Effects of biochar and peat on salt-affected soil extract solution and wheat seedling germination in the Yellow River Delta

Salt-affected soils are widely distributed in arable croplands, so it is important to reclaim these soils. In this study, the effects of different biochar/peat doses (1, 3, and 5%) on 1:5 salt-affected soil: water extract solutions with different soil salinity levels after seven days shaking; and on winter wheat seedling growth after 80 hours are discussed. Results showed that the SAR and Cl-/SO42- ratio varied because of the changes of ion composition in the soil extract solution caused by the addition of biochar and peat. The maximum length of root and sprout of wheat grown in S1 (very slightly saline) soil extract treated by biochar/peat were 8.0/7.14 and 4.86/4.50 cm, respectively. The average length of wheat root and sprout grown in S2 (moderately saline) soil extract treated by peat was higher than that in soil treated by biochar. The results indicated that biochar and peat modified the ion composition of salt-affected soil extract solutions, as well as that of wheat. The abundant beneficial ions K+ or Ca2+ in biochar/peat might be beneficial to reclaim the salt-affected soil, and the exogenous ions altered the composition of the soil solution to promote the seedling growth or enhance the resistance of plants to the salt stress. Moreover, cation exchange took place among soil, biochar/peat, and soil solution. The proportion of harmful Na+ declined (SAR decreased) in the soil solution, which could be beneficial for the reclamation of the salt-affected soils.