直灌咸水与施氮磷对重盐碱柽柳地的改良效应

Effects of direct saline irrigation and nitrogen and phosphorus application on a coastal saline-alkali soil planted Tamarix chinensis

为解决滨海重盐碱地春旱、返盐以及缺N、贫P的突出问题,利用当地丰富的地下咸水资源和柽柳固C、排盐的特性,在华北低平原区滨海重盐碱区人工柽柳地开展了为期4年的咸水[不灌水和灌溉地下咸水(含盐量8.02~9.34 g·L^(−1),W)]与NP[不施肥(CK、WCK),单施氮(N、WN)和施氮磷(NP、WNP)]的2因素定位试验,研究不同处理对土壤盐分、养分和微生物量碳和微生物量氮的影响,以达到生物改良盐碱地、提升绿色生态景观的目标。研究结果显示,柽柳地首次灌溉咸水,0~30 cm土壤盐分平均下降32.7%;但连续3年灌溉咸水柽柳地0~30 cm土层盐分平均上升11.2%~18.3%;0~90 cm土壤有效磷(Olsen-P)含量下降19.4%~32.1%,0~30 cm微生物量碳与微生物量氮含量显著下降。灌溉咸水条件下施用NP(WNP)比对照(WCK)的0~30 cm土层的含盐量下降36.1%,土壤0~30 cm全氮、含水量和30~60 cm的Olsen-P含量均显著下降;而0~30 cm土层有机质、微生物量碳和有效钾含量显著提升。P是滨海重盐碱地关键限制性营养元素,灌溉咸水促进了柽柳对P吸收,进一步加剧土壤P消耗;灌溉咸水并施NP(WNP)可缓解滨海重盐碱柽柳地营养元素匮乏的限制,激活土壤微生物活性,有效降低因连续直灌咸水引发的土壤次生盐渍化的风险。研究结果为重盐碱地人工柽柳咸水灌溉及养分管理提供依据。

In order to cope with the outstanding problems of spring drought,salt return,and lack of both N and P in coastal severe saline-alkali region,we utilized the rich underground saline water resources and the Tamarix’s characteristics of both fixation carbon(C)and discharge salt to achieve the goals of elimination of salt and drought stress,deficiency of both soil N and P,and improvement green ecological landscape in coastal severe saline soils as well.Tamarix chinensis Lour.,a shrub species,is a species with strong salttolerant and water conservation ability that is widely planted in saline-alkali soils.This species plays an important role in improving the regional ecological landscape reformation and maintaining the stability of the coastal ecosystem,like the coastal wetlands in northern China.A two-factor experiment was conducted about saline water and fertilization in the Tamarix chinensis soil over a four-year period in coastal saline-alkali soil in the low plain of North China.Six treatments included no fertilizer as control(CK,WCK),only applying N(N,WN),applying both N and P(NP,WNP),each corresponding to no irrigation(the first)and irrigation with local phreatic saline water containing 8.02−9.34 g·L^(−1) salt(the second),respectively.The results showed that the salt content in the 0−30 cm soil layer of Tamarix chinensis land decreased by 32.7%on average after the first saline irrigation,which had a significant desalination effect on the severe saline-alkali coastal soil,but after three consecutive-year saline irrigation,the salt content in 0−30 cm soil layer averagely increased by 11.2%−18.3%;yet the available P(Olsen-P)content in 0−90 cm soil layer decreased by 19.4%−32.1%,the contents of microbial carbon(Cmic)and microbial nitrogen(Nmic)in 0−30 cm soil decreased by 15.5%and 19.7%respectively.However,compared with the control WCK,the WNP treatment,i.e.saline irrigation and applying NP,decreased the salt content of 0−30 cm soil by 36.1%,in the meanwhile significantly decreased the total N,water content and contents of 0−30 cm soil layer,Olsen-P of 30−60 cm layer as well.WNP was conducive to increase of 0−30 cm Cmic,soil organic matter(SOM)and ammonium acetate extractable K(Kex)content.Our experiment provides evidence that P was a strongly limited nutrient,saline irrigation-associated fertilization of N and P can effectively alleviated the risk of soil secondary salinization caused by continuous saline irrigation,relieve the limitation of key nutrients deficiency like P and N,and promote the soil microbial activity,with the strongest evidence for saline irrigation and soil nutrient management for artificial Tamarix chinensis in severe saline-alkali coastal soil.