Puddling

EFFECT OF PUDDLING ON SOIL PHYSICAL PARAMETER

1. Puddling and its Effects on SOIL PRESENTED BY; RAVIKIRAN K B 2016602009

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.

5. 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.

6. 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;

7. 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.

8. 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.

9. 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.

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

11. 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

12. 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 .

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

14. 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.

15. 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 .

16. 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 I nitial submergence before tillage also decreases bulk density.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.