• Chemical Control of Weeds in Potatoes in Southcentral and Interior Alaska

      Carling, Don E.; Conn, Jeff S. (Agricultural and Forestry Experiment Station, School of Agriculture and Land Resources Management, University of Alaska Fairbanks, 1990-05)
      Weeds cause serious problems for commercial potato growers in Southcentral and Interior Alaska. Reductions in potato yields of 20 to 70 percent due to weeds have been observed in previous studies (Carling, unpublished data). Competition by weeds generally is so intense that profitable yields cannot be produced unless weed growth is controlled. Mechanical methods alone, including cultivation and hilling, have not provided acceptable levels of control. For many years, commercial potato growers relied on the chemical herbicide Premerge® (dinoseb) to control weeds. Premerge killed weeds by contact and was very effective in controlling the most troublesome broad leaf weeds when applied just prior to emergence of the potato plants. In addition, Premerge left no chemical residues in the soil to damage vegetable or other crops grown in succeeding years. Unfortunately, several years ago Premerge was found to be a hazard to human health and now may not be used as an herbicide. Commercial growers have been trying other chemicals as they search for alternatives to Premerge. Several of these chemicals are promising but, unlike Premerge, all leave chemical residues in the soil that could be toxic to crops that potato growers plant in rotation. In 1988, a field study was initiated to evaluate the efficacy and carryover of several herbicides. Five chemicals including: Treflan® (trifluralin), Enide® (diphenamide), Eptam® (ETPC), Sencor® (metribuzin) and Lorox® (linuron) were evaluated at Fairbanks and Palmer. Eptam, Sencor and Lorox controlled weeds most effectively of the five and were selected for reevaluation in 1989. Summarized in this report are data on potato yields and weed control from the study in 1989. Information on phytotoxic residues associated with some of these chemicals will be presented in later publications.
    • The Effect of Hilling on Yield and Quality of Potatoes

      Carling, Don E.; Walworth, James L. (Agricultural and Forestry Experiment Station, School of Agriculture and Land Resources Management, University of Alaska Fairbanks, 1990-06)
      Traditionally, commercially grown potatoes are hilled in the production cycle between emergence and closure of the canopy. Hilling is usually accomplished with disks, sweep shovels, or similar tools that lift soil from between rows and deposit it beside and on top of the row. Reasons for hilling may include: improved weed control, improved drainage, minimization of greening of tubers, and raising of soil temperatures. Proper management of each of these factors may result in an increase in quality and quantity of tuber yield. Negative aspects of hilling have also been noted. Saffigna et al. (1976) reported that water distribution was uneven under potato hills, resulting in uneven availability of water to plants and increased loss of fertilizer due to leaching. Hilling operations may also damage potato plants, and significant reductions in yield are known to result from hilling and other types of cultivation (Nelson and Giles, 1986). Many commercial growers wait until vines are 12 or more inches tall before hilling. This scheduling is preferred because at this time the danger of covering plants is minimal. However, the vines of larger plants may sustain greater damage from hilling than smaller plants. Also, the possibility of damaging roots and stolons increases as the plants increase in size, so there may be advantages to hilling when plants are younger and smaller. Four different treatments including variations in time of hilling and height of hill were compared with no-hilling on four varieties of potato in the 1988 and 1989 growing seasons. This report contains a preliminary summary of data collected from these studies.