Adaptation and improvement of the seed-plot technique in smallholder

potato production

Presentation by

Z.M. KinyuaPlant Pathologist & National Coordinator

Crop Health Programme Kenya Agricultural Research Institute

kinyuazm@gmail.com+254 (0)733 999444

Presentation during the 9th Triennial African Potato Association ConferenceThe Great Rift Valley Lodge, Naivasha, Kenya

30 June-4 July 2013

Common sources of seed potato

Farmers commonly obtain seed potato for planting from:• own previous crop harvests• ‘neighbours’ • market places • Distant potato-producing areas (high altitude zones)

Other sources (Kenya)• KARI (e.g. Tigoni station & its sub-centres)• Agricultural Development Corporation -Molo• Individual private companies (e.g. Kisima Farm, Midlands Ltd)• Farmer groups/CBOs producing clean seed potato• Individual farmers with reputable seed potato

> 95%

< 5%

Different inputs, different expectations

Poor quality seed

Good quality seed

Bacterial wilt - a consequence of planting infected seed tubers

A devastated potato field

A healthy, promising potato crop

The principle

Improving seed potato quality through a seed-plot technique

Site selection for seed-plot establishment

Might be contaminated, especially if low-lying!

Probable sites (bush land, other crops, homestead, etc.)

Schematic presentation of seed-plot practice

Seed plot

Seed plot

Seed plot

Seed plot Main field

Main field

Main fieldMarket or

home consumption

Market or home

consumption

Market or home

consumption

Season 1

Season 2

Season 3

Season 4

(Initial multiplication)

1. Adaptation of potato seedplot technique10 seed-plot trial sites in Kenya, managed by farmer groups:• Kianthumbi - 3 seed plots • Mutethia Mbuyene - 3 seed plots • Kibaranyaki - 3 seed plots • Muchicha - 3 seed plots

Done during the 2010 long rains season (April-July) Repeated during the 2010 short rains (October-December)

5 seed plots hosted by farmer groups for three seasons (2010-2011)in Uganda:• Rushebeya • Kayanga • Kyambura • Burema • Mpangango

Productivity assessed by determining tuber yields (number & weight per unit area)

Methodology

Active participation of a farmer group in establishment of a potato seed plot

Establishing a potato seed plot

• A well-dug bed (loosened soil)

• Narrow bed marked (1.8m width) to avoid stepping in when working.

• Fertilizer applied (DAP - 18: 46: 0) and raked in.

• Furrows made and tubers placed at a spacing of 30cm by 30cm.

Methodology (cont’d)

Established potato seed plots

2. Effect of fertilizer application in potato seed plots

General informationCultivar used: Asante Trial location: Abo West Division, Meru Central District, Kenya. Seedplot size: 2.4m by 1.8mSpacing: 30x30cm

thus accommodating 8 rows of 6 tubers (48 plants) per plot.

Two fertilizer types:diammonium phosphate, DAP (18: 46: 0) Mavuno Planting (10: 26: 10)

Three fertilizer rates:no fertilizer application (0kg N/ha), DAP low level (45kg N/ha)DAP high level (90kg N/ha)

Methodology (cont’d)

CountryTrial site (Group name or host farmer)

%Small tubers

%Medium tubers

%Large tubers

Tubers/m2

Multiplication ratio

Yield (t/ha)

