AGRICULTURAL UNIVERSITY OF ATHENS
DEPARTMENT OF CROP SCIENCE
LABORATORY OF AGRONOMY
Effect of deficit irrigation practice on the weed flora in a corn crop
V. E. Kotoulas, K. Karfi, I. S. Travlos, D. Voloudakis, G. Economou and A. Karamanos
HUESCA
4-8 SEPTEMBER 2011
THE STATE OF THE ART


At present and more so in the future, irrigated
agriculture will take place under water scarcity
Irrigation
management
will
shift
from
emphasizing production per unit area towards
maximizing the production per unit of water
consumed, the water productivity.
THE STATE OF THE ART



To cope with scarce supplies, deficit irrigation,
defined as the application of water below full cropwater requirements (evapotranspiration), is an
important tool to achieve the goal of reducing
irrigation water use.
2 ways: a. During whole growing period
b. only during “biological windows”
The level of deficit irrigation is calculated according
to plant water demands based on Penman-Monteith
equation.
THE STATE OF THE ART


Many researches were conducted on the effects
of deficit irrigation on several crops or trees.
However, it is not still clear the way that deficit
irrigation practices affects the growth of the
weeds.
THE OBJECTIVE

The way that water shortage affects the
weed development in relation to corn crop
yield.
Sub objective
 The physiological effects of water
shortage on the weed flora.
THE SCOPE OF THE STUDY
To investigate if the deficit irrigation can
be used as an effective mean for weed
management.
MATERIALS AND METHODS

Crop: Zea mays L.

Weeds: Amaranthus retroflexus, Solanum eleagnifolium,

No application of herbicides


Tribulus terrestris
Irrigation method: Drip irrigation (except the first 2
irrigations that were applied with sprinklers)
Beginning of DI treatments: When the corn developed 5-6
leaves
MATERIALS AND METHODS


Irrigation dose: Based on Penman – Monteith equation we
calculated ET0 and we used it to calculate Etc (ETc=
Kc*ET0).
Data we used in order to calculate Evapotranspiration
(ET0): Air Temperature, Relative Humidity, Wind speed
and Solar radiation.
Treatments:

Full Irrigation (A): 80%*Etc

Deficit Irrigation 1 (B): 65%* Etc

Deficit Irrigation2 (C): 50%* Etc
MATERIALS AND METHODS
Measurements and observations:





Weed density (plants/m2)
Dry weight
Stomatal resistance
Leaf water potential
Corn yield
RESULTS
CLIMATIC CONDITIONS
METEOROLOGICAL DATA
Fig. 1. Air temperature during the experimental period
Fig. 2. Relative humidity during the experimental
period
Fig. 3. Solar radiation during the experimental period
Fig. 4. Wind speed during the experimental period
RESULTS
Precipitation during
the experimental period
ET0
Reference (ET0)and
Crop (Etc) Evapotranspiration
ETc
DAS
RESULTS
Weed density of the 3 weed species 110 DAS
RESULTS
Dry weight of the 3 weed species and the corn 110 DAS
RESULTS
Fig.9. Leaf water potential of the 3 weed species and the corn 110 DAS
RESULTS
Fig.10. Stomatal resistance of the 3 weed species and the corn 110 DAS
RESULTS
Fig.11. Corn yield
DISCUSSION
1.
2.
As far as the density of weeds concerns,
no significant differences were observed
among the water treatments
The highest dry weight values were
observed for the second level of deficit
irrigation for S. eleagnifolium and T.
terrestris, but not for A. retroflexus. On
the contrary, corn showed the highest
value of dry weight when irrigated full
DISCUSSION



Physiological point of view
Leaf water potential values were higher in
full irrigation treatment and lower in the
second level of deficit irrigation both for
weeds and corn.
Stomatal resistance values were higher in C
treatment and lower in A and B.
Especially for Solanum and Tribulus did not
differ between A and B treatments.
DISCUSSION
Corn as a C4 plant reacts faster and
better than the other species (C3 plants),
making corn more competitive against the
weeds in full irrigation conditions.
 On the other hand, when deficit irrigation
is applied, weeds (Solanum and Tribulus)
are presented more competitive against
corn.

CONCLUSIONS

S. eleagnifolium at high risk as an
invasive weed to Mediterranean type
regions have was affected from water
shortage.
 A. retroflexus: DI could be an effective
method for the control of these weeds,
especially in other crops (cotton) that
respond better than corn in water
shortage.
CONCLUSIONS
The expected climate change will cause
an expantion of the xerothermic zone and
this will favour the occurance of such
xerophytic weeds.
Thank you for your attention