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Senescence occurs at the cellular and tissue levels. It is under genetic and environmental control and factors affecting initiation and speed of development of senescence can be passed from parental to F1 plants. This study was conducted in the greenhouse and field to determine how senescence patterns in F1 plants of a shrunken2 sweet corn (Zea mays L.) hybrid compared to those of parental inbreds. Greenhouse grown plants were left intact and field grown hybrids and parental inbreds had one or both reproductive organs removed or were left intact. Senescence patterns in stalk internodes were similar in greenhouse and field grown F1 and inbred plants. Senescence patterns in shank internodes in greenhouse grown plants were different from those of field grown plants. Senescence ratings in stalks increased as developmental stage advanced. Expression of stalk senescence in internodes below the node bearing ears appears to be suppressed by hybrid vigor. In field tests, destruction of the tassel before expansion (decapitation) appears to suppress senescence in internodes above I7, with this effect somewhat dependent on plant developmental stage.
The efficacy of using potting media and fertilizers that are alternatives to conventional materials to produce vegetable transplants needs clarification. Bell pepper, onion and watermelon seed were sown in Container Mix, Lawn and Garden Soil, and Potting Soil, which can be used for organic production in greenhouse transplant production. The alternative media were amended with a 1× rate of Sea Tea liquid fertilizer. Comparisons were made to a system using a conventional potting medium, Reddi-Earth, fertilized with a half-strength (0.5×) rate of a soluble synthetic fertilizer (Peters). Watermelon, bell pepper and onion seedlings were lifted at 3, 6, and 8 weeks, respectively, and heights and dry weights determined. Watermelon were sufficiently vigorous for transplanting regardless of which medium and fertilizer was used. Bell pepper and onion at the scheduled lifting were sufficiently vigorous only if produced with conventional materials. Additional experiments were designed to determine the reason(s) for the weaker seedlings when the alternative products were used. Seedlings maintained in transplant trays, in which media amended weekly with Sea Tea were required to be held for up to an additional 34 days before being vigorous enough for transplanting. Six-week-old bell pepper, or 8-week-old onion, seedlings were transferred to Reddi-Earth in pots and supplied with Sea Tea or Peters fertilizer. Bell pepper treated with Peters were taller and heavier, but onions plants were similar in height and weight regardless of fertilizer used. Other pepper seed were planted in Reddi-Earth and fertilized weekly with Sea Tea at 0.5×, 1×, 2×, or 4× the recommended rate, or the 0.5× rate of Peters. There was a positive linear relationship between seedling height and dry weight for seedlings treated with increasing rates of Sea Tea. Other pepper seed were planted in to Potting Soil, or an organically certified potting medium (Sunshine), and fertilized with a 2× or 4× rate of Sea Tea or a 1×, 2×, or 4× rate of an organic fertilizer (Rocket Fuel), or in Reddi-Earth fertilized with a 0.5× rate of Peters. There was a positive linear relationship between the rate of Rocket Fuel and heights and dry weights of bell pepper seedlings. However, even at the highest rate seedlings were not equivalent to those produced with conventional practices. Plants treated with the 4× rate of Sea Tea were similar to those produced using conventional materials. Use of Sunshine potting medium and the 4× rate of Sea Tea will produce bell pepper seedlings equivalent in height and dry weight to those produced using conventional materials. The 4× rate of Rocket Fuel used in Sunshine potting medium will produce adequate bell pepper seedlings. The original poor showing of seedlings in the alternative potting media appears to be due to fertilization with Sea Tea at a rate that does not adequately support seedling development.
The effects of soil depth on yields of dry bean (Phaseolus vulgaris) produced under different types of tillage is not well understood. Black and pinto bean yields were evaluated under conventional and reduced-tillage for 2 years in a 3.24-ha (8-acre) commercial field in southeastern Oklahoma. Before planting, a grid pattern was laid out on the field with points at every 13.7 m (45.0 ft) north to south and 6.1 m (20.0 ft) east to west. Samples were taken at each intersection of the grid lines (496 sites) to determine pH, and the amounts of nitrogen, phosphorus, and potassium present in soil. Depth to an impervious clay pan was determined at these sites, and were grouped as being one of the following: <25 cm (9.8 inches), >25 to 50 cm (19.7 inches), >50 to 75 cm (29.5 inches) and >75 cm. Irrigation was supplied, if needed, at 50% flowering and, in both years, at 50% pod set. There was no significant effect on yield due to year. Black bean yields from conventional tillage averaged 1166 kg·ha-1 (1040.4 lb/acre) across soil depths and were better than yields from reduced-tillage which averaged 136 kg·ha-1 (121.3 lb/acre). Pinto bean yields from conventional tillage were 611 kg·ha-1 (545.2 lb/acre) across soil depths and were better than for reduced tillage, which averaged 403 kg·ha-1 (359.6 lb/acre). Yields generally were reduced as soil depth increased regardless of tillage type. The reduction in input for reduced-tillage would not compensate for the reduced yields for plants grown on the most productive soil depths.
