Saline soil organic matter characteristics of aggregate size fractions after amelioration through straw and nitrogen addition

Saline soil organic matter (SOM) composition and distribution are largely unknown. A coastal field experiment was designed to investigate the effects of straw and nitrogen addition on SOM characteristics by diffuse reflectance Fourier‐transform mid‐infrared (FTIR) spectral and amino sugar analysis. In each growing season, maize/wheat straw was applied at rates of 5.0 × 103 kg ha−1 (S5) and 1.0 × 104 kg ha−1 (S10), and inorganic nitrogen was applied at rates of 75 kg ha−1 (N75), 150 kg ha−1 (N150), and 300 kg ha−1 (N300). N150 without straw addition was the control treatment (CK). Dry‐sieving technique was used to fractionate soils into macroaggregates (>0.25 mm, MA), microaggregates (0.053–0.25 mm, MI), and silt‐plus‐clay particles (