土壤盐碱化对紫花苜蓿(Medicago sativa L.)生物学特征的影响

Biological characteristics responses of alfalfa (Medicago sativa L.) to soil salinity-alkalinity

松嫩草地由于自然及人为因素的影响,出现了严重的次生盐碱化现象。盐碱化与次生盐渍化导致草地生物量急剧下降,许多优质牧草(如羊草等)消失,严重影响该区域畜牧业的发展,因此改良盐碱土,发展人工草地已成为该区域畜牧业可持续发展的重要途径。鉴于吉林西部草地的气候与土壤特点,本研究选择砂土改良之后建植的人工草地,开展了土壤盐碱化对紫花苜蓿生物学特征影响的研究。采用大地电导率仪(EM38)将研究区域分成3个盐碱程度(轻度、中度与重度);测定土壤(1.0m深度)盐碱指标,并对紫花苜蓿生物学特征进行长期调查。结果显示,紫花苜蓿的生长速率、生物量、鲜干比(FWR)、Na/K和叶绿素(SPAD)与土壤盐碱化程度呈负相关关系。随着土壤盐碱程度的增加,紫花苜蓿第一茬的生长速率由1.70cm·d^-1显著降低到0.40cm·d^-1(P<0.05),而第二茬的生长速率则由1.40cm·d^-1降低到0.45cm·d^-1;SPAD由62.3下降到53.2;Na/K由1.49减小到0.78;生物量(干重)由1.88t·hm^-2降低到0.20t·hm-2;鲜干比由2.59降低到1.80;而随着土壤盐碱化程度的增加,紫花苜蓿的茎叶比由1.72增加到了2.61。因此,土壤盐碱化降低了紫花苜蓿产量与品质。本研究结果可为盐碱化土地的利用以及盐碱化人工草地生产力提升提供理论依据。

The salinity-alkalinity of Songnen grasslands in Northeast China is aggravated due to natural and other human activities.Therefore,the local livestock husbandry is significantly hindered by decline of grassland biomass and the disappearance of high-quality forage species,thus salinity-alkalinity soil needs to be improved for sustainable animal husbandry development.Considering the soil,climate and water resources,we selected artificial grassland,which was set up on saline-sodic soils and ameliorated by sandy soils,to investigate the effects of soil salinity-alkalinity on alfalfa ( Medicago sativa L.) bio-characteristics.Three degrees of soil salinity-alkalinity (mild,moderate and severe) were detected by EM 38,and soil samples (1.0 m depth) were collected for measuring the soil background of the field in 2015;in addition,alfalfa samples were collected twice for revealing the dynamics of alfalfa characteristics from 2016 to 2017.The results showed that there were negative correlations between soil salinity-alkalinity degrees and the growth rate,biomass,ratio of dry/fresh,Na/K and SPAD.With increasing salinity-alkalinity degrees,the growth rate of first and second harvests declined from 1.70 to 0.40 cm · d^-1 and from 1.40 to 0.45 cm · d^-1 ,respectively;SPAD diminished from 62.2 to 52.8;the Na/K decreased from 1.49 to 0.78;the forage biomass (dry weight) reduced from 1.88 to 0.20 t · hm -2;the ratio of fresh and dry weight decreased from 2.59 to 1.80;while,the stem/leaf ratio increased from 1.72 to 2.61.Finally,results of this study indicated that the alfalfa dry yield and quality could be impacted by soil salinity-alkalinity.This study would offer basic theory support of the utilizations of saline-sodic lands and the promotion of saline-alkali artificial grassland productivity.