonal phase extending from .the monsoon to the winter through the post-monsoon. This is followed by the regime from the, monsoon to the post-monsoon (26.1 per cent) and the time from the post-monsoon to the winter (11.2 per cent). In the seasonal category of fruiting, the Gramineae too contain a high number of weeds. Whether by single method (fruit and seed) or dual method of reproduction (rhizome, tuber, etc. in addition to fruit and seed), the Gramineae finds a prominent place in the list of perennial species and the Cyperaceae among the annuals. The implications of the above findings are discussed.