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  • Author or Editor: C. S. Tan x
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Abstract

Germination of tomato (Lycopersicon esculentum Mill.) seeds in petri dishes at various levels of water stress was comparable, except under conditions of severe stress when a PEG pretreatment improved final percentage germination and enhanced the onset and rate of germination. At intermediate or high watering levels, PEG-pretreated seeds germinated more rapidly than untreated seeds, but final germination was not altered by PEG. Germination of seeds in soil, under controlled laboratory conditions, was similar to that in petri dishes except under the driest conditions (5% ASM) when little emergence occurred whether the seeds were pretreated or not. A majority of the seeds which failed to germinate after 2 weeks under dry soil conditions were still viable, since subsequently they could be induced to germinate by moistening the soil to 100% ASM. Water requirement of tomato seeds for optimal rate of germination was cultivar dependent; PI-341988 seeds germinated well at 60% ASM or greater, whereas ST-24 required 100% ASM for best germination.

Open Access
Authors: and

Abstract

The effects of irrigation and tree density on peach [Prunus persica (L.) Batsch cv. Harken/Siberian C] production were investigated over 11 years. Irrigation improved growth of peach trees, lowered levels of winter injury and perennial canker (Leucostoma spp.), and promoted tree survival. Annual and cumulative marketable yields were increased, especially in the later years. Tree density did not affect perennial canker, winter injury, or tree survival. Reducing tree spacing increased resulted total growth per hectare and annual and cumulative marketable yields. Irrigation and density treatments usually did not interact and had an additive effect on growth and fruit production. The most productive management system (a combination of 50% available soil moisture and 536 trees/ha) resulted in accumulated yields over 8 years of 179 tonnes (t)/ha comparted with only 74 t/ha for the check treatment (no irrigation and 266 trees/ha).

Open Access

Abstract

Three cultivars (early, midseason, late), two ground covers (clean cultivation followed by temporary cover vs. permanent sod strips), and trickle vs. no irrigation were studied in a high-density (633 trees/ha) experimental peach orchard established in 1980 on Fox sand. Growth rate in the first 5 years was similar for all three cultivars. It was retarded up to 12% by permanent sod relative to temporary cover and enhanced up to 30% by trickle irrigation vs. no irrigation. Total marketable yields and that of large-sized fruit (>6.3 cm) were significantly influenced by cultivars in the first and second, but not the third year of production. Ground cover treatments did not influence total marketable yields, but did affect the yield of large fruit in one year. Irrigation increased total marketable yields each year and also increased the yield of large fruit. Yields were up to 30.7% higher in trickle vs. non-irrigated plots. Cold hardiness of flower buds and shoot xylem in 1982 was significantly influenced by cultivar and irrigation treatments, but not by ground cover treatments; In 1984, each of these factors affected cold hardiness. Foliation in 1984 was affected by ground cover and irrigation treatments but not by cultivars. The best treatment combination across cultivars for management of the orchard floor consisted of permanent sod strips of creeping red fescue (Festuca rubra L.) in the row middles combined with trickle irrigation in the tree row.

Open Access
Authors: and

Abstract

Peach [Prunus persica (L.) Batsch] seedlings were grown in large sectional boxes with root systems divided into 4 separate quadrants. Groups of peach seedlings with 3, 2, 1, and 0 quadrants of the root system deprived of water for 3 weeks, were further subjected to moisture stress in all quadrants by withholding water for 5 days, and they were then rewatered. In another treatment, seedlings were subjected to 2 cycles of water stress, applied 3 weeks apart, by completely depriving all quadrants of water until the plants wilted. Transpiration, photosynthesis, stomatal conductance, and xylem pressure potential were measured. Subjecting a large portion of the root (50%) to stress by withholding water only caused a small reduction (17%) in transpiration, photosynthesis, and stomatal conductance. Subjection of various fractions of the root system to severe moisture stress did not affect the shoot:root ratio. The reduction in root growth in dry quadrants was accompanied by the production of more roots in wet quadrants and less transpiring leaf surface and branch growth. The rate of recovery of transpiration and photosynthesis from water stress was greatly influenced by the duration and intensity of wilting as well as by the rate of regeneration of new root systems.

Open Access

Abstract

An experimental peach (Prunus persica [L.] Batsch cv. Harken/Siberian C) orchard was planted on Fox sand in 1973 at 266, 358 and 536 trees/ha. The plots were either not irrigated or irrigated at a frequency necessary to prevent the available soil moisture (ASM) from falling below 25 or 50%. Irrigation stimulated tree growth in the earlier but not in the later years of the experiment. Growth was reduced by an increase in tree density especially in the later years at the highest density. Only in 50% ASM plots was growth not affected by high tree density. Irrigation (50% ASM) increased cumulative, marketable yields in the first 5 years of production by up to 9.7% while tree density (536 trees/ha) increased similar yields by up to 74.6% without irrigation and up to 99.5% with irrigation (50% ASM + 536 tree/ha). Irrigation consistently improved the proportion of large and medium-sized fruit while reducing the proportion of small, unmarketable fruit. Tree density had a smaller and less consistent influence on fruit size. Neither irrigation nor tree density adversely affected split pits, raw product fruit quality, cold hardiness or canker (Leucostoma spp.) susceptiblity. There were no significant interactions of irrigation and density treatments in any year, indicating that each treatment might be used to advantage without adversely affecting the other, at least in the first 7 years of growth and first 5 years of production.

