| Aiming to solve the indeterminacy relationship between the crown width of jujube trees and rainfall in middle arid region of Ningxia.A field experiment which is based on theory of water saving irrigation,soil hydrodynamic and crop science,has been finished with different simulated rainfall and crown width.We used geothermometer,tubular TDR system,ruler,fernier caliper,electronic scales,hanging temperature and humidity meter and drying oven,to observe soil temperature,soil water content,stem diameter,plant height,length of fresh treetop,diameter of fresh treetop and so on.We analyzed the above observational data through chart comparision,difference analysis,regression analysis,principal component analysis,factor analysis and other methods,explored the soil water dynamics,the growth traits of jujube trees in different simulated rainfall,and the optimal crown width in dry year.The main research results are as below.(1)Jujube trees have a certain role in regulating the field temperature in the case of distance 3m,but the effect is not obvious.Compared with the control group(CK),the daily mean temperature of the jujube tree field changed-0.07,-0.18,-0.03,-0.06 and-0.04℃ respectively at 0-2m height.The pot experiment and gravel-mulched field can improve the soil temperature significantly.Compared with the bare soil,the daily mean temperature of pot experiment increased 1.64,3.15.3.79,4.96 and 5.99°C at 0-25cm depth,the daily mean temperature of gravel-mulched field increased 0.92,1.42,2.92,2.67 and 3.35℃at 0-25cm depth.(2)The field holding capacity in the test area is 26.65%(mass),and the soil desity is 1.412g/cm3.In the dry year,the average water consumption per 10 days accounted for 60.5%,26.5%,13%,that is,more than half of the rainfall was consumed within the first 10 days.In the extremely wet year,the average water content of A15,A25,A35,A45 and A55 are 8.11%,9.13%,6.44%,5.42%and 8.85%respectively,the ranges are 13.29%,13.33%,12.15%,12.79%and 12.60%respectively.In the wet year,the average water content of A14,A24,A34,A44 and A54 are 4.56%,5.31%,7.52%,7.88%and 5.91%respectively,the ranges are 16,09%,15.41%,15.06%,14.83%and 14.70%respectively.In the normal year,the average water content of A13,A23,A33.A43 and A53 are 3.81%,4.13%.6.92%.2.98%and 7.81%respectively,the ranges are 13.04%,12.48%.12.44%,32.74%and 12.43%respectively.In the dry year,the average water content of A12,A22,A32,A42 and A52 are 6.40%,6.38%,4.93%,3.61%and 1.93%respectively,the ranges are 9.68%,9.25%,8.81%,8.73%and 9.29%respectively.In the extremely dry year,the average water content of A11,A21,A31,A41 and A51 are 5.52%,1.76%,4.97%.2.15%and 2.57%respectively,the ranges are 5.29%,5.55%,5.31%,4.88%and 5.06%respectively.In general,with the increase of simulated rainfall,the average soil water content increased in turn,and as the depth of soil increase,the average soil water content increase,the range becomes smaller,and it is stable relatively.(3)The cumulative growth of stem diameter,plant height.new diameter and new length showed quadratic distribution,linear distribution,quadratic distribution and logarithmic distribution,and R2 reached above 0.85.Under different simulated rainfall,water stress had a significant inhibitory effect on the growth traits of jujube trees.The cumulative growth of A15,A25,A35,A45 and A55 in each month accounted for 47.57%,12.75%,23.79%,and 15.90%respectively.The cumulative growth of A14,A24,A34,A44 and A54 and A55 in each month accounted for 24.85%,16.89%,23.07%and 35.19%respectively.The cumulative growth of A13,A23,A33,A43 and A53 in each month accounted for 40.21%,50.67%.6.73%and 2.39%respectively.The cumulative growth of A12,A22,A32.A42 and A52 in each month accounted for 40.06%,14.89%,15.45%and 29.60%respectively.The cumulative growth of A11,A21,A31,A41 and A51 in each month accounted for 20.08%,24.62%,33.13%and 22.17%respectively.(4)Based on the principal component analysis,the optimal ordering of crown width in dry year was A42>A12>A22>A52>A32.Based on the factor analysis,the optimal ordering of crown width in dry season was A42>A12>A52>A22>A32.The A42 is the optimal under the dry year in middle arid region of Ningxia.In other words,the 0.60m crown width is the optimum crown width in dry year. |
