| Huaniu apple,belonging to the Rosaceae,is mainly distributed in Tianshui City and is a specialty of Tianshui City,Gansu Province.At present,the Tianshui Huaniu apple planting area is about 2.0205 million mu,mainly distributed in arid and shallow mountain areas below 1750m.The orchard has a relatively large slope,serious soil erosion,and weak infrastructure.The perennial planting of Huaniu apple also changes the physical and chemical properties of the soil.This experiment took the apple orchard soil of Tianshui City Fruit Research Institute for 3,5,8 and 10 years as the research object,analyzed the soil physical and chemical properties of different planting years and different soil layers,the changes of soil active organic carbon component and soil organic nitrogen component content were also analyzed.The test results are as follows:(1)With the increase of apple tree planting years,the soil pH of 0-20cm soil layer had an upward trend.The planting soil pH of 8 years,10 years was significantly higher than that of 3 years,5 years;there was no obvious change in soil pH of20-40cm soil layer;soil organic carbon content in 0-20cm soil layer increased first and then decreased.After 10 years of planting,the soil organic carbon content decreased significantly;Soil total phosphorus and available phosphorus content showed an increasing trend;soil available potassium content showed a decreasing trend;soil microbial biomass nitrogen(MBN)and microbial biomass phosphorus(MBP)content showed a trend of increasing and then decreasing in the 0-20cm soil layer,with the highest content in the 5th year of cultivation.Soil nutrient content was higher in the 0-20cm soil layer than in the 20-40cm layer.(2)With the increase of apple tree planting years,the proportion of soil active organic carbon fraction showed an increasing trend,in which the proportion of soil active organic carbon fraction was 59.63%-80.94%in 0-20cm soil layer,and47.12%-78.18%in 20-40cm soil layer;in 0-20cm soil layer,the content of soil easily oxidized organic carbon(EOC)andparticulate organic carbon(POC)showed an increasing trend;the content of MBC showed an increasing trend and then decreased,with the highest content in the 5 years of cultivation;in the 20-40cm soil layer,the content of soil POC and MBC showed an increasing trend.The proportions of soil reactive organic carbon components are in the order of POC>EOC>MBC>DOC.Correlation analysis showed that soil active organic carbon components had a significant positive correlation with organic carbon and available phosphorus,and a negative correlation with pH.(3)With the increase of apple tree planting years,the content of acidolytic ammonium nitrogen(AN)in soil showed an increasing trend;the content of acid hydrolyzed amino acid nitrogen(AAN)showed a trend of first increasing and then decreasing.The order of soil organic nitrogen content was non-acid hydrolyzed nitrogen(NHN)>AAN>AN>acid hydrolyzed unidentified nitrogen(HUN)>acid hydrolyzed amino sugar nitrogen(ASN).Correlation analysis showed that ammonium nitrogen was negatively correlated with soil organic nitrogen components,and pH and MBC were negatively correlated with non-acid-degradable nitrogen.(4)With the increase of apple tree planting years,the soil C/N in the 0-20cm soil layer tended to increase and then decrease,with the highest soil C/N in the 8 years of planting,and the increasing trend of soil B_C/B_N in the 5-10 years of planting;in the20-40cm soil layer,the soil C/N in the 3 years of planting was higher than that in the other years of planting.Correlation analysis showed that EOC,POC and soil organic nitrogen fractions were significantly positively correlated;MBC was positively correlated with acidolytic nitrogen and negatively correlated with non-acidolytic nitrogen;C/N was negatively correlated with B_C/B_N.Stepwise regression analysis showed that the main factors affecting C/N were organic carbon,total nitrogen and MBN;the main factors affecting B_C/B_N were MBC,EOC,NHN,POC and organic carbon.The N components affecting EOC were mainly AN and AAN;the N components affecting POC were mainly AN and ASN;the N components affecting DOC were mainly ASN.In summary,with the increase of apple tree planting years,soil pH rises,soil total phosphorus and available phosphorus content increases,soil available nitrogen and available potassium content decreases;soil organic carbon activity increases;soil organic carbon,MBC,MBN,MBP content and soil C/N increased first and then decreased with the increase of planting years,indicating that after a certain number of years of planting,the soil microbial activity was inhibited and the soil quality of the orchard was at risk of degradation.Therefore,orchard management is being carried out.Attention should be paid to the regulation of soil pH and nutrient elements such as carbon,nitrogen and potassium. |
