Summary

Description

A simple, inexpensive and practical method for raising healthy plant seedlings

During the winter in Nepal’s middle mountains, the soil temperature generally remains at 5-10 degree celsius above the ambient air temperature. This principle was used to design a simple, inexpensive, and effective nursery technology for raising vegetable and horticulture seedlings in colder regions. The polypit technology allows seedlings to be raised by protecting them from the freezing temperatures that occur mostly at night.
Polypits are about 1m deep pits dug into the ground and covered with semitransparent polythene sheets, preferably UV stabilised and supported on bamboo frames. A 30 cm high mud wall is built across the slope on the upper side of the pit. The polythene sheet is sealed on the upper side of the pit, leaving three sides unsealed but held down with stones that can be lifted to access the pit. The base and sides of the polypit are left as they are with no form of plastering.
The polythene sheet covering the pit reduces the photosynthetic photon flux (PPF) by around 30% inside the pit, still allowing sufficient sunlight to reach the plants inside. The polythene is usually removed during the day from 11 am to 4 pm to allow full sunlight to reach the plants except on rainy and very cold days. A modified version of these polypits - only 70 cm deep - were used in the Jhikhu Khola watershed to grow vegetable seedlings during the winter. The pits can be made of any reasonable size depending on the number of seedlings to be grown and the layout of the land. The Jhikhu Khola pits were about 3m long, 1.5m wide, and 0.7m deep.
Since the polypits are closed at night, the CO2 released by the plants and soil microbes accumulates and increases to well above levels outside the pit. In a completely sealed polypit, the CO2 concentration could reach up to 3000 ppm during the night which would be harmful for plants. Thus the polythene cover is only loosely sealed along the edges at night to regulate and maintain the concentration of CO2 at about two to four times the ambient concentration.
The warmer protected conditions and CO2 enrichment leads to extra growth and biomass gain for plants grown inside the pits during the winter. This technology is easy to maintain with the only maintenance costs being to repair damaged polythene sheets and frames.
The polypit technology is useful for mountain farmers where water scarcity and low temperatures limit the potential to raise quality seedlings. The technology is being promoted in the northwest Indian state of Uttarakhand, although only a few farmers have adopted it so far. It is a very promising technology and its use should be encouraged by hill farmers and research and development organisations engaged in raising seedlings. The technology needs more participatory action research to improve it and to encourage more farmers to adopt it spontaneously.

Location

Location: Kavrepalanchowk district/Jhikhu Khola watershed, Nepal

No. of Technology sites analysed:

Geo-reference of selected sites

85.68449, 27.68362

Spread of the Technology: applied at specific points/ concentrated on a small area

In a permanently protected area?:

Date of implementation: less than 10 years ago (recently)

Type of introduction

through land users' innovation
as part of a traditional system (> 50 years)
during experiments/ research
through projects/ external interventions

Classification of the Technology

Main purpose

improve production
reduce, prevent, restore land degradation
conserve ecosystem
protect a watershed/ downstream areas – in combination with other Technologies
preserve/ improve biodiversity
reduce risk of disasters
adapt to climate change/ extremes and its impacts
mitigate climate change and its impacts
create beneficial economic impact
create beneficial social impact

Land use

Cropland
- Annual cropping: cereals - maize, legumes and pulses - other, oilseed crops - sunflower, rapeseed, other, vegetables - other, rice, wheat
Number of growing seasons per year: 3

Water supply

rainfed
mixed rainfed-irrigated
full irrigation

Purpose related to land degradation

prevent land degradation
reduce land degradation
restore/ rehabilitate severely degraded land
adapt to land degradation
not applicable

Degradation addressed

SLM group

full year planting

SLM measures

structural measures - S4: Level ditches, pits

Technical drawing

Technical specifications

Poly pit covered with semi transparent plastic sheet which is supported on a bamboo farme.

Technical knowledge required for field staff / advisors: low

Technical knowledge required for land users: low

Main technical functions: protecting seedlings from frost, reduction of water loss, carbon dioxide enrichment

Structural measure: pit
Depth of ditches/pits/dams (m): 0.7m
Width of ditches/pits/dams (m): 1.5 m
Length of ditches/pits/dams (m): 3 m

Construction material (earth): a mud wall is made about 30 cm high from the ground, sloping on the two sides.

Construction material (wood): to place semi transparent plastic on a frame.

Construction material (other): plastic sheet: to cover the pit, rope, wire: frame preparation

Author: Madhav Dhakal, A.K. Thaku

Establishment and maintenance: activities, inputs and costs

Calculation of inputs and costs

Costs are calculated: per Technology unit (unit: Polypit nursery)
Currency used for cost calculation: USD
Exchange rate (to USD): 1 USD = n.a
Average wage cost of hired labour per day: 2.10

Most important factors affecting the costs

The plastic sheet , but it is easily affordable by the land users.