Kenya Muchicha (Munyugi P) 5.99 54.43 39.58 49.4 4.5 41.7Kenya Muchicha (Bundi H) 7.16 61.30 31.54 48.5 4.4 32.1Kenya Kianthumbi (Kimathi S) 10.33 70.41 12.37 54.4 4.9 28.4Kenya Kianthumbi (Kaimenyi E) 5.27 71.14 23.60 62.7 5.6 40.7Kenya Kianthumbi (Kinoti R) 5.51 60.64 33.84 44.5 4.0 45.1Kenya Mutethia Mbuyene (Wambui) 6.84 56.16 36.94 65.9 5.9 69.8Kenya M Mbuyene (Mbijiwe T) 7.45 54.02 33.69 41.5 3.7 44.6Kenya M Mbuyene (Kinya M) 5.85 67.02 26.61 60.4 5.4 40.7Kenya Kibaranyaki (Murithi I) 8.96 66.92 24.12 28.6 2.6 21.6Kenya Kibaranyaki (Agwima S) 8.52 67.41 27.58 39.7 3.6 30.9Uganda Kyambura 20.16 75.22 4.63 54.7 4.9 45.1Uganda Kayanga 26.45 66.19 7.36 69.6 6.3 74.1Uganda Rushebeya 20.35 73.74 5.91 40.0 3.6 21.6Uganda Burema 29.49 61.22 9.29 63.6 5.7 66.4Uganda Mpangango 49.35 45.86 4.79 47.2 4.3 15.1

ResultsSeed-plot potato yields in various sites in Kenya and Uganda

• Productivity of seed plots: 28.6 to 69.6 tubers/m2

• Mean multiplication ratio: up to 6 tubers per plant.

• Yield in most of the sites was above 40 tonnes/ha.

indicating that the technique was easily adaptable in many areas

• Sites that had low yields also had poor tuber multiplication ratios.

Results (cont’d)

Fertilizer regime

Number of tubers by size

Total tubers

Total tuber yield (kg)

Average weight

per tuber (g)

Tuber multiplication rate

Small Medium Large Zero 32.25a 102.50a 12.50a 147.25a 3.80a 25.82a 4.09a

DAP-Low 23.25a 163.25b 33.75ab 220.25b 10.16b 46.12b 6.12b

DAP-High 31.50a 162.00b 43.00b 236.50b 12.04b 50.93b 6.57b

Mavuno-Low

29.75a 155.75b 30.75ab 216.25b 10.35b 47.85b 6.01b

Mavuno-High

26.75a 133.50ab 49.25b 209.50b 11.14b 53.19b 5.82b

Note: The parameters are taken from plots measuring 1.8 x 2.4m (4.32m2)

Tuber productivity in seed plots with different fertilizer application regimes

Results (cont’d)

0

10

20

30

40

50

60

70

80

Small Medium Large

Seed size categories

Prop

ortio

n of

tota

l tub

ers

(%)

ZeroDAP-LowDAP-HighMavuno-LowMavuno-High

Potato tuber sizes under different fertilizer application regimes

Results (cont’d)

• Seed-size (medium) tuberslow DAP & low Mavuno more than DAP-high and Mavuno Planting-high

• Ware-size (large) tubers:high DAP and high Mavuno Planting more than DAP-low and Mavuno Planting-low

No. of tubers and corresponding total tuber yield in plots without fertilizer was significantly lower than fertilized plots.

The fertilized plots did not differ significantly across all the treatments

Results (cont’d)

ConclusionThe seed-plot technology, with improved productivity through fertilizer application, can increase the availability of quality seed potato.

RecommendationThe seed-plot technology should be widely promoted, especially in smallholder farming systems where frequent replenishment of seed stocks is hampered by financial inadequacies.

Discussions/clarifications

Seed plot measurements

Estimated amount of seed to plant in a seed plot

Size of ware potato field to be covered with seed

from a seed plotWidth

(m)Length

(m)Number of

tubersWeight (kg) Acres Hectares

1.81.81.81.81.81.81.8

4.592132436486

90180420640860

12801720

6-712-1528-3543-5358-7186-106115-143

0.10.20.5

0.751

1.52

0.040.080.200.300.400.610.81

Approximate seedplot sizes to produce adequate seed tubers for ware fields

Thank you• ASARECA• KARI and other host institutions • Participating farmer groups • Organizers, 9th Triennial APA Conference• Sponsors, 9th Triennial APA Conference• The Session Participants

Z.M. Kinyua