| Soil salinization is one of the major limiting factors affecting the exploitation of salt and saline-alkaline soils.Lots of researches have been carried out on salty soil improvement technologies.There are many types of soil ameliorants which have different compositions and improvement mechanism.Domestic and overseas researches of screening and developing soil ameliorants have been reported frequently,which is an important and effective means on exploitation of saline-alkali lands.Based on the characters of coastal saline-alkali soil in Dafeng,Jiangsu,our group has developed a new ameliorant.It contains various effective components,containing pumice with a loose and porous structure,vermiculite and medical stone powder with ion exchange and adsorption in soil.Besides,it adds some microbe nutrients to raise microorganism activity,such as amino acids,vitamins and glucose,etc.All components are mixed through a series of processing in accordance with a specific proportion.Effects on plant growth were conducted by using Salicornia europaea L.as indicator plant.1).The effect of ameliorant applications at 0-15 cm layer was better than that at 20 cm layer in the experiment of the interaction between two ameliorant of the new developed ameliorant(A)and cow dung(B).Single application experiment showed cow dung(B)had better effects than the new ameliorant.Co-application experiments showed that optimal experimental treatment was A2B3(the new ameliorant of 15 t/ha and cow dung 300 t/ha),and soil layer desalting rates were 63.7%,64.88%,49.38%,and 41.52%from Jul.to Nov.,respectively.In addition,co-application effects between the new developed ameliorant(A)and cow dung(B)were more significant for improving coastal saline soil.2).By a triple factors orthogonal experiment,all the three ameliorants and their combinations could improve soil physical and chemical properties and increased the plant height and stem diameter under different treatments.Among the three ameliorants,the most obvious effective one was cow dung(C),followed by gypsum(B),and the new ameliorant(A).The beat treatment,A2B2C3,was as follows the new ameliorant of 45 t/ha,gypsum 18 t/ha and cow dung 300 t/ha.3).The results of single application experiments and co-application experiments showed that three soil ameliorants could decrease soil electric conductivity in certain degree,especially that of the surface soil.By compared with the control,in the single application experiment,the effect of gypsum on surface soil electrical conductivity was the most significant.Cow dung could keep stable improvement effects during experimental period.For single application experiment of new developed ameliorant,the level A2 was the best treatment.With increasing the amount of the new developed ameliorant,the electrical conductivity of surface soil increased.It was important to control the application amount of the new developed ameliorant.Results of the co-application of the new developed ameliorant(A),gypsum(B)and cow dung(C)showed that treatments of A2B3(the new ameliorant of 15 t/ha,gypsum of 36 t/ha),A2C3(the new ameliorant of 15 t/ha and cow dung of 300 t/ha.)and B3C2(gypsum 36 t/ha and cow dung 75 t/ha.)were the optimal combination treatments.Results showed that the best combination was A3B2C3,namely,the new ameliorant of 45 t/ha,gypsum of 18 t/ha,cow dung of 300 t/ha.According to further analysis of the best treatment,the bacterial community in soil layers of 0-5cm,5-20cm and 20-40cm were improved obviously,compared with the control.There was the most abundant species and highest diversity in the 5-20cm soil,following 0-5cm.Species richness in 5-20cm and 20-40cm soil layers were 2 times those of the control.The cluster analysis of DGGE patterns showed that bacterial community of different soil layers were divided into two groups.The results of similarity analysis showed similarity between A2B3C2 and CK was 30.5%in 0-5cm,38.5%in 5-20cm and 38.7%in 20-40cm.Therefore,the optimal treatment can improve the micro-flora significantly in coastal salt soil.In conclusion,respectively,the new developed ameliorant(A),gypsum(B)and cow dung(C)could decrease the contend of salt of different soil layers,improve the soil properties and enhance plant growth.In particular,treatments of the co-application of different ameliorants could gain better improving performance.The optimal treatment in this thesis could improve microbial biomass of different soil layers. |
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