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  • Author or Editor: P.J. Sinclair x
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NIR-based tissue analysis has proven useful in Australia for making fertilizer recommendations for rice and wheat growers. Viticulturists have for some time made fertilizer recommendations based on tissue analysis, although there is some debate in the literature as to whether younger or older leaves or petioles provide the best indicator of vine nutrient status for diagnostic purposes. The aim of our research has been to develop NIR-based nutrient analysis for grape producers. Aspects of sample collection, including leaf lamina vs. leaf petiole; leaf opposite the basal cluster vs. youngest leaf; aspects of drying (microwave vs. convection oven), have been reexamined from the viewpoint of convenience, cost, accuracy, and turnaround time with respect to NIR analysis. We have refined procedures for collecting and microwave-drying samples. The samples of leaves and petioles were collected from vines in most wine-growing regions of Australia and included all the major wine grape and some dried fruit cultivars on their own and, in some cases, on rootstocks. At this stage, we have developed preliminary NIR calibrations for the major nutrient elements in both leaf lamina and petioles.

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Conditions for priming tomato (Lycopersicon esculentum Mill.), carrot (Daucus carota L.), and onion (Allium cepa L.) seeds in solutions of K3PO4 + KNO3 and K2HPO4 + KNO3 were optimized in a series of laboratory and field experiments. When primed in K3PO4 + KNO3 (−1.6 MPa) for 7, 14, or 21 days at 15°, 20°, or 25°C, the percentage of emergence was unchanged in tomato, increased in carrot, and decreased in onion. Although there were some species differences, all priming treatments reduced time-spread and increased median rate of emergence. For this solution, priming at 15° for 14 days was optimal for all 3 species. Detailed experiments using optimized priming solutions in an aerated column for tomato (K2HPO4 + KNO3, −1.0 MPa) and for carrots (K3PO4 + KNO3, −1.5 MPa) demonstrated that 18 days was necessary to prime tomato seeds maximally by reducing the time-spread of germination from 73 to 12 hr. With carrots, the maximal response was obtained after 16 days of priming. For both species, continued gains in germination could be obtained from prolonged priming, although only at the expense of a reduced percentage of germination. Air-drying and storing of tomato and carrot seeds for up to 28 days had no effect on subsequent emergence in the field. Conversely, air-drying of onion seeds reduced the percentage of emergence and increased time-spread and rate of emergence. In contrast, salt-primed tomato seeds exhibited an increase in percentage and rate of emergence, and a decrease in time-spread of field emergence. Primed carrot seeds exhibited a faster rate of field emergence than those not primed.

Open Access

Although summer soil solarization is a viable technique for the control of soilborne pests, periods of cloudy skies and high rainfall typical of the southeastern United States limit the heating of soils. This study was devised to evaluate whether polyethylene films designed for improved heat conservation could increase soil solarization temperatures under humid environmental conditions. Soil solarization was conducted in Summer 1996 at Quincy, Gainesville, and Bradenton: located in north, north central, and west central Florida, respectively. Temperatures at soil depths of 5, 10, and 25 cm were higher under clear solarization films than under black polyethylene. A clear, thermal-infrared absorbing film (TIR) was consistently more effective in increasing soil temperature than was a double-layered, clear bubble film or a 30 μm clear, low-density polyethylene film. Soil temperatures under all film types were reduced by rainfall, but remained highest under TIR film. On cloudy days with light rainfall, temperatures under TIR film exceeded 45 °C at 5 cm depth. Soil temperatures rose rapidly when rainy weather was followed by a clear day. Cumulative exposure to temperatures ≥45 and 50 °C was greater with the TIR film than with the other films, indicating that it has the greatest potential for soil solarization in humid climates.

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