Conventional flooded and puddled rice systems on flat land are detrimental to the growth of post-rice crops, and also require enormous amounts of energy for tillage in switching between rice and wheat crops. Permanent beds are a radical change in practice, offering the possibility of providing and maintaining suitable soil conditions for the growth of both rice and wheat crops in the rotation, increased cropping flexibility, minimum tillage, increased water-use efficiency and reduced deep percolation losses. Over the past three decades, rice-wheat cropping has assumed vital significance in the Indo-Gangetic Plains (IGP) and in India in particular. But there are major economic and environmental threats to agricultural sustainability, including groundwater depletion, water-logging and salinity, deteriorating soil physical conditions, declining soil organic matter content, contamination of groundwater- and atmospheric pollution.
The sustainability of irrigated agriculture in the rice-growing areas of southern Australia is also threatened by salinisation as a result of rising watertables. The availability of water for irrigation is decreasing (largely due to allocation of water for the environment) while its price is increasing, and the amount of water available for irrigation each year is uncertain.
The project is increasing the sustainability, yield, resource-use efficiency and profitability of the rice-wheat systems of the Indo-Gangetic Plain and of the cropping systems in the rice-growing areas of Australia, using permanent beds to improve soil, water and nutrient management.
This project comprises the following subprojects.
1. Preliminary field experiments in India to evaluate layout and agronomic options for permanent bed systems, with particular emphasis on rice; scientists will evaluate planting, water, nitrogen and stubble management options, and the results will be used to refine the design of the main field experiments (subprojects 2 and 3).
2. Field evaluation of permanent bed and conventional RW/rice-based cropping systems of Punjab and NSW; scientists will quantify and compare crop performance, soil properties, water balance and dynamics and selected nutrient balances for traditional and permanent bed layouts. The results, together with those of the simulation modelling in subproject 5, will be used to develop guidelines for improved soil, water and nitrogen management.
3. Field evaluation of stubble management options for permanent bed and direct drilled cropping systems for rice-wheat and soybean-wheat rotations; scientists will evaluate a range of stubble management options for rice-wheat in Punjab, and for the establishment and growth of soybeans in rotation with rice.
4. Nitrogen use efficiency in RW cropping systems in Punjab (with IAEA); scientists will use 15N to study the fate of fertiliser nitrogen applied to selected treatments. Soil mineral nitrogen dynamics will also be studied. The results will help to refine fertiliser recommendations and provide inputs to the model development and validation in subproject 5.
5. Development and application of models to identify management options for maximising the productivity of RW cropping systems in Punjab and the IGP, and of rice-based systems in NSW; calibrated and validated models for bed and conventional RW cropping systems will be developed, building on existing models.
6. Assessment of the economic impacts of changing from conventional to permanent bed systems in Punjab, including the impacts of changed labour requirements for cultivation, planting and weeding.
Rice-wheat (RW) cropping systems are critical for food security and livelihoods in South Asia. However the sustainability of RW systems in South Asia is now in question, faced with yield stagnation or decline of rice and/or wheat, soil degradation, declining groundwater levels, air pollution from rice stubble burning, and declining terms of trade. In Australia, the sustainability of rice-based systems is threatened by reduced availability and increasing price of water. ACIAR Project LWR/2000/089 sought to increase the sustainability, yield, resource use efficiency and profitability of RW and alternative irrigated cropping systems in Punjab, India and New South Wales (NSW), Australia, through the development of permanent raised bed (PRB) rice-based cropping systems and machinery capable of direct drilling wheat into rice residues.
