Phytotoxizitat von Paraquat zu verringern. Die phytotoxischen Ruckstande wurden nicht durch Oberflachenbewasserung verringert, sie verschwanden jedoch bei mechaniseher Bearbeitung der Bodenoberflache.

No abstract

Summary Glasshouse studies showed that low doses of paraquat inhibited the germination of Lolium perenne L. broadcast directly onto the paraquat‐sprayed surfaces of a sphagnum and a peat soil, but that higher doses were necessary to produce phytotoxic symptoms on mineral soils, a compost and a loam. On all soils residual activity increased rapidly with increasing dose once the minimum phytotoxic dose was reached. On a sandy soil, residual activity increased almost linearly from the lowest to the highest dose applied. At 9·0, 4·5 and 2·24 kg/ha phytotoxicity on a compost was not affected by changes in the volume of application, but at 1·68 kg/ha and lower, reducing the volume from 562 1/ha to 281 and 112 1/ha resulted in increased phytotoxicity. Phytotoxic residues were eluted from paraquat‐treated compost surfaces by percolating de‐ionized water up soil columns but residual activity was not removed from the eluted surfaces. Surface irrigation of paraquat‐treated surfaces with water previously percolated through columns of untreated soil reduced residual activity by 45%.

Trials were conducted to determine the feasibility of combining granular dalapon, P fertilizer and birdsfoot trefoil seed in mixtures for renovating natural grass pastures in Ontario. The aim was to develop a ‘once‐over’ method to facilitate the renovation of pastures characterized by rough topography, rock outcrops or surface boulders. Dalapon at 4 lb. a.i./ac (4.4 kg/ha) controlled the growth of Canada bluegrass (Poa compressa L.) and did not affect the germination and seedling growth of trefoil when applied simultaneously with the seed. Up to 100 lb/ac (112 kg/ha) P2O5 could be added to the mixture without detriment to trefoil establishment. The application of dalapon, P and seed in mixture by fixed‐wing aircraft, helicopter or ground equipment gave five‐to ten‐fold increases in pasture productivity and proved to be a practical method of pasture renovation.