Effects Of Long-term Fertilization Pattern On Weed Community And Weed Seed Bank In Double Rice Field

Effects of long-term combined application of different fertilizer on weed population and weed seed bank of paddy field were evaluated in this paper. Nine different fertilization treatments, each with three replicated plots and30years of fertilization, were investigated on paddy field in Changsha region.The results showed that:1.15kinds of weeds were recorded during growth period of early rice,including Eleocharis yokoscensis, Scirpus juncoides, Lemna minor L, Alopecurus aequalis, Cyperus difformis, Sagittaria pygmaea, Alternanthera sessilis, Leptochloa chinensis, Cyperus rotundas, Echinochloa crusgalli, Fimbristylis miliacea, Monochoria vaginalis, Paspalum distichum, Rotala indica (Willd.) Koehne and Polygonum hydropiper. Among them, Lemna minor L, Eleocharis yokoscensis, Scirpus juncoides, Sagittaria pygmaea and Cyperus difformis,these five kinds of weeds were common weed species of early rice growth periods, and were the dominant weed species. Echinochloa crusgalli, Monochoria vaginalis, Sagittaria pygmaea and Paspalum distichum were dominant weed species of the heading stage. During the whole growth period of early rice,the Shannon evenness index (E), Shannon diversity index (H’) and Margalef species richness index (DMG) of CK was the highest(these three index in heading date values to NK). In the early growth stage, the effect of the rice canopy light transmittance on the total density of weeds was smaller. In the late growth stage, total density of weeds is proportional to rice canopy light transmittance.2.13kinds of weeds were recorded during growth period of early rice,including Eleocharis yokoscensis, Scirpus juncoides, Lemna minor L, Alopecurus aequalis, Cyperus difformis, Sagittaria pygmaea, Leptochloa chinensis, Cyperus rotundus, Echinochloa crusgalli, Fimbristylis miliacea, Monochoria vaginalis, Paspalum distichum and Rotala indica (Willd.) Koehne. Among them, Lemna minor L, Eleocharis yokoscensis, Fimbristylis miliacea and Paspalum distichum,these four kinds of weeds were common weed species during late rice growth periods, and were the dominant weed species. Paspalum distichum, Echinochloa crusgalli and Fimbristylis miliacea were dominant weed species of the heading stage.During the whole growth period of late rice,the Shannon evenness index (E), Shannon diversity index (H’) and Margalef species richness index (DMG) of CK was the highest(these three index in heading date values to NK). In the mid growth stage, the total density of weeds was negatively related to the rice canopy light transmittance. In the early growth stage and the late growth stage, total density of weeds was proportional to rice canopy light transmittance.3.There were4kinds of weeds in spring,including Alopecurus aequalis, Stellaria media (L.) Cyr, Mazus japonicas and Beckmannia syzigachne. Alopecurus aequalis was the dominant weed specie. Number of weed species in winter was the same with in spring.They were Cardamine flexuosa, Alopecurus aequalis, Eleocharis yokoscensis and Stellaria media (L.) Cyr. Alopecurus aequalis and Stellaria media (L.) Cyr were common weed species.4.The number of weed species of paddy soil weed seed bank was12.They were Alopecurus aequalis, Mazus japonicas, Cyperus difformis, Eleocharis yokoscensis, Lindernia procumbens, Echinochloa crusgalli, Leptochloa chinensis, Polygonum hydropiper, Fimbristylis miliacea, Cardamine flexuosa, Scirpus juncoides and Stellaria media (L.) Cyr. The dominant species was relatively stable. Total density of weed seed bank of PK was maximum and NPK+Ca’s was minimum.