China - 膜下滴灌
Drip irrigation under plastic mulch, associated with drainage, to reduce water demand and improve cotton yields in Xinjiang Province, China.
The dry climate and the long hours of sunshine make Xinjiang especially suitable for production of high quality cotton, and as a result some 40% of China’s cotton is grown here. But there are two main problems: shortage of water and salinization of the soil.
Farmers who use the traditional flood irrigation method, and don’t have a drainage system, tend to abandon their fields when they become too saline - and then they look for new land to cultivate. A combination of mulching and drip irrigation can be very effective but still needs careful management. Drip irrigation helps to save water for farmers - and for the environment. But it is still very important to install a drainage system to dispose of surplus water in order to reduce the risk of salinization of the soils. Every four cotton rows are covered with transparent polyethylene film and as a result approximately 80% of the ground surface is covered by the plastic mulch.
Plastic mulch and drip lines are placed with a specially equipped tractor.
Low temperatures and dry soil at sowing, in combination with soil salinity, hinder early plant growth. Plastic mulching increases soil temperature, reduces the need for irrigation, and also helps control salinity in the root zone and suppresses weeds, thereby increasing yields by 10–30% (and improving quality also) (Wang, R. et al., 2011). In the first stages after sowing the climate is particularly cold. With plastic mulching the cotton plants can be sown earlier, because the soil will not cool down during the night as much as without plastic mulch.
For the establishment of the new technology of drip irrigation under plastic mulch, it is simultaneously essential to install a drainage system to avoid raising the groundwater level and causing salinity. For the installation of the drip lines, the transparent plastic film and the seeding, a tractor and a special tool for the installationis needed: one acre can be installed in a day. After the emerging of the cotton plants, holes must be cut in the plastic film so that the cotton plants can emerge. After harvesting, the drip lines and the plastic film must be collected and recycled. If the plastic is left behind it will pollute the soils and injure livestock if they eat it. Furthermore plastic residues in the soil can reduce subsequent yields, as roots are physically inhibited. After the collection of the plastic residues, if there is no adequate drainage system, the field needs to be flooded to flush the salt layer, which has accumulated below the root zone, deeper into the soil. If the field is not flooded the salt will negatively affect the next years’ cotton plantation.
Southern Xinjiang is an arid region with 50 to 90 mm per year. Most precipitation occurs between June and August. It is classified as a temperate cold desert climate.
For drip irrigation under plastic mulch, it is principally surface water that is used, which is delivered to the field via channels from reservoirs to the fields. The reservoirs are filled in summer with the floods along the Tarim River. The untreated surface water is of poor quality - for agricultural use only. For drip irrigation, the water needs to be treated to avoid blocking the drip outlets. The overall technology is expensive, and only land user groups and communities can afford the machines and the materials.
left: Overview of the drip irrigation system under plastic mulch. (Photo: Shamaila Zia-Khan).
right: Detailed view of the system. The large black hoses provide the main water supply for the whole irrigation system. (Photo: Shamaila Zia-Khan).
Location: China / Xinjiang Province Region: Tarim River Basin Technology area: > 10,000 km2 Conservation measure: management Stage of intervention: mitigation / reduction of land degradation
Origin: developed through experiments / research, recent (<10 years ago); externally / introduced through project, recent (<10 years ago)Land use type: cropland: annual cropping (cotton); forest: natural vegetation (before) Climate: arid, temperate
WOCAT database reference: T_CHN057en Related approach: none
Compiled by: Christian Rumbaur, Technical University of Munich, Chair of Hydrology and River Basin Management, 80333 München, [email protected]
Date: 14thMay 2015, updated August 2016
SLM Technologies – Drip irrigation under plastic mulch for cotton production in Xinjiang province, China
Soil depth (cm) 20-500-20 50-80 80-120
>120
Growing season(s): 220 days(March to October with irrigation)
Soil texture: coarse / light (sandy), medium (loam) Soil fertility: medium, low
Topsoil organic matter: low (<1%) Soil drainage/infiltration: medium
Soil water storage capacity: high, medium Ground water table: < 5 m, 5 - 50 m Availability of surface water: good Water quality: poor drinking water
Tolerant of climatic gradual change and extremes: temperature increase, seasonal rainfall increase, seasonal rainfall decrease, wind storms / dust storms, droughts / dry spells, decreasing length of growing period
Sensitive to climatic gradual change and extremes: heavy rainfall events (intensities and amount), floods If sensitive, what modifications were made / are possible: not to use this technology in flood-prone areas Classification
Land use problems: Water use conflicts between agriculture and natural vegetation, soil salinization, desertification (expert's point of view). Soil salinization and water shortage (land user's point of view).
Land use Climate Degradation Conservation measure
cropland: annual cropping , forests / woodlands: riparian forest / natural vegetation (before), level, major change in timing of activities
Stage of intervention Origin Level of technical knowledge
Prevention
Introduced by state specialists: 10-50 years ago
Agricultural advisor Land user
Main causes of land degradation:
Direct causes - Human induced: soil management, crop management (annual, perennial, tree/shrub), deforestation / removal of natural vegetation (incl. forest fires), over abstraction / excessive withdrawal of water (for irrigation, industry, etc.).
Direct causes - Natural: wind storms / dust storms, droughts.
Indirect causes: population pressure, land tenure, poverty, education, access to knowledge and support services.
