Investigation of winter weed community in double rice cropping paddy applied by herbicides

In order to identify the impact of different herbicides on the shift of weed community, the main weed community of the rice-rice-winter follow field(WF), rice-rice-potato(RRP) and rice-rice-field ridge(FR) in the high yield demonstration area of double rice cropping in Enping City, Guangdong was surveyed from November of 2011 to March of 2012. The results showed that there were 10 586 weed plants, including 18 families, 50 species and 4 unknown species collected in 10 sampling plots. The biodiversity index of weeds in RRP, WF and FR had significant difference(P0.05) under the influence of different herbicides. The indexes of diversity(H), evenness(J) and dominance(C) of weeds in RRP were the highest. The destiny-group(DG) index of weeds in WF was the highest. To the Sorenson's similarity index(S1), all those three weeds plots of the RRP, WF and FR were greater than 50%. However, the Whittaker's similarity index(S2) was relatively low. Besides, the dominant species weed in those communities after the reconstruction from double rice cropping were Malachium aquaticum(L.) Fries, Polygonum aviculare L, Cynodon dactylon and Alopecurus aequalis Sobol. They developed a succession pattern of caryophyllaceae+ polygonaceae+ gramineae. The results showed that the dominant weed species were gradually succeeded from annual less-damage weeds to the perennial virulent weeds. It was clear that tillage method and herbicide could affect the weed composition, diversity and stability significantly.