Tolerances rotational crops

Sulfentrazone is a broad-spectrum, pre-emergent herbicide that provides good control over broadleaf weeds, grasses and sedges in crops and turf. The metabolism of sulfentrazone in animals and plants is similar. The major plant metabolite of sulfentrazone is 3-hydroxymethyl sulfentrazone (HMS). The soybean tolerance of 0.05 mg kg includes residues of sulfentrazone plus its major metabolite, HMS. The rotational crop tolerance includes residues of sulfentrazone and its major metabolites, HMS and... 

Tolerance toward the sulfonylureas is known to occur naturally due either to the presence of a form of ALS that is insensitive to the inhibitors (7) or to a mechanism for detoxification of the inhibitors (8). Another mechanism that could in principle lead to tolerance is the overproduction of the target (ALS) enzyme. We are interested in engineering herbicide tolerance in crop plants in order to increase the margin of safety for the application of existing selective chemicals, to achieve selectivity in crops where selective chemicals do not currently exist, and to reduce damage in rotated crops which is due to the presence of herbicide residues. 

Keeping to a strict rotation for vegetable crops (see also p.230) not only allows better use of nutrients, but also prevents the buildup of pests and pathogens in the soil. With perennial crops, such as roses, strawberries, apples, and pears, do not replant with the same species in the same place. New plants may fail to thrive due to high levels of host-specific pests or pathogens in the soil. The old established plants may have built up tolerance to these. 

A more recent factor affecting weed management has been the introduction of crops genetically altered for tolerance or resistance to herbicides. The first herbicide-tolerant field com (IMI hybrid corn) was developed as a way to reduce the effects of carryover from imidazolinone and sulfonylurea herbicides applied to soybean in a corn-soybean rotation. These hybrids also soon found use in areas where triazine use was restricted. 

A methodology was developed to estimate quantities of crop residues that can be removed while maintaining rain or wind erosion at less than or equal to the tolerable soil-loss level. Six com and wheat rotations in the 10 largest com-producing states were analyzed. Residue removal rates for each rotation were evaluated for conventional, mulch/reduced, and no-till field operations. The analyses indicated that potential removable maximum quantities range from nearly 5.5 million dry metric t/yr for a continuous corn rotation using conventional till in Kansas to more than 97 million dry metric t/yr for a corn-wheat rotation using no-till in Illinois. 

For each county in the 10 states evaluated, all cropland soil types in land capability classes (LCCs) I—VIII are identified. For each individual soil type, acres of that particular soil type, field topology characteristics (percentage low and high slopes), erodibility, and tolerable soil-loss limit are obtained from the USD A. These data are used in the rain and wind erosion equations described later. In each of the states analyzed, the following crop rotations are considered (where applicable) continuous corn, corn-soybean, corn-winter wheat, corn-spring wheat, continuous winter wheat, winter wheat-soybeans. 

It acts on germinating weeds. Absorbed through the roots it is scarcely translocated. The tolerance of soybean is due to the fact that oryzalin is not absorbed by the plant neither is it absorbed by wheat following soybean in crop rotation. 

The results of the FSE when they were released in the autumn of 2003 were not as crucial to the public debate as they might have been because the controversy was largely around other issues. The findings were even handed in that GM crops that were herbicide tolerant had both advantageous and disadvantageous impacts on wildlife. The oil seed rape and beet crops led to declines in the flora and fauna, whilst the maize crops benefited wildlife. This neat symmetry would be of course more complex if the crops were commercialised, as the size of the plots, the rotations and specific location of the crops would have differential impacts. The only unalloyed finding of the research was that UK field ecologists are now the world leaders in this form of field scale evaluations that are required by EU r ulation. 

Wide rotations are effective at reducing the risk as well as having a rotation with few if any brassica crops or host weed species. Grow tolerant varieties. No nematicides are currently approved for use in the UK. 

Repeated use of one herbicide in a field tends to result in the appearance of herbicide-resistant weeds (P). The most practical approach to delaying the evolution of resistance is to rotate several herbicides in crop monocultures (ICf) thus, the combination of transgenic crop plants and rotation of different herbicides should prevent the appearance of mutant weeds tolerant to herbicides. 

Crop rotation, adequate cultivation techniques, resistant/tolerant cultivars and standard/certified seed and planting material, balanced fertilization, liming and irrigation/drainage practices, hygiene measures, protection and enhancement of important beneficial organisms... 

It is tolerant to poor growing conditions and will produce seed in a large variety of soils and at altitudes far above 2000 m. Seed yields range from 400-1500 kg per ha. N. is useful in the rotation as a broad-leaved crop. 

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