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  • Author or Editor: C. S. Tan x
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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

Abstract

Tomato (Lycopersicon esculentum Mill.) cultivars well-adapted to sandy soils and reportedly flood-tolerant genotypes were subjected to a range of flooding stresses in a controlled environment growth room and in the field. Root systems were partitioned into stem-borne adventitious roots, roots in the upper 10 cm of the soil profile, and the remaining roots. There was no difference between the reportedly flood-tolerant genotypes and cultivars adapted to sandy soils in response to the flooding stresses. In continuously flooded plants, adventitious roots accounted for more than one-half the root biomass. In plants subjected to periodic flooding, adventitious root growth was restricted.

Open 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

We have found time domain reflectrometry (TDR) to be a rapid and effective method of measuring soil water content (SWC) in microirrigated orchards, particularly in applications where many sites are monitored frequently. With simple modifications to commercially available systems, it has been possible to measure up to 100 sites per hour. TDR SWC measurements have been successfully applied for scheduling irrigation and for in situ determination of SWC characteristics. The determination of plant water use from changes in SWC of microirrigated trees, however, requires that a sufficient number of probes be used to detect the spatial distribution of water within the root zone. Due to water redistribution in the soil following an irrigation, measurements made near drip emitters depend highly on the time after irrigation that the measurement is made. It is therefore important to be consistent in the timing of SWC measurements relative to irrigation events if the effects on SWC of different irrigation management practices are to be compared.

Full 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

Seven treatment combinations of irrigation and fertilizer were compared in a high-density (606 trees/ha) management system for peach [Prunus persica (L.) Batsch cv. Harrow Beauty/Bailey] on Fox sand in southwestern Ontario. Each treatment combination had an irrigation component (N = nonirrigated, D = drip irrigated, or M = microsprinkler irrigated) and a fertilizer placement component (B = banded fertilizer, L = low fertigation, or H = high fertigation). NB and DB are commonly used systems in Ontario, while the other five treatment combinations were experimental. Total soil water in the top 110 cm of soil was lowest under NB but was never at the permanent wilting point. Trunk cross-sectional area was largest under DH and DB, smallest under ML and NB, and intermediate for the other three treatment combinations. No symptoms of N or K deficiency or toxicity were noted for any of the fertilizer treatments. Leaf analyses in July and September indicated that most major and minor elements were in the adequate to slightly excess range. However, there were no significant treatment effects on leaf nutrient concentrations in July or September when averaged over the five years, except for Mg in July. There were large and significant year effects on leaf nutrient concentrations but no significant treatment × year interactions. During the first four cropping years, there were no significant treatment effects, averaged over years, for total yield, marketable yield, or cumulative yield efficiency; however, there were large year effects but no treatment × year interactions for these factors. There was no detectable yield advantage for D vs. M irrigation. B application of N and K promoted no higher yields than fertigation equivalent to the B rate or 50% of this rate. Fertigation of N and K during the first 4 years of this experiment did not provide a detectable yield advantage to warrant the added cost and labor associated with this system compared with the B applications of N and K.

Free access