Weed Control and Issues in Developing Countries

Peter R Hobbs

609 Bradfield

Department Crops and Soil Science

Challenge for Agriculture

• To increase food production sustainably to meet food security needs of a growing population now and in the future while at the same time minimizing the effects on the environment and improving the livelihoods of those involved in agriculture

• Improve the efficiency of natural resource use needed for agriculture

Convergence of opinions

• Demand for food - increasing• Harvested area - possibly shrinking• Traditional sources of productivity growth

– are they exhausted?• More competition for blue water• More severe weather as a result of GHG

emissions and global climate change• In addition, there is resource and

environmental degradation?

Resource Poor Farmers?Subsistence Farmers?

• Not produce enough food to feed their family or market any excess. Nutritional quality of food produced can also be poor.

• Lack basic infra-structure to transport, store and sell the food they grow

• Lack income and access to credit to invest in new technology

• Little capacity to manage risks associated with technology

Nepal

Bangladesh

Pakistan

India

South Asia

IGP

Indo-Gangetic Plains• The population of South Asia is over 1.5

billion and increased at 1.8% per year over last 6 years. 27.3 million more mouths to feed each year!! 75K/day; 3,116/hr– (IRAQ = 23 million; NY + Mass = 25m;

• More than 400 million are poor (< $1/day)• The per capita rice-wheat growing areas

have shrunk from 1200 m2 in 1961 to less than 700 m2 in 2000.

• Demand for rice and wheat will grow at 2.5% per year in the next 20 years. This has to come from yield growth.

Source: Indian Census Report

Population Dynamics

200

400

600

800

1000

1200

1400

me

ter

sq

ua

re

19611971198119912001Census years

R+W

Rice

Wheat

Rice plus wheat area per capita

Compound rates of decrease for decade shown as a % per year for rice+wheat area

Population density in RW area of Indo-Gangetic Plains

Source: Dave Hodson, GIS Lab, CIMMYT RW zoneMid-hills NorthTransition South

RW area population = 280 millionRW area pop density = 517 /sq kmGreen area population = 430 millionGreen area pop density = 452 /sq km

Rice-wheat systems in South Asia

• Rice and wheat grown in the same calendar year in S. Asia (13.5 m ha’s)– Rice in the wet monsoon summer and wheat

in the dry cool winter– Rice grown by puddling soil and transplanting

seedlings– This creates a problem for the next wheat

crop because of poor soil physical properties – This also affects soil biology

R-W Systems Calendar

J F M A M J J A S O N D J F M A

Month

Rice

Wheat

Wheat

Rice-1 Rice-2

Wheat

Wheat

There are also rotations of RW with Sugarcane

Rice NR

NR = potato, vegetable, legume, oilseed

WheatWheat

Wheat GM Rice Wheat

Summer Winter

Phalaris minor issue

• This WAS a major problem in NW India and Pakistan in wheat in the 1990’s.

• Herbicide resistant Phalaris to Isoproturon started show in early 1990’s

• It became a major problem by mid-1990’s

• Need for integrated weed management approaches – – rotations, tillage, seed, variety etc.

Promote Integrated Weed Management Systems

• Hand weeding• Rotations – use of a fodder crop• Inter-cultivation• Mulching – allelopathic properties of some

residues and cover crops• Prevent seed set of weeds• Clean seed• Use herbicides when needed in proper manner• Etc.

Crisis in Haryana (and Punjab, UP)

• Herbicide tolerant Phalaris minor seen as early as 1992-93 wheat season

• Crisis level reached by 1995-96

• In affected fields, Phalaris populations up to 3000 plants/ m3 – wheat crop squeezed out

• Problem spreading fast into neighboring states

Photo: LW Harrington

Phalaris minor (little seeded canarygrass)

A desperate search for solutions

• Improved management - crop rotations, timely sowing, clean seed, etc. of limited help

• New herbicides

• Zero tillage (?)

• Major role played by R.K. Malik, Haryana Agricultural University

Photo: LW Harrington

0200400600800

10001200140016001800

1997-98 1998-99 1999-2K 2000-01 2001-02

Year

Ph

alar

is p

op

ula

tio

n (

no

/m2)

4600

4800

5000

5200

5400

5600

5800

Gra

in Y

ield

(kq

/ha)

ZTPOPCTPOPZTYIELDCTYIELD

0200400600800

10001200140016001800

1997-98 1998-99 1999-2K 2000-01 2001-02

Year

Ph

alar

is p

op

ula

tio

n (

no

/m2)

4600

4800

5000

5200

5400

5600

5800

Gra

in Y

ield

(kq

/ha)

ZTPOPCTPOPZTYIELDCTYIELD

Grain yield of wheat and population of Phalaris under zero and conventional tillage.

