Influence of Tree Pollarding on Crop Yield in a Mediterranean Agroforestry System

INFLUENCE OF TREE POLLARDING ON CROP YIELD IN A MEDITERRANEAN AGROFORESTRY SYSTEM

Lydie Dufour , Jérémy André, Jimmy Le Bec and Christian Dupraz

2016 EURAF Conference, Montpellier 23-25 May 2016

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Introduction Why pollarding adult trees ?Pollarding trees is a way to reduce shade on the crop

Pollarded and not-pollarded alley - June 2014 2

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) • Previous experiment 1 Shade without roots root pruning (80 cm deep, 1.5 m to the trees) has a few effect on the crop yield reduction Poplars in Vézénobres (6 years old – 18 m high, 16 m between tree rows) – August 2002

Root pruned Root unpruned Sole crop control Yield (qx ha-1) 18.00 ± 1.00 16.86 ± 0.89 34.24 ± 3.16 Relative yield (% of 52.7 49.3 100 control) Durum winter wheat yields in 2003 3

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) • Previous experiment 2 Tree pruning Poplars in Vézénobres (8 years old – 22 m high) – May 2004

10 m pruning

6 m pruning

6 m high pruned 10 m high pruned Sole crop control

Yield (qx ha-1) 14.38 ± 2.49 23.52 ± 1.12 41.89 ± 7.11

Relative yield (% of 34.3 56.2 100 control)

Durum winter wheat yields in 2004 4

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) • Previous experiment 3 Shade without roots

Artificial shade induced a yield decrease

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) • Previous experiment 4 (Dufour et al – JACS 2015) in Restinclières

yield 2007 yield 2008 % total transmitted radiation 100

60 Percentage of yield or of radiation 50 3 m 6.5 m 11 m Percentage of global radiation on the crop measured by hemispherical photographs taken in june 2008 (trees height 8.3 m) and durum wheat relative yield (compared to a sole crop control) 6

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) • Tree crowding index = tree height/alley cropping width

Vézénobres North-South Vézénobres East-West Restincliéres North-South Restincliéres East-West

1,2

0,8

y = -0.39x + 1.08 y = -0.76x + 1.42 0,4 R² = 0.30 R² = 0.85 Relative Yield

0,0 0 0,5 1 1,5 2 Tree Crowding Index

Relative yield is calculated taking into account the area without crop (on the tree row) 7

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods • The study site Domaine de Restinclières (South of France – North of Montpellier, 43.42°N – 3.51°E ) Soil : deep alluvial fluvisol, silty (50 % silt, 20% clay), calcareous (ph= 8,2) Watertable 3 m to 7m depth, according to the season Climate sub-humid - yearly average temperature ≈15 °C, Plantation of trees in 1995 ; Hybrid walnuts (Juglans nigra X Juglans regia – NG23 X RA) ; East – West tree rows separated by 13m wide alleys ; initial trees density 200 trees ha-1 thinned in 2004 to 100 trees ha-1 Crop rotation : Durum wheat (2013- 2014), barley (2014-2015), pea (2015-2016) Sole crop control available 9

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods

• 50 walnut trees :18 years old, 10 m high (average for the field), pollarded 4 m high in 2013 • 2 pollarding methods : without branches left on the trunk,

with 30 cm of branches left

• An agroforestry tree control for each pollarded tree

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods • Crop measurements in sole crop control : 5 subplots of 1m², in agroforestry : 5 transects of 3 subplots each, in pollarded trees area : 5 transects of 3 subplots each,

North Middle South

13 m 11

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods

• Crop measurements during growth : phenology, height, biomass, leaf area, Ntester, greenseeker,

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods • Crop measurements at harvest : yield and yield components : number of spikes m-2, number of grains spikes-1, 1000 grains weight, harvest index, proteins content

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods • Trees measurements every year : height, pruning height and diameter at breast height are measured for all the trees, phenology of pollarded trees and their control : budburst, short shoots expansion long shoots expansion, leaf fall

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Materials and methods •Radiation measurements by hemispherical pictures

Trees stage Wheat Barley Pea 22/05/15 – South plot budburst Vegetative Vegetative Flowering 23/04/14 14/04/15 15/04/16 Short shoots Flowering Milky growth 06/05/14 22/05/15 End of short Milky Mature shoots growth 04/06/14 19/06/15 Dates of hemispherical shots – trees and crops corresponding stages 15

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results

Sowing Tillering Bud- Flowering Short Grain Harvest Long burst shoots filling shoots Wheat (‘Claudio’) 13/10/23 13/12/01 14/05/04 14/05/28 14/06/16 Barley (‘Augusta’) 14/11/06 14/12/05 15/04/24 15/05/15 15/06/10 Pea (‘Igloo’) 15/12/03 16/04/06 16/04/20 2014 Walnut 04/14 05/15 06/30 2015 Walnut 04/20 05/13 07/05 2016 Walnut 04/14 • Crop and trees phenology (beginning of each stages)

Barley and walnuts - 2015/04/15 16

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results • Tree phenology is modified by pollarding

Budburst Short shoots Leaf fall Some pollards kept on growing Pollard 05/06 06/08 11/27 after the beginning of leaf fall in 2014 2014 and 2015 Control 04/30 05/20 11/13 Pollard 05/13 06/19 11/26 2015 Control 05/13 06/05 11/12 control Pollard 04/15 2016 Control 04/15 Mid-dates of main phenological stages of pollarded walnut compared to control

pollard

Leaf fall – 15/11/15 17

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results • Light avalaibility for the crop

