Search Results

You are looking at 141 - 150 of 1,350 items for :

  • physical properties x
Clear All

. Despite these measured differences, there were relatively few and minor differences in the nutrient concentration of the substrate. Furthermore, there were no measurable differences in sunflower growth or physical appearance (SPAD foliar chlorophyll), and

Free access
Author:

Abstract

Phosphorus is ubiquitous and multi-functional in plant metabolism and possesses chemical and physical properties that facilitate experimentation. Consequently, it has been extensively studied and the accumulated literature almost defies condensation. A major goal of this presentation is to be provocative with the hope that valid questions will be raised that could lead to productive research.

Open Access

Abstract

The leafminer, Liriomyza trifolii (Burgess), was attracted more to short day (SD) grown chrysanthemums for feeding and oviposition than to long day (LD) grown chrysanthemums. Densities of feeding punctures and mines within SD grown plants were positively related to leaf height. A physical property of chrysanthemum leaves influencing the preference of feeding and oviposition sites by the female leafminer was trichome density.

Open Access

Abstract

Humidity as related to horticulture is discussed in terms of: ways of expressing humidity levels; physical properties of water vapor; and temperature-humidity and air circulation-humidity interactions. The role of humidity in transpiration, killing freezes, and storage and transport of fruits and vegetables is discussed. Also given are sources of information on methods of recording and controlling humidity in postharvest applications.

Open Access

Abstract

In addressing the subject of nondestructive evaluation of internal quality of horticultural crops, the establishment of an understanding of quality is needed at the outset. Dull (4) has defined nondestructive quality evaluation (NDQE) as “a gaining of meaningful information which can be used in making judgments, both positive and negative, about the degree of excellence of a food with out altering the physical and chemical properties of that food.” In order to make judgments about a specific quality situation, one must select specific physical and/or chemical properties to be measured. A list of those properties would include weight, diameter, titratable acidity, pH, total nitrogen and concentration of soluble solids, sucrose, glucose, fructose, malic acid, citric acid, chlorophyll, carotene, anthocyanins, dry matter, proteins, amino acids, fat, starch, cellulose, pectins, and hemicellulose.

Open Access

Soil disinfestation strategies for intensive vegetable crop production, which have relied heavily on chemical fumigants for the past 40 years, are now undergoing rapid change. The principal driving force of change has been governmental regulatory action to phase out chemicals with properties deemed to be hazardous to the environment and/or public health. Softer methods of soil disinfestation, which rely more on physical, cultural, biological, or integrated modes of action, likely will predominate in future vegetable-cropping systems. In conducive (i.e., warm) climates, solarization can be adopted economically in plasticulture systems. Solarization can be combined with other chemical, physical, and biological methods for enhanced management of soil and root pests and diseases.

Full access

Abstract

Selected physical and chemical properties of fresh spent mushroom compost were evaluated and compared to the properties of spent mushroom compost which was aged aerobically for 6 weeks. Bulk density, total pore space, total water at saturation, and percentage air space in fresh and aged spent composts were acceptable for plant growth. Both contained very high levels of soluble salts which were readily leachable. Concentrations of metals were acceptable, but concentrations of K, Ca, and Mg could lead to plant nutrient imbalances. Concentrations of NH4-N in fresh spent mushroom compost were high.

Open Access

Sustainable alternatives for saline drainage water management in areas such as California's San Joaquin Valley are needed. Previous work has demonstrated the short-term potential for reuse of saline drainage water for irrigation in this area. Results from our 6-year cyclic drainage reuse study, however, indicate that soil structural problems may occur which can greatly reduce stand establishment and crop yields in periodically salinized soils. To prevent these problems, we are evaluating the effectiveness of winter cover crop incorporation and gypsum applications relative to conventional fallows, for improving/maintaining soil physical properties and crop productivity in cyclically salinized soils. Six winter cover crop/fallow treatments have been imposed upon a rotation of tomatoes, tomatoes and cotton as summer crops. By monitoring water use, relevant soil physical and chemical properties as well as crop performance during the course of this 3-year rotation study, we are assessing the potential benefits and constraints of using winter cover crops in drainage water reuse systems.

Free access

Abstract

Trials were conducted using paclobutrazol (PP333) either as a foliar application or a soil drench to improve berry set and yield of ‘Roumi Red’ grapes (Vitis vinifera L.). Concentrations of 100 and 250 ppm (foliar applications) and 2 ml/vine as a ground application had no effect on either chlorophyll and carotenoid leaf content or physical and chemical properties of berries, other than cluster weight and number of berries/cluster, which increased significantly. Concentrations of 1000, 1500, and 2000 ppm and 4 ml/vine reduced shoot and internode length as well as °Brix, whereas physical and chemical properties of berries, bud fertility, chlorophyll, and carotenoid leaf content were increased. A carry-over effect was noticed the year following the year of application with concentrations of 750 ppm and 3 ml/vine or higher. Chemical name used: β[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Open Access

Aqueous foam was developed to serve as a barrier to conductive, convective, and radiative heat transfer. Through the use of a bulking agent, the physical properties of gelatin-based foam were more stable, adhesive, biodegradable, and long lasting. The phytotoxicity, possible environmental hazard and removal of the foam were also considered. Resistance to freezing-thawing, heating-evaporation, and wind were evaluated. Studies to determine the foam's long-term stability under field weather conditions were completed. The handling and performance characteristics of the foam necessary for development of this application were determined. Factors that affect the physical properties and the utilization of the foam were quantified. These included the proportions of the foam components, the mixing temperature of the prefoam solution, the application temperature, and the rate of foam generation. The newly developed foam might be ideal for freeze and frost protection in agriculture.

Full access