THE INFLUENCE OF TYLOSES ON THE MANUFACTURE OF MATCHES

This article deals with the results of time studies of pruning P. radiata from 22 ft. to 35 ft. with pole saws. The influence on pruning time of mean diameter and number of branches removed in the pruning operation, number of cones removed and time of day is investigated and a multiple regression equation, expressing the relationship between pruning time and these variables, is computed. A taper table is prepared and used to investigate the effect of pruning on the formation of knot-free timber. The economics of high-pruning is discussed.     

Using LC-MSMS to assess glutathione levels in South African white grape juices and wines made with different levels of oxygen

The effect of oxygen on the levels of glutathione, an important antioxidant, in must and wine was studied using a novel LC-MSMS method for the analysis of reduced and oxidized glutathione. This study found that the storage of grape juice at high SO2 and ascorbic acid levels at -20 degrees C did not lead to a decrease in reduced glutathione levels. The effect of varying the oxygen levels in South African white grape juices, which included a reductive treatment (less than 0.3 mg/L dissolved O2 added), a control treatment (between 1.0 and 1.5 mg/L dissolved O2 added), and an oxidative treatment (3.5-4 mg/ L dissolved O2 added, without SO2) on reduced glutathione levels in the juice and resulting wine was also investigated. A custom build press was used to press whole bunches of two different Sauvignon Blanc and Colombard grapes. Alcoholic fermentation and oxygen additions to the must led to lower reduced glutathione levels in the wine. Reduced glutathione levels were only significantly higher in the wine made from reductive juice that had the highest initial reduced glutathione levels in the grapes.     

The Influence of Plant Water Stress on Net Photosynthesis and Yield of Sunflower (Helianthus annuus L.)

The effect of plant water stress on net photosynthesis, leaf growth, yield and yield-related components were investigated in a single experiment in order to determine in which way water deficits affect sunflower yields.
Sunflower plants, grown under controlled temperature regimes, were stressed during budding, anthesis and seed filling by withholding water until the leaf water potential reached -1600 and -2000 kPa. Leaf area of unstressed plants significantly exceeded that of plants under severe stress during all growth stages investigated. The CO₂ uptake rate per unit leaf area as well as the total uptake rate per plant, significantly diminished with stress, while this effect drastically increased during the reproductive phase of the plant. Although this resulted in significantly smaller heads and kernels, it did not affect the number of seeds borne in the inflorescence. Severe stress during anthesis and seed filling resulted in more empty kernels. Moderate and severe stress during budding significantly lowered both grain and oil yields while plants that experienced moderate stress during anthesis and seed filling significantly outyielded those under severe stress.     

Research note: Grazing‐index method procedures of vegetation surveys

Abstract

In the past, veld condition in the Karoo was assessed using the ecological index method. This recently changed to the grazing‐index method on account of the differently estimated grazing‐index values being used. The principles governing the method of survey remain the same. The method employs canopy‐spread‐cover strikes to record the species composition of different sites. By appropriate management of these line‐point data, different sites can be compared with one another by employing the Z‐index of agreement (similarity).     

Survival and long-term growth of eucalypts on semi-arid sites in a Mediterranean climate,South Africa§

Four experiments were established on the semi-arid west coast plain of South Africa during the 1990s. The trails tested the survival and growth of several eucalypt species and hybrids, some of which were established in a climate that is drier than their natural distribution range. The aridity indices (AI; defined as mean annual precipitation [MAP]/mean annual potential evapotranspiration) ranged from 0.21 to 0.36 and MAP from 228 to 423 mm. The driest trial site (AI = 0.21 and MAP = 228) had high levels of mortality. However, a number of species (in particular, Eucalyptus gomphocephala, E. camaldulensis and E. tereticornis, as well as individual hybrids of the latter two species with E. grandis) survived and grew well at the remaining sites. Eucalyptus cladocalyx survived well and attained competitive growth rates only on the wettest site in the group (AI = 0.36). The dominant height of the top-performing genotypes at age 5 ranged between 9 and 10 m on the two wetter sites. This corresponded to mean annual increment values in excess of 10 m³ ha^?1 a^?1, which is comparable to volume obtained at more favourable aridity indices in the summer rainfall zone of South Africa and exceeds the growth rates obtained in several other arid zone studies globally. The E. grandis × E. camaldulensis hybrid ranked among the top performers in two trials, but its susceptibility to recently introduced pests and relatively poor wood quality makes it a less attractive choice for planting. The high density and durability of timber, acceptable growth rate (given the low rainfall conditions), and low pest and disease incidence make E. gomphocephala and E. cladocalyx the species of choice for planting in the drier and relatively wetter sections of the semi-arid zone, respectively.     

Lessons from 10 years of stakeholder adoption of a soil bioassay for assessing the risk of spinach Fusarium wilt

Although the maritime Pacific Northwest (PNW) is the only region of the United States suitable climatically for spinach seed production, the acidic soils are highly conducive to spinach Fusarium wilt caused by Fusarium oxysporum f. sp. spinaciae. A soil bioassay developed to quantify the risk of spinach Fusarium wilt in fields has been offered to seed growers annually since 2010. Soil sampled from growers' fields each winter was planted with highly susceptible, moderately susceptible, and partially resistant spinach inbred lines, and the plants rated weekly to calculate a Fusarium wilt severity index (FWSI) and the area under the disease progress curve (AUDPC). Results for 147 soils tested from 2010 to 2013 have been published. This study examined results for an additional 248 soils tested from 2014 to 2019 with the bioassay modified to include an option of agricultural limestone amendment to the soils tested. FWSI and AUDPC were affected significantly (p < .001) by the main effects of soil and spinach inbred line, and the interaction of these factors. Correlation analyses showed a range in degree of association of FWSI and AUDPC with spinach seed crop rotation duration and soil properties, depending on the spinach inbred line (r = −.255 to –.267, n = 172 soils with characteristics suitable for correlation analyses). Stepwise regression models for 172 soils with relevant parameters for regression analyses identified spinach seed crop rotation interval, rate of agricultural limestone amendment, soil pH, and soil Fe, Mn, and Zn concentrations as most strongly associated with FWSI and AUDPC. However, the models accounted for ≤33.4% (R²) of the variability in Fusarium wilt risk. The soil bioassay remains a primary tool for spinach seed growers to select fields with low risk of Fusarium wilt.