Effect of Initial Moisture and Soil Texture on some Characteristics of Puddling Process in Paddy Soils

Puddling process is a part of land preparation in rice cultivation. In other words, puddling is an important method of soil management, which is done to disturb the structure of the surface layer of the soil and prepare the field for rice transplanting. Usually, in this process, the soil is flooded and tillage is done on it. The soil texture and the soil moisture conditions before flooding are factors that affect the process of the puddling. Therefore, this study was conducted to determine the effect of initial soil moisture and soil texture on some properties of paddy soils puddling process in Guilan province.

The experiment was conducted as a factorial based on a randomized complete block design in three replications. Three textures (silt, silty clay, and clay) of paddy soils were prepared under four initial soil moisture treatments (85, 90, 95, and 100% degrees of saturation). After preparing the soil samples, they were puddled using a laboratory panel. During and after the puddling process, the amount of net water consumed, the depth of water collected on the soil 2 and 6 days after puddling, the soil swelling at the end of the operation, the depth of soil settlement after 2, 4 and 6 days and the final depth of the soil were measured. Statistical analysis of the effect of the experimental treatments on the measured properties and their mean comparison was done with LSD test using SPSS 23 software. Calculations and graphs were done using EXCEL software.

The results showed that the independent effects of initial soil moisture and soil texture on all of the measured properties except the depth of soil after 6 days were statistically significant at 1%. With increasing initial soil moisture, the amount of net water consumption and the final depth of soil decreased and other measured parameters increased. On the other hand, the effect of soil texture on net water consumption, water collected on the soil 2 and 6 days after puddling, soil amass at the end of the operation, depth of soil after 2 and 4 days, and the final depth of the soil were statistically significant at 1%. The interaction effect of initial soil moisture and soil texture on soil amass at the end of the operation and final soil depth was statistically significant at 1%, and for the depth of water accumulated on the soil 2 days after puddling and the depth of soil after 2 days was statistically significant at 5%. By increasing the initial soil moisture content from 85 to 100% of saturation degree, the amount of water used for the puddling process decreased by 61%.

According to the results, the features of the puddling process are affected by the initial moisture and soil texture. Therefore, the results of this research can be used in the agricultural management of paddy fields in Guilan province. With increasing soil clay content, the measured parameters include the amount of net water consumed, the depth of water collected on the soil 2 and 6 days after puddling, the soil swelling at the end of the operation, the depth of soil settlement after 2, 4 and 6 days and the final depth of the soil were increased. The range of net water consumed in the puddling process for experimental treatments varied between 31 and 114 mm, and the lowest was obtained in silty soil texture with 20% clay and initial moisture treatment of 100% degree of saturation. Estimating water consumption in the puddling process and its correlation with initial soil moisture and clay percentage can inform the management of the agricultural calendar and water allocation program in the Sefidroud irrigation network for paddy fields. This information can help optimize water usage, especially in light of rainfall events at the start of the irrigation season, with the goal of reducing overall water consumption.