Influence of Amount and Distribution Depth of Walnut Raw Material and Its Biochar on Evaporation and Soil Moisture

Because of the limited water resources in the world, especially in arid and semi-arid regions, the study of water loss causes is necessary for optimal use of them. The results of such research can be effective in water management and increase irrigation efficiency especially in low water areas. Since evaporation from the uncovered soil surface as one of the most important parts of water balance components, causes water loss, providing solutions to reduce it seems necessary. The use of soil amendment (such as biochar) can be an effective solution for decreasing evaporation from soil. Therefore, this study was conducted to investigate the effect of walnut raw material (sawdust) and it’s biochar on evaporation and soil moisture in Shahrekord university research farm, during the 5 moths form Mordad to Azar.

The experiment was conducted in a completely randomized design with 13 treatments and 3 replications. The investigated factors include the experimental material including walnut raw material, as sawdust, and its biochar at two levels of 1 and 2% and their distribution depth in soil (mixed at 3 and 8 cm above the pot and mixed in 30 cm or the soil of the whole pot). Evaluation of soil evaporation in the treatments was done by measuring the amount of inlet and outlet water to the pots and based on the water balance equation.

Comparison of the mean of different biochar and walnut raw material treatments showed that walnut raw material treatments significantly reduced evaporation from soil surface compared to the control treatment (soil without any amendment). The average amount of evaporation in treatments containing walnut raw material is 1450 ml, while this amount is higher for treatments containing biochar and 1820 ml. The average of soil moisture content in these treatments is 27.8% that was also significantly higher than the control treatment (25%). Regarding biochar effect on soil evaporation and moisture, the results showed that except for 2% biochar treatment and distribution in the whole pot soil in, the difference between the other treatments and the control was not significant. The results also showed that the soil evaporation in treatments containing raw material (1450 ml) is significantly lower than treatments containing biochar (1820 ml). Unlike biochar, the depth of distribution of the raw material in the soil also had a significant effect on evaporation. The evaporation values for distribution depths of 3, 8 and also mixed in the soil of the whole pot (30 cm), were obtained 1360, 1440 and 1550 ml, respectively, which had significant difference with the control treatment (1800 ml) at 5% significant level.

Overall, due to the decreasing and significant effect of using 1% and 2% of raw walnut material (in the form of sawdust) compared to its biochar, on the soil evaporation and considering the rational and economical use of 1% and 2% raw material, it can be recommended to use this material with the mentioned percentages to reduce evaporation form the soil surface.