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  • Author or Editor: Ronald D. Morse x
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Advantages of no-till (NT) production systems are acknowledged throughout the world. During the 1990s, production of NT vegetable crops has increased for both direct seeded and transplanted crops. Increased interest in reduced-tillage systems among research workers and vegetable growers is attributed to: 1) development and commercialization of NT transplanters and seeders, 2) advancements in the technology and practice of producing and managing high-residue cover crop mulches, and 3) improvements and acceptance of integrated weed management techniques. Results from research experiments and grower's fields over the years has shown that success with NT transplanted crops is highly dependent on achieving key production objectives, including: 1) production of dense, uniformly distributed cover crops; 2) skillful management of cover crops before transplanting, leaving a heavy, uniformly distributed killed mulch cover over the soil surface; 3) establishment of transplants into cover crops with minimum disturbance of surface residues and surface soil; and 4) adoption of year-round weed control strategies.

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Potato (Solanum tuberosum L.) yields in Virginia and other hot climates are considerably lower than in cooler areas, predominately because of high soil temperatures during set and bulking of the tubers. Although organic surface mulches conserve soil moisture and lower soil temperature, often resulting in increased tuber yields, applying organic mulches is commercially cost-prohibitive. Preliminary experiments were conducted in 1995 and 1996 at the VPI&SU Agricultural Research Farm to compare production of `Yukon Gold' potato in no-till (NT) raised-bed systems with standard conventionally tilled (CT) methods. No-till yields were higher than CT both years, although differences were not significant. Based on these data, the NT production system used in these experiments is a viable management option, at least in hot climates such as Virginia. Rainfall during tuber bulking in 1995 and 1996 was above average, even excessive at times, which possibly negated the beneficial soil-cooling and moisture-conserving effects of the in situ mulches on potato yield enhancement. Greater yield increases would be expected in NT plots in normal rainfall years.

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Conservation tillage systems offer distinct advantages for crop production under erosive and droughty soil conditions. This report contains 4 years of data on the effects of in situ cereal rye and wheat mulches on yield of cabbage (Brassica oleracea L. var. capitata) grown under limited-irrigation, conservation-tillage systems. Three tillage systems were studied: conventional plow-disk (CT); strip tillage (ST) and no-tillage (NT). The summers of 1987 and 1990 were characterized by below-average total rain and periods of prolonged (45 days) of dry weather during head enlargement; cabbage yields were highest in the mulched ST and NT plots. In contrast, the 1988 and 1989 growing seasons were above average in total rain and there were no prolonged periods of dry weather. Cabbage yields were unaffected by tillage treatments in 1988, while, in 1989, yields with NT were 65% and 60% lower than with CT and ST, respectively. A combination of abundant rain, soil compaction, and delayed planting retarded plant growth in the 1989 NT plots, resulting in smaller, less-productive plants than in the tilled ST and CT plots. These data show that: 1) conservation tillage and particularly strip tillage systems are viable options for production of cabbage; and 2) rain-irrigation patterns, site selection, and planting dates are major determinants of the relative advantages of conservation tillage compared to conventional tillage systems.

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Experiments were conducted with `BigSur' broccoli (Brassica oleracea L. var. italica) at two sites in Fall 1993 and at two sites in Spring 1994 on a Hayter loam in southwestern Virginia. Our objectives were to determine the effects of tillage main plots (conventional tillage = CT and no tillage = NT) and weed control subplots [no overseeding or preemergent herbicide, oxyfluorofen, red clover (Trifolium pratense L.), `Dutch' white clover (Trifolium repens L.), and hairy vetch (Vicia villosa Roth)] on broccoli yield and weed suppression. In all sites, weed suppression and marketable broccoli yield with NT were equal to or higher than with CT. Overseeded legume living mulches did not affect broccoli yield in any site compared to the control plots and suppressed weeds as well as the oxyfluorofen in three of the four sites. Thus, the NT systems used in these experiments can suppress weeds and produce high broccoli yields. Also, overseeded legume living mulches can be established effectively after transplanting to suppress weeds without reducing broccoli yield. Chemical name used: 2-choro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (oxyfluorofen).