Open Access

Abstract

The trench profile method was used to map peach [Prunus persica (L.) Batsch cv. Harken/Siberian C] roots in an 11-year-old experimental orchard with 3 levels of irrigation and 3 tree densities. Roots near the drip line, 150 cm from the trunk, were mapped to a depth of 120 cm, while those 30 cm from the trunk were mapped to a depth of 240 cm. Location, number, and diameter of roots near the drip line were greatly affected by irrigation and only moderately affected by tree density. The total number, and number of small-diameter (<2 mm) roots were highest in nonirrigated plots and decreased with increasing levels of irrigation. A similar but much reduced pattern was evident for medium- (2 to 5 mm) and large- (>5 mm) diameter roots. Irrigation promoted shallow rooting near the drip line. Trees receiving the low and high level of irrigation had 35% and 42%, respectively, of their roots in the top 30 cm of soil, compared with only 18% for those in nonirrigated plots. At depths of 30 to 120 cm in nonirrigated plots, 82% of the roots near the drip line were found in these soil layers, compared with 65% for the low and 58% for the high level of irrigation. Tree density had no effect on total root number near the drip line, although there was an increase in root number with an increase in tree density 90 to 120 cm from the trunk on both sides of the tree, and a decrease in root number with an increase in tree density within 60 cm of the trunk. Rooting occurred readily in the Ap, Bm, and Bt soil horizons, but very little rooting occurred in the gray sand comprising the Ck horizon, which had a high pH (7.8) and poor soil water retention characteristics.

Open Access

Three cultivars (`Garnet Beauty', `Harbrite', `Canadian Harmony'), two ground covers (temporary cover vs. permanent sod), and no irrigation vs. season-long trickle irrigation were studied in a high-density (633 trees/ha) peach [Prunus persica (L.) Batsch] orchard established on Fox sand in 1980. From 1985 to 1989, soil water content in the top 130 cm was similar in nonirrigated and trickle-irrigated plots except during the growing season (May to September). Total soil water was lowest in nonirrigated plots that had permanent sod strips in the row middles and fell below the-permanent wilting point for ≥11 months in summer but not at depths below 130 cm. Trunk cross-sectional area (TCA) was greater for `Canadian Harmony' and `Harbrite' than `Garnet Beauty', ground-cover treatments had no effect, and irrigated trees were generally larger than those not irrigated. Photosynthetic rate and stomatal conductance differed by cultivar, were unaffected by ground cover, and were enhanced by irrigation. Defoliation differed by cultivar, ground cover had little effect, and irrigation usually delayed defoliation. Flower bud and shoot xylem hardiness differed by cultivar but not by ground cover and were generally enhanced by irrigation. Tree survival was significantly affected by cultivar, being best with `Harbrite' and `Canadian Harmony' and poorest with `Garnet Beauty'. Permanent sod enhanced tree survival while trickle irrigation reduced it. Cumulative marketable yields were affected more by cultivar than by ground cover or irrigation. `Canadian Harmony' had the highest yield, followed by `Harbrite', then `Garnet Beauty'. Yields in sod were slightly higher than in temporary cover and yields with trickle irrigation were slightly higher than without irrigation. The best soil-management system when TCA, marketable yield, and tree survival were considered was a combination of permanent creeping red fescue sod strips in the row middles and trickle irrigation in the tree row. This system is being recommended to commercial growers in southwestern Ontario.

Free access

Abstract

Tomato (Lycopersicon esculentum Mill.) plants were grown in specially designed sectional treatment boxes which divided the root systems into 4 separate quadrants. Transpiration, photosynthesis, and stomatal conductance were determined in tomato plants with 4, 3, 2 and 1 quadrants of the root system supplied with water. The results suggested that there was no simple relationship between the percentage of root available for water uptake and transpiration rate. The shoot: root ratio of tomato plants increased as the proportions of roots supplied with water increased. The application of water to only 50% or 75% of the root system did not reduce transpiration, photosynthesis, stomatal conductance, or leaf surface area compared to a fully-watered plant. Where a substantial part of the root system (75%) was subject to moisture stress, only a small reduction in transpiration rate (20%) was observed. These results suggested that tomato roots had a greater relative absorption capacity for water uptake in response to the transpirational demand. The recovery of transpiration, photosynthesis, and stomatal conductance following the return to a fully watered state indicated that there had been no damage to the roots in the dry quadrants in any of the treatments.

Open Access