100 POL 2014 AF 2014 POL 2015 AF 2015 90 POL 2016 AF 2016

80 2 6,5 11 April hemipherical pictures corresponding to trunk and branches shade, during the crop vegetative growth 18

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results • Light avalaibility for the crop

Near one tree Middle of the alley Near one tree 2014 98.0 ± 0.3 96.3 ± 0.9 94.5 ± 1.5 Pollarded trees 2015 97.0 ± 0.3 % 95.2 ± 0.4 % 81.0 ± 2.1 % Agroforestry - not 2014 89.4 ± 2.3 84.6 ± 3.3 73.6 ± 1.1 pollarded trees 2015 89.5 ± 0.8% 84.0 ± 1.7 % 75.9 ± 2.9 % Percentage of radiation remaining in the cropped alleys compared to the incident radiation in full sun integrated on the whole crop growth cycle. Intervals are standard errors 19

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) • Crops growth Results Wheat sampled the 14/04/24 Barley sampled the 15/04/22 150 80 AF Pollard SCC AF Pollard SCC 60 100 40

50 20

0 0 Wheat heigth (cm) Green leaf Total aerial Barley heigth (cm) Total aerial biomass/10 area/plant (cm²) biomass/10 plants plants (g) (g) 300 AF Pollard SCC

200 Pea sampled the 16/04/18 100

0 Green leaf area/plant (cm²) Total aerial biomass/10 20 plants (g)

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results • Crops yield

-1 Wheat-2014 (qx ha-1) Barley-2015 (qx ha )

60 60

40 40

20 20

0 0 AF North Pollard AF AF South Pollard SCC AF Pollard AF Pollard AF Pollard SCC North Middle South North North Middle Middle South South

58 92 75 70 76 100 92 96 102 96 91 96 100 Relative yields of the different plots in % of the sole crop control

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results

• Crops yield

Agroforestry Agroforestry with Sole crop with pollards non-pollards control Yield (qx ha-1) 32.9 ± 1.0 27.7 ± 4.1 44.8 ± 1.7 Wheat-2014 % of SCC 74 62 100 Yield (qx ha-1) 47.5± 1.6 47.7 ± 0.6 55.5 ± 0.6 Barley - 2015 % of SCC 86 86 100

Wheat and barley yields, taking into acount the non cropping tree row (1.5 m width) 22

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results • Crops yield components

Nb of Nb of 1000 grains Harvest spikes m-2 grains weight (g) Index (%) spike-1

2014 258 ± 24 29.4 ± 1.3 48.2 ± 1.3 42.9 ± 0.9 Pollarded trees 2015 530 ± 19 18.7 ± 0.6 54.7 ± 1.2 28.6 ± 0.6

Agroforestry - 2014 257 ± 28 25.3 ± 1.7 46.8 ± 1.0 41.3 ± 3.6 not pollarded 2015 542 ± 27 18.0 ± 0,7 54.2± 1.0 29.6 ± 1.2 trees 2014 291 ± 16 32.9 ± 0.9 47.3 ± 1.6 41.0 ± 3.9 Sole crop control 2015 501 ± 14 20.6 ± 0.8 53.9 ± 1.0 30.7 ± 1.0

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Results • Crops yield components

Nb of Nb of 1000 grains Harvest spikes m-2 grains weight (g) Index (%) spike-1

2014 258 ± 24 29.4 ± 1.3 48.2 ± 1.3 42.9 ± 0.9 Pollarded trees 2015 530 ± 19 18.7 ± 0.6 54.7 ± 1.2 28.6 ± 0.6

The number of grains per spike is the most impacted24 component. Then comes the number of spikes per m² You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Discussion

• Pollarding adult trees in an agroforestry field increases the light available to the crop.

• For durum wheat, the crop yield is consequently improved by the pollarding. The most sensitive period for wheat yield elaboration is at flowering, after trees budburst 25

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Discussion • For barley, there is no influence of trees, pollarded or not, on the yield. The barley blossomed around 10 days before the wheat, when the trees budburst just began. • What will be the result for pea ? In 2013 (previous pea cropping), the sole crop control yield was 34.6±1.5 qx.h-1 , while the agroforestry plots was 26.3±2.1 qx.h-1 (76%) in average. The pea seems to be more sensitive than the barley. 26

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Discussion control • The advantage of pollarding for the light transmission pollard

to the crop quickly The 3rd of Sptember 2015 decreases : In average, +5.2 % of shade for pollard trees, +0.1 % for non-pollarded between 2014 and 2015.

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Conclusion • Preliminary experiment, we need to : 1. measure the crop (pea) yield 3 years after pollarding 2. define the pollarding frequency 3. estimate the consequence of pollarding on timber tree production DBH increase (cm) Pollard AF non-pollard 2013-14 0.26 0.79 2014-15 0.68 1.35 4. take into account the energy or mulch product 5. difficulty to calculate a Land Equivalent Ratio: 3 productions, what can be the controls ?

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Thanks to the team

The technicians : J. F. Bourdoncle A. Sellier The researcher : C. Dupraz

The postdoctorants : J. André J. Le Bec

The trainee students : 29 C. Gosset P. Deltour M. Péquignot

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 30

You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)