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Seed tubers of `Yukon Gold' (Solanum tuberosum L.) exhibit strong apical dominance, resulting in relatively poor stem emergence. Cutting seed tubers to overcome apical dominance in `Yukon Gold' results in irregular, uneven stem emergence. In 1992 and 1993, experiments were conducted to evaluate the effects of dehaulming (excising stems to ground level after field emergence) whole, cross- and longitudinal-cut seed tubers of `Yukon Gold' on canopy growth and tuber yield. For all seed piece types, dehaulming during the first week of field emergence produced uniform plant stands and increased yields of U.S. no. 1 tubers by 16 and 42% and large tubers (> 6.4 cm dia.) by 340 and 64% in 1992 and 1993, respectively. Our data indicate that tuber bulking rate was increased by dehaulming. The possible causes and implications of increased tuber bulking rates in dehaulmed potato plants are discussed.

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Abstract

Green-manure systems of a tall fescue (Festuca arundinacea L.) sod and a rye (Secale cereale L.)-soybean (Glycine max. L.)-rye rotation were grown for 2 years to provide organic amendments to minesoil. One year after incorporating the green-manure crops, tomato (Lycopersicon esculentum Mill.), pepper (Capsicum annuum L.), and eggplant (Solanum melongena L.) were grown on the amended minesoil and on adjacent, unamended minesoil. Six levels (0.05 to 2.4 ppm) of solution P were established within each plot, based on phosphate sorption isotherms. P sorption decreased in the organic-amended minesoils, thereby reducing the inorganic P fertilizer needed to establish each P solution level. Levels of amorphous Al oxides decreased while exchangeable Al remained relatively constant in the amended minesoil. Moisture relationships and other physical properties were improved in each green-manure regime. Organic amendments had no effect on optimum solution P requirements as tomato and pepper produced highest yields at 0.20 and 0.40 ppm solution P while eggplant produced highest yields at 1.60 and 2.40 ppm solution P in all minesoils. Yields of vegetables were higher in the amended minesoils for most solution P levels, while tissue P and other nutrient concentrations remained unchanged. Yield increases at each P solution level were attributable to improvements in minesoil moisture properties, not to nutritional factors. No differences between the 2 green-manure systems were apparent in their effect on external (solution P) or internal (tissue P) P requirements of the vegetable crop.

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Abstract

Phosphate-sorption isotherms were used to predict the rates of P fertilizer required to establish 6 concentrations of solution P in reclaimed minesoils. Tomato (Lycopersicon esculentum Mill.), pepper (Capsicum annuum L.), and eggplant (Solanum melongena L.) were grown during 2 successive years on the same minesoil plots, fertilized each year with sufficient P to establish the desired solution P levels. At every solution P level, the rate of fertilizer P required the second year was less than the initial year, with the relative amount needed to re-establish the solution P levels considerably reduced at the higher solution P concentrations. Optimum solution P was reached at 0.2 ppm for tomato and pepper, while eggplant required 1.6 ppm P in solution for optimum yield. Regression analysis estimated optimum levels of solution P at 1.56 ppm for eggplant and 0.28 ppm for tomato and pepper. The optimum minesoil solution P levels for each species was similar to that reported for these same crops on other soils, indicating the broad applicability of these data and the sorption isotherm method for assessing P-fertilizer requirements. Marginal leaf necrosis and yield reductions of 73–75 % occurred with tomato and pepper when solution P concentrations were increased to 2.4 ppm. Yield response at suboptimal solution P levels was greater for tomato and pepper than eggplant, suggesting that the P nutrition of the latter crop is less efficient than the former species.

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Abstract

The effects of pH and temperature were determined on NAA sorption by enzymatically isolated tomato (Lycopersicon esculentum Mill. cv. Sprinter) fruit cuticles. Both cuticular membranes (CM) and dewaxed CM (DCM) sorbed more NAA at pH 2.2 than at pH 6.2. At each pH, increasing temperature (15° to 35°C) decreased NAA sorption by both CM and DCM. The same qualitative temperature (5° to 25°) response was observed with 2,4-D for CM at low (0.8) pH. Chemical names used: 2-(1-naphthyl)acetic acid (NAA); (2,4-dichlorophenoxy)acetic acid (2,4-D).

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There is a strong consumer demand for single-head broccoli (Brassica oleracea L. var. italica) that yields more florets per unit weight than bunching broccoli. Two spatial arrangements (single vs. twin row) and five plant densities (10.8, 7.2, 5.4, 4.3, and 3.6 plants/m2) were examined for single-head broccoli production. Spatial arrangement had no significant effect on any measured attribute, although the twin-row arrangement resulted in less plant damage with each harvest. For exclusive production of quality, single-head broccoli with high yields of marketable florets, 3.6 plants/m2 (46-cm within-row spacing) should be used.

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