| Soil salinity is one of forth major hazards of the world. Remediation and utilizationsaline-alkali soil is one of the hot issues for a long time in the world’s areas of governancedegraded land. And remediation and utilization saline-alkali soil is a long time, complex andsystematic engineering, and the core is to reduce the harmful soil salinity, and to improve thesoil environment for crop growth. Traditional technology can not solve the problem of theimprovement saline-alkali soil and continued to increase its agricultural productivity. Explorenew saline-alkali soil improvement techniques become an urgent difficult scientific problemsto be solved. At present, the halophyte availability as the core technology is generallyconsidered a breakthrough of remediation and efficient utilization saline-alkali soil in thefuture.The objective of this article was to investigate further the effects and mechanisms ofdifferent halophytes growing in a saline-alkali soil.A saline-alkali soil was planted with threerepresentative halophyte (Tamarix ramosissima Ledeb. Festuca arundinacea Schreb.Helianthus annuus) monocultures in the north region of Yin Chuan City, Ning Xia Province,uncultivated soil was used as a control for comparison. The field experiment was conductedfor3years (2008-2010), and soil chemical and physical properties, soil salt content,microbiological properties, halophyte absorption and transportation salt and biologicalresponse of halophyte were systematically investigated and analyzed. Main results lie below:(1) Soil physical properties was mproved clearly. Soil bulk density decreas, soil porosityincreased improved significantly. Soil layer of improvement was0-20cm＞20-40cm＞40-60cm. With planting Tamarix ramosissima Ledeb. Festuca arundinacea Schreb.Helianthus annuus, in0-20cm depth soil layer, soil bulk density were debased by14.04%,15.73%,10.11%and soil porosity were increased by15.05%,18.50%,10.45%. Ability ofimproving soil physical was in the order of Tamarix ramosissima Ledeb.＞Festucaarundinacea Schreb.＞Helianthus annuus. With planting Festuca arundinacea Schreb.andHelianthus annuus, physical properties of0-40cm depth soil improved clearly and so as to0-60cm depth soil with planting Tamarix ramosissima Led.. The soil moisture profiles showthat halophytes inhibiting salt movement to the soil surface in spring and enhancing salt leaching through the soil profile in autumn. The initial soil infiltration rate and the stable soilinfiltration rate increased significantly, and in the order of Tamarix ramosissima Ledeb.＞Festuca arundinacea Schreb.＞Helianthus annuus.. Halophytes improved soil physicalproperties, increased soil surface coverage and absorpted soil water, so changed soil watermovment, which could be shown to affect the soil by inhibiting salt movement to the soilsurface and enhancing salt leaching through the soil profile, and will help cultivated soil saltdrainage.(2) Soil organic matter showed an increasing trend, in the order of Tamarix ramosissimaLedeb.＞Festuca arundinacea Schreb.＞Helianthus annuus. Soil salinity showed fluctuatingchanges which could be shown that sailt content in spring was higher than that in the lastautum, because salt back to the soil surface was more serious in spring. The same can be seenthat the degree of salt backing was in the order of0-20cm＞20-40cm＞40-60cm, and the totalsalt content of soil reduce in the same order with halophyte-reclamation. The sequence ofreducing the total salt content was Tamarix ramosissima Ledeb.＞Festuca arundinaceaSchreb.＞Helianthus annuus. Soil nutrients in halophyte roots depth showed fluctuatingchanges, that is soil nutrients in spring was higher than that in the last autum. Availibal N inthe soil with planting Tamarix ramosissima Ledeb was higher than that before reclaimation,but Festuca arundinacea Schreb and Helianthus annuus consumpted more available N, andalso explained that application N fertilizer during growing season could enhance reclamationeffects. Tamarix ramosissima Ledeb and Helianthus annuus could promote the slowlyavailable P translating to available P in the soil, but P fertilizer would be applicated to theFestuca arundinacea Schreb to increase its reclamation effects. Under Helianthus annuus,available K increase slight, but decreased in soil with planting Tamarix ramosissima Ledeband Festuca arundinacea Schreb. Soil physical properties was improved and soil retentionK was released that could be absorpted and utilizated by halophyte. Therefore, releasing Kand fertility were both closely relating to the total salt content. With thehalophyte-reclamation time gone, ESP%changes showed a fluctuating decreasing trend. Inthe first growing season, substitution Na+in20-40cm depth soil under Helianthus annuusshowed by the "clustering" phenomenon, therefor shallow plouge and rake little halpe to soilsalt drainage. Improve the permeability of the soil is a prerequisite of washing salt.(3) With planting halophyte, microbial environment of saline-alkali soil was improvedsignificantly. The ability of improvement was in the order of Tamarix ramosissima Ledeb.＞Festuca arundinacea Schreb.＞Helianthus annuus. Salt content, bulk dencity and ESP%allcorrelate to bacteria and fungi negativly in soil. Salinity stress is bad to soil microbialenvironment development. Organic matter, available K correlate to both fungi andactinomyces negativly in soil respectively, reducing salt content, bulk dencity and application organic fertilizer can increase soil microbial quantity and improve the soil microbialenvironment.(4) The test result show that soil total salt content and halophyte emergence (reviving)rate was a negative linear correlation. Emergence (reviving) rate in three consecutive yearsshowed that soil salt content was gradually reduced, and soil structure was graduallyimproved. The relative growth velocity (RGV) together with the ratio of free water and boundwater showed that salt tolerance of this three types of halophytes are Festuca arundinaceaSchreb.＞Tamarix ramosissima Ledeb.＞Helianthus annuus. The increase of biomass annualcash crops can be more clearly reflect the treatment effect.(5) The distribution of salt ions in root, stem and leaf of halophyte was ensured (In theorder of Tamarix ramosissima Ledeb, Festuca arundinacea Schreb and Helianthus annuus,distributions of Cl-in root, stem and leaf of halophyte was1.7:1:7.0,0.5:1:2and0.3:1:0.3,Ca2+was1.5:1:4,4.7:1:2and1:1:5, K+was1.4:1:2.1,0.6:1:1.5and0.2:1:1, Na+was1.3:1:2.2、5:1:1.3and2.5:1:0.8respectively). The capacity of Tamarix ramosissima Lede.absorption and transport Na+was strongest in this three types of halophyte, so Tamarixramosissima Ledeb. is more suitable for cultivation in the saline-alkali soil full of Na+. Theactive absorption of halophytes to soil salinity was calculated, and (Tamarix ramosissimaLedeb, Festuca arundinacea Schreb, Helianthus annuus)“AM desalination rate”(0.8%,2.0%and4.3%) and “EPIE desalination” rate (81.1%,65.9%and46.8%) were calculated. Thereforthe reduction of soil salinity is not only relating to the leaching of water but also to absorptionof halophyte. With the active of absorption and migration salt of halophyte,halophyte-reclamation is irreplaceable in a number of reclamation measures. Test showedTamarix ramosissima Ledeb reclamation scope of soil properties, which would proposeTamarix ramosissima Lede planting mode——80×80cm, and the “品”shaped staggeredplanting is appropriate.In summary, halophyte-reclamation is an effective way of saline-alkali soil improvement,which not only can improve soil physical, chemical and microbiological propoties, but alsocan absorb and migrate the salt, and which also can produce some economic benefit. Therefor,halophyte-reclamation is irreplaceable. In addition, the complex halophyte-reclamation,halophyte-reclamation cooperating to farming measures would made more significantreclamation effects. |
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