Permanent raised beds to improve productivity and control salinity in Pakistan

• Pakistan Agricultural Research Council, Pakistan

Waterlogging and salinity exacerbate land degradation problems in Pakistan and Western Australia. Raised beds have been found an effective means of dealing with these problems and in an earlier ACIAR project permanent raised-bed technology, developed for irrigation agriculture, was adapted to improve yields and prevent waterlogging in fragile soils in WA. In this small project scientists assessed the potential of this technology to rehabilitate waterlogged, salt-affected land in Pakistan, increase crop productivity and improve irrigation efficiency. They continued monitoring of permanent raised-bed experimentation in WA

The overall objective was to improve the use of permanent raised beds under both irrigated and dryland conditions. Two sub-objectives were: 1) to use field testing and monitoring to assess the potential of the combination of permanent raised beds and no-tillage crop establishment practice to improve soil conditions, irrigation efficiency and productivity; and 2) to use simulation modelling to identify the soil conditions required to improve irrigation efficiency and control capillary rise, and to assess the extent to which such soil conditions can be created by no-tillage crop establishment practices on raised beds.

Field testing of permanent raised beds on a practical farm-scale was undertaken in Pakistan. Pre-requisites for this work were the export from Australia of specially down-sized machinery for forming, renovating and no-till seeding permanent raised beds, plus the training of Pakistan staff to operate the machinery. The experimental work was undertaken on typical farm fields with experimental areas ranging from 0.5 to 1.0 ha.
There were only two treatments, which were tri-replicated. The treatments applied contrasting soil and water management practices - permanent no-tillage raised beds with furrow irrigation, and cultivated seedbeds in basins with flood irrigation. Soil conditions, plant growth and irrigation applications were monitored. Derived data included soil-water potential gradients, plant water use efficiency, and gross margin profits.
Additional data from self-funded initiatives of the Pakistan collaborators were incorporated into the project. They were obtained from a duplicate set of experiments on a field adjacent to the ACIAR-funded experimental site at Mardan and a program of on-farm demonstrations of the technology.
The Australian work included: supplementary monitoring of the salinity (electrical conductivity) of the 0-30cm depth of soil in permanent raised beds and normal seedbeds; simulation modelling of the effects of varying surface soil conditions on (i) capillary rise from shallow water tables and (ii) infiltration into raised beds. The Australian project team also analysed the data from the continuous monitoring of soil-water content and soil-water potential from the Pakistan experimental area.
The Australian team undertook preliminary work to compile specifications for and/or execute the design of machinery scaled to match the size of field commonly used in Pakistan farming. In addition the team organised the export of the machinery to Pakistan, its assembly and testing and the training of operators in Pakistan.

In just two years this project introduced new technology into Pakistan. Field trials produced the following results: increased productivity of the wheat-maize cropping system by 10-30%; reduced irrigation requirements for wheat and maize by 20-40% and lower risk of aquifer recharge; improve irrigation efficiency and lower risk of salinity. The permanent raised beds provide the methods and means for improving soil conditions, increasing the profitability of the wheat-maize farming system by 20-50%, and providing inexperienced farmers with immediate success that equals or betters the research results.
At Mardan experimental site around 150 km northwest of Islamabad raised beds were prepared and sown to both maize, wheat and rice in different seasons. Data were recorded for yield, water consumption and soil observations for all experiments.
In four experiments with maize the crops grown on raised beds outyielded the maize in traditional basins (29% increase) yet all received less irrigation water (11% less). This was corroborated by farmer field information for Kharif (summer) 2000 where beds yielded 3.45 tonnes per hectare (38% more than the basins) yet the irrigation time per ha was 36% less. Thus gains in water use efficiency were substantial. Some reasons for greater yield on beds were less waterlogging damage and fewer weeds.
Follow-on observations of the experimental sites have shown that over four years summer maize yields on beds yielded 54% higher than on the flat while using 33% less irrigation water. Wheat crops grown on raised beds over a three-year period yielded only 3% above those on the flat, but they needed 37% less water. Nearby farmers who have adopted raised beds are achieving similar efficiency gains with the new system.
These achievements were possible because the machinery required for this technology was successfully downsized to match the small size of paddocks and tractors in Pakistan; and developed to install, seed and renovate raised beds.
In addition, the field monitoring data in Australia, although only exploratory and compromised by the dry seasons, showed indications that salinity may be reduced and controlled in loosened raised beds that have salt levels low enough for plants to grow. This, too, was reinforced by other data. The simulation modelling illustrated that loose soil conditions will substantially reduce capillary rise (and by implication salinity). This modelling work has provided the theoretical basis for selecting soil management treatments for a separate project in Western Australia to adapt raised bed farming to waterlogged and saline sites and so return them to profitable production.