Analysis of oat-straw salt ion accumulation and the potential for improvingsaline-alkali soils in coastal Hebei Province

Because oat is highly nutritious and resistant to drought, barren and saline conditions, it is extensively cultivated around world. However, there is less oat cultivation in low-latitude coastal saline areas. Therefore the absorption of soil salt ions and the potential for improvement of saline-alkali soils via oat cultivation has been rarely researched. To investigate the characteristics of straw salt accumulation and the potential for improving saline-alkali soils via oat cultivation in coastal Hebei Province, the single factor randomized block design experiments of two factors (variety and soil salinity) was analyzed for oat biomass, straw ion concentration and accumulation, and straw-soil ion concentration ratio. The results showed that variety "Bayou1" oat biomass was 2.9 t·hm^-2 at flowering-filling stage, which increased to 3.8 t·hm ^-2 at maturity. When "Bayou1" oat harvest was delayed for 20 days, biomass yield decreased to 2.5 t·hm ^-2. "Baiyan2" oat biomass was 3.1 t·hm ^-2 in low saline soils (containing 1.0 g·kg ^-1 salt), which was significantly greater than in medium (1.7 t·hm^-2) and high (0.4 t·hm^-2) saline soils (containing 2.0 g·kg^-1 and 3.0 g·kg^-1 salt, re-spectively). Under the medium salinity conditions, "Bayou1" biomass (3.8 t·hm^-2) was significantly higher than "Baiyan2" (3.1 t·hm^-2) and "Huazao2" (2.2 t·hm ^-2) biomass. Na⁺ and K⁺concentrations in "Bayou1" straw from flowering to maturity stage significantly increased, while Mg²⁺, Ca²⁺ and Cl decreased. When oat harvest was delayed, straw ion concentration (with the excepting of Ca²⁺) significantly dropped. Na+, Mg²⁺, Ca²⁺ and Cl in "Baiyan2" straw significantly increased with increasing soil salinity, whild K⁺ significantly decreased. There were significant differences in Na⁺, K⁺ and Mg²⁺ concentrations among the three oat varieties, but no notable differences in Ca²⁺ and Cl . Cl concentration was highest in the oat straws, followed by K⁺+Na⁺, Mg²⁺, Ca²⁺, Na⁺, K⁺, Mg²⁺and Cl accumulations in "Bayou1" straw were highest at maturity, which significantly dropped under delayed harvest. Na+, K+, Mg2+, Ca²⁺ and Cl accumulations in "Baiyan2" dropped with soil salinity increasing. With the exception of Ca²⁺, there were significant differences in straws Na⁺, K⁺, Mg²⁺ and Cl accumulations among the three oat varieties. For "Bayou1" straw-soil ion concentration ratio, Na⁺+K⁺ was highest (with ratio of 46~63), followed by Cl (30~46), Mg²⁺ (24~30) and Ca²⁺ (3~15). With the exception of Mg²⁺ and Ca²⁺, the ratios dropped significantly when oat harvests were delayed. With soil salinity increasing, Na⁺+K⁺ and Cl ratios of oat-straw to soil significantly dropped, Ca²⁺ ratio changed unsignificantly. There were significant differences in straw-soil ion ratios among the oat varieties. The oat had the potential for improving saline-alkali soils in theory, but harvest time and soil salinity significantly affected oat biomass, ion concentration and accumulation. Furtherly, the influences of application of subsurface drainage system on topsoil salt balance and the effect of drought on oat salt accumulation during the oat growth season needed further research.