Weed competition and conservation agriculture for smallholders: Insights from

maize systems in the hills of Nepal

Tika Karki1, Andrew McDonald2 and Adam Davis*3 1Tribhuvan University, Kathmandu; 2CIMMYT, South Asia Regional

Office; 3USDA-ARS Global Change and Photosynthesis Research Unit

Context

Multi-phase study

• Farmer survey (2009):– labor, food security, fertility, cultivars, weeds

• On-farm (2010): – observations of farmer practices vs. BMPs

• On-station (2009-present):– replicated CA cropping system trials

Farmer survey

77 householdsin Myagdi,Baglung andParbat

Finger millet (Eleusine coracana)

Maize

Finger millet

cultivation,followed byfingermilletplanting, 60-90 DAPpre-tasselingin maize

Planting Hand-weeding30 DAP

urea 10-15dbefore millet

On-farm trials

Weed population densityParbat: 688 plants m-2

Baglung: 1244 plants m-2

Gra

in y

ield

(kg

ha-1

)

0.6

0.9

1.2

1.5

Weed free FP Weed free FP

Parbat Baglung

Solid line inside the box indicates median and the dotted mean

Millet

Crop population

Plan

t pop

ulat

ion

(ha

-1)

30000

35000

40000

45000

50000

55000

60000

65000

70000

20 DAE At harvest 20 DAE At harvest

Parbat Baglung

Solid line inside the box indicates median and the dotted mean

Parbat Baglung Myagdi

Th

inn

ing

(d

ays a

fete

r e

me

rgn

ece

)0

10

20

30

40

50

60

70First SecondThird

DistrictsN = 25 N = 23 N = 29

BMP: 52,000 plants +/- 150 ha-1

Farmer: 36,900 +/- 500 plants ha-1

BMP FarmerCrop population (practice)

0

1

2

3

4Y

ield

(M

g/h

a)

Maintaining maize cropat recommended populationdensity resulted in a yieldincrease of over 160%compared to the farmerpractice of heavy thinning.

On-station trial (2009-present)

• Maize-rice crop rotation• Split plot design with full factorial of:

– Tillage (main): no-till, conventional (ox-drawn plow)

– Residue Retention (split): removed, 40 cm– Soil fertility (split-split): farmer practice (FYM),

BMP: FYM + Urea (110 kg N ha-1)