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substrates are routinely classified as aggregate materials by particle size ( Handreck, 1983 ). The physical properties of substrates (i.e., bulk density and porosity) are, mostly, consequences of the particle size distribution (PSD) of a material or blend of
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.
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.
hindering its release to plants and influencing the plant growth ( Atkinson et al. 2010 ; Zulfiqar et al. 2021 ). The selection of appropriate feedstock is important because the physical and chemical properties of the biochar depend on the type of
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.
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.
Static hydrological properties [aeration capacity, easily available water, reserve water, water release curves: θv(Ψm), and specific humidity curves] and dynamic hydrological properties (saturated and unsaturated hydraulic conductivity) of sub strates based on industrial cork residue (the bark of Quercus suber L.) and cork compost were studied. Samples of similar granulometry have been used to establish the effect of cork composting on the afore mentioned physical properties. Different models were tested to describe the mechanism of water release from these materials. Van Genuchtens model (Van Genuchten, 1978) was the best fit and produced specific humidity curves that revealed slight differences in the ratio of water capacity function. When cork residues were composted for 7 months, important changes occurred in hydrological properties of the material as it became more wettable. Water retention significantly increased from 45% to 54%, at a potential of 5 kPa, although this did not necessarily result in increased water available to plants. A study of the unsaturated hydraulic conductivity (Kunsat) of these materials revealed a significant de crease in the Kunsat water potential at 0-5 kPa, which corresponds to the range in which the irrigation with these substrates was usually carried out. The long composting process resulted in increased Kunsat between 4 and 5 times that of uncomposted material, which would improve the water supply to the plant.