摘要:

Summary:Soybean yields, pod and branch numbers were inversely related to the height of velvetleaf (Abutilon theophrasti). This effect was attributed to increasing interception of light with increasing height ofA. theophrasti. Reduction; in soybean yield and yield components were greater ifA. theophrastiwas maintained at various heights for only 3 weeks rather than 6 weeks following soybean emergence. This effect was attributed to a longer duration of light competition by the weed. Even when theA. theophrasticanopy was kept 25% below that of soybean for 4 weeks, soybean yields, pod and branch numbers decreased when the weed was allowed to regrow during the remainder of the season, but not if the weed was removed after the initial 4‐week clipping period. No reduction in seed yields, pod and branch numbers was noted ifA. theophrastiplants 25% shorter than soybeans were removed or allowed to resume growth after the initial 6 or 8 weeks of clipping. Soybean seed size was slightly affected byA. theophrasticanopy height and duration of competitio

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01750.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:Black (BPE) and clear polyethylene mulches (CPE), 0.08 and 0.06 mm thick, respectively, were compared for their effectiveness for soil solarization over three seasons during 1986–1989 in weedy fields. Solarization for 6 weeks reduced weed growth and enhanced crop yields. However, further mulching with BPE after solarization with either BPE or CPE gave the best results. Not all weeds were sensitive to solarization. Some weed species were completely controlled; others were reduced to varying degrees; yet other weed species seemed to be enhanced by solarization. Solarization without further mulching was no better than farmer‐practice in reducing weed growth or in increasing crop yield. Weeds required further removal after the middle of the growing season. Any soil disturbance after solarization reduced the weed control effect of solarization. Crops grew best in plots after solarization with BPE if they were planted in the same mulch after it was perfora

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01751.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:The foliar surface of 4‐leaf maize plants was found to be poorly wettable and retained 106 μl g−1dry matter when sprayed with a U46D (2,4‐D formulation) blank. The third leaf retained 141 μl g−1. A 7‐day cold spell (17/9°C) increased retention per unit dry matter by 53% (135% on the third leaf). Cold stress lowered epicuticular wax quantity by 29% on the third leaf. Contact angles of formulated 2,4‐D lay between 115 and 125° and were not significantly affected by cold stress. 2,4‐D rapidly entered into maize third leaf (66% in 24 h) but migration from it was less than 1.5%. 2,4‐D was readily degraded in maize (80% in 72 h). The most abundant metabolite was probably an ester conjugate; little of the hydroxy derivatives were found. Cold stress reduced 2,4‐D degradation, and 72 h after treatment the amount of undegraded 2,4‐D was 78% higher in cold‐stressed maize plants. It was concluded that 2,4‐D selectivity in maize results from low spray retention per unit dry matter and active degradation of penetrated herbicide. Cold

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01752.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:Soil samples taken in summer 1989 and winter 1990 at different depths from three citrus orchards of the Valencia region (Spain) with a long history of residual herbicide treatments were analysed with bioassays and chromatographic procedures. The herbicides involved were atrazine, bromacil, diuron, simazine, terbuthylazine, terbumetone, terbutryn and trifluralin. Water samples from wells in the orchards were also analysed. The concentrations of the herbicides were very low, often below the limit of determination, and were always highest in the upper layers of soil. After a very unusual period of heavy rain, small quantities of some chemicals were found in the well water. The conclusion was that in these orchards the herbicides applied at currently used rates are unlikely to accumulate in any layers of the soil.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01753.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary:To assess the potential contribution of growing highly competitive crops to controlCyperus esculentusin the Netherlands, the influence of silage maize, hemp, winter barley and silage winter rye on emergence, growth and reproduction of this weed was studied in two field experiments. Growth and reproduction ofC. esculentus(determined both as tuber production per plant and density of the weed in the subseuent crop maize) was reduced by each crop, compared to plots in which no crop was grown. In hemp, hardly any tuber production was observed. By growing a green manure crop after harvest of the winter barley the tuber production of the weed was reduced to about 40% of that in winter barley followed by fallow. Decreasing the light regime in a greenhouse experiment in the same order as was observed in the crops winter barley, maize and hemp, caused a similar reduction of tuber production to that found in the field. Therefore, it is suggested that competition for light is the main factor explaining the observed crop effects on the population dynamics of the weed. It is concluded that growing competitive crops as hemp in rotation may effectively complement chemical control ofC. esculentus.

ISSN:0043-1737    

DOI:10.1111/j.1365-3180.1991.tb01754.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY