Plastic Shelters Research Articles

Direct seeding techniques to regenerate white spruce in interior Alaska

Direct seeding techniques for regenerating white spruce (Piceaglauca (Moench) Voss) were tested on 12 logged areas near Fairbanks, AK. Techniques examined included spot seeding on scarified seed spots with and without plastic cone shelters and spot seeding on nonscarified seed spots with and without plastic funnel shelters, all at three sowing times. After the second growing season, scarified treatments produced greater seedling survival. Cone shelters usually produced greater survival than unsheltered seeding on scarified seed spots and funnel shelters usually produced greater survival than unsheltered seeding on non-scarified seed spots. Sowing time had little effect on survival.

Raven Damage to Plastic Seeding Shelters in Interior Alaska

Abstract Two types of plastic seeding shelters are being tested in interior Alaska for regenerating white spruce. Raven damage to shelters has been observed on sites seeded shortly after burning. Damage averaged 68% with cones and 50% with funnels on a burned upland site, and 26% with funnels on a burned floodplain site. Damage was highly variable and appeared to be related to time of sowing and vegetation development near the seedspots. Care should be taken when considering use of seeding shelters after burning. North J. Appl. For. 2:41-43, June 1985.

Root and Foliage Growth of Oats at Several Levels of Fertility and Moisture1

AbstractThe effects of fertility and moisture on root and shoot gorwth of oats (Avena sativa L.) were studied in potculture experiments. An experimental unit was a 75‐liter garbage can filled with low‐fertility Thurman sand, embedded 0.6 m deep in the soil. Forty‐eight can were covered with a plastic shelter to permit controlled moisture regimes. A factorial set of fertilizer treatments using two levels each of N (0 and 140 kg/ha), P (0 and kg/ha), and K (0 and 93 kg/ha) were applied at seeding time. At the initiation of stem elongation, wet (field capacity) and dry (wilting coefficient) moisture regimes were imposed across all fertility treatments.Traits measured on the plant tops were plant height, number of tillers, number of spikelets per panicle, dry weight and stem diameter. Weights were taken on roots extracted from 0.007‐m3 soil samples from the 0‐15‐, 15‐30‐, 30‐45‐, and 45‐60‐cm soil depths.The root and shoot growth responded more to fertilizer application when moisture was adequate than when deficient. Nitrogen and phosphorus, applied alone and in combination, gave more shoot and root growth than any other element or combination of elements. Shoot growth responded to added fertilizer in both the high and low moisture regimes, but root growth responded only in the wet regime. Leaching of the nutrients with surface irrigations caused maximum root response to N in the 30‐45‐ cm zone, but for P, which resists leaching, maximum response was in the 0‐15‐cm zone. Reduced root‐top ratios resulting from added moisture and fertilizer elements were due largely to large increases in top growth without concomitant increases in root growth.Increase in shoot weight from added fertilizer under the dry regime was not accompanied by increased root weight. We concluded that root response to added fertility could not be responsible for oat plants utilizing subsoil (30‐60‐cm depth) moisture to produce increased shoot weights.

The microclimate of plastic shelters used for vegetable production

does not appear. First page follows. Introduction In many areas of California, warm-season crops such as cantaloupes, cucumbers, tomatoes, and peppers are planted during winter or early spring and are artificially provided with an environment suitable for growth during a period of adverse temperature conditions. This is accomplished by means of paper or plastic structures placed over the growing plants which provide, in effect, a miniature greenhouse. In the past, paper was used almost exclusively as hot-cap material. Recently, however, plastic has been used as continuous row covers or tunnels and has been shown to be superior in many respects to the conventional paper (Shadbolt and McCoy, 1960).5 As these covers often remain in place for as long as three months, temperature, humidity, and other environmental factors must be maintained in order to provide good growing conditions for the plants. Previous studies (Shadbolt and McCoy, 1960) have indicated that the shape and method of ventilation of these continuous covers have a marked influence on the soil and air temperatures as well as on plant response. It was considered desirable to expand these studies and to determine more critically the effects of these factors on the temperature patterns throughout the enclosed air and soil. Accordingly, experiments were conducted at the University of California Imperial Valley Field Station near Holtville and at the University of California, Riverside, during the winters of 1960 and 1961. Polyethylene mulching has also been used in many vegetable-growing areas of the country to increase earliness and yields. In contrast to raised covers, mulches involve the control of conditions primarily below the soil surface. Both clear and black films have been successfully used. Clear film has been shown to provide a greater increase in soil temperature than black film (Voth