basics of puddling

1. Puddling and its
Effects on SOIL

2. Puddling
▶ Wet cultivation or soil puddling is the common soil
preparation technique used for lowland rice
production.
▶ One striking feature of most of the world’s wetland
rice is that it is grown on soils whose structure is
deliberately destroyed and the soil dispersed by
plowing and harrowing the soil in a flooded or
saturated state.
▶ The operation is an important management
practice in wetland rice culture and is called
puddling.

3. definition
▶ Ghildyal (1978) defined puddling as mixing
soil and water to render it impervious.
▶ Puddling can be defined as the process of
breaking down soil aggregates into uniform
mud, accomplished by applying mechanical
force to the soil at high moisture content.

4. ▶ It may also be defined as the mechanical
reduction of the apparent
specific volume of soil.
▶ To a farmer, puddling is mixing soil with
water to make it soft for transplanting and
impervious to water. To put it simply, it is an
act or method of making a puddle.

6. The steps involved in puddling
are:
▶ 1. saturating and flooding the soil;
▶ 2. plowing the supersaturated soil;
▶ 3. plowing or harrowing at progressively lower water
contents
When the soil moisture content increases, soil aggregates
swell, soften, and weaken.
Cohesion between aggregates increases, reaches a peak
at field capacity, and decreases.
When such a soil is plowed or harrowed the aggregates
are destroyed.

7. Effects of puddling on soil
properties (Ghildyal 1978):
▶ 1. coarse aggregates are broken down;
▶ 2. non capillary pore space is destroyed;
▶ 3. apparent specific volume decreases;
▶ 4. water-holding capacity increases;

8. ▶ 5. hydraulic conductivity and permeability decreases;
▶ 6. evaporation decreases;
▶ 7. soil reduction is favored
▶ 8. alters the distribution of sand silt and clay in soil by
mixing particles from different soil horizons.

9. 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.

10. ▶ Weed control.
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.
Water conservation.
Puddling significantly decreases water loss by percolation.
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.

11. Advantages of puddling:
▶ Reduces soil permeability
▶ Preserves aquatic, anaerobic conditions
▶ Controls weeds, improves water and nutrient availability
▶ Facilitates transplanting

12. Disadvantages of puddling:
▶ Destroys soil aggregates
▶ Breaks capillary pores
▶ Disperses fine clay particles
▶ Lowers soil strength in the puddled layer
▶ Plough pan (compacted layer) resists root penetration of
following crop
▶ Can cause water logging
▶ Forms large clods in finer textured soils preventing seed-soil
contact
▶ Forms impermeable clayey layer on the surface in coarser
soil

13. During puddling, soils are subjected to two kinds of
deforming stresses:
▶ (a) the normal stress (load) associated with compression and
The compression is more effective below the upper plastic
limit
moisture content at which the soil-water system can flow
as a sticky fluid paste.

14. ▶ (b) tangential stress causing shear.
Shearing effects dominate above the upper plastic limit.

15. ▶ Puddling or wet tillage coupled with submerged conditions
are responsible for making drastic effects on soil physical
characteristics of rice soils.
▶ These effects can be continued either for short time or long
time.
▶ During rice-rice or rice-wheat cropping sequence the system
undergoes transition from saturated to unsaturated
conditions. While this happens, the soil physical properties
again undergo changes.

16. ▶ Soil structure
▶ Puddling destroys and coverts aggregates and peds into
plastic mud.
▶ Continuous wet tillage (repeated plowings and harrowings)
converts the soil into a plastic mud with massive structure.
▶ The soil matrix exhibits a two phase system
▶ i.e. solid and liquid,
the gaseous phase is either missing or some air is
entrapped in storage and residual pores.
The practice of lowland rice-rice has made the soils excessively
soft due to puddling season after season .

17. Bulk density and soil strength
▶ Puddling effects on bulk density are dependent on
the aggregation status of the soil before puddling.
▶ If a parallel oriented, closely packed structure is
produced from a well aggregated open structure, bulk
density would increase.
▶ The strong inter-particle forces favor well oriented
structure, while weak inter-particle forces favor an
open gel structure. I
▶ Initial submergence before tillage also decreases bulk
density.

18. The pore space
▶ Change in the orientation of soil particles in puddled
layer brings about changes in soil porosity.
▶ tillage effects on lowland rice observed that puddling
decreased drainage pores and increased water
retention pores.
▶ Changes in pore space (pore size distribution) upon
puddling effects other soil physical properties like the
aeration status, the retention-transmission
characteristics and evaporation losses of soils.

19. Water retention and
transmission characteristics
▶ water retention in puddled soils is always higher than
the non puddle soil.
▶ when the submerged puddle soils revert back to
upland non puddle condition, its water retention falls.
▶ Resaturation of such soils may not necessarily restore
the soils original water retention capacity.
▶ Percolation rates have been found to fall rapidly with
the increase in intensity of puddling in several soils.

20. The thermal regime
▶ Wet tillage (puddling) in rice soils affects the thermal
regime by changing soil properties, such as
▶ bulk density,
▶ moisture regime and
▶ the transmission characteristics.
Thermal conductivity (k) and the volumetric heat
capacity (c) increase with bulk density and moisture
content, because the k and c of soil particles and water
are much higher than those of air.

21. ▶ Thermal diffusivity (k/c), which denotes the
temperature changes in any part of soil,
also increases with increasing moisture
content to about - 0.1 MPa water potential
and then it falls, because above -0.1 Mpa
water potential, c increases much faster
than k. Increase in percolation rates may
increase or decrease soil temperature
depending on irrigation water temperature
and solar radiation received.

22. REFERECES;
▶ Ghildyal, B. P. 1978. Effects of compaction and
puddling on soil physical properties and rice growth.
Soils and Rice. International Rice Research Institute,
Los Baños, Philippines.
▶ Sanchez, P. 1976. Properties and management of soils
in the tropics. John Wiley. New York. 618 p.
▶ WIKIPEDIA.