Cover crop tissues

Potentially, a safener could increase the tolerance of the crop by reduction of herbicide uptake and translocation, or by enhancement of metabolic herbicide inactivation in the crop tissue. Furthermore, a safener could counteract the effect of a herbicide at its biochemical target site, with a resultant reduction of crop susceptibility. Evidence for and against these potential modes of action is presented in the following sub-sections. In addition, aspects of safener specificity (crop versus weed) are covered for situations where the safener is applied in tank mix with the herbicide. 

Adding Hoagland s solution in addition to sunflower tissues eliminated the inhibitory effects of sunflower tissues on pigweed seedling biomass. Thus, it would appear that nutrients in plant tissues mixed into soil might modify plant-plant allelo-pathic interactions differently than nutrients/fertilizer directly applied to surface of the soil or mixed into the soil. The functional role of nutrients in small grain and clover cover crop residues is presently not known. 

Another feedback uncertainty involves the response of plants to rising CO2 levels. Some studies indicate that agricultural crops grow faster in a high-C02 environment, pulling more carbon out of the atmosphere and storing it in plant tissues. Little is known about the response of the forests, grasslands, and tundra that cover much of the Earth. 

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