Establishment activities

Determine the appropriate size (length, width and depth) of the pit (Timing/ frequency: beginning of the winter season)
Mark the area for soil excavation (Timing/ frequency: beginning of the winter season)
Excavate soil from the marked area (Timing/ frequency: beginning of the winter season)
Make a mud wall (~30 cm high) from the ground, sloping on two sides (Timing/ frequency: beginning of the winter season)
Make a bamboo fram of an appropriate size (Timing/ frequency: beginning of the winter season)
Lay the frame over the pit with one end resting on the mud wall (Timing/ frequency: beginning of the winter season)
Lay the plastic sheet over the frame (Timing/ frequency: beginning of the winter season)
Seal the polythene sheet on the higher side of the mud wall and leave three sides unsealed (Timing/ frequency: beginning of the winter season)
Lay the other three sides of the polythene sheet normally at ground level and weigh down with stones that can be removed to access the pit (Timing/ frequency: beginning of the winter season)
The base and sidesof the polypit do not need any form of plastering (even with mud) (Timing/ frequency: beginning of the winter season)

Establishment inputs and costs (per Polypit nursery)

Specify input	Unit	Quantity	Costs per Unit (USD)	Total costs per input (USD)	% of costs borne by land users
Labour
Construction of polypit nursery	Persons/unit	1.0	2.1	2.1	100.0
Construction material
Plastic	unit	1.0	4.0	4.0
Bamboo	unit	1.0	1.3	1.3	100.0
Rope	unit	1.0	0.2	0.2	100.0
Total costs for establishment of the Technology				7.6
Total costs for establishment of the Technology in USD				7.6

Maintenance activities

The polythene cover is opened to acclimatized the plants to the outside environment (Timing/ frequency: 11:00- 16:00/Every day)
Cleaning the pit (Timing/ frequency: After trasplanting the seedlings/ once or twice in)
Replacing the frame and polythene sheet if it gets damaged. (Timing/ frequency: before raising nursery/In case of damage)

Maintenance inputs and costs (per Polypit nursery)

Specify input	Unit	Quantity	Costs per Unit (USD)	Total costs per input (USD)	% of costs borne by land users
Labour
Maintaining the pit	Persons/unit	1.0	2.1	2.1	100.0
Total costs for maintenance of the Technology				2.1
Total costs for maintenance of the Technology in USD				2.1

Natural environment

Average annual rainfall

< 250 mm
251-500 mm
501-750 mm
751-1,000 mm
1,001-1,500 mm
1,501-2,000 mm
2,001-3,000 mm
3,001-4,000 mm
> 4,000 mm

Agro-climatic zone

humid
sub-humid
semi-arid
arid

Specifications on climate

Average annual rainfall in mm: 1200.0
Thermal climate class: subtropics

Slope

flat (0-2%)
gentle (3-5%)
moderate (6-10%)
rolling (11-15%)
hilly (16-30%)
steep (31-60%)
very steep (>60%)

Landforms

plateau/plains
ridges
mountain slopes
hill slopes
footslopes
valley floors

Altitude

0-100 m a.s.l.
101-500 m a.s.l.
501-1,000 m a.s.l.
1,001-1,500 m a.s.l.
1,501-2,000 m a.s.l.
2,001-2,500 m a.s.l.
2,501-3,000 m a.s.l.
3,001-4,000 m a.s.l.
> 4,000 m a.s.l.

Technology is applied in

convex situations
concave situations
not relevant

Soil depth

very shallow (0-20 cm)
shallow (21-50 cm)
moderately deep (51-80 cm)
deep (81-120 cm)
very deep (> 120 cm)

Soil texture (topsoil)

coarse/ light (sandy)
medium (loamy, silty)
fine/ heavy (clay)

Soil texture (> 20 cm below surface)

coarse/ light (sandy)
medium (loamy, silty)
fine/ heavy (clay)

Topsoil organic matter content

high (>3%)
medium (1-3%)
low (<1%)

Groundwater table

on surface
< 5 m
5-50 m
> 50 m

Availability of surface water

excess
good
medium
poor/ none

Water quality (untreated)

good drinking water
poor drinking water (treatment required)
for agricultural use only (irrigation)
unusable

Water quality refers to:

Is salinity a problem?

