Yield weeds

Horton DK, Frans RE, Cothren RT. 1983. MSMA-induced straighthead in rice (Oryza-sativa) and effect upon metabolism and yield. Weed Science 31 648-651. 

Brandsaeter, L.O., Netland, J. and Meadow, R. 1998. Yields, weeds, pests and soil nitrogen in a white cabbage-living mulch system. Biological Agriculture and Horticulture 16 291-309. 

Schreiber, M.B. (1992). Influence of tillage crop rotation, and weed management on giant foxtail (Setaria faberi) population dynamics and com yield. Weed Sci., 40 645-653. 

Patterson, M.G. and W.D. Goff (1994). Effects of weed control and irrigation on pecan (Carya illinoinensis) growth and yield. Weed Technol., 8 717-719. 

Curran, W.S., L.D. Hoffman, and E.L. Wemer (1994a). The influence of a hairy vetch (Vicia villosa) cover crop on weed control and com (Zea mays) growth and yield. Weed Technol., 8 777-784. 

Reddy K.N., Zablotowicz R.M., Locke M.A., Koger, C.H. Cover crop, tillage, and herbicide effects on weeds, soil properties, microbial populations, and soybean yield. Weed Sd 2003 51 987-994. 

Wyse, D.L., Young, F.L., and Jones, R.J., Influence of Jerusalem artichoke (Helianthus tuberosus) density and duration of interaction on soybean (Glycine max) growth and yield, Weed Sci., 34, 243-247, 1986. 

Potatoes are a veiy competitive crop once they meet across the rows, but early weed emergence, which is not controlled, can reduce yields. Weeds can also affect potato quality and ease of harvesting. 

Chemical, cultural, and mechanical weed control practices have been relatively successful ia reducing yield losses from weeds (448). However, herbicide-resistant weed populations, soil erosion, pesticide persistence ia the environment, and other problems associated with technologies used (ca 1993) to control weeds have raised concerns for the long-term efficacy and sustainability of herbicide-dependent crop production practices (449). These concerns, coupled with ever-increasing demands for food and fiber, contribute to the need for innovative weed management strategies (450). 

Another significant use of 3-methylphenol is in the production of herbicides and insecticides. 2-/ f2 -Butyl-5-methylphenol is converted to the dinitro acetate derivative, 2-/ f2 -butyl-5-methyl-4,6-dinitrophenyl acetate [2487-01 -6] which is used as both a pre- and postemergent herbicide to control broad leaf weeds (42). Carbamate derivatives of 3-methylphenol based compounds are used as insecticides. The condensation of 3-methylphenol with formaldehyde yields a curable phenoHc resin. Since 3-methylphenol is trifunctional with respect to its reaction with formaldehyde, it is possible to form a thermosetting resin by the reaction of a prepolymer with paraformaldehyde or other suitable formaldehyde sources. 3-Methylphenol is also used in the production of fragrances and flavors. It is reduced with hydrogen under nickel catalysis and the corresponding esters are used as synthetic musk (see Table 3). 

A sound crop rotational system is of basic importance to the organic farmer. It reduces the risk of diseases and pests associated with monoculture, gives better control of weeds, spreads the labour requirements more evenly over the year, reduces the financial risk if one crop yields or sells badly and provides more interest for the farmer. For instance, take-all is a disease that cannot even be controlled chemically. Winter crops are more susceptible to take-all than spring sown crops and wheat is more susceptible than barley, so the safest position for winter wheat is immediately after a break crop. 

Fodder crops are useful in organic rotations they are high yielding crops with high levels of metabolisable energy. They will also serve as a cleaning crop for weeds. 

A weed, which is a form of a natural resource, is simply a living organism whose presence conflicts with the interests of people. Undesirable as they may be, weed species are natural occurrences in the agricultural ecosystems created by man s food and fiber production. Over 300,000 species of plants inhabit the earth, but only 30,000 of these are weeds. About 1,800 weed species cause serious economic losses in crop production, and about 300 weed species are serious in cultivated crops throughout the world. Most cultivated crops are plagued by 10 to 30 weed species that must be controlled to avoid yield reductions (1). 

Weeds are an enormous problem affecting field crops in the Mid-South. They reduce yields, increase the cost of production, reduce the quality of the harvested produce, and decrease the value of the marketed product. These effects of weeds are present wherever crops are grown however, they seem to be more devastating... 

The presence of crop residues has been reported to both increase (5, 6) and decrease crop yields ( 7) and not tilling to increase certain difficult to control weeds (8). However, other reports indicate that the presence of certain mulches can reduce the biomass of certain weeds (9-15) and allow for higher crop yields ( 5, 6). Thus, under certain conditions, mulches can suppress certain weed species, but determining the reason(s) presents many logistical problems, especially under field conditions. To determine the cause(s), the physical and chemical (i.e., allelopathy) effects of the mulch and the role of soil disturbance (or the lack of, as would be the case in a no-till system) must be separated. 

In fields where some weeds were cleared using herbicides, other, more herbicide-resistant, species have appeared, such as common horsetail, coltsfoot, foxtail, wild oats, false wheat, etc. As a result of herbicide use, scratchweed, which cannot be destroyed by any herbicide, is making inroads into cereal crops, and chamomile has taken over rapeseed [6]. Using herbicides on rice fields caused the spread of wild, pesticide-resistant, low-yield forms of red-grain rice. 

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