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- Author or Editor: S.R. James x
For 2 successive years, compost at rates of 0, 12, 24, and 48 t/acre were applied to a previously highly infertile field. Timothy was grown and harvested for these 2 years. Subsequently, for 3 consecutive years, through 1996, `Earliqueen' muskmelons were grown in the same plots without any additional compost being added. Subplots consisted of plastic and paper mulch and bare soil. Yields increased with increasing rates of compost for each of the 3 years, although yields for all treatments declined in the 3rd year. Highest yields were with the higher rates of compost coupled with IRT mulches and red mulch. Generally, organic matter and pH increased with increasing compost rates. Foliar diseases were suppressed with compost; however, there was an interaction of suppression with plastic mulches.
N03-N is readily leached from mineral soils with rain or overhead irrigation. To determine the amount of N03-N conserved with plastic mulch, `Northstar' bell pepper was grown with and without 2-mil black plastic mulch, with 0, 80, and 160 lbs/acre of preplant N. One treatment consisted of unplanted rows. At 1, 2, 3, and 5 months after planting on 26 May 1994, soil samples for N03-N analyses were taken at 0–6” and 6–12”. Not only was N03-N conserved under the mulch, but it was also enhanced. N03-N levels increased up to 595 ppm in plots with mulch, no crop, and 160 lbs N/acre. The pepper crop utilized about one-third of the nitrogen under the mulch. After 5 months, nitrate levels averaged about 6 ppm in all plots without mulch, whereas, in plots with mulch, nitrate levels averaged about 97 ppm. For most of the season nitrate were higher at 0–6 inches than at 6–12 inches, but, nearer the end of the season, nitrates in plots without mulch were nearly the same or greater at 6–12 inches than at 0–6 inches. Yields were highest with mulch and 80 lbs N/acre.
In 1992 and 1993, a run-down, infertile field was treated with 0, 12, 24, and 48 T/A (day weight) of compost. Timothy was grown on the plots each year and removed. In 1994 and 1995, `Earliqueen' muskmelon was grown in the same plots, along with four types of synthetic mulch (black plastic, IRT-100 plastic, IRT-200 plastic, and paper). Over the two years, there was a consistent crop response. As compost rates increased, crop yield increased. The highest yields were with the higher rates of compost coupled with the IRT mulches. After 2 years of cropping, the soil nutrient status remained at acceptable levels at the 24 and 48 T/A rates of compost. Generally, organic matter, pH, and CEC increased with increasing compost rates. Foliar diseases were suppressed with the compost at all rates.
A study was conducted in Puerto Rico to estimate the outcrossing rate of six common bean (Phaseolus vulgaris L.) genotypes when planted in December or May. Two experiments were conducted for each date, one using indeterminate and the other determinate genotypes. In each experiment, homozygous dominant and recessive genotypes were planted in alternate rows to permit natural cross-pollination. Percent outcrossing was calculated based on the number of heterozygous individuals observed in the progeny of the homozygous recessive rows. Significant differences in the rate of outcrossing were observed between genotypes and between planting dates. The dwarf outcrossing (do) genotype had rates of 15.9% and 39.3% for the December and May planting dates, respectively. Outcrossing rates of stipelless lanceolate leaf (sl) and dark green savoy (dgs) genotypes did not differ significantly from the white-flowered (p) genotype, which was < 1% for both dates. Outcrossing rates < 1% were also observed for both planting dates for the determinate genotypes.
Field reaction of 25 red mottled bean (Phaseolus vulgaris L.) genotypes to common bacterial blight [Xanthomonas campestris pv. phaseoli (Smith) Dye] was evaluated in Puerto Rico over 2 years. The average disease severity (percent leaf area with symptoms) was similar over years. The determinate red mottled genotypes had almost twice as much disease as indeterminate genotypes. Eight of the indeterminate genotypes had significantly less disease than the mean of the field experiments. These genotypes may serve as useful sources of resistance to common bacterial blight. The size of the chlorotic zone around necrotic lesions varied between growing seasons, showing that environment can influence the expression of common bacterial blight symptoms.
In chlorotic, K-deficient leaves of prune (Prunus domestica L. cv. Agen), leaf water potentials were greater and transpiration less than in green, K-sufficient leaves. These results bring into question the role of leaf desiccation as the primary factor in the browning of K-deficient leaves.
Genetic variation for abaxial leaf pubescence was detected among dry bean (Phaseolus vulgaris L.) cultivars/lines. Inheritance of pubescence (long, straight hairs) was studied in the dry bean crosses of pubescent `Pompadour Checa-50' (Dominican Republic) × eight glabrous cultivars/lines. Segregation for pubescence vs. glabrousness indicated that pubescence was determined by a single major gene or by duplicate recessive epistatic genes, depending on the cross involved. Trichome density (number trichomes per mm) was a quantitative trait. Thus, pubescence was a discrete trait, but trichome density ranged from low to high.
This paper describes a moderately high-density orchard training system (1000 trees/ha) developed at the Univ. of California's Kearney Agricultural Center for peach and nectarine trees grown on standard rootstocks. This two-leader system was developed to increase production during the early years of the orchard while minimizing specialized management operations during orchard maturity. Early selection of two primary scaffolds oriented perpendicular to the tree row is recommended during the first season of growth. During subsequent years, summer and dormant pruning requirements are similar to the standard open-vase system grown in California. Because of the uniform and relatively simple tree structure, individual scaffolds, rather than whole trees, can be used as functional units for crop load management.