Herbicides organic weed control

Metal Organics and Inorganics. The metal organic herbicides are arsenicals used for the selective, post-emergence control of grass and broadleaved weeds in cropland and noncroplands. These herbicides are particularly usehil for weed control in cotton and turf crops (2,296,294). CacodyUc acid is a contact herbicide used for nonselective weed control in cropland and noncropland (299). Ammonium sulfamate [7773-06-0] (AMS) is an inorganic herbicide used for control of woody plants and herbaceous perennials (2). 

Organic farming systems rely more on mechanical weed control and in certain crops on considerably more intensive soil tillage as the use of synthetic herbicides is prohibited. This can have negative effects on other key species of soil meso-fauna, i.e. a reduction of population of Collembola with organic cultivation (Krogh 1994). 

Substitution of the chloro atom by bromine, by fluorine, by nitrilo-, hydrazion-, alkyl-, haloalkyl-, alkoxyalkoxy groups leads very often to remarkable herbicidal but seldom -from the practical point of view - to superior activity. It is thereby obvious to everybody active in this field that the qualification superior activity can never relate to one parameter alone activity against the target organisms is, of course, an absolute prerequisite but this activity can, outside the field of industrial weed control, only be made valuable by a complementary suitable crop selectivity pattern. The following compounds resulting from our project reached the level of practical use ... 

Ametryn, another triazine herbicide, was previously used for weed control in citrus. This herbicide first appeared in recommendations in 1979 for control of broadleaf weeds, annual grasses, and some perennial grasses. Ametryn was recommended at use rates of 3.6-7.2kg a.i./ha, with a maximum of 5.4kg a.i./ha for both shallow, poorly drained flatwood soils (soils having more organic matter and clay) and bedded groves (trees planted on raised beds). It was recommended that ametryn should not be applied to trees less than 2 years old. Between 1984 and 1988 the application rates were increased to 7.2-10.8kg a.i./ha, with the annual rate not to exceed 13.6kg a.i./ha, and with lower rates... 

Triazine herbicide soil activity, movement, and residues depend primarily on content of organic matter, and to a lesser extent, clay colloids (Nearpass 1965 Day et al, 1968 Weber et al, 1969). Soils that are low in organic matter or clay usually require lower herbicide rates, but result in more potential phytotoxicity (Lange et al, 1969a). Simazine (4.0kg/ ha) or diuron (5.0kg/ha) gave season-long weed control in soils of the Northwest (Hogue and Neilsen, 1987). 

The herbicides commonly used as arboricides include members of the triazines, ureas, and uracils, for grass and weed control in nursery and Christmas tree plantings. Other compounds include phosphonate and phosphate derivatives, pyridine-based organic acids of high activity, and organic arsenicals. Such a wide... 

These older compounds each represented attempts at weed control, sometimes selective weed control, through chemicals. The last 30 years has been a time of rapid development of new herbicides, mainly organic chemicals, in the United States. Over 40 basic and specialty chemical manufacturers (such as pharmaceutical, oil, rubber, and paint companies) have participated in this chemical revolution of weed control. 

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