Journal of Taiwan Agricultural Research

Author:Chiao-Ling Hsiao, Chewn-Ming Yang*, and Chia-Hsun Ho

Abstract:

    Changes in population and density of weeds occur in different cropping systems with time. To delineate variation and progress of weeds under paddy-paddy agro-ecosystem (PP) and paddy-upland rotation agro-ecosystem (PU) of a two-crop system, studies were conducted at long-term agricultural ecological research (LTER) station located in Sikou Experimental Farm of Taiwan Agricultural Research Institute. Within each agro-ecosystem, there were two types of practice, conventional cropping system (CC) and low-input cropping system (LC), making up four agro-ecosystems in total, namely, PP-CC, PP-LC, PU-CC and PU-LC. This paper summarized the results from investigations and analyses of data acquired in 2010 and 2011. As the results shown, weed density was higher in LC than in CC and in 2011 than in 2010 in firstcrops, suggesting that cropping treatments were not yet stabilized so that LC treatment was not have less weeds as ex-pected. Because of such a situation, weed biomass of CC was higher than LC in 2010, but not in 2011. In second crops, PP had a larger weed population and density than that of PU, particularly in 2010, indicating richer weeds in paddy fieldsthan in uplands. Among these four agro-ecosystems, generally larger numbers of weed family and species were found in second crops, yet vary yearly, reflectinga complicated factors intervention in weed infestations. The most populated weed family of PP was Lythraceae in 2010 and was Scrophulariaceae in 2011 for firstcrop, and was Scrophu-lariaceae for second crop in both years. Of the PU, family of Compositae and Lythraceae were the most populated weeds for PU-CC and PU-LC, respectively, in frst crop of 2010, and it was family of Cyperaceae and Compositae, respectively, in 2011. Weeds of family Compositae were predominant in both agro-ecosystems in second crop of 2010 and weeds of family Compositae and Solanaceae were the predominated ones in 2011 for PU-CC and PU-LC, respectively. As for weed species, plants of Ammannia baccifera occupied the most in PP in firstcrop of 2010, while Lindernia procumbens took the lead in 2011 as well as in second crop of both years. In PU, population of Agcratum conyzoides was the highest, followed by Cyperus rotundus in firstcrop of 2010. The top two populations in 2011 were Ammannia baccifera and Eclipta prostrate. In second crop, Agcratum conyzoides and Eclipta prostrata were listed in the firsttwo rankings in 2010, but were Cyperus rotundus and Physalis angulata in 2011. Apparently, changes in weed family and species will be affected by multifactors such as ecology, cropping system and climate and hence, will fluctuatein seasons and years. It requires more investigations to clarify how long weed populations will reach a dynamic balance among each other.

Key words:Long-term agricultural ecosystem, Paddy-paddy agro-ecosystem, Paddy-upland rotation agro-ecosystem, Conventional cropping system, Low-input cropping seasons

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