Many research studies have evaluated potential organic and mineral container substrate components for use in commercial potting substrates. Most studies report results of plant growth over a single production season and only a few include physical properties of the substrates tested. Furthermore, substrates containing predominantly organic components decompose during crop production cycles producing changes in air and water ratios. In the commercial nursery industry, crops frequently remain in containers for longer periods than one growing season (18 to 24 months). Changes in air and water retention characteristics over extended periods can have significant effect on the health and vigor of crops held in containers for 1 year or more. Decomposition of organic components can create an overabundance of small particles that hold excessive amounts of water, thus creating limited air porosity. Mineral aggregates such as perlite, pumice, coarse sand, and calcined clays do not decompose, or breakdown slowly, when used in potting substrates. Blending aggregates with organic components can decrease changes in physical properties over time by dilution of organic components and preserving large pore spaces, thus helping to maintain structural integrity. Research is needed to evaluate changes in container substrates from initial physical properties to changes in air and water characteristics after a production cycle.
The horticulture industry continues to show interest in using stabilized organic wastes as a component of container media. Vermicompost, also known as worm-worked waste or worm castings, is one of these materials of interest and can be produced from a number of organic wastes, including manure wastes. One issue that has not been addressed is the uniformity of vermicomposts produced from wastes of different sources. Are all vermicomposts created equal? The uniformity of vermicompost is important for growers to consider when using as a medium amendment. This research project investigated the physical properties of vermicompost 1) from different sources of wastes and 2) from a single waste source sequentially sampled over time. The first stage determined the physical properties of vermicompost from beef manure, hog manure, and peat-based media used by two earthworm growers. There were significant differences between the four vermicomposts in bulk density, air volume, percent air volume, percent volumetric moisture, total porosity, and water holding capacity. The second stage involved determining the physical characteristics of vermicompost produced from beef manure collected at the Illinois State University Research Farm from cattle receiving a consistent diet through the year. Manure was collected bimonthly. There was no difference in vermicompost bulk density among the samples. There were significant differences in air volume, percent air volume, percent volumetric moisture, total porosity, and water holding capacity. These changes in vermicompost physical characteristics must be quantified for growers to accurately predict performance as a growth medium amendment.
In the southeastern United States, inconsistent pine bark (PB) supplies and overabundance of cotton gin by-products warrant investigation about the feasibility of replacing PB with cotton gin compost (CGC) for container horticultural plant production. Most research on the use of composted organic substrates for horticultural plant production has focused on shoot growth responses, so there is a need to document the effect of these substrates on root growth. In 2004, `Blitz' tomato (Lycopersicon esculentum), `Hot Country' lantana (Lantana camara `Hot Country'), and weeping fig (Ficus benjamina) were placed in Horhizotrons to evaluate root growth in 100% PB and three PB:CGC substrates containing, by volume, 60:40 PB:CGC, 40:60 PB:CGC, and 0:100 PB:CGC. Horhizotrons were placed in a greenhouse, and root growth in all substrates was measured for each cultivar. Physical properties (total porosity, water holding capacity, air space, and bulk density) and chemical properties (electrical conductivity and pH) were determined for all substrates. Physical properties of 100% PB were within recommended guidelines and were either within or above recommended ranges for all PB:CGC substrate blends. Chemical properties of all substrates were within or above recommended guidelines. Root growth of all species in substrates containing CGC was similar to or more enhanced than root growth in 100% PB.
Cotoneaster dammeri Schneid. `Skogholm' liners were potted into combinations of pine bark (PB), horticultural rockwool (RW), composted municipal yardwaste (CYW), composted turkey broiler litter (TBL) and washed builders sand (S). The objective of the study was to characterize the physical and chemical properties, subsequent plant growth and foliar tissue levels of the resultant substrates. Of the physical parameters tested the three component substrates PB:RW:CYW and PB:RW:TBL (70:20:10 by v) appeared to have the most consistent favorable physical properties. Electrical conductivity (EC) was extremely high the first day after initiation in the substrates containing TBL but was not different for other sampling dates. Leachate pH initially ranged from 4.9 to 6.1 but through most of the study ranged from 5.2 to 5.8. As with EC all nutrient levels were very high one day after initiation. Leachate phosphate levels were maintained at recommended levels in the substrates containing TBL throughout most of the study while other substrates were generally deficient. The same was true for foliar tissue phosphate levels. The greatest top dry weight was yielded in the PB:RW:TBL (70:20:10, by v) substrate and least in the PB:S (80:20) substrate.
