Effects of puddling on rice.
The benefits of puddling for rice listed by De Datta (1981) include:
1. reduced draft requirements for tillage
2. weed control
3. easy transplanting
4. conservation of rain and irrigation water
5. increase in nutrient availability
Of these, weed control and water conservation are the most important.
Puddling buries weeds and weed seeds in the soft mud where anaerobic conditions kill the weeds and retard germination of the seeds. According to De Datta (1981), tillage is the most important weed control factor in transplanted rice.
This is perhaps the most important benefit of puddling. Puddling significantly decreases water loss by percolation. In a drum study of six Philippine soils whose clay content ranged from 9 – 64% and clay composition included montmorillonite, kaolinite, and allophone, Sanchez (1976) observed that puddling decreased percolation by 1000 times. Field measurements indicate that the reduction by puddling reduces percolation losses to about one third of those in nonpuddled soils (Wickham and Singh 1978). But the long-term effects of puddling lead to plow pan or traffic pan formation that may reduce percolation drastically.
The main disadvantages of puddling are excessive water use, low trafficability, and difficulty of regenerating soil structure for the dryland crop following wetland rice.
Most of the world’s rice is grown on puddled soils. Puddling is wet cultivation of land that mixes soil and water to produce an impervious layer. It is achieved by plowing the flooded soil and harrowing it at progressively lower water contents.
A clay content exceeding 20%, dominance of smectitic clays, and sodium saturation facilitate puddling. Soils with a high content of organic matter, oxides of aluminum and iron, 1:1 clays or exchangeable calcium puddle less readily.