The response of alfalfa regrowth, yield and plant populations to halosulfuron applied following cuttings and irrigations in the summer and fall of 1999 was studied in an experiment conducted at the University of Arizona Maricopa Agricultural Center. A single application of halosulfuron applied when there was little alfalfa foliage slightly reduced plant heights for several cutting cycles with increasing rate decreasing plant height. The cumulative forage fresh weight yields for the October 4th, November 15th, and February 22nd harvests for treatments receiving no halosulfuron or 0.032, 0.047, or 0.063 lb a.i./A were (means ± std. dev.): 15.94 ± 0.91, 14.99 ± 0.66, 14.80 ± 1.74, and 14.46 ± 0.97 tons/A, respectively. The trend of decreasing cumulative forage fresh weight with increasing halosulfuron rate was significant (Adj. R2 = 0.178, P = 0.015) indicating that for the three harvests after August 25th, halosulfuron had a small but negative effect on forage fresh weight. The harvest on April 5, 2000, the fourth harvest following the halosulfuron applications on August 25, 1999, indicated that there was no longer any residual effect of halosulfuron on alfalfa growth. Plant populations measured on April 10, 2000 were not affected by either one or two halosulfuron applications in this experiment. A set of sequential halosulfuron treatments applied when there was substantial alfalfa foliage (about 80% of the ground surface covered) severely suppressed alfalfa regrowth. Little regrowth occurred in these plots in October or November after the sequential applications compared to the untreated control or to the plots that received only the initial application of halosulfuron. The change in mean percent yield loss with successive harvests on November 15th, February 22nd and April 5th of 85, 40 and 14% indicated that the alfalfa plants were recovering from the halosulfuron applications. The cumulative forage fresh weight yields for treatments receiving sequential halosulfuron treatments (0.032+0.032, 0.047+0.047, or 0.063+0.063 lb a.i./A) were (means ± std. dev.): 11.67 ± 1.46, 10.85 ± 1.06, and 10.44 ± 0.98 tons/A, respectively, and were much less than the cumulative yield of 18.97 ± 1.17 tons/A from the untreated plots. The data suggest that the critical factor in determining the degree of alfalfa injury caused by halosulfuron is the amount of foliage present at the time of application.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/204095 |
| Date | 10 1900 |
| Creators | McCloskey, William B. |
| Contributors | Ottman, Michael |
| Publisher | College of Agriculture, University of Arizona (Tucson, AZ) |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Article |
| Relation | Series P-124, AZ1185 |
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