الملخص الإنجليزي
Salinity is one of the major issues in Gulf countries, including Oman. Two experiments were conducted to determine the ability of specific soil amendments to reduce the effect of high salinity on a common crop in Oman; cucumber. The soil amendments were biochar, produced locally from mango wood, and a soluble silica product imported from Australia. A high salt soil was compared to a control in experiment #1, and high salt irrigation water was compared to a control for a low salt soil in experiment #2. Both experiments were conducted with cucumber seedlings for a 4-5 week period under growth chamber conditions. Results showed that in both experiments, the addition of soluble silica raised the silica level in the soil. Biochar did not affect silica levels, but raised the organic matter level in both experiments, and resulted in a higher water holding capacity in experiment 2. Biochar also significantly increased soil levels of water soluble K and Olsen P in both experiments. In experiment 1, biochar also resulted in increased water-soluble soil NO3. Plant yields were not significantly different in experiment #1 for any of the soil amendments used. Sap nutrient tests showed similar levels of sodium and nitrate, but the biochar significantly increased sap levels of K. In experiment #2, plant biomass was significantly greater in the biochar treatment and biochar plus silica, and the silica alone treatment was also higher than the control. Yield increases were approximately 1.7 and 1.6 for biochar and biochar plus silica, and 1.3 for silica alone. There was no significant increase when biochar and silica were added together over the biochar alone. Treatments with biochar showed decreased levels of sap NO3, increased levels of sap K, and no effect on sap Na. The silica treatments had lower levels of sap Na, but it was not significantly different. In summary, neither of the amendments tested had a negative effect on the plants, and both show possible benefits, especially under saline conditions. The biochar had the effect of adding nutrients (P and K), as well as increasing organic matter at the rates used. Under growth chamber conditions, rates for both amendments of 10% by volume were applied, and lower rates would likely be used under field conditions. Further testing under field conditions would also provide valuable information about whether these amendments benefit plants that are under additional stress such as insect or disease pressure in addition to soil salinity.
