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This article in AJ

  1. Vol. 71 No. 4, p. 634-638
     
    Received: Sept 18, 1978
    Published: July, 1979


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doi:10.2134/agronj1979.00021962007100040028x

Time and Rate of Paraquat Application for Curing Meadow Vegetation for Winter Grazing1

  1. Forrest A. Sneva and
  2. F. B. Gomm2

Abstract

Abstract

Winter grazing of paraquat (1,1 dimethyl-4,4 bipyridinium ion)-cured meadow vegetation has been shown to hold potential as an alternative to the conventional cut-stack-feed practice in the Great Basin meadowlands. Additional information was needed to define (i) the minimum levels of paraquat required for curing; (ii) the best application time; (iii) the comparative effectiveness of above-canopy spray release with within-canopy spray release.

Plots were treated with paraquat at rates from 0.06 to 0.56 kg/ha in July of 2 years. Paraquat applied in the morning, midday, and evening hours evaluated plant maturity, illumination, temperature, relative humidity, and surface soil moisture in relation to the chemical's effectiveness to arrest the loss of herbage N.

Vegetation was satisfactorily cured with 0.11 kg/ha paraquat. Crude protein concentrations of meadow vegetation exceeded 7% in July, and treatments in that month maintained concentrations above 5.5% for 160 days; naturally cured vegetation then contained less than 4%. Yield losses in treated plots 90 days after treatment ranged from 22 to 30% but were no greater than those in control plots. Dispensing the spray above the canopy was more efficient than dispensing it within the canopy, but the difference is believed to be a result of poor spray coverage from the within-canopy treatments. Morning, midday, and evening applications did not produce significantly different treatment means. Crude protein concentration was higher in vegetation treated on sunny days than on overcast days, but this was due to sunny day effect rather than an increase in effectiveness of paraquat. Paraquat residue at 100 days after treatment at the rate of 0.34 kg/ha or less ranged from 3 to 15 ppm.

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