Biochar and fulvic acid amendments mitigate negative effects of coastal saline soil and improve crop yields in a three year field trial

China with large area of land planted with crops are suffering secondary salinization in coastal area for the lack of fresh water and saltwater intrusion to the groundwater. The purpose of this study was to investigate the effects of biochar (BC) and fulvic acid (FA) on the amelioration of coastal saline soil and their impact on crop yields under maize-barley rotation system. A three year field experiment was conducted in a saline soil on a farm in coastal area of east Jiangsu Province, China. A maize-barley rotation system had been carried out for ten years with local conventional management before the experiment. The saline soil was amended with BC at rates of 0, 7.5 t ha(−1) (BC1), 15 t ha(−1) (BC2) and 30 t ha(−1) (BC3) alone or combined with fulvic acid (1.5 t ha(−1)) compared with control. Fertilizers were applied under normal planting strategies. The BC was added only once during the four growing seasons, and the FA was applied before each sowing. Soil salinity changed significantly during the three year field experiment. This was mainly due to the great quantity of rain during the period of maize cultivation. Although Na(+), Cl(−) and SO(4)(2−) in BC and /or FA treatments significantly decreased, the pH value increased up to 9.0 as the CO(3)(2−) + HCO(3)(−)content increased. Total organic carbon (TOC) and phosphorus (TP) responded positively to biochar addition rate. BC applied with appropriate rate at 15 t ha(−1) (BC2) in combination with FA showed optimal effects on soil salinity amelioration, soil physics properties regulation, soil nutrition improvement and crop yields increase. The TOC and TP was 5.2 g kg(−1) and 507 mg kg(−1) in BC2 + FA treatment, which were lower than BC3 and BC3 + FA treatments. However, the highest total grain yield was obtained in the BC2 + FA treatment, and the total yield was increased by 62.9% over the CK. This study emphasizes that using combined organic amendment of BC with FA for profitable and sustainable use of salt-affected soils would be practicable.