1. Raising Awareness and the Use of Different Irrigation Strategies to Promote
Water Efficiency During Drought
Miriam Morua and Emily Wieber
Plants &Water Lab, Department of Biological Science
California State University Fullerton
Effect of RDI on Navel Orange Physiology and Yield
Introduction
Comparing Surface vs. Subsurface Irrigation on Peppers
New Study: To Find the Best Plant-Based
Method for Avocado Irrigation
Strategies to Conserve Water
• California is currently in a drought crisis due to lack of rainfall, low snow pack melting, and diminished groundwater levels.
• About 80% of the state‘s water goes to irrigation. CA is the biggest farm state in the United States ($447 billion a year).
• Drought is known to limit plant productivity and alters biochemical and physiological processes. This will lead to increased water costs and
ultimately high food prices.
• Efficient irrigation methods, such as regulated deficit irrigation (RDI) and drip irrigation (DI), can reduce water use in agriculture such as
avocado and citrus orchards (Goldhamer et al., 2000).
• The goal of this research is to raise awareness regarding the use of water-saving irrigation strategies. The intention is to promote, inform
and motivate students, staff, faculty, and the public to consider using the water-saving strategies presented in this research project for their
personal gardening in their homes.
• Previous studies have shown that these irrigation strategies can increase productivity while reducing water usage.
• Regulated deficit irrigation (RDI) application during the
early fruit growth and fruit ripening phases can save
water without compromising fruit yield.
• The research objective was to measure the plant’s
physiological responses and fruit yield when the trees
were subjected to RDI.
• Navel orange trees were subjected to a control, RDI1,
RDI2, and RDI3.
Fig.2: Irrigation Setup for 1.2 Acre of Navel Orange Trees at UC Riverside Citrus Experiment Station
• The orange trees irrigated 25% less during the fall, their
fruit yield and quality remained the same as irrigated at
100%.
• Although smaller fruits were watered less, the fruit
sweetness remained the same as those irrigated at 100%.
• Surface irrigation (SDI) involves slow dripping of water on the
surface of the soil by emitters that carry a low flow of water under
low pressure to plants. It is adaptable and minimizes water loss
through runoff.
• Subsurface irrigation (SSDI) involves delivering water directly to
the root systems by burying the drip tape underground. It reduces
water loss due to evaporation, runoff, and wind drift but it is more
expensive and labor intensive.
• The research objective was to investigate whether there was a
difference between (SDI & SSDI) to assess the efficiency of water
management by comparing soil moisture retention,
photosynthesis, and yields.
• Peppers irrigated with subsurface irrigation had higher
productivity (lbs) and stomatal conductance (mmol/s2) compared
to surface while maintaining higher levels of soil moisture content.
Fig.1: An Update on Dramatic Reduction in Percent Normal Precipitation
• Current efficient irrigation scheduling mostly relies on
atmospheric and soil-water data but these are often
unreliable (Geerts et al, 2009).
• Alternative indirect continuous measures of plant water
need may help conserve water.
• The research objective is to identify the best measure of
water stress for avocado trees to guide irrigation by
comparing direct soil-based measures to indirect plant-
based measures.
• The goal of this new study is to promote better water
management practices that can be applicable to other
orchards.
• Using RDI reduces water usage by 20% (Wieber, 2014).
• SSDI retained 25% more water compared to subsurface
(Morua, 2012).
• Simply by installing a water meter to monitor water use in
residency can cut down water usage by 25% as mandated
by Gov. Jerry Brown (Fresno Water District, 2015).
Geerts, S., Raes, D., 2009. Agric. Water Manag. 96, 1275–1284.
Goldhamer D.A. & Salinas M. 2000. Proc. Int. Soc. Citricult. IX. 227-231
Figure 4: Subsurface irrigation set up (left) and surface irrigation set up (right) at the
Fullerton Arboretum.
Figure 3: Schematic of irrigation set up for both methods.
Treatment
Yield
(kg/tree)
Number
of
Fruit/Tree
Percentage of Weight Distribution of Different Fruit Size Across Treatments
Juice
Brim A
Very Tiny
50 – 59
mm
Tiny
60 – 63.4
mm
X-Small
63.5 –
68.9 mm
Small
69 – 74.9
mm
Medium
75 – 80
mm
Large
81 – 88
mm
X-Large
> 88
mm
Control 47.70 a 192 a .5 a 4.2 a 12.8 a 19.5 ab 25.9 a 20.3 a 5.6 a 10.85 a
RDI1 35.83 b 163 a 1.0 a 9.4 a 18.6 a 13.7 a 11.0 b 10.6 ab 2.6 a 10.81 a
RDI2 52.18 ab 212 a 1.2 a 5.7 a 20.9 a 26.1 b 28.8 a 14.2 ab 3.1 a 11.04 a
RDI3 42.22 ab 192 a 1.4 a 10.1 a 21.1 a 21.3 ab 13.1 b 7 b 4.9 a 11.17 a
Table 1: Effect of irrigation treatment on fruit yield and fruit size