Occurrence of flooding

Species diversity

high
medium
low

Habitat diversity

high
medium
low

Characteristics of land users applying the Technology

Market orientation

subsistence (self-supply)
mixed (subsistence/ commercial)
commercial/ market

Off-farm income

less than 10% of all income
10-50% of all income
> 50% of all income

Relative level of wealth

very poor
poor
average
rich
very rich

Level of mechanization

manual work
animal traction
mechanized/ motorized

Sedentary or nomadic

Sedentary
Semi-nomadic
Nomadic

Individuals or groups

individual/ household
groups/ community
cooperative
employee (company, government)

Gender

women
men

Age

children
youth
middle-aged
elderly

Area used per household

< 0.5 ha
0.5-1 ha
1-2 ha
2-5 ha
5-15 ha
15-50 ha
50-100 ha
100-500 ha
500-1,000 ha
1,000-10,000 ha
> 10,000 ha

Scale

small-scale
medium-scale
large-scale

Land ownership

state
company
communal/ village
group
individual, not titled
individual, titled

Land use rights

open access (unorganized)
communal (organized)
leased
individual

Water use rights

open access (unorganized)
communal (organized)
leased
individual

Access to services and infrastructure

Impacts

Socio-economic impacts

land management

hindered

simplified

the pit interrupted land preparation

farm income

decreased

increased

Socio-cultural impacts

SLM/ land degradation knowledge

reduced

improved

About the polypit and their advantages

Ecological impacts

soil moisture

decreased

increased

Inside the polypit high relative humidity is maintained.

Protection of seedlings against frost

low

high

Quality of seedlings

reduced

improved

customers prefer to buy seedlings grown in polypits compared to those grown outside

Off-site impacts

Conclusions and lessons learnt

Strengths: land user's view

The survival rate for vegetable seedlings is higher and seedlings mature about two weeks earlier than if grown outside where they take about one month to be ready, leading to additional income for farmers

How can they be sustained / enhanced? Every aspect of the technology should be highlighted through experience sharing programmes

Strengths: compiler’s or other key resource person’s view

Polypits are a simple, inexpensive, practical and effective technique for raising and protecting plant seedlings from severe winter temperatures.They can be called ‘poor farmers greenhouses’

How can they be sustained / enhanced? More dissemination and awareness raising activities are needed to inform more farmers about the benefits of this technology
The high relative humidity in polypits means that watering only needs to be carried out once or twice a month in comparison to fi ve to six times for open nursery beds, thus saving labour and water

How can they be sustained / enhanced? Every aspect of the technology should be highlighted through experience sharing programmes
The more physical conditions and CO2 enrichment in the pits during the winter months are refl ected in the extra growth and biomass gain of plants grown inside the pits

How can they be sustained / enhanced? As above

Weaknesses/ disadvantages/ risks: land user's viewhow to overcome

In the demonstration, the bamboo frame to hold the sheet was too heavy making it diffi cult for the farmer to remove the frame and work inside. Use a modifi ed frame with a space built in to allow a person to enter the pit easily without having to remove the frame.

Weaknesses/ disadvantages/ risks: compiler’s or other key resource person’s viewhow to overcome

In completely sealed polypits, the CO2 concentration can become so high during the night that it harms the plants Only loosely seal the sheet at night to regulate and maintain the CO2 concentration

References

Compiler

Madhav Dhakal

Editors

Reviewer

David Streiff
Alexandra Gavilano

Date of documentation: June 7, 2011

Last update: June 4, 2019

Resource persons

Sanjeev Bhuchar - SLM specialist
Isabelle Providoli - SLM specialist
Madhav Dhakal - SLM specialist

Full description in the WOCAT database

https://qcat.wocat.net/en/wocat/technologies/view/technologies_1498/

Linked SLM data

n.a.

Documentation was faciliated by

Institution

ICIMOD International Centre for Integrated Mountain Development (ICIMOD) - Nepal

Project

n.a.

Key references

Bhuchar, S. (2004) Polypit: a Green-chamber for Poor Farmers, an article prepared for PARDYP Quarterly e-Newsletter-8, ICIMOD, Kathmandu: ICIMOD
Palni, L.M.S.; Bhuchar, S.; Kothyari, B.P. (1994) ‘A Simple Polypit can Greatly Reduce Nursery Time of Tree Seedlings”. In Journal of HIMA-PARYAVARAN, 6(2):10-11: GBPIHED- Almora
Vyas, P.; Bisht, M.S.; Bhuchar, S.; Sharma, S.; Palni, L.M.S. (1999) ‘Polypit: An Improved Technique for Raising Nursery Plants’. In Journal of Sustainable Forestry, 8(1): 43-59: GBPIHED- Almora

Polypit nursery (Nepal)