| Soil weed seed banks (potential weed communities) in south of Jiangsu province were studied. With the method of induced emergence in green house, the Soil weed seed banks in rice-wheat rotation fields in different cultivating mode, the Soil weed seed banks in rice-duck field were studied. And the weed community complex in different farming system was studied. What is more, the potential weed harmfulness in the rice-wheat rotation fields in different cultivating mode is evaluated. The results as followed:1 the structure characteristics of potential weed communities in rice-wheat rotation fields in different cultivating mode in south of Jiangsu province.Spring weeds and autumn-winter weeds were found in the fields. Though the same nine type weeds were found in the fields, the number and the predominant weed were different: the weed number in free cultivation is No.1 and Malachium aquaticum(L.) Fries and Cyperus difformis L were predominant weeds; that in plowingis No.2, Malachium aquaticum(L.) Fries, Leptochloa chinensis(L.) Nees were predominant weeds; rotary cultivation is No.3, Malachium aquaticum(L.) Fries, Fimbristylis miliacea(L.) Vahl were predominant weedsMalachium aquaticum(L.) Fries is the predominant weed of autumn-winter weeds in the 3 fields and the proportion is 28%-40%,while the predominant weeds of spring weeds were different: Cyperus difformis L. in free cultivation field, Leptochloa chinensis(L.) Nees in plowing, Fimbristylis miliacea(L.) Vahl in rotary cultivation,though their proportions are all about 30%. It is probably the different cultivation mode that caused the variety of soil ecology which influenced the construction of seed bank, the kind and distributing of potential weed communities arenearly related with the cultivation mode.In the rice-wheat rotation field in south of Jiangsu province, the proportion of weed in 0-10cm was 50-70% of the weed in 0-20cm. in the vertical distributing of weed, characters were different in different cultivation fields: the weed seeds were mainly in 0-5cm in free cultivation field and the number decreased with the increase of depth; the weed seeds were mainly in 10-15cm in plowing cultivation field; the weed seed distributing in rotary cultivation field is relatively even. The cultivation mode was the main reason that caused the difference. If free cultivation went on for some years, the potential weed communities in deep-seated soil would vanish; if rotary cultivation went on for some years, the proportion of the potential weed communities in every arrangement would be even.2 the distributing trait of weed potential communities in different irritation measureIn different irritation measure, by simulating the weed density in the field, it was found that the weed density in soil ditch field accorded with the model y= k+a*ln(x), while the weed density in concrete ditch field accorded with the modely=kx+b. it is primary outcome and on the base the type and the number of weed in different irritation measure can be studied. Besides, the transverse and lengthways distributing of weed and the distributing of every weed can be researched. If these rules can be found, the input of weed can be reduced ,the output of weed can be increased, the scale of weed seed bank can be dwindled and the system of controlling weed can be established and the weed in rice-wheat rotation field in different irritation measure in south of Jiangsu province can be effectively managed.3 the distributing trait of potential weed communities in rice-duck mode fieldThe weed harmfulness in the rice-duck mode field is alleviative and the number of Leptochloa chinensis(L.) Nees, Lindernia procumbens(Krock.) Philcox, Cyperus difformis L diminished clearly. In the dimensional distributing, the weed number in 0-5cm soil reduced in the rice-duck mode field and the vertical distributing of weed seed bank was changed and the trend is 5-10cm>10-15cm>0-5cm>15-20cm. besides the difference of weed seed bank in rinsing region and turbid region was not obvious.4 study on weed community complex of fieldReal a... |
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