Feb, 2013

Maria da Penha PADOVAN - PhD student CATIE/BU Dr. Bruno RAPIDEL - Major advisor – CATIE Dr. Robert BROOK - Major advisor – BU

Water dynamics and use in coffee shaded with Tabebuia rosea Bertol. andSimarouba glauca D.C. compared to full sun coffee in sub optimal environmental condition for coffee cultivation

1

Nicaragua in the global climate change context

1. INTRODUCTION

Source: WRI 2014

Agroforestry is a promising strategy to adapt to climate change. Shade tree may take up water from deep layers and improve water

use throughout the soil profile. Moreover shade trees can improve incomes for farmers. However, shade tree may use a lot of water and compete with coffee.

2

2. STUDY AREA

Coffea arabica with deciduous Tabebuia rosea and evergreen Simarouba glauca

Mean annual rainfall 1470 mm with six months dry seasons

Mean annual temperature between 26-27°C

455 m.a.s.l.

Andisol with 2m depth and a hard layer (talpetate)

3

968 mm

1312 mm

3. HYPOTHESES

1. Under restrictive soil conditions, tree roots cross the compact soil layer

and improve coffee root growth and coffee water uptake throughout the soil

profile depending on the shade tree root system characteristics and water

availability.

2. Plants transpiration and soil evaporation may lead to a competitive

relationship between coffee and shade tree depending on tree species

characteristics, soil conditions and available water in sub optimal

environmental condition for coffee cultivation.

4

4.1. ROOTS DISTRIBUTION

4. METHODOLOGY

Root Impact Counting Method (Tardieu, 1988)

10 profiles in FS and 24 in AFS (8 near Tr, 8 near Sg and 8 far from them)

5

TREE SAPFLOW

Thermal Dissipation Probes (Granier, 1987)

Calibration was performed by Stem Heat Balance (Dynagages/Dynamax Inc.)

COFFEE SAPFLOW

Stem Heat Balance in 4 shoots in FS and 4 in AFS 4 times per year over 2 years.

COFFEE AND TREE TRANSPIRATION

4.2. COMPLEMENTARITY OR COMPETITION

6

LEAF AREA

TREE LEAF AREA

INDIRECT MEASUREMENT – HEMISPHERICAL PHOTOGRAPHS

Images analyzed by Gap Light Analyzer software (Frazer et al. 1999).

DIRECT MEASUREMENT – CUT DOWN 4 TR AND 4 SG

7

Nikon Coolpix 4500/fish eye lens

COFFEE LEAF AREA

Length and width of every 20th leaf were measured.

Leaf Area = 0.7243*length*width

Leaf Area Index was calculated by multiplying the mean leaf area of the shoots per

shoot density in FS and AFS.

8

SOIL EVAPORATION

- Weighing lysimeters were placed in FS (7) and AFS (8) in the rows and between rows.

- From 275 days of measurements 52 were selected assuming 24h period after a

rainfall event for the drainage to occur. Measurements were taken in the wet and

dry seasons.

- The time course of soil evaporation was obtained by using the Ritchie model.

9

10

SOIL WATER CONTENT

45 Time Domain Reflectometers - TDR probes:

12 in three trenches in FS and 33 in six trenches in AFS.

CR1000 Datalogger /multiplexor.

Data were calibrated for each soil layer (Udawatta 2011).

COFFEE LEAF WATER POTENTIAL

11

We used a pressure chamber and a gas cylinder (Scholander et al., 1965) overperiods of 3 consecutive days at predawn and midday in the dry and wet seasons.

12

- Coffee root growth was reduced in 15% in the average by the talpetate layer.

- Shade tree root system had not a great effect on coffee root growth.

Coffee root growth was similar in FS and

agroforestry treatments.

Mean coffee root impacts were greater and

deeper near Sg compared to Tr trees.

Simarouba glauca root system was denser

below 110 cm depth compared to Tr root

system.

13

Coffee and Simarouba glauca shade tree exhibited root niche differentiation whileTabebuia rosea root system was more widely distributed.

Coffee and tree root niche differentiation

14

15

In this investigation shallower coffee root and deeper tree root

distribution patterns suggest a potential complementarity in soil water use

throughout the soil profile.

