Abstract:
Soil salinization is a critical environmental issue restricting
agricultural production. Straw deep returning as interlayer
(40 cm) has been a popularized
practice to alleviate salt stress.
However, the legacy effects of
straw interlayer associated with the straw input amount on
soil organic carbon (SOC) and
total nitrogen (TN) in saline soil remain unclear. Therefore, a
four-year (2015-2018) field experiment was conducted with four levels
(i.e., 0, 6, 12 and 18 Mg ha-1) of straw returning as
interlayer. Compared with no straw interlayer (CK), straw interlayers
increased SOC content by 14-32%
and 11-57% in 20-40 cm and 40-60 cm, respectively. Lower increases were
for soil TN content (8-22% in 20-40 cm and 6-34% in 40-60 cm) than SOC
content, which led to increase soil C:N ratio in the 20-60 cm soil
depth. Compared with CK, remarkable increases of SOC and soil TN
contents in 20-60 cm led to the
decrease of stratification ratios (0-20: 20-60 cm), which promoted
uniform distributions of SOC and TN in soil profiles.
Even though soil parameters ranged
widely according to the straw input, straw interlayer with 12 Mg
ha-1 had higher SOC, TN, C:N ratio, and lower soil
stratification ratio in 2015-2017, which contributed to salt leaching,
water retention, and yield increment. These results highlighted the
legacy effects of straw interlayers maintained more than four years,
which led to an underestimation for previous short-term experiments, and
demonstrated a great potential for subsoil fertility and salt-affected
soil amelioration.