Pattern of Seasonal Water Use of Asian Pears Determined by Lysimeters and the Heat-pulse Technique

Abstract

<jats:p>Seasonal water use data are presented for 4-year-old <jats:italic>Pyrus serotina</jats:italic> Rehder cv. Hosui growing in drainage lysimeters and trained onto a Tatura trellis. Weekly water use (WU) was calculated using the mass balance approach. For 8 consecutive weeks during late summer, instantaneous WU was also measured by the compensation heat-pulse technique for measuring sap flow. Although good agreement was found between the two methods for 4 weeks after probe installation, discrepancies increased after this time. Water use was highest in early to mid-January in New Zealand, averaging ≈8 liters/tree per day, or 2 liters·m<jats:sup>-2</jats:sup> canopy surface area/day. Total water use over the growing season was 1070 liters/tree, or 245 liters·m<jats:sup>-2</jats:sup> canopy surface area. The correlation coefficient between weekly WU and evaporation from a nearby Class A pan was 0.81 for the season. Weekly crop coefficients thus calculated for the well-watered trees ranged from 0.15 to 0.55 and 0.20 to 0.83 when calculated using canopy surface area and projected ground area, respectively. Low values were due to low values of canopy leaf area early in the season. Withholding irrigation during three periods resulted in a gradual decline in water use. Water-stressed trees had a lower predawn water potential than fully irrigated trees. This pattern was followed by a more-rapid decline during the morning, and a slower recovery during late afternoon and early evening. Midday leaf water potential never fell below -2.5 MPa.</jats:p>

A Simple Model for Rapid and Nondestructive Estimation of Bell Pepper Fruit Volume

“…Analyses of variance using data on the deviations from the actual values of volume (measured with the water displacement method) showed highly significant differences among pepper cultivars (P < 0.0001). This observation confirms previous reports that the assumption of spherical fruits in volume estimation is erroneous (Caspari et al, 1993;Mitchell, 1986). Both the equation proposed by Currence et al (1944) and the new equation improved accuracy of fruit volume estimates (Table 2).…”

“…Several approaches have been proposed to estimate fruit volume (Assaf et al, 1982;Caspari et al, 1993;Chalmers et al, 1981;Currence et al, 1944;Russo, 1996). The simplest approach has been to assume that fruits are spherical and use diameter or circumference to calculate volume (Caspari et al, 1993;Chalmers et al, 1981).…”

“…Several approaches have been proposed to estimate fruit volume (Assaf et al, 1982;Caspari et al, 1993;Chalmers et al, 1981;Currence et al, 1944;Russo, 1996). The simplest approach has been to assume that fruits are spherical and use diameter or circumference to calculate volume (Caspari et al, 1993;Chalmers et al, 1981). Although this method provides adequate estimation of volume for some fruits, it does not work for fruits with irregular shapes, such as peppers (Caspari et al, 1993;Mitchell, 1986;Russo, 1996).…”

“…The simplest approach has been to assume that fruits are spherical and use diameter or circumference to calculate volume (Caspari et al, 1993;Chalmers et al, 1981). Although this method provides adequate estimation of volume for some fruits, it does not work for fruits with irregular shapes, such as peppers (Caspari et al, 1993;Mitchell, 1986;Russo, 1996). Russo (1996) used the formula for a cone to estimate bell pepper (Capsicum annuum) fruit volume.…”

The use of sap flow measurements for scheduling irrigation in olive, apple and Asian pear trees and in grapevines

“…Irrigation experiments began during the 1990/1991 season. Irrigation water was withheld from four trees, at three different growth stages for up to 14 days at a time, in order to induce short-term water stress (Caspari et al 1993a). Long-term (up to 73 days) deficit irrigation was also applied, either early or late in the 1991/1992 season, on four trees each, while the remaining four trees received full irrigation (Caspari et al 1994).…”