Diversity in Weed Phenological Pattern and Seed Rain in Dryland and Irrigated Agroecosystems of Indian Dry Tropics

Abstract

This study was carried out to compare the diversity in weed phenological events, seed production and seed rain in a dryland and an irrigated agroecosystems of Indian dry tropics. Diverse weed phenological patterns were noted in dryland and irrigated agroecosystems. During winter season, in dryland agroecosystem, dominant weeds like Anagallis arvensis, Chenopodium album and Phalaris minor showed approximately one month early germination and vegetative stage compared to irrigated agroecosystem for same species. The annual flower, fruit and seed production were higher in the dryland agroecosystem (344-351, 219-238 and 365-397 x 103 m-2, respectively) compared to irrigated agroecosystem (211-237, 132-142 and 252-261 x 103 m-2, respectively). The estimated annual seed rain by all species in the dryland agroecosystem (102-112 × 103 m−2) significantly exceeded (P less than 0.05) the seed rain in the irrigated agroecosystem (73−80 × 103 m−2) during both annual cycles. The difference was more marked during the winter season, when more than 3 fold the number of seeds were collected in seed rain during the dryland agroecosystem. There was strong positive correlation between seed production and seed rain, showing the dependency of seed rain (mostly dominated by annual species) on seed production in agroecosystems. Two different agricultural practices that continued for more 50 years on same type of land have cause changes in weed phenological pattern. Greater seed production, seed rain, and longer seed formation period indicate an adaptive mechanism of weed seeds in the dryland agroecosystem.