Another pleasant surprise

• It took the Phalaris crisis for farmers to try no-till

• Result of farmer trials – huge enthusiasm for cost reduction

• Increasing number of projects, farmer trials

• Traveling seminars helped promote awareness in1998

• Private sector kept improving implements

Photo: LW Harrington

Means and ends keep changing!

• No till originally seen as a means of advancing sowing dates

• Breakthrough with farmers came with no-till as a means of helping control Phalaris minor

• Essential local manufacturers were involved and linked to farmers

• Continued farmer interest in no-till as a means of reducing costs

Photo: LW Harrington

New Herbicides

• Topik -- Clodinafop

• Puma -- Fenoxyprop

• Leader – Sulfosulfuron -- Sulfonylurea

• Grasp -- Tralkoxydim

• Need to be applied with a sprayer – low quantities active ingredient used per hectare used (10-50 grams/ha)

No-Tillage with Inverted-T

• Based on inverted-T coulter from NZ

• Good where no loose residues including anchored straw

• Locally made and low cost

• Can adapt present farmer machinery

• Uses 15-25% less water• Less weeds germinate• Service providers means

small farmers can use

No-Till Conventional

Phalaris population over time

0

500

1000

1500

2000

2500

NT CT

Tillage system

Ph

ala

ris

po

pu

lati

on

96-97

97-98

98-99

a1

a

b

b

b

a

Herbicide Application Using Knapsack Sprayers essential

A. Miller and R. Bellinder, Cornell University, in cooperation with Dr. R.K. Malik (HAU), Dr. L.S.

Brar (PAU) G. Singh (GBPUAT Pantnagar) J. Ranjit (NARC) and Dr. P. Hobbs (CIMMYT)

Resource poor farmer systems for herbicide application

Los Banos, Philippines. Puddling rice soils with carabao

Rice planting methods

Weeding in Rice

TaiwanGirls weeding rice

No-till rice-wheat

• In order to get the full benefit of no-till wheat, also need to no-till rice– Problems of weeds because difficult to pond

water when no puddling– Traditionally hand weeded – Tedious and usually done by women

• One solution would be to introduce herbicide resistant rice varieties

• Use of cover crops

Other Future Issues Rice

• Better 0-till and DSR varieties– Oryza sativa by O. glaberimma crosses– Chromosome substitution lines

• Use of Genetic Engineering– Roundup ready rice– Blast resistant rice– Drought tolerant rice

• Improved equipment for seeding rice

Herbicide Tolerant (HT) RiceHerbicide Tolerant (HT) RiceWeed Control: Mechanical, Herbicides

Herbicides: Broad Spectrum – ie. Glyphosate, GlufosinateNarrow Spectrum – ie. 2,4 - D

LD50 = 4320 mg/kgDDT = 115Parathion = 30Bt = >5000

• Gene Source: various bacteria

• How does it work:1. Insert gene for herbicide de-toxification

2. Replace herbicide target with gene that is resistant to herbicide

Herbicide Tolerant (HT) CropsHerbicide Tolerant (HT) Crops

Benefit of HT to Environment?Benefit of HT to Environment?

• Depends on Herbicide not GM Plant

• Post emergence broad spectrum Roundup herbicide replace numerous narrow spectrum herbicides that are more toxic– Depends on breakdown product of herbicide

in plant/soil

• Allows farmer to practice no-till and conservation agriculture practices

Negative issues

• Weeds used for fodder

• Employment of the poor for weeding

• Availability of technology to resource poor farmers:– Credit to buy sprayer and herbicide– Training in proper use– Spurious products on the market– Extension of improved system poor

Maize in Zambia -- Traditional

Zambia – Basin System

Conservation AgricultureConservation AgricultureResidue retention distinguishes Residue retention distinguishes Conservation Agriculture from Conservation Agriculture from conventional farming systems, conventional farming systems,

which are characterized by which are characterized by leaving the soil bare and leaving the soil bare and unprotected, exposed to unprotected, exposed to

climatic agents.climatic agents.The soil cover is not The soil cover is not

incorporated into the soil by incorporated into the soil by tillage.tillage. (FAO, 2002)