Drip irrigated with fulvic acid improves soil environment and enhances fruit yield and quality of fragrant pear planted in saline-alkali land

Soil salinization restricts the sustainable development of agriculture, organic amendments can ameliorate the saline–alkali soil environment, and appropriate irrigation interval reduced the root zone soil salinity by leaching salt into deeper soil. While, it remains unclear how the application of soluble amendments under drip irrigation affects the soil environment, which is crucial for understanding their role in the yield and quality formation of deep-rooted crops such as fruit trees. A two-year experiment was conducted in a Korla fragrant pear orchard to investigate the effects of irrigation interval, fulvic acid (FA) application rate, and application timing on soil environment indices, i.e., soil water content (SWC), soil salinity, soil nitrate nitrogen content, and thus fruit yield and quality of drip irrigated fragrant pear. The treatments included three irrigation intervals: 10 (P1), 15 (P2) and 20 days (P3), three FA application rates: 0 (H0), 200 (H1) and 400 kg ha ^− 1 (H2), and two FA application timings: once (T1), three times (T2). In addition, insoluble organic amendment (CK) was used as a control treatment. Compared with the P1 and P3 treatments, the P2 treatment increased the SWC in the root zone by 5.6% and 9.4% and decreased the soil salinity by 8.6% and 13.7%, respectively. FA application increased the SWC and nitrate nitrogen content by 5.7–14.7% and 8.3–35.1%, respectively, and reduced the soil salinity by 7.6–23.5%. With the same organic carbon content, the SWC and nitrate nitrogen content of H2 treatment were 8.5% and 9.2% greater than that of the CK treatment, respectively, and soil salinity was 6.9% lower. Compared with single application, split application of FA resulted in a significant 17.5% increase in soil nitrate nitrogen content. In addition, the overall fruit quality was determined through principal component analysis (PCA) of various fruit quality parameters. The yield and overall quality of fragrant pear initially increased and then decreased with increasing drip irrigation interval, but increased with increasing application rate and number of FA applications. Random forest analysis revealed that the interaction of irrigation interval and FA application rate had significant effects on soil salinity, and the FA application rate was the dominant factor. In summary, the recommended irrigation interval, application rate and number of FA applications were 15 days, 400 kg ha ^− 1 , and three, respectively, for saline-affected fragrant pear orchards in arid region.