Effects of Biochar produced from date palm’s leaves on saturated hydraulic conductivity and soil moisture coefficients of sandy clay loam soil

Soil organic matter plays an important role in improving physical, chemical, and biological properties of soil in agriculture. Biochar is a carbon-rich organic material that produced by pyrolysis of biomass under oxygen limited conditions and it improves the physical and chemical properties of soils. In recent years, biochar application in soil has been considered as a desirable way to improve physical conditions and increase soil moisture storage capacity. Achieving any of the above objectives depends on the physical and chemical structure of the biochar and its application to the soil.The main objective of this paper was to evaluate the effects of biochar, produced from date palm’s leaves, on the physical properties and hydrological behavior of a sandy clay loam soil by carrying out under greenhouse conditions.

For this aim, Pyrolysis at 400 degree of centigrade at 2 hour in an electric furnace biochars was obtained. Biochars were in powdered form and evenly added to soil (air-dried and passed through a 4 mm sieve) and incubated for 2 months. Therefor with determination of soil moisture content at field capacity, one, three, six and nine months after mixture soil and biochar, were measured hydraulic conductivity (kS) by taking soil samples from the pots. By measuring gravimetric water content at saturation percentage (SP), field capacity (FC) and permanent wilting point (PWP), plant available water content (PAWC) and relative field capacity (RFC) calculated. The Factorial experiment was conducted in a completely randomized design with two factors. The factors of this experiment was including amendment (palm’s leaves and biochar), application level (0, 0.5, 1, and 2% w/w), and time (1, 3, 6, and 9 month incubation).The treatments in this experiment were zero (B0), 0.5 (B1), 1 (B2) and 2% (B3) of biochar and zero (control) (D0), 0.5 (D1), 1 (D2) and 2% (D3) of palm leaves (zero, 18, 36 and 72 ton/ha, respectively) in three replications. Biochar were in powdered form and evenly added to soil (air-dried and passed through a 4 mm sieve) and incubated for 2 months.

The results showed a significant difference (P <0.01) between treatments. The effects of soil conditioner on relative field capacity (RFC), permanent wilting point (θPWP) and plant available water content (PAWC) and the effect of application levels on all soil moisture coefficients were significant (P <0.01) and increased these coefficients. The results showed that with increasing palm’s leaves amount, saturation kS of soil is increasing and there is a significant difference (P <0.01) between treatments. The results showed that application of biochar and date palm’s leaves enhanced soil kS. Increasing palm’s leaves from 0.5, 1 and 2 percent w/w (18, 36 and 72 ton ha-1) compared to control increased kS by 24.2, 17.7, and 74.3% respectively. Increasing biochar from 18 to 72 ton ha-1 compared to control increased kS by 29.4 and 41.4 % respectively. The results indicate that date palm leaves have a higher effect on θFC than it is biochar. The results showed that adding of palm’s leaves from 0.5, 1 and 2 % w/w compared to control increased θFC by 12, 11.3 and 12.4 percent, and biochar application increased by 10.3, 9.2 and 8.4 percent in field capacity respectively. Also the results showed that the adding of palm’s leaves from 0.5, 1 and 2 % w/w compared to control increased θPWP by 15.7, 12 and 10 percent, and biochar application increased by 9, 5.6 and 12.6% θPWP respectively. The results showed that the addition of 1% w/w biochar after 9 months and adding 2% w/w of date palm leaves after 6 months produced the highest increase PAWC. The effect of biochar on PAWC indicates that there is a dramatic effect compared with the control, which can be attributed to the extracted surface and the increase of the micro porous pores, which increased water storage. Soil moisture behavior in the high matric suction is under the control of soil texture and its fine pores, but in the low suction it is under the control of the soil structure and its large porosity. There is a significant difference (P <0.01) between the short and long term effect of date palm leaves and biochar on hydraulic conductivity. The effect of biochar supplemental in long-term was more than the effect of palm leaves on increasing kS, while in the short term, the effect of date palm leaves was more than the effect of biochar on increasing kS. The interaction effects between time, type of soil conditioners (biochar and date palm’s leaves) and application levels on PAWC and θPWP were significant (P <0.01) and also (RFC were significant (P <0.05) but their effects on the θFC were not significant. The results revealed that biochar application is considered one of the best methods for soil management and improvement, which increased soil constant organic matter and improve soil physical properties. It is concluded that biochar can be used as a soil amendment in fine textured soil to increase water holding capacity and to improve the drainage and hydraulic conductivity. The results showed that the application of biochar in a sandy clay loam soil could be used as an effective modifier to improve the physical properties of the soil and increase the FC, PWP and PAWC. Increasing the time and amount of biochar in soil resulted in significant changes in physical properties and soil moisture behavior. Unconventional application in sandy clay loam soils, especially in arid and semi-arid regions, due to lack of water resources in these areas, will be a good solution.