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Virginia I. Lohr, Georgia K. Goodwin and Caroline H. Pearson-Mims

Foliage plants were added to different environments, including an office and a computer lab. Relative humidity and air-borne particulate matter were monitored in the presence and absence of the plants. When the relative humidity was low, the addition of plants increased the relative humidity slightly, but significantly, over that when no plants were present. Particulate matter accumulation was not increased in the presence of plants. Some have hypothesized that the growing medium could be a source of increased particulates when plants are used indoors. Some of our experiments used self-watering containers, irrigated from below, resulting in very dusty conditions in the top of the container. If the growing medium could contribute to increases in particulate matter, we should have detected it in this study.

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A.M. Boland, P.H. Jerie, P.D. Mitchell, I. Goodwin and D.J. Connor

Individual and interactive effects of restricted root volume (RRV) and regulated deficit irrigation (RDI) on vegetative growth and mineral nutrition of peach trees [Prunus persica (L.) Batsch (Peach Group) `Golden Queen'] were studied over 3 years (1992-95). Trees were grown in lysimeters of five different volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3) with either full or deficit (RDI) irrigation. Increasing soil volume increased vegetative growth as measured by trunk cross-sectional area (TCA) (linear and quadratic, P < 0.011) and tree weight (linear, P < 0.001) with the final TCA ranging from 29.0 to 51.0 cm2 and tree weight ranging from 7.2 to 12.1 kg for the smallest to largest volumes. Root density measured at the completion of the experiment decreased with increasing soil volume (linear and quadratic, P < 0.001) with root length density declining from 24.0 to 2.0 cm·cm-3. RDI reduced vegetative growth by up to 70% as measured by weight of summer prunings. Root restriction was effective in controlling vegetative vigor and is a viable alternative for control of vegetative growth. Mineral nutrition did not limit tree growth.

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A.M. Boland, P.H. Jerie, P.D. Mitchell, I. Goodwin and D.J. Connor

Individual and interactive effects of restricted root volume (RRV) and regulated deficit irrigation (RDI) on productivity and water use of peach trees [Prunus persica (L.) Batsch `Golden Queen'] were studied over 3 years (1992-95). Trees were grown in lysimeters of five different soil volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3) with either full or deficit (RDI) irrigation. In Years 3 and 4, fruit size was reduced by up to 30% on trees in the two smallest volumes. Tree water use was positively related to increasing soil volume (linear, P < 0.001; quadratic, P < 0.011) in all years ranging from 1.8 to 4.4 L·mm-1 Epan in the post-RDI period of Year 2. Water use of deficit-irrigated trees was less than fully irrigated trees and there was an interaction between soil volume and irrigation treatment during RDI. Water relations did not limit growth or productivity. Tree water use was reduced under root restriction as a consequence of canopy demand rather than leaf function. Results suggest that a combination of restricted root volume and development of water stress achieve the RDI response in the Goulburn Valley, Australia.

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A-M. Boland, P.D. Mitchell, I. Goodwin and P.H. Jerie

An experiment designed to study the effects of different root volumes was installed in Fall 1991. `Golden Queen' peach trees [Prunus persica (L.) Batsch.] were planted into different isolated soil volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3), which were essentially individual drainage lysimeters. Trunk cross-sectional area (TCA) increased from 5.76 to 14.23 cm2 for the smallest and largest volumes, respectively, while leaf area was 4.56 and 21.32 m2 for the respective treatments. Leaf size was not affected by soil volume. Soil volume was positively related to the number of lateral shoots produced, lateral shoot density, and internode length. Total flower bud number and flower bud density were inversely related to soil volume. Fruit set was similar among treatments despite an almost 4-fold difference in tree size. Tree water use (liters·mm-1 pan evaporation) increased with soil volume; however, when adjusted for tree size (tree water use per TCA), there were no consistent differences between treatments for tree water use over the season. These results suggest that trees planted in the smaller soil volumes were more efficient reproductively per unit of tree size and would be easier to manage in an ultra-high-density planting.