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  • Author or Editor: C. S. Tan x
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A time domain reflectometry (TDR) technique was used to measure water in the soil profile to derive wetting patterns of drip and microjet irrigation systems in a peach [Prunus persica (L.) Batsch] orchard. A distinct cone shape of >50% available soil water (ASW) extending from the emitter down to a depth of >45 cm was observed in the drip system. The 50% ASW zone in the microjet system was an elongated semicircle from the soil's surface down to a depth of 35 cm. TDR can be used successfully to determine wetting patterns of various irrigation systems to develop better irrigation scheduling.

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Abstract

Root systems were studied to determine if differences in utilization of soil moisture were associated with the extent and number of roots produced by corn and tomato. Growth room studies for both crops indicated that the reduction in transpiration when the upper portion of the root zone was dry was greater than when the lower portion was dry. Total root length of corn was about twice that of tomato roots. However, no direct relationship between the total amount of root length and transpiration was found. Roots of corn and tomato in the field extended beyond the maximum depth measured (100 cm) between 42 – 46 days after establishment. The spatial density of corn roots was much greater than that of tomato roots, especially as depths increased. This difference possibly explains the use of stored soil moisture by corn. On the other hand, the capacity of tomatoes to extract large amounts of water from the soil cannot be explained by the density and rooting depth. Perhaps this capacity is due to total root surface area differences or high absorption capacity of tomato root system.

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Three-year-old peach [Prunus persica (L.) Batsch] trees in a growth room under well-watered conditions were subjected to photosynthetically active radiation (PAR) levels (400-700 nm) of 444, 287, 144, 61, and 19 μmol°s−1m−2. At very low PAR levels (19 and 61 μmol°s−1m−2), the photosynthetic rate (P) declined with increasing temperature. Multiple regression analyses for the 3 highest PAR levels showed that an increase in PAR increased the optimum temperature for both P and stomatal conductance (gs). The highest leaf water potential (ψL) was found at 21°C in all 3 PAR levels. The regression equations also showed that PAR was the main determinant of P and gs, but that temperature was the main determinant of ψL.

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A 2-year study was made of 2 methods of scheduling irrigation of peach (Prunus persica (L.) Batsch cv. Harken/Siberian C). In each year, irrigation schedules necessary to prevent the available soil moisture (ASM) from falling below 50% level in the top 30 cm were essentially the same, whether determined from direct measurement of soil moisture or predicted from a simplified Priestley and Taylor évapotranspiration model.

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Abstract

Stomatal conductance, transpiration, and photosynthesis declined steadily with decreasing leaf water potential in seedlings of peach [Prunus persica (L.) Batsch] grown in large pots containing about 84 kg of steam-sterilized sandy loam soil under controlled environmental conditions. Growth and transpiration were reduced mainly through the effect of stomatal closure as soon as water stress commenced.

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

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.

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