Cold-hardiness evaluations and soluble and insoluble-nonstructural carbohydrate analysis of dormant Vitis vinifera L. cv. Cabernet Sauvignon buds and cane tissue indicate a positive relationship between soluble carbohydrates and primary bud cold hardiness. Seasonal variations in soluble and insoluble carbohydrates appear to be related to changes in air temperatures and the dormancy status of the tissues. No differences were found in bud cold hardiness and only limited differences in carbohydrate levels of buds or stem tissues collected over 3 years from early harvest, normal harvest, or unharvested vines. These findings contrast with the widely held opinion that delayed harvest or failure to remove fruit results in reduced cold hardiness as a consequence of low storage carbohydrate content of the plants.
Robert L. Wample and Andy Bary
Robert L. Wample, Guy Reisenauer, Andy Bary, and Fred Schuetze
A computerized system capable of controlling the freezing rate and collecting, storing, and analyzing data from multiple samples to determine their freezing point using low-temperature exotherm analysis is described. Details include electrical diagrams of modifications to the multiplexer/amplifier interface to provide additional signal amplification and permit control of the freezer's compressor. Computer software is described that permits variable temperature decline rates. Data analysis consists of a program in “C” that sequentially compares each data point in a low-temperature exotherm profile. Low-temperature exotherms are identified by a user-specified minimum differential between sequential data points. Examples of exotherm output and data analysis are given.
Craig Cogger, Rita Hummel, Jennifer Hart, and Andy Bary
Although compost can improve soil properties related to plant growth and water quality, the value of amending landscape beds for trees and shrubs has been questioned. This research assesses short and midterm effects of compost application and bark mulch on soils and plants in landscape beds and compares the effects of compost applied to the surface or incorporated. Trees and shrubs were established in 2001 in a replicated field experiment with the following treatments: 1) unamended control; 2) compost (7.6-cm depth) applied to the surface; 3) 7.6 cm compost incorporated by rototilling to a depth of 20 cm; 4) bark mulch (7.6 cm); 5) compost surface-applied (7.6 cm) + bark mulch (7.6 cm); and 6) compost incorporated + bark mulch. Soil measurements were made one or more times between 2001 and 2007, including bulk density, compaction, infiltration, aggregate stability, soil moisture tension, total carbon (C) and nitrogen (N), nitrate-N, Bray-phosphorus, exchangeable potassium, and pH. Bark and compost mulch depths were determined three times and plant growth measured annually. Half the depth of surface-applied compost and 26% to 41% of the initial soil C increase from incorporated compost remained 5 years after application; and significant changes in bulk density, compaction, infiltration, and nutrients were apparent. Compost incorporation had a greater effect than surface application on soil C, N, and bulk density. Infiltration was similar in incorporated and surface treatments, and nutrient availability was similar except for N. Soil moisture retention was improved with surface-applied compost. Bark had similar effects as surface-applied compost on bulk density, soil moisture retention, and infiltration. During the first 4 years after transplanting, dogwoods in the compost incorporated + bark mulch treatment typically had larger shoot growth indices. By Year 5, treatment no longer influenced shoot growth. Plants in compost-treated plots had darker green leaves. Surface application of compost could provide significant benefits where incorporation is not feasible.
Rita L. Hummel, Craig Cogger, Andy Bary, and Robert Riley
Composts made from organic wastes have the potential to substitute for peat and bark as components of container growth substrates. Composts for this research were produced in small-scale aerobic bins using biosolids blended with construction debris, storm debris, or horse waste in a 1:3 (v:v ratio). The composts were screened and blended 1:1 (v:v) with douglas fir (Pseudotsuga menziesii) bark to produce substrates. They were compared with a peat–perlite control substrate, a biosolids blend control substrate, and substrates made from a commercial biosolids compost mixed 1:1 with bark and from fiber from an anaerobic digester (dairy manure and food waste) mixed 1:1 with bark. Chemical and physical properties of the substrates were measured before transplanting, and growth, quality, and leaf color of ‘Little Hero Flame’ marigold (Tagetes patula) and ‘Golden California Wonder’ bell pepper (Capsicum annuum) were measured in a replicated greenhouse study comparing the substrates at two rates of nitrogen (N) application. The experimental biosolids composts-bark substrates performed similar to the peat–perlite and biosolids blend controls for growing marigold and pepper. The commercial biosolids compost mixed with bark did not perform as well as the experimental substrates or the controls. Digester fiber-bark was intermediate between commercial biosolids compost-bark and other treatments. Higher N rates improved plant growth and quality across all container substrates in pepper, but had fewer significant effects on marigold. Experimental substrates were coarser texture than the peat–perlite or biosolids blend controls, resulting in higher aeration porosity (AP) and lower water-holding capacity (WHC), but performed well nonetheless under the drip irrigation used in this study. Using locally sourced organic waste materials as container substrates can help capture value from organic wastes and contribute to the sustainability of nursery production practices.