The Control Techniques Of Water-nutrient-salt And Plant Root In A Saline-alkali Wasteland Of Ningxia Irrigation Area

The moderately and strongly saline-alkali wastelands of Ningxia Irrigation Area are characterized by high evaporation/precipitation ratio,low groundwater table,the predominantly upward migration of salts,and low soil nutrients.Different mulches?plastic mulch,PM;sand mulch,SM;rice straw mulch,RSM;and CK with no mulch?,buried layers?maize straw layer,MSL;sand layer,SL;plastic layer,PL;and CK?,and different contents of seaweed fertilizer plus PM-MSL,were conducted to ameliorate the wastelands.Besides,the impacts of these methods on the growth adaptation strategies of Amorpha fruticosa in saline soils were also investigated to explore the characteristics and feasibility of these techniques.The main findings are as follow:?1?In the moderately saline-alkali soil,RSM retained higher soil water content?SWC?than others.However,excessive SWC further aggravated its low effect of soil temperature(T_soil),thus inducing that A.fruticosa at the early transplanting period suffered from the stresses of both low T_soil and high salinity.In the two-year experiment,PM had the highest reduction of soil salinity?the electrical conductivity of a saturated paste extract,EC_e?.Soil organic carbon?SOC?in the 0?60 cm layer tended to decrease first and then increase.PM performed best in mean weight diameter?MWD?.The comprehensive improvement indexes?CII?indicates that PM performed best in the amelioration effect of moderately saline-alkali soil in the Ningxia Irrigation Area.?2?SOC and T_soil promoted the use of extensive strategy?fine root biomass density,FRBD;fine root length density,FRLD?,while EC_e inhibited it.As AN decreased with soil depth,A.fruticosa used more intensive strategy?specific root length,SRL;specific root area,SRA?.In both years,the fine roots of A.fruticosa under PM employed exploitation potential and‘extensive strategy'more successfully in the 0?40 cm and in the 40?60 cm,respectively.?3?MSL,SL,and PL that set in the 40 cm depth layer could increase effectively SWC in the 20?60 cm layer,in which PL retained higher SWC than MSL and SL.SOC in the 0?20 cm under the three buried layers decreased first and then increased from 2016 to 2017,in which PL increased most.Only MSL increased SOC in the 20?40 cm layer.PL had a best performance in MWD to the depth of 20 cm,while MSL did in the 20?40 cm depth layer.Similarly,SBD in the 0?20 cm under PL decreased most,while that in the 20?40 cm did most under SL.The comprehensive improvement indexes?CII?indicates that PL was inferior to MSL,but its better water-salt environment was more conducive to the growth and development of A.fruticosa.?4?In 2016 and 2017,the fine roots of A.fruticosa under PL employed extensive strategy more successfully in the 0?20 cm,owing to its higher nutrient requirements under the condition of less salt stress.In the second year,PL used higher exploitation efficiency or‘intensive strategy'than did MSL,which might be caused by the lower soil nutrients and more blocking.?5?In the strongly saline-alkali soil,PM plus MSL could block the capillarity of soil,and inhibit the topsoil evaporation and salinity accumulation especially in the 0?40 cm.The improvement of soil nutrient and structure also increased with the increase of seaweed fertilizer concentration.The CII shows that the amelioration effects of G1?1:50 and G2?1:100 were much better than other treatments.Although there are differences between their rankings,there were no significant differences in their soil properties and the growth of A.fruticosa.Considering the conservation of seaweed fertilizer,we recommend that G2?1:100 should be used in the strongly saline-alkali soil of Ningxia Irrigation Area.