Organic agriculture is growing in importance worldwide. In the United States, the rate of increase of organic growers was estimated at 12% in 2000. However, many producers are reluctant to undertake the organic transition because of uncertainty of how organic production will affect weed population dynamics and management. The organic transition has a profound impact on the agroecosystem. Changes in soil physical and chemical properties during the transition often impact indirectly insect, disease, and weed dynamics. Greater weed species richness is usually found in organic farms but total weed density and biomass are often smaller under the organic system compared with the conventional system. The improved weed suppression of organic agriculture is probably the result of combined effects of several factors including weed seed predation by soil microorganisms, seedling predation by phytophagus insects, and the physical and allelopathic effects of cover crops.
Monte Carlo simulation has proven useful to understand container media properties. Although use of container media in horticulture is widespread, their physical properties are often misunderstood. Container media usually have larger external pores than natural soils, and the components from which they are formulated may have internal porosity that often accounts for half the total porosity. Traditional laboratory methods have provided limited insight into container media phenomena because of the difficulty in distinguishing between internal and external pores. By means of computer simulation we have characterized external porosity and pore size of container media. We have also been able to study volume shrinkage upon mixing components with different particle sizes. Pore size can be correlated with water retention characteristics, and size of external pores is related to the sizes of the particles that are mixed. With Monte Carlo simulation one can mix different particle sizes in different proportions, thus determining the relationships between pores and particle sizes.
Foliar sprays of pinolene (0,2 and 4%) and abscisic acid (ABA) (0,50 and 100ppm)were used to reduce heat stress effect on “Balady” orange trees under the Riyadh region,Saudi Arabia for two seasons. Pinolene treatments maintained higher leaf chlorophyll content than the control. Yield was slightly increased by pinolene treatments. Fruits had high values for most physical properties due to these treatments. TSS% and TSS/acidity ratio were increaced, acidity was decreased, while vitamin C was unaffected. Abscisic acid treatments reduced leaf chlorophyll content, compared to the control, but had no effect on yield. Such treatments increased fruit diameter (at 50 ppm) and fruit weight and juice volume (at 100 ppm). ABA showed no influence on most of the chemical properties of the fruits. In view of these results, it can be stated that pinolene was more influencial in reducing heat stress effect than ABA on “Balady”orange trees.
Abstract
The perception of food acceptability may be divided into 3 major categories: (a) appearance (color, shape) is based on optical properties; (b) flavor (taste and odor) is the response of the receptors in the oral cavity to chemical stimuli; (c) touch, is the response of the tactile senses to physical stimuli that results from contact between some part of the body and the food. The sensation of touch is commonly called “texture” but has also been called “kinesthetics” (24) and “haptaesthesis” (30). Texture is an important quality attribute of horticultural products and should be given equal weight with appearance and flavor for most commodities.
Abstract
Seed of snap bean, Phaseolus vulgaris L. cv. Avalanche were separated into 3 length or 3 diameter groups and then each group separated into 3 classes based on aerodynamic properties. The grading procedure resulted in seed grades having large differences in physical characteristics, growth and yield responses. Yield response potential of snap bean was determined primarily by seed weight. A grading method utilizing size grading based on seed diameter followed by aspiration in a vertical air column was the most effective method of eliminating seed with low yield potential.
The positive influence of fertilizing `Red Roomy' grapevines with four biofertilizers (active dry yeast, phosphorene, rhizobacterium, and nitrobein) on berry set and productivity was investigated during 1995 and 1996. The improvement occurred in berry set and yield, as well as physical and chemical properties in vines treated with the four biofertilizers in the following ascending order: active dry yeast, nitrobein, rhizobacterium, and phosphorene. Highly significant differences in characters were observed between treated and untreated vines. The best results with regard to yield and quality of berries was obtained in `Red Roomy' vines biofertilized with phosphorene or rhizobacterium.