The Geotechnical and Biogeochemical Consequences of Soil Puddling in Lowland Rice Systems: A Comprehensive Review of Physical, Chemical, and Biological Transformations

Abstract

Puddling, the mechanical manipulation of soil at saturated moisture levels, remains a cornerstone of traditional rice cultivation. This review synthesizes the multifaceted impacts of puddling on soil properties and its long-term agronomic consequences. Physically, the process leads to the collapse of soil aggregates and a significant reduction in macropores, which are replaced by micropores. This structural destruction facilitates the formation of a subsurface hardpan, increasing bulk density in the 10–20 cm layer to values often exceeding 1.70 g cm⁻³. While this creates a favorable environment for rice by minimizing percolation losses and enhancing water retention, it poses severe challenges for subsequent upland crops, such as wheat, through restricted root penetration and poor aeration. Chemically, the transition to anaerobic conditions triggers a rapid decline in redox potential (Eh) and a convergence of soil pH toward neutrality. The reductive dissolution of Iron (Fe²⁺) and Manganese (Mn²⁺) increases their solubility, alongside enhanced Phosphorus (P) availability. However, these benefits are often offset by the energy-intensive tillage required to remediate the degraded structure for non-rice crops. Understanding these transformations is critical for optimizing resource-use efficiency and maintaining soil health within intensive cereal-based cropping systems. The trade-off between immediate benefits for rice and long-term structural degradation underscores the need for sustainable management practices, such as reduced tillage or direct-seeded rice, to mitigate the negative physical legacy of intensive puddling.