| Safflower(Carthamus tinctorius L.)has important economic,medicinal and ecological values.Xinjiang is the main planting area of safflower in China,accounting for about 80%of the yield in the whole country,and known as"the hometown of Chinese safflower".Due to drought in Xinjiang,water shortage has become one of the main limiting factors in land exploitation and utilization.Studies on soil and microbial characteristics of safflower with different water gradients and irrigation regimes can provide some theoretical reference for improving the yield of safflower and cultivation and management measures.In this paper,the physiochemical properties,enzyme activity and microbial diversity characteristics of rhizosphere and non-rhizosphere soil with different water gradients(1000,2000,3000 and 4000 m~3/hm~2)and different irrigation methods(drip irrigation and diffuse irrigation)were studied in the important season of safflower lifecycle—breeding season.The results were as follows:1)Nonlinear relationship between the soil physiochemical properties,enzyme activity,microbial biomass and quantity with water addition in rhizosphere soil were found in blooming stage of safflower under different water gradients,that is soil organic matter,total nitrogen,total potassium and total phosphorus content,soil nitrate and reductase activities,bacteria,fungi,nitrogen-fixing bacteria and microbes all increased first and then decreased with the increase of water addition.2)The physiochemical properties and enzyme activity of rhizosphere soil were higher or significantly higher than that of non-rhizosphere soil under both drip irrigation and diffuse irrigation.While under drip irrigation,the microbial carbon source utilization efficiency and microbial functional diversity(Shannon diversity index H and dominance index D)of non-rhizosphere soil were lower than those of rhizosphere soil,which was contrary to the results obtained under flood irrigation and there was no significant difference between the results of integrated analysis the two irrigation methods of rhizosphere and non-rhizosphere.3)The results showed that the soil physiochemical properties and enzyme activity were higher or significantly higher than those of flood irrigation,However,soil microbial carbon source utilization efficiency and soil microbial functional diversity(H,D)were lower in drip irrigation than flood irrigation.4)Under different irrigation methods,the results of microbial functional diversity of rhizosphere and non-rhizosphere soil cultured for 72 h and 96 h were similar,but the microbial carbon source utilization efficiency of rhizosphere and non-rhizosphere soil under different irrigation methods was quite different.The main carbon sources used by non-rhizosphere soil microorganisms were carbohydrates and amino acids,while the main carbon sources used by rhizosphere microbes were sugars,amino acids and polymers.5)Under different water addition treatments,the microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),microbial biomass phosphorus(MBP)and the number of bacteria were significantly positively correlated with soil nitrate reductase.There was a significant positive correlation between MBN and bacterial number in the rhizosphere soil of safflower.Under different irrigation conditions,total nitrogen and available nitrogen,urease and cellulase,total phosphorus and catalase,available nitrogen and soil moisture content,urease,alkaline phosphatase and sucrase,available phosphorus and alkaline phosphatase and soil moisture content in safflower soil were significant positive correlated.However,the correlation relationship between available nitrogen and pH and conductivity,pH and soil moisture content and sucrose enzyme,conductivity and alkaline phosphatase were significantly negative.Under different irrigation conditions,there were significantly negative relationships between AWCD with catalase,urease with cellulase,H with catalase and cellulase in safflower soil.Soil microorganism AWCD was positively correlated with H and D,as well as H with D.The results showed that proper water irrigation(3000 m~3/hm~2 drip irrigation)had a beneficial effect on the cultivation of safflower.That is the soil physicochemical,enzyme activity and microbial diversity were higher than those of other irrigation levels.The effects of different irrigation regimes on the soil physiochemical properties,enzyme activity,microbial biomass and quantity and function of microbial diversity were not the same in the rhizosphere and non-rhizosphere.The soil microbial carbon source utilization efficiency and soil microbial functional diversity were improved by diffuse irrigation and drip irrigation improved soil physiochemical properties and enzyme activities.These results can provide a theoretical basis for further analysis of water resources allocation and irrigation methods of safflower cultivation. |
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