The technical problems of direct drilling wheat into rice residues has been solved for conditions in Punjab with the development of the Happy Seeder, which cuts and picks up the residues in front of the sowing tynes, and deposits them as a mulch behind the sowing tynes. The machine is currently being manufactured by two commercial machinery companies in Punjab. The project has comprehensively demonstrated that wheat can be successfully established and grown by direct drilling into rice residues without burning or removal, on both flat fields and raised beds. Preliminary results suggest some water saving through reduced soil evaporation, but this requires further field and modelling work to quantify the savings more clearly. Whether the approach will be successful in the heavy rice straw loads (10-14 t/ha) in NSW is yet to be established. Preliminary financial analysis suggests that the Happy Seeder technology is more profitable for Punjabi farmers than both conventional tillage and direct drilling after burning the straw. However there are a number of assumptions in the analysis that can only be validated after prolonged testing (e.g. cost of repairs and maintenance, and potential reductions in herbicide, N fertiliser and irrigation water applications). Furthermore, there may be significant economic, environmental and social benefits, which need to be quantified, particularly as a result of reduced air pollution and reduced use of inputs subsidised by the government. The main needs now are to develop a smaller machine capable of being powered by the 35 h.p. tractors commonly used in Punjab, to develop management guidelines, to create a favourable policy environment to encourage adoption, and to implement a major program to demonstrate and disseminate the technology with farmers across the RW districts of Punjab, and across the north west Indo-Gangetic Plain.
The performance of RW systems on PRB on the sandy loam and loam soils commonly used for RW systems in Punjab was disappointing, and not viable with current technology. Contrary to expectations, yield of wheat on beds almost never exceeded yields with conventional tillage, and was sometimes significantly lower. The topsoil of the beds dried faster than the flat fields, and more skilled management may be required to ensure planting at optimal soil moisture and to avoid early water deficit stress on beds on these soils. Yield of transplanted rice on fresh beds (TRB) was usually similar to yield of puddled transplanted rice (PTR) with the same alternate wetting and drying irrigation scheduling (irrigating 2 days after the floodwater or furrow water had dissipated, which is recommended practice for PTR), however, yield of TRB declined relative to yield of PTR as the beds aged. The decline was even greater for direct seeded rice on permanent beds. The lower rice yields on beds were associated with cereal cyst nematode infestation, compaction of the beds, and iron deficiency in direct seeded rice. Three to four hand weedings were needed to control weeds on the beds. There was no benefit of mulching the beds with wheat and rice straw in terms of yield or nitrogen fertiliser requirement. Our findings were generally consistent with the findings of others in the north west Indo-Gangetic Plain (IGP), but in contrast with findings from the wetter environments and less mechanised systems of the eastern IGP. The reasons for the differences need to be investigated to help identify how to improve the performance of RW systems on PRB in the north west, and in particular to determine whether compaction of the sides of the beds by the tractor tyres is a significant factor.
Irrigation water savings of 30-50% were achieved with furrow-irrigated TRB in comparison with continuously flooded PTR. However, field and modelling studies showed similar irrigation water savings when water management of PTR is changed from continuous flooding to the same irrigation scheduling as the beds (irrigate 2d after the furrow or floodwater has dissipated). The depth to which the furrows were filled, and age of the beds, also had a large effect on irrigation amount. Our studies demonstrate the importance of providing appropriate control treatments and sufficient contextual detail in reporting the results of comparisons of soil and water management for RW systems to enable sound interpretation and extrapolation of the results. Further detailed investigations are needed in farmer field sized blocks for a range of soil types, watertable conditions and irrigation management to understand the effects of raised beds on components of the water balance for RW systems, and to develop irrigation management guidelines for rice and wheat on PRB. Our field and modelling studies also demonstrated that deep drainage from PTR using recommended water management, and from beds, is excessive (~1,000 mm), raising the question of the suitability of sandy loam and loam soils for rice culture in this environment, and the need for lower water use alternatives. In contrast, deep drainage from wheat was negligible to less than one tenth of that from rice.
In our 3-year maize-wheat and soybean-wheat experiments in Punjab on a loamy sand with no history of rice cultivation, and under dry to average rainfall conditions, yields of maize, wheat and soybeans on PRB were comparable to yields with conventional tillage and direct seeding on the flat. The application of the technology in wetter conditions and on heavier soil types with a history of rice cultivation (and thus a well-developed hard pan) has not been assessed. It is likely that beds may be an advantage for non-rice crops on such soils due to reduced waterlogging of the beds, and this needs further investigation.
