Comparison of Biochar effects of cow manure and sugarcane residues on moisture content of sandy loam soil

Using stable organic modifiers is a way to improve soil quality. In developed countries in the field of sustainable agriculture, due to high attention to the issue of carbon stabilization in the soil and its role in reducing greenhouse gas emissions, and therefore minimizing damage to the environment, the production of soil modifiers has been taken into consideration. In recent years, Biochar has been used as a soil modifier and a tool for carbon sequestration in agricultural soils. In fact, Biochar is a carbon-rich organic material that produced by pyrolysis of biomass under oxygen limited conditions, that can improve the physical and chemical characteristics of soils. Biochar is one of the most stable organic compounds used nowadays to modify soil properties. Saturated hydraulic conductivity and soil moisture coefficients are the most important physical properties of soils that affect water and solute transport and plant growth. Despite the importance of soil physical properties in increasing soil production and quality, less attention has been paid to the effects of Biochar on these properties compared to the chemical. This study was carried out to investigate the effects of two types of Biochar (cow manure and sugarcane residues) on saturated hydraulic conductivity and soil moisture coefficients of sandy loam texture in greenhouse conditions. For this purpose, Biochar was produced from cow manure and sugarcane residue at temperature of 400° C, for 3 hours. Biochar which was prepaird in powdered form evenly added to the soil that was air-dried and passed through a 4-mm sieve. In this study, according to the number of experimental treatments, 27 plastic pots were used, that 3 kg of soil was added to each one. In the bottom of the pots, holes were made for drainage and a sand filter (with a grain size of 2 to 4 mm) with a thickness of 2 cm was placed in the bottom of the pot. The pots were kept in the greenhouse for 60 days, at an average daily temperature of 35c. During the experimental period, irrigation was performed based on the discharge of 50% of soil moisture content at field capacity. The experiment was conducted in a completely randomized factorial design with two types of Biochar (cow manure and sugarcane residues) and application rates of five levels (zero, 0.5, 1, 1.5 and 2% by weight), in 3 replications. Saturated hydraulic conductivity (Ksat) and soil moisture coefficients including field capacity (FC), permanent wilting point (PWP), plant Available water (PAWC) and relative holding capacity (RFC) were determined. The results showed that the effect of Biochar application on saturated hydraulic conductivity and soil moisture coefficients including field capacity, permanent wilting point, plant Available water and relative holding capacity was significant (p<0.01). The effect of sugarcane Biochar was greater on saturated hydraulic conductivity, field capacity moisture and plant available water, in compare with cow manure. Application of 2% Biochar weight in both types (produced from cow manure and sugarcane) had the highest effect on increasing saturated hydraulic conductivity and moisture coefficients in sandy loam soil, compared to control treatment. Although the consumption level of 2% had the greatest effect, no significant difference was observed in the studied characteristics between the consumption level of 2% and 1.5%. Therefore, it can be stated that in order to select the optimal and economic level, the level of 1.5% of Biochar can be introduced as the optimal consumption level. In the optimum amount, the best results can be obtained due to time and low cost. Therefore, according to the results of this study, it can be concluded that apply of Biochar as a modifier is an appropriate method, especially in light textured soils that have low water storage capacity. Therefore, adding Biochar in dry and semi-arid areas that have shortage of water resources can also be beneficial. However, it should be noted that increasing levels of Biochar in soil can have negative effects such as increasing soil salinity. Regarding the positive effect observed due to adding Biochar on the physical parameters measured in sandy loam texture, the best level of Biochar should be chosen in such a way that is economically viable to use. Hence, in order to obtain the optimum level in field conditions further research is required.