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The 2 nd International Conference on: Novel and Sustainable Weed Management in Arid and Semi-Arid Agro-Ecosystems. Factors affecting soil sub-surface phase of purple nutsedge ( Cyperus rotundus ) development. Tal Naamat 1,2 , Hanan Eizenberg 1 and Baruch Rubin 2

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slide1

The 2nd International Conference on: Novel and Sustainable Weed Management in Arid and Semi-Arid Agro-Ecosystems

Factors affecting soil sub-surface phase of

purple nutsedge (Cyperus rotundus) development

  • Tal Naamat1,2, Hanan Eizenberg1 and Baruch Rubin2

1 NeweYa’ar Research Center, ARO; 2The faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot

slide2

The problem:

Purple nutsedge

A troublesome weed

causes heavy damages

in irrigated summer crops

Photographed by Baruch Rubin

A sweet potato field in Israel infested with purple nutsedge

slide3

The biology:

Mostly vegetative reproduction

by tubers and bulbs

The tuber contain many buds

It can survive in moist soil long time

Although the sub-surface

development affects the above ground growth

the knowledge of the factors affecting the soil sub-surface development of purple nutsedge is limited

slide4

Temperature:

  • Temperature is considered as a main regulator in purple nutsedge development
  • Based on preliminary experiments, temperature data can be converted to physiological age (thermal time) units, expressed in Growing Degree Days (GDD)
slide5

Objectives:

  • To study the effect of various environmental conditions on key stages in the sub-surface development of purple nutsedge
  • Specifically, to study the effect of:
  • Temperature
  • Radiation
  • Tuber burial depth
  • Desiccation
  • To appoint the development on a time course of GDD
slide7

1. Sprouting:

Temperature

Desiccation

Depth

slide8

The relations between temperature and sprouting were addressed for developing a prediction means for purple nutsedege sprouting

The effect of temperature on sprouting

Heat Source

80-120 GDD at sprouting

R2=0.86; P<0.0001

30 35 40 45 50 55

Temperature (°C)

slide9

1. Sprouting:

Temperature

Desiccation

Depth

slide10

The effect of desiccation on sprouting

Thermal time (GDD) accumulation

Time (Days)

15°C

20°C

25°C

30°C

35°C

the effect of desiccation on sprouting
The effect of desiccation on sprouting

R2=0.95; P<0.0001

R2=0.9; P<0.0001

Later than 200 GDD

A tuber loses 55% of its biomass

It has 30% chance to sprout

slide12

Illustration

Illustration

slide14

Irrigation at 200 GDD

Control

90-100% sprouting

30% sprouting

slide15

1. Sprouting:

Temperature

Desiccation

Depth

slide16

The effect of tuber burial depth on sprouting

Tested in 2 methods:

Minirhizothron

experiment

Field

experiment

30

20

Bud elongation(mm)

Heterogeneous temperature regime

Homogeneous temperature regime

10

50 cm

2

3

4

Days from burial

slide17

The effect of tuber burial depth on sprouting

Field expt.

Minirhizothron expt.

N.S

LSD

4 DAP

4 DAP

N.S

LSD

Sprouting (%)

7 DAP

7 DAP

N.S

N.S

11 DAP

11 DAP

Tuber’s depth (cm)

slide19

2. Underground biomass accumulation

3. Tuber production

Temperature

Radiation

slide20

The effect of radiation on tuber production

  • Natural sun light
  • 35% shade
  • 60% shade
  • 90% shade

Control

35%

60%

90%

slide21

The effect of radiation on tuber production

Temperature and radiation are key factors affecting the sub-surface biomass accumulation

Therefore, both factors and their interactions must be taken into consideration when developing a mathematical predictive model for the sub-surface growth of purple nutsedge

slide22

Conclusions:

  • The sub-surface development of purple nutsedge is environmental related
  • The effect of sub-surface biomass accumulation on shoots biomass
  • accumulation can be quantified
  • The combined effects can be theoretically integrated for the entire model on a GDD time course
  • This empirical model must be validated in field conditions
slide23

The predictive model might be of use as a tool in control management; e.g. – to imply on the optimal time frame of control

Emergence of deep tubers

Beginning of tuber production

Average time of sprouting

Thermal time frame of control

0

100

300

400

GDD

slide24

Thanks…

  • My advisors – HananEizenberg and Baruch Rubin
  • EWRS - for funding my trip
  • NeweYa’ar, the Department of Weed Research:
  • Joseph Hershenhorn, Radi Ali, Daniel Joel,
  • Evgeny Smirnov, Tal Lande, Guy Achdari,
  • EvgenyaDor, Dina Plakhin
  • The Faculty of Agriculture,
  • Weed Lab
  • My fellow students