G.V. Post Harvest Deficit Irrigation Report 1: The Field Day

Introduction:

Two experiments were established in Williams pears and Tatura 204 peaches on commercial orchards in the Goulburn Valley. Soil moisture and the amount of stress on the trees were measured so that the results could be used by growers to determine how much water to apply after harvest in their orchards.

This page contains some of the notes and observations from the first field day held in autumn 2008.

You can read more about the trial by following this link to the complete Field Day Article (3.22 mb .PDF), or the Postharvest Deficit Irrigation in Peach and Pear article for a more scientific view.

Field Day Notes and Observations:

In both WBC pears and the T204 peaches tree water stress levels were measured using Stem Water Potential and Stomatal Conductance weekly from harvest until leaf fall. Both allowed us to measure how stressed the trees were as a result of water application deficits.

Stem water potential was measured using a pressure chamber. Which is a measure of the level of water tension in the tree, and therefore water stress. A high pressure reading indicates that the tree is water stressed. A low reading indicates the opposite. The data indicated that the trees being delivered low irrigation (50%) were more stressed than that receiving the high irrigation (200%).

Leaf conductance was also used as a measure of tree water stress. The instrument estimates how open the leaf pores (stomata) are and the ability of the leaf to release water vapour into the air. As indicated by the graphs on the field day handout a high number for the 200% treatment, indicates less water stress than the low number seen on the 50% treatment..

View Complete T204 Peach Field Day Handouts and Graphs (77 kb .PDF)

Post Harvest Irrigation, Rainfall and Evaporation on T204 Peach (until 28 April 2008)
Treatment % of normal	Irrigation (Litres/tree)	Irrigation (Megalitres/ha)	Irrigation (millimetres)	Rainfall(mm)	Reference Crop Evapotranspiration (mm)*
50%	1772	1.77	177	23	422
75%	2098	2.09	209	23	422
100%	2602	2.60	260	23	422
160%	3938	3.93	393	23	422
200%	4929	4.92	492	23	422

Soil moisture levels (kPa) were monitored using gypsum blocks – all treatments followed a similar drying pattern following an irrigation event, with the 0% treatment on the pears steadily drying out.The graphs on the handouts show clearly that the trees delivered no irrigation (0%) were more stressed than those receiving the high irrigation (200%).

View Complete WBC Pear Field Day Handouts (74 kb .PDF)

Post Harvest Irrigation, Rainfall and Evaporation on WBC Pear (until 28 April 2008)
Treatment % of normal	Irrigation (Litres/tree)	Irrigation (Megalitres/ha)	Irrigation (millimetres)	Rainfall(mm)	Reference Crop Evapotranspiration (mm)*
0%	0	0	0	28	359
50%	2158	1.48	148	28	359
100%	4116	2.82	282	28	359
160%	6980	4.79	479	28	359
200%	8885	6.09	609	28	359