Greater precipitation use efficiency (PUE) and economic returns by increasing cropping frequency through the addition of summer crops to the dryland winter wheat-fallow (WF) cropping system have been reported in the semiarid Central Great Plains of USA. However, due to the highly variable nature of precipitation and uncertain water availability, selection of a crop with assured positive net ret...

in order to evaluate the effects of cover crops on reduced weed biomass in hybrid sunflower an experiment was carried in the research stations, natural resources medicinal plants (samian_ardabile) with 3 replicates in 1390-1391. the first factor was considered three type of cover crops, winter rye, spring barley, winter wheat with 2 control treatment, second factor was mulch management at two l...

A review of the literature shows that the environmental risks and benefits of genetically modified crops have varying degrees of certainty. For example, field studies have documented growing resistance to highly used pesticides. However, the risks of gene flow and deleterious effects on non-target organisms have not been evaluated at large field scales. Similarly, reduced pesticide use and toxi...