Crop rotations can reduce problems that occur in monoculture planting systems. In 1990, at Lane, Okla., 0.5 ha of Bernow fine-loamy soil was planted to peanut (Arachis hypogaea L.). In the following 5 years, bell pepper (Capsicum annuum var. annuum L.), cucumber (Cucumis sativas L.), navy bean (Phaseolus vulgaris L.), and cabbage (Brassica oleracea L. Capitata group) were planted in one of four rotations after 1, 2, or 3 years of peanut. The first vegetable planting in each annual rotation was followed by either vegetables or peanut in following years. In 3 of the 6 years, peanut or vegetables were planted in each rotation. Peanut yields in the first year averaged 6.6 Mg·ha-1, but were <1.9 Mg·ha-1 thereafter. Yields of the first vegetable planting, which followed 1 or 2 years of peanut, were normal for this location, but were significantly lower after 3 years of peanut. For second or third plantings of vegetables in rotations, yields were reduced up to 50% compared to the first vegetable planting. For most crops, the rotation that had 3 years of peanut followed by 3 years of vegetables generally produced the least cumulative yield. Numbers of sclerotia produced by soilborne plant pathogenic fungi fluctuated over the years, but were the same in the spring of the second and sixth years. Rotating these crops appears to have limited applicability for maintaining high vegetable or peanut yields.
This experiment was conducted to determine the effects of bed type (single or parallel raised bed vs. nonbedded); plant density (1991: ≈148,300 or 269,500 plants/ha; 1993: ≈148,300, 269,500, or 432,400 plants/ha); and use of black or white degradable mulch vs. nontreated soil on total and marketable yields and number of marketable seed per kilogram (seed count) of `Fleetwood', an erect bush, white-seeded navy bean (Phaseolus vulgaris L.). Spray-on mulch degraded before canopy closure, but a residue was present at harvest. In 1991, treatments did not affect yield or seed count. In 1993, bedding did not affect yield over nonbedded seedbeds. Black spray-on mulch increased marketable yield over plants grown with white spray-on mulch. Total and marketable yields were significantly higher at 269,500 than at 148,300 plants/ha. Bed type and plant density did not affect seed count, but seed count increased with black spray-on mulch. Dry beans should not be grown on beds under soil conditions such as those in our experiment. White spray-on mulch had no beneficial effect, but using black mulch needs additional evaluation. Planting at 269,500 plants/ha likely will yield ≈2 Mg seeds/ha in most years.
There is little known about how cultural methods affect yields of nonpungent jalapeño peppers (Capsicum annuum L.). Seedlings of the nonpungent jalapeño peppers `Pace 103', `Pace 105', `Pace 108', `Dulce', and `TAM Sweet2', as well as the pungent jalapeño peppers `Delicias' and `TAM Jalapeño1', used for comparison, were grown in a greenhouse with either one or two seedlings per cell in transplant trays. Transplanting to the field was in mid-April and mid-June of 2000 and 2001. In-row spacing was 0.46 m between transplanting sites. Density was varied by placing either one or two seedlings at a transplant site with resultant plant densities of 24,216 or 48,432 plants/ha. Marketable and cull yields, on a per hectare basis, were determined. In both years there were more fruit produced, and higher yields (25+% greater), at the higher plant density, especially for the mid-April planting. The exception for the mid-April planting date was `TAM Jalapeño1', which was not different at the two densities. If the increased income from higher yield can compensate for the cost of producing two seedlings in each transplant tray cell, then this technique should be employed when these types of peppers are used in early plantings.
Commercially produced bare-root onion (Allium cepa L.) transplants may not be uniform in size and require a period following planting in which to begin regrowth. There is little information on how, when established in the field, plants developed from greenhouse grown onion transplants differ from those that develop from bare-root transplants. Development and yield for onions grown from bare-root transplants were compared to plants produced from transplants grown in single cells with volumes of 36 or 58 cm3 in seedling production trays in a greenhouse. `Texas Grano 1015Y' and `Walla Walla' onions were established in the field with commercially available bare-root transplants or with greenhouse grown transplants produced in trays. Bare-root transplants were heavier than 8-week-old greenhouse grown transplants. Fresh weights of transplants produced in 58-cm3 cells were heavier than those from 36-cm3 cells, but dry weights were similar. From when about 20% of onion tops were broken over, onion bulb diameters did not increase sufficiently to justify delaying harvest until 50% of tops had broken over. Yields of `Walla Walla' were better than those of `Texas 1015 Y' and yields from plants developed from seedlings grown in 58-cm3 cells were similar to those from plants developed from bare-root transplants and better than those from plants developed from seedlings grown in 36-cm3 cells. Individual bulb weights of `Texas 1015 Y' were not affected by transplant type and averaged 162 g. Individual bulbs for `Walla Walla' from plants developed from bare-root transplants and those produced in 58-cm3 cells were similar in weight (averaged 300 g) and were heavier than those from plants developed from transplants grown in 36-cm3 cells (240 g). Greenhouse transplants produced in trays with the larger cells may provide an alternative to the use of bare-root transplants, if transplant production costs are comparable.
Planting date, fertilizer rate, and timing of harvest can affect yield of Jalapeño and banana peppers (Capsicum annuum L.). Seedlings of the Jalapeño `Mitla' and Long yellow wax `Sweet Banana #504' were transplanted in Apr. and July 1995 into beds fertilized with either a recommended or a higher rate. Fruit were harvested either three times or once, the latter corresponding to the last of several harvests. Significantly higher yields were produced from the July planting of both cultivars and with once-over harvesting. The recommended rate of fertilizer increased yield of `Sweet Banana #504' and decreased that of `Mitla' compared to the higher rate.