Main technical functions:
− increase of water use efficiency
− increase of biomass (quantity)
− improvement of ground cover / reduces evapotranspiration
Secondary technical functions:
− improvement of surface structure (crusting, sealing)
− increase / maintain water stored in soil
Environment Natural Environment Average annual rainfall
(mm) Altitude (m a.s.l.) Landform Slope (%)
SLM Technologies – Drip irrigation under plastic mulch for cotton production in Xinjiang province, China 185 Human Environment
Cropland per household (ha) <0.5 (household) 0.5-1
1-2 2-5
5-15 (enterprise) 15-50
50-100 100-500 500-1,000 1,000-10,000 >10,000
Land user:groups / community, medium scale land users, average land users, mainly men Population density: 10-50 persons/km2 Annual population growth:> 4%
Land ownership: state
Land use rights: leased (all the land belongs to the state. Farmers have the right to use the land for 70 years).
Water use rights: leased
Relative level of wealth: very rich, which represents 5% of the land users; 10% of the total area is owned by very rich land users
Importance of off-farm income: less than 10% of all income is in form of remittances: Farmers who have not implemented the drip irrigation under plastic mulch also generate off-farm income.
Access to service and infrastructure: moderate:
technical assistance, employment (e.g. off-farm), drinking water and sanitation, financial services;
high: health, education, market, energy, roads &
transport
Market orientation: commercial / market Mechanization: manual labour
Livestock grazing on cropland: yes
Technical drawing
There are double rows of cotton 20 cm apart, with a drip line between. 40 cm then separates each double row. Two double rows are covered by one length of plastic mulch. There is a small strip of bare soil between each length of plastic mulch. Mulch covers around 80% of the soil surface (Shamaila Zia-Khan).
Implementation activities, inputs and costs
Establishment activities Establishment inputs and costs per ha
1. Tractor for field preparation
2. Initial drip line and plastic mulch installation Inputs Costs (US$) % met by
land user
Labour 3.00 100%
Equipment
− tractor use 5.00 100%
Other
− transparent plastic mulch 32.00 50%
− black drip lines 380.00 50%
TOTAL 420.00 50.59%
Maintenance/recurrent activities Maintenance/recurrent inputs and costs per ha per year 1. Ploughing and levelling of field.
2. Installation of drip lines, plastic mulch and seeding of (cotton) plants.
3. Making holes for the (cotton) plants in the plastic mulch.
4. Maintaining hoses 5. Irrigation
6. Removal of the drip lines and the plastic mulch
7. Flooding after harvest/ flushing or salt into lower soil layers
Inputs Costs (US$) % met by
land user
Labour 5.00 100%
Agricultural
− seeds 90.00 100%
− irrigation and flooding water
(pumps) 8.00 100%
Other
− transparent plastic mulch 32.00 100%
− black drip lines 380.00 100%
TOTAL 515.00 100%
Remarks:
The costs for the machine, the plastic hoses and the plastic mulch are calculated above are for 1 ha and were calculated on the basis of 2013 (subsequently costs have risen). Water price: 0.019 CNY/m3. Farmers need 3000 m3per ha.
Assessment
Impacts of the Technology
Production and socio-economic benefits Production and socio-economic disadvantages reduced demand for irrigation water
increased crop yield
increased expenses on agricultural inputs increase of salinization below root zone
Socio-cultural benefits Socio-cultural disadvantages
worse situation of disadvantaged groups
Ecological benefits Ecological disadvantages
reduced evaporation improved soil cover
reduced soil loss from wind erosion
increased salinity, if no drainage system is installed in the field
Off-site benefits Off-site disadvantages
reduced wind transported sediments Contribution to human well-being/livelihoods
Applying this technology saves farmers water and thus money.
Benefits/costs according to land user Benefits compared with costs short-term: long-term:
Establishment slightly negative positive Maintenance/recurrent slightly negative positive
Acceptance/adoption: 100% of land user families have implemented the technology with external material support. The government gives subsidies to the farmers to install the drip irrigation under plastic mulch. No land user families have implemented the technology voluntarily. The government’s strategy is to spread the technology over the whole region by giving subsidies to the farmers.
Concluding statements
Strengths and how to sustain/improve Weaknesses and how to overcome It helps to save water during the growing period and thus helps to
reduce conflicts between upstream and downstream farmersThe technology (drip + mulch) needs to be supplemented by installing a drainage system in the fields otherwise there will be a build-up of salinity and farmers will abandon land and move on.
Helps to save water thus saves costsIt is subsidised by the government
Salinization of the soils is increasing The consequence is that the fields are flooded after harvest in November/December to leach out the salt. The water used for drip irrigation plus the water to flush the salts to lower soil layers add up to almost the same amount as if farmers were using the original flood irrigation technology drainage system in the fields required
Key reference(s): Zia-Khan,S., Spreer, W., et al. (2015) Effect of dust deposition on stomatal conductance and leaf temperature of cotton in Northwest China. Water 2015, 7, 116-131; doi: 10.3390/w7010116. www.mdpi.com/journal/water open access
Contact person(s): Christian Rumbaur, Technical University of Munich, Chair of Hydrology and River Basin Management, Arcisstr. 21, 80333 München, Email:
[email protected] • Joachim Müller, University of Hohenheim, Institute of Agricultural Engineering in the Tropics and Subtropics, Grabenstr. 9, 70599 Stuttgart, Email: [email protected] • Shamaila Zia-Khan, University of Hohenheim, Institute of Agricultural Engineering in the Tropics and Subtropics, Grabenstr. 9, 70599 Stuttgart, Email: [email protected]
187