Synopsis
Dacthal at 10 pounds, betasan at 15 pounds, dipropalin at 6 pounds, trifluralin at 2 pounds, and enide at 4 pounds per acre significantly controlled annual bluegrass for periods of 9 to 12 weeks. Dacthal and betasan were completely nonphytotoxic to mature turf. It is possible under field conditions to achieve good preemergence control of annual bluegrass if applications of these preemergence herbicides are made to coincide with the germination periods of the seed.
Ophiobolus patch disease developed rather quickly on young bentgrass turf after an initial methyl bromide fumigation. The disease occurred at random in 1961, but generally was much worse on plots receiving 9.8 kg of N per 100 m3 per season, regardless of P and K levels, than on plots receiving less or no N. However, by 1964, Ophiobolus patch was much more severe in the 5.9 kg of N plots than in those receiving 2.9 or 9.8 kg of N. Phosphorus had little effect on the disease in 1961, but by 1964 plots treated with 0.86 kg of P had only 15% as much infection as those receiving 0 P. Potassium exhibited a suppressing effect on the amount of disease throughout the experiment regardless of the P level. There was about five times as much disease in the 0 P and 0 K plots in 1964 as in the 0 P and 1.6 kg of K plots at all N levels. Interactions between P and K probably account for some of this difference, since this does not occur when P is added.
Dwarf type Poa pratensis L. selections (‘Merion,’ ‘Newport,’ and Washington State University selections 602, 402, 104, and 205) and “tall” or erect types (‘Park’ and ‘Delta’) were planted in replicated plots 2.5 ✕ 3.1 m on a Caldwell silt loam soil. Levels of P, K, and Ca were considered adequate for normal turfgrass growth. The plots were allowed to establish for 1 year and were then split into four subplots of two cutting heights (1,27 and 2.54 cm) and two nitrogen levels (3.6 and 1.1 kg/92.9 m2 per season). The plots were mowed once weekly for 20 weeks and all clippings were saved for yield and nitrogen analysis. Cores of soil 10.2 cm in diameter and 20.3 cm deep were analyzed for roots at the end of the season each year.
There were significant differences (P = .05) in yield of shoots among varieties in the first but not the second treatment year. Significant differences were found in root yield among varieties both years. Cutting heights produced significant differences both years. Most shoots in 1957 were produced at the 2.54‐cm cutting height, but more shoots in 1958 were produced at the 1.27‐cm height.
Significantly more shoots were produced both years from the highest N rate. The same treatment produced significantly fewer roots both years. The high N treatment resulted in higher tissue nitrogen content, but the greatest percentage nitrogen was recovered by the grass with the low N treatment.
Shoot:root ratios were computed and are shown.
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