Partial Root-zone Drying Increases Water Use

Partial Root-zone Drying Increases Water Use
Efficiency and Marketable Yield of Potato
Mathias N. Andersen1, Poul E. Laerke1, Seyed H. Ahmadi1,2, Ali Shahnazari3, Finn Plauborg1,
Fulai Liu2, Christian R. Jensen2
1
Department of Agroecology and Environment, Faculty of Agricultural Sciences, University of Aarhus, Denmark,
[email protected]
2
Department of Agriculture and Ecology, Faculty of Life Sciences, Copenhagen University, Denmark
3
Department of Irrigation, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
Potatoes rank fourth in production volume among the world’s agricultural products after wheat, rice
and corn (FAO, 1995). Potato is relatively sensitive to soil water deficits (Doorenbos and Kassam,
1979), and studies to introduce water saving techniques such as deficit irrigation (DI) have often
yielded discouraging results (e.g. Shock et al., 1998). As a shallow-rooted crop, irrigation remains
crucial for growing potato plants even in humid areas, and this consumes large quantities of fresh
water. During the last decade a novel irrigation strategy, partial root-zone drying (PRD), has been
developed (Dry and Loveys, 2000). The PRD approach is to use irrigation to alternately wet and dry
two spatially distinct parts of the plant root system. This could potentially be superior to DI because
inter alia PRD maintain easily available water in the main root-zone (Shahnazari et al., 2007;
Shahnazari et al., 2008). In this study we analysed the effect of PRD versus full (FI) or DI irrigation in
different plant growth stages on water use, plant growth and product quality.
Methodology
We conducted experiments on potato (Solanum tuberosum L. cv. Folva) response to PRD-irrigation
during three years 2005-2007 in outdoor rain-protected lysimeter facilities. The potatoes were planted
with 30 cm plant distance and 75 cm between rows. Three irrigation methods were applied in three soil
types: loam, sand loam, and coarse sand with c. 20, 10 and 5% clay respectively. The irrigation
treatments were full (FI), deficit (DI), and partial root-zone drying (PRD), with four replications. The
plants were fully irrigated till tuber-bulking and then irrigation treatments started as DI and PRD where
plants received 70% of fully irrigated plants. On coarse sand also PRD and DI throughout the growing
season and PRD during tuber-initiation was tested.
Results
PRD increased the concentration of abscisic acid in xylem sap expressed from stems, which in turn
decreased stomatal conductance. The lysimeter experiments allowed a full evaluation of the water
balance components. Evapotranspiration was reduced by c. 30 mm or 10-15% by PRD during the
tuber-bulking phase of growth compared to FI (Table 1).
Table 1. Water balance in FI and PRD treatments on three soils as average of 2006 and 2007
Soil
Treatment
Irrigation
1Soil water Drainage
Total ET
(mm)
(mm)
(mm)
(mm)
Coarse
FI
245
11
24±4.5
232
sand
PRD
207
23
23±3.5
207
Sand
FI
220
20
8±0.6
232
loam
PRD
177
40
8±0.4
209
Loam
FI
245
23
26±1.4
242
PRD
196
34
12±1.6
218
635
10
2
Yield difference (t/ha)
Marketable yield (t/ha)
Total yield (t/ha)
Yield difference (t/ha)
A meta-analysis using bioequivalence tests on data from coarse sand during 2005 and 2006 showed that
the total yield was essentially the same in PRD and FI, while marketable yield was increased by 14% in
PRD due to a larger fraction of tubers with sizes between 40-60 mm. The occurrence of quality defects:
scab and malformed tubers was essentially the same in PRD and FI. Consequently, the irrigation water
use efficiency was significantly increased by over 20% by PRD during the tuber-bulking phase
compared to FI (Fig. 1). PRD during the tuber-initiation stage of growth, however, decreased the yield
and quality of tubers.
70
15
Figure 1. A-left: Total yield (Y) of potatoes in the
PRD
A
FI
PRD and FI treatments during two years 2005 and
60
12
PRD-FI
2006, bars indicate ±SEM (n=4).
50
9
A-right: Bio-equivalence test of weighted average
40
6
yield difference between PRD and FI for the two
+L
years, bars indicate ±CI90. As threshold limit
30
3
(±L) in the test we used 4.5 t/ha.
20
0
B-left: Marketable yield of potatoes in the size
10
-3
classes from 40-60 mm in the two treatments.
-L
B-right: Difference in marketable yield between
0
-6
PRD and FI as average of the two years. PRD
60
12
B
increased marketable yield with 4.9 t/ha.
50
10
C-left: Irrigation water-use-efficiency in the two
treatments.
*
***
40
8
C-right: Difference in irrigation water use
30
6
efficiency between PRD and FI as a weighted
average of the two years. PRD increased irrigation
20
4
water use efficiency with 38.3 kg/(ha mm).
Conclusions
Collectively, the results indicate that intelligent
350
70
C
irrigation management, even in a drought
***
300
60
sensitive crop as potatoes, can achieve
250
50
***
*
considerable water savings. However, during the
200
40
early, most sensitive potato growth-stages
evaporative demands have to be met. This
150
30
corresponds well with recent results obtained by
100
20
Saeed et al. (2008). PRD is a new and relatively
50
10
unexplored biological water saving technique,
0
0
which still can be optimised with respect to ABA2005
2006
Both years
signalling effects. We have demonstrated here that
PRD can induce an increase of middle-sized tubers and marketable yield, and this effect also need
further investigation, in order to be optimised and used in potato crop management.
0
IrrWUE diff. (kg/ha mm)
IrrWUE (kg/ha mm)
0
References
Doorenbos J. and Kassam A.H. 1979. Yield response to water. Irrigation and Drainage Paper 33. FAO, Rome.
Dry P. and Loveys B.R. 2000. Partial drying of the rootzone of grape. I. Transient changes in shoot growth and gas
exchange. Vitis 39:3–7
FAO, 1995. Production Book, vol. 48. FAO, Rome, p. 243.
Saeed H. et al. 2008. Potential of partial rootzone drying as an alternative irrigation technique for potatoes (Solanum
tuberosum). Ann. Appl. Biol, 152:71–80
Shahnazari A. et al. 2008. Nitrogen dynamics in the soil-plant system under deficit and partial root zone drying irrigation
strategies in potatoes. Euro. J. Agron.. 28:65-73
Shahnazari A. et al. 2007. Effects of partial root zone drying (PRD) on yield, tuber size and water use efficiency in
potato (Solanum tuberosum L.) under field conditions. Field Crops Res. 100:117-124.
Shock C.C. et al. 1998. Potato yield and quality response to deficit irrigation. HortScience 33:655–659
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