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Vegetable Crops
Vegetable Crops
Abstract
The Philippines have available more complete meteorological data than do many other tropical countries. Thus, the situation there can serve as a basis for the discussion of the aerial environment of the tropics and the way in which the environment influences the growing of vegetables.
58 ORAL SESSION 18 (Abstr. 124-131) Vegetables: Stress
Polyculture mixtures of several species of cover crops may be the best way to optimize some of the benefits associated with cover crop use. In the first year of a three year study, 16 polyculture mixtures of cover crops (4 species/mixture) were screened at seven sites throughout the state. Five of the mixtures were seeded at two planting dates. Fall evaluation of the cover crop mixtures included ease of establishment, vigor, percent groundcover, plant height, and relative biomass. The two mixtures with the highest percent groundcover were (1): sudex, rye, mammoth red clover, and subterranean clover (62% and 80% groundcover, one and two months after planting respectively), and, (2), annual alfalfa, hairy vetch, ryegrass, and rye (56% and 84% groundcover one and two months after planting respectively). The six mixtures with the highest percent groundcover did consistently well, relative to other mixtures, at all locations. Mixture (1) above also had the highest relative biomass throughout the state. Yellow and white sweet clovers, hairy vetch, winter oats, subterranean clover, red clover, rye and barley established well and maintained high vigor ratings throughout the fall. Ladino clover, timothy, and big flower vetch consistently had poor vigor ratings.
Three cropping sequences and three tillage systems were evaluated for increasing returns on small farms under reduced tillage. The sequences were spring 'Packman' broccoli followed by 'Sunny' tomatoes, spring broccoli/tomatoes/fall broccoli, and tomatoes/fall broccoli. Each sequence was grown conventionally tilled with no winter cover, conventionally tilled with a wheat winter cover and no-till transplanted directly into killed wheat. The study was conducted at Knoxville, TN (elev. 251m, Greeneville, TN (elev. 400m) and Crossville, TN (elev. 549m) during 1989 and 1990. Experiments were arranged in a strip plot design with sequences stripped across tillage treatments. No. 1 tomato yield was reduced in no-till at Greeneville (1989). Percentage of No. 1 tomatoes was not affected by tillage but the tomato-broccoli system produced a greater percentage at Greeneville (1990). Percentage of cull fruit was greater in Knoxville (1990) for conventional/no cover. A tomato-broccoli sequence produced more cull fruit at Knoxville (1990) and Greeneville (1989). Broccoli head size and subsequent yield and value was generally greater at most environments in conventionally tilled plots. Sequence generally had little affect on broccoli production.
Abstract
The use of micro-computer programs as a management teaching aid has enabled horticulture students to understand economic relationships involved in the production of apples (2, 3), strawberries (4), and selected greenhouse crops (7). By incorporating uncertainty about final crop yield and selling price, these models can be used to generate information about the relative “riskiness” of crop production, where risk is measured by the probability that total revenue will exceed total costs (1, 8). The objective of this research was to develop a micro-computer model that would assist students and/or producers in understanding the economic relationships between yield and price variability and overall risk.
Abstract
Plants exist as integrations of their many parts and processes. Each part is conditioned by a distinct collection of genes that interact and integrate with the genes that condition other plant parts or processes (44). Root characteristics are conditioned by about 30% of the plant genome, and one-third of these (10% of the total) condition only root characteristics (39). This level of control for a single plant organ is in agreement with that of other plant organs (25) and implies that root characteristics are as amenable to genetic manipulation as the characteristics of any other plant organ or tissue. Root characteristics are not normally emphasized in plant breeding programs because of the difficulty in observing them in situ, rather than because of a reduced potential for improvement. The level of genetic control described (39) should allow the development of isogenic root mutants that have modified physiological and developmental controls to be used for precise experimentation. Data derived from experimentation with these isogenic root mutants would provide a sound basis for developing and testing hypotheses leading, ultimately, to genetic improvement of vegetable root systems.
Abstract
Mycorrhiza refers to a mutualistic, symbiotic relationship formed between fungi (Gr. mukes) and living roots (Gr. rhiza) of higher plants. These associations are prevalent among most plant species and have been observed in most vegetables except the Cruciferae and Chenopodiaceae. In fact, some vegetables do not appear to grow or develop normally without mycorrhizae. In addition to their wide distribution in the plant kingdom, these nonpathogenic relationships are geographically ubiquitous. Thus, the mycorrhizal condition is the rule, as both host plant and fungus specificity is minimal and usually not observed.