Coastal saline soil aggregate formation and salt distribution are affected by straw and nitrogen application: A 4-year field study

• Published in: Soil & tillage research Vol. 198; p. 104535
• Main Authors: Xie, Wenjun, Chen, Qingfeng, Wu, Lanfang, Yang, Hongjun, Xu, Jikun, Zhang, Yanpeng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2020
• Subjects: Aggregate formation and stability; aggregate stability; calcium; coasts; corn; fertilizer rates; field experimentation; growing season; microaggregates; nitrogen; Saline soil; saline soils; salinity; soil organic carbon; soil restoration; soil salinity; Straw and N application; wheat; wheat straw; CS; LM; AR; SOC; Straw and N application; DOC; SM; MWD; MI; Aggregate formation and stability; Saline soil
• ISSN: 0167-1987; 1879-3444
• DOI: 10.1016/j.still.2019.104535

[Display omitted] •Straw and N application increased saline soil aggregate formation and stability.•Soluble Na+ and Ca2+ contents were significantly higher in soils with poor structure.•Saline soil aggregate formation affected soluble salt distribution and salinity.•Sufficient N supply played an important role in aggregate formation and stability. Little is known about the effects of straw incorporation on saline soil aggregate formation or salt distribution in coastal zones. In this study, a 4-year coastal wheat/maize rotation field experiment was employed. In each growing season, maize/wheat straw was applied at the rates of 5.0 × 103 kg ha−1 (S) and 1.0 × 104 kg ha−1 (2S), and inorganic N was applied at the rates of 75 kg ha−1 (N1/2), 150 kg ha−1 (N), and 300 kg ha−1 (N2). Treatment without straw addition and applied with 150 kg ha−1 inorganic N was used as the control (CK). Dry- and wet-sieving techniques were used to fractionate the soils into large macroaggregates (> 2 mm, LM), small macroaggregates (0.25–2.0 mm, SM), microaggregates (0.053–0.25 mm, MI), and silt-plus-clay particles (< 0.053 mm, CS). Results revealed that the proportion of dry and water-stable macroaggregate fractions (> 0.25 mm, LA + SA) ranged from 74.2 %–88.3 % and 28.4 %–37.6 % in straw applied treatments, which significantly increased by 14.7 %–19.0 % and 21.1 %–32.4 % compared to CK, respectively (p < 0.05). The mean weight diameter (MWD) and aggregate stability rate (AR) enhanced as straw and N application rate increased. After straw application, soil organic carbon (SOC) preferentially accumulated in MI fractions, which was significantly higher than other aggregate fractions, except SN1/2 and CK (p < 0.05). MWD and AR were significantly negatively correlated with soil salinity (p < 0.05), and soil salinity decreased by 20.5 %–26.9 % in straw treatments compared to the initial soil salinity. In the CK and SN1/2 treatments, soil salinity of LA + SA fractions was significantly higher than < 0.25 mm fractions (MI + CS) (p < 0.05). The same difference in soluble Ca2+ was also observed in CK, SN1/2, or SN. In conclusion, saline soil aggregate formation and stability improved after straw and N application, which caused the salinity to decrease and affected salt distribution in aggregates. The findings of this study suggest that adequate N should be applied in order to maximize saline soil reclamation efficiency with straw.