Control Effects of 3 Kinds of Herbicides against Weeds in Dogbane (Apocynum venetum) Field

[ Objective] The paper was to explore the control effects of 3 kinds of herbicides against weeds in dogbane （Apocynum venetum） field. [ Method ] Using haloxyfop-R-mithyl and quizalofop-ethyl EC specifically killing monagenns gramineous weeds and chipton specifically killing dicotyledonous broad-leaf weeds, the control test against weeds in 2-year-old dogbane field was carried out. [ Result ] Haloxyfop-R-mithyl had good control effect against gramincous weeds, and its control effect against both barnyard weed （ Echinochloa crusgalli） and green bristleweed （ Setaria viridis ） was greater than 35.0% ; the control effects of quizalofop- ethyl EC against barnyard weed and green bristleweed were 14.8% and 28.6%, respectively; chipt0n had good control effect against Chenopodium album, and the control effect reached 30.8%. Moreover, 3 herbicides did not cause damage to dogbane. [ Conclusion] The study provide theoretical basis for completing cultivation technique of dogbane.

Potential of weed species applied to remediation of soils contaminated with heavy metals

To screen out a series of ideal plants that can effectively remedy contaminated soils by heavy metals is the main groundwork of phytoremediation engineering and the first step of its commercial application on a large scale. In this study, accumulation and endurance of 45 weed species in 16 families from an agricultural site were in situ examined by using the pot-culture field experiment, and the remediation potential of some weed species with high accumulation of heavy metals was assayed. The results showed that Solanum nigrum and Conyza canadensis can not only accumulate high concentration of Cd, but also strongly endure to single Cd and Cd-Pb-Cu-Zn combined pollution. Thus 2 weed species can be regarded as good hyperaccumulators for the remediation of Cd-contaminated soils. Although there were high Cd-accumulation in Artemigia selengensis, Znula britannica and Cephalanoplos setosum, their biomass was adversely affected due to action of heavy metals in the soils. If the problem of low endurance to heavy metals can be solved by a reinforcer, 3 weed species can be perhaps applied commercially.

Effects of salinity and desalination on seed germination of six annual weed species

The effects of various salinities and desalination on seed germination of six annual glycophytes （Artemisia sieversiana, A. scoparia, Chloris virgata, Eragrostis pilosa, Chenopodium acuminatum and Chenopodium glaucum） were studied in Horqin Sandy Land, Inner Mongolia, China. NaCl solutions of five concentrations （0 mM, as the control, and 50, 100, 200 and 300 mM） were used for saline stress and desalination treatments. Increasing salinity significantly reduced germination percentages of A. sieversiana, A. scoparia, Ch.virgata and Ch. acuminatum, but had no effect on the germination percentages of E. pilosa. Lower salinity levels （50 mM） significantly increased germination percentage of Ch. glaucum. High salinity might be a precondition for germi- nation after desalination for five of the six species, excepting E. pilosa at NaCl concentration of 300 mM in comparison with non-primed seeds. Higher salinity （200 mM） led to some specific ion toxicity and reduced seed viability of A. sieversiana. No specific ion toxicity but an osmotic effect limited the germination of other five species was observed The final germination percentages （salinity stress and desalination） of the six species showed three variations in comparison with the controls, namely, indiscrimination, stimulation, and reduction. Germination responses to salinity and desalination suggested that the six species were separated into three categories. Three species （A. sieversiana, Ch. virgata and Ch. acuminatum） showed similar germination responses to salinity with those of halophyte, but also showed a lower tolerance limit than most halophytes, although this was not always the case. A. scoparia and Ch. glaucum exhibited some ‘salt stimulation’ in seed germination percentages after desalination, whereas E. pilosa did not show any obvious responseto salinity. Therefore, salinity usually induces dormancy of seeds with strong germination capacity in fresh water, but has few, or even positive, effects on seeds with strong innate dormancy.

Phytosociological Survey of Weeds in Areas of Crop-Livestock Integration

The dynamics of the weeds in the areas of crop-livestock integration is constantly changing depending on the various uses of the area. This study identified and quantified the floristic composition of weeds in areas of integration of maize for silage with Urochloa ruziziensis cv. Common at different densities of grass (0, 4 and 10 kg·ha-1) to grazing of beef cattle. The experimental design was completely randomized. A square of side0.5 m(0.25 m2area) was launched 24 times in each study area. The survey was conducted at the grain filling stage of maize. The specie contained in each frame were identified and counted. The phytosociological survey identified 9 families of weeds in areas assessed, with 7 families in every area of integrated cultivation maize with Urochloa ruziziensis at densities of 10 kg·ha-1 and 4 kg·ha-1 and 8 families in the area of maize cultivated alone. The Asteraceae family was the most represented in number of species. Sida spp (Malvaceae) showed greater potential to cause damage to maize. Urochloa ruziziensis at planting density of 10 kg·ha-1 provided greater competition with weeds in the integration with maize.

Selectiveness of Cnaphalocrocis medinalis to Host Plants

A field experiment was conducted to study the selectiveness of Cnaphalocrocis medinalis Guenee （commonly known as the rice leaffolder or rice leafroller） towards five rice varieties （Yangfujing 8, Yangdao 6, Shanyou 136, Huaidao 9 and Nin.gjing 1） and three weed species （Echinochloa crusgalli, Leptochloa chinensis and Leersia hexandra）. The results showed that the rice varieties carried significantly higher numbers of C. medinalis moths and eggs than the weed species. Among the rice varieties, Yangfujing 8 was associated with a higher moth number. However, there was little difference in the number of C. medinalis eggs among the rice varieties. Additionally, a laboratory experiment was performed to investigate the olfactory response of female C. medinalis towards volatile compounds from different rice varieties, as well as its oviposition preference towards these rice varieties. The volatiles of Yangfujing 8, Yangdao 6 and Shanyou 136 attracted C. medinalis similarly to those of TN 1. In contrast, the volatiles of Huaidao 9 and Ningjing 1 clearly deterred C. medinalis. Nevertheless, C. medinalis did not exhibit clear oviposition preference towards any of the five tested rice varieties.

Effects of fertilizer and weed species richness on soil nematode community in a microcosm field experiment

Both fertilizer and plant species richness may affect the soil nematode community.However,the influence of fertilizer and weed species richness interaction is unclear.Nematode abundance and biodiversity in wheat and weed plots soil treated with nitrogen,phosphate and potassium fertilizer addition and weed species richness(0,1,2 and 4 weed levels)were investigated in a long-term microcosm experiment established in 2010 at Kaifeng,China.The results demonstrated that fertilizer treatment increased the abundance of total nematode,bacterivores,and plant parasites whereas it decreased the total genera number,the Shannon-Wiener diversity index(H'),Margalef richness index(SR),the total maturity index(∑MI),and structure index(SI),and degraded the structure of the nematode community.In contrast,weed species richness increased these ecological indices and enhanced the structure of the nematode community.Principal component analysis(PCA)indicated that the fertilizer's effect was more significant than weed species richness.Redundancy analysis(RDA)demonstrated that fertilizer affected soil nematode mainly through increasing soil available phosphorus by 4.71 times and ammonium nitrogen content by 74.03%;weed species richness increased the diversity indices of soil nematode mainly through enhancing soil moisture by 2.07%.Our results suggest weed species richness may relieve the negative effect of fertilizer on the diversity of soil nematode community.