Comprehensive economic analysis showed that RW was slightly more profitable to farmers than maize-wheat (MW) cropping systems, and much more profitable than soybean-wheat (SW) systems, mainly due to the low yield of soybean. PRB were more profitable than all other layouts for MW and SW, but not for RW due to the yield decline in rice on PRB. If the rice yield decline could be reduced to 10%, there would be significant financial benefits of PRB over all other layouts except for zero-till wheat after PTR, which had similar net benefit. With no rice yield loss, PRB were superior to all other layouts, mainly due to reduced machinery costs. A 10% increase in wheat yield on PRB would also result in higher financial returns to PRB than any other layout, despite the rice yield decline on TRB.
In contrast to the situation in Punjab, direct seeded rice grew successfully on PRB on the heavy clay soil in Australia. Direct seeded rice was successfully grown in close rotation with winter cereals and other summer crops on PRB in terraced (zero grade), bankless channel layouts. Barley-soybean double cropping was also successful on PRB on this layout. Yields of wheat on beds and flats were similar, in contrast with past experience showing higher yields on beds due to improved drainage on the clay soils used for rice-based systems in Australia. Economic analysis showed that there were significant financial benefits in switching to PRB in terraced rice layouts due to reduced tillage costs and the opportunity to switch to more intensive cropping systems. Adoption of zero graded bankless terraced rice field irrigation designs potentially incorporating raised beds should be promoted now to rice growers in locations with suitable slopes and access to high irrigation flows. The evaluation of PRB for rice-based systems in NSW was undertaken during a prolonged period of very dry climatic conditions (drought). Monitoring in commercial fields during higher rainfall conditions conducive to waterlogging is needed to evaluate PRB terraced rice layouts in terms of crop performance, trafficability and damage to the beds under wetter conditions. Further work is also needed in commercial fields on irrigation distribution uniformity and the potential to save irrigation water.
The project has achieved many scientific, capacity building and community impacts to date. By far the most significant is the strong interest in promoting the Happy Seeder Technology in India and Pakistan by the Rice-Wheat Consortium of the Indo-Gangetic Plains, Punjab Agricultural University, the Indian Council of Agricultural Research, ACIAR and others. Happy Seeders are now made by two manufacturers in Punjab. Initiatives are underway to promote adoption of the technology through many demonstrations in farmers' fields, together with the development of a smaller version of the Happy Seeder capable of being powered by a 35 h.p. tractor. In the future, widespread adoption of the technology will result in many benefits including improved air quality (and therefore health) and soil quality through retention of rice residues instead of burning, reduced water depletion (from reduced soil evaporation), and financial benefits to farmers from more timely wheat sowing and reduced inputs (herbicides, water, fertiliser).
Another highly significant impact of the project is enhanced capability of PAU researchers to work in multi-disciplinary, cross-department teams and with the private sector, partnerships which continue today. Four of the project's Research Fellows are now undertaking PhD programs, three of these as John Allwright Fellows. The fourth is completing his PhD in collaboration with the world leading hydrology group at Charles Sturt University.
The project has also made many important findings in relation to knowledge of the performance of rice and wheat on permanent raised beds, including components of the water balance. Through presentations and publications, the project has influenced discussion on what constitutes real water savings within the RW region. Much of this knowledge, together with that of other RW researchers in the IGP, is documented in "Permanent beds and rice residue management for rice-wheat systems in the Indo-Gangetic Plain", the proceedings of a workshop organised by the project team at Ludhiana in September 2006 (ACIAR Proceedings No. 127). To date the project team has published 14 papers in prestigious scientific journals and books, 35 conference and workshop papers, 13 articles in farmer publications and a range of other publications.
Links:
[1] http://www.aciar.gov.au/country/India
[2] http://www.aciar.gov.au/programarea/Land and Water Resources