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- Author or Editor: Delbert D. Hemphill Jr. x
Abstract
Injection of gibberellic acid (GA3) into crowns of field grown rhubarb (Rheum rhaponticum) stimulated early petiole growth and increased total and marketable yields. The GA3 treatment was most effective in late January and February, less effective in early March, and ineffective in June. Growth was stimulated by injection of 2.5 to 40 mg GA3/crown, with 10 to 20 mg sufficient for optimal growth. Spray applications of GA3 to soil-free buds and application through a trickle irrigation system did not increase rhubarb yield or earliness. Costs for the GA3 injection treatment are very favorable compared to indoor forcing or to field forcing with clear polyethylene mulch.
Abstract
‘Ithaca’ lettuce (Lactuca sativa L.) seed imbibed at 17°C emerged from warm (> 25°) soils more rapidly than did untreated seed. Planting seed in a gel also increased emergence, in part because of an anticrustant effect of the gel. The combination of imbibition and gel produced more rapid emergence than did either treatment alone. Mean head weight at harvest increased and head weight variability decreased with imbibition or gel treatment. The combination of imbibition and gel compared favorably with transplanting in reducing head size variability.
Abstract
Soil mechanical resistance or crusting was reduced by vermiculite, H3PO4, Nalco 2190, neutral NH4H2PO4, and sulfuric acid when applied as a band over the seed row. Vermiculite was the most effective anticrustant followed by H3PO4. The greatest stands and yields of carrot (Daucus carota L.), cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.), and onion (Allium cepa L.) were usually obtained with vermiculite. Phosphoric acid tended to increase yields even when the stand was thinned to equal that in the control treatments. Other anticrustants had little effect on stands or yields.
Abstract
Phosphoric acid (H3PO4), applied as an over-the-row banded spray to Willamette silt loam, significantly hastened the emergence of seedlings of carrot (Daucus carota L.), cauliflower (Brassica oleracea L. var. botrytis), cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.), and onion (Allium cepa L.). Final stands were usually improved. The effect was particularly pronounced in early plantings. Banded H3PO4 decreased soil crusting as measured by decreased mechanical resistance to penetration of the soil surface. Phosphorus content of seedlings of carrot, cucumber, lettuce, and onion was significantly increased with H3PO4 anticrustant. Yields were usually greater on soils treated with H3PO4 than on soils treated with either broadcast or subsurface banded applications of concentrated superphosphate (CSP). Subsurface bands of CSP resulted in poorer stands, lower leaf P content, and smaller yields of carrot, lettuce and onion than did banded H3PO4 at the same rate of P application. However, both leaf P content and yield of cucumber tended to be greater with CSP than with H3PO4. Phosphoric acid treatment improved stand of carrot and lettuce at soil pH between 5.0 and 6.1 but decreased stand at pH 6.6.
Agricultural plastics area significant contributor to solid waste disposal problems, particularly in areas with heavy use of plastic-covered greenhouses or mulch films. Field-burning and landfilling are no longer viable options for disposal in many areas. Reuse and reduced weight of films are two methods to reduce the amount of material requiring disposal. Recycling, incineration, and on-site degradation appear to be the most-promising technologies for disposal. Each technology has its drawbacks. These include dirt and pesticide residues on mulch films, the presence of stabilizers and photoactivators, possible limitations to recycling mixtures of types of plastics, and high costs for recycling and incineration facilities. This is an active area of research for many members of the American Society for Plasticulture.
Abstract
Five weed-control treatments (unweeded; hand-weeded; bensulide and naptalam; bensulide, naptalam, and paraquat; black polyethylene mulch) were combined factorially with three row-cover treatments (no cover, spun-bonded polyester, highly perforated polyethylene) in a 2-year experiment. Slicing cucumbers (Cucumis sativus L.) were transplanted 26 (1985) or 23 (1986) days after application of the bensulide-naptalam. This combination of herbicides provided weed control for up to 4 weeks after transplanting, but was less effective in 1986 than in 1985. Row covers reduced herbicide efficacy. Spraying paraquat through the covers 2 to 3 days before setting transplants significantly improved weed control and cucumber yield. Soil crusting was reduced, and earliness and total yield were enhanced by mulch and row covers. Greatest yields and estimated net economic return in both years occurred with row covers with mulch followed by mulch alone in 1986 and by mulch alone or hand-weeding with row covers in 1985. Weed control, earliness, and yield were not affected significantly by type of row cover in either year. Chemical names used: O,O-bis(1-methylethyl)-S-[2-(phenylsulfonyl)amino]ethyl]phosphorodithioate (bensulide); 2-[(1-napthalenylamino)carbonyl]benzoic acid (naptalam); 1,1′-dimethyl-4,4′-bipyridinium salts (paraquat).
Abstract
Floating row covers increased air and soil temperatures compared to black polyethylene ground mulch and increased both early and total yield of muskmelon [Cucumis melo (L.)]. In 1983, all 3 row covers increased transplant survival and total yield/plant but decreased mean fruit weight. Cover removal date had little effect on yield or earliness. Due to greater plant survival, total yields were higher with perforated (PCP) and slitted clear polyethylene (SCP) floating covers than with spunbonded polyester (SPE) covers. Direct-seeded plants under floating SCP produced higher total yields and reached peak production earlier than the noncovered transplants. In 1984, SPE and PCP increased yield and earliness but had no effect on mean fruit weight. Transplants outyielded direct-seeded plants and early yield increased with late row cover removal. Neither total nor early yield were significantly affected by type of row cover. Projected economic return was usually increased by the row covers for both transplants and direct-seeded plants.
Abstract
Bush beans (Phaseolus vulgaris L.), carrots (Daucus carota L.), and lettuce (Lactuca sativa L.) were grown for 3 years on soils amended with S or lime and N fertilizer. Yields of all crops increased with lime application but response to N varied among crops and years. Lettuce head weight tended to increase with N application at pH greater than 6.0, but it decreased with N application at lower pH levels. A soil pH of 5.6 to 6.4 was optimal for carrots and beans, and of 6.1 to 6.6 for lettuce. Plant tissue K and Mg concentrations were not affected by soil pH or N rate. Phosphorus and Ca concentration of plant tissue generally increased with lime application. Plant tissue Zn and Mn concentration usually decreased with increasing soil pH between pH 5.1 and 6.4. The reduction in bean and lettuce leaf Mn concentration between pH 5.1 and 5.7 ranged from 30 to 71%. Low bean yields at pH 5.1 were possibly caused by a combination of Mn toxicity and P deficiency. Failure of lettuce to head at low pH may have been caused by Mn toxicity.
Abstract
Green bunching onion (Allium cepa L.) is a high-value crop that is seeded nearly year around in western Oregon. Late winter and early spring plantings often result in unsatisfactory stands because of low soil temperatures, excessive precipitation, and soil crusting. A method to speed emergence and improve stands would benefit growers.