Root niche differentiation reinforced the ecological hypothesis (Cannell et

al. 1996) in which tree deep root system may improve soil resources use

that are not available for crops.

Soil profile water content and rainfall

Soil water content in the whole soil profile was often lower in AFS than in FS

DRY WET DRY WET DRY WET

5.2. COMPLEMENTARITY OR COMPETITION

TREE TRANSPIRATION

Tabebuia rosea transpiration rate was greater than evergreen Simarouba glauca.

Tree transpiration tended to follow Eto in the wet seasons but not in the dry seasons.

Soil water availability seems to be the main driver of tree transp instead of atmospheric demand.

Water availability effect was observed in the lower transpiration rate in 2013.17

DRY WET DRY WET DRY

Time course of tree Leaf Area Index - LAI

Tabebuia rosea leaf area index varied with seasonal pattern whileSimarouba glauca LAI was lower variable over the period of study.

18

DRY WET DRY WET

2012 DRY

Tree hourly transpiration rates and vapor pressure deficit (VPD) - atmospheric demand

2012 WET

2013 DRY 2013 WET

Tree transpiration was great in the wet compared to the dry season. Tr and Sg daily transpiration rate was lower in the hard dry season despite the high evaporative demand. 19

Hourly trends in coffee transpiration and atmospheric demand

2012 DRY 2012 WET

2013 DRY 2013 WET

Coffee transpiration was greater in the dry seasons following the atmospheric demand. Transpiration was lower in 2013 dry season when SWC was lower despite of the greater VPD

20

• Drought stress effect was observed in the 2013 dry season.

• Lowest LWP values reached -2.33 MPa in midday at the end of the 2013 dry season.

COFFEE LEAF WATER POTENTIAL

WET DRY WETDRY

21

22

TRANSPIRATION PARTITIONING

Contrary to our initial expectations that trees would use more water, on

average coffee transpiration comprised 75% of the total transpiration in

AFS while Tabebuia rosea represented 17% and Simarouba glauca 8%.

Most of coffee transpiration was in the dry while most of tree

transpiration was in the wet season.

SOIL EVAPORATION

Soil evaporation was often greater in the wet than dry seasons.

In the wet seasons soil evaporation was greater in FS than in AFS and in the inter-row

than in the row while in the dry no difference was found between systems or location.

In the dry seasons soil evaporation did not follow the evaporative demand.

DRY WET DRY

23

Soil evaporation measured and modelled in FS and AFS

Ritchie model allowed estimating mean soil evaporation in both systems Wet season: 50% in FS and 33% in AFS Dry season: 20% in FS and 12% in AFS of the total evapotranspiration.

DRY WET DRY WET DRY

24

Evapotranspiration was calculated by two different and independent approaches:

Measured by coffee transpiration plus tree transpiration plus soil evaporation.

Estimated by differences in SWC obtained by TDR when we were sure that there was no drainage.

Similar results and the same tendency on greater water use in AFS although the different methods used

Daily Evapotranspiration in FS and AFS

26

TOTAL EVAPOTRANSPIRATION

Total evapotranspiration was greater in the wet periods compared to the

dry influenced by tree transpiration and soil evaporation.

Of total evapotranspiration:

- Soil evaporation accounted for 17% in AFS and 30% in FS.

- Coffee and tree transpiration accounted for 83% in AFS and 69% in FS.

6. CONCLUSIONS

In agroforestry, a greater proportion of water was used for plant

growth than in full sun coffee, because less water was lost by soil

evaporation.

In sub optimal conditions for coffee cultivation, Simarouba glauca

root niche differentiation and water consumption pattern indicated

that it is more suitable as a coffee shade tree compared to deciduous

Tabebuia rosea.

27

28

Soil water was not usually a constraint for coffee water consumption in

agroforestry except in a severe dry season. This supports the idea of

complementarity of coffee and shade trees even when associated with

water spending tree species such as Tabebuia rosea.

However, competition was found in the 2013 very hard dry season

when coffee and tree root systems exhausted the soil water in AFS and

the soil water stock in the 2m soil profile was not enough to avoid a

high level of coffee water stress.

29

ACKNOWLEDGEMENTS

We are grateful to

FONTAGRO Caf’Adapt project

CIRAD

INCAPER

who funded this research