Annual dynamic change of N, P and K contents as well as fertilizer requirement of jujube trees(Zizyphus jujuba 'Tongxinyuanzao') in Ningxia

Abstract:【Objective】Chinese jujube is one of the important industries of rural economic development in Ningxia. Extensive management and improper fertilization have resulted in lower fertilizer utilization rate poor yield and quality and other problems. The distributive dynamics of dry matter, nitrogen,phosphorus and potassium as well as the pattern of fertilizer requirement of‘Tongxinyuanzao'trees in Ningxia were studied, so as to provide a theoretical basis for efficient and rational fertilization and nutrition management.【Methods】Eight years old‘Tongxinyuanzao'were chosen as the sample trees and the dry matter accumulation and the dynamic change of nutrients in different types of organs were analyzed by digging the root, to explore the pattern of fertilizer requirement in each growing stage. The experiment was carried out in the Ningxia dryland water-saving high-efficiency agricultural science and technology park from March to October 2018. The park was located in Tongxin county, with 105° 59′east longitude and 36°51′ north latitude. The trial area was 0.6 hm2, and the jujube trees were grafted on the wild jujubes. The plant spacing was 3 m × 4 m, and the planting density was 840 plant · hm-2. There was a drip irrigation equipment in the trial area, and fertilization was applied by fertigation. During the growing stage,the irrigation amount was fixed at 1 500 m3∙hm-2, and urea(N ≥ 46%) 900 kg∙hm-2,monoammonium phosphate(N-P2O5-K2O: 12-61-0) 360 kg∙hm-2 and potassium sulfate(K2O ≥ 52%)600 kg∙hm-2. The soil in thetrial area was common gray calcium soil, which was alkaline with low organic matter. The total nitrogen content was extremely low the total phosphorus content was moderate,and available nitrogen, phosphorus and potassium decreased with the depths of the soil layer. The soil samples were collected once at the bud break stage, and the plant samples were collected 6 times from the bud break stage to the fruit maturity stage. The sampling time was pre-emergence stage(March 28 th), bud break stage(April 21 th), and leaf-extension stage(May 23 th), flowering stage(June 26 th), fruit swell stage(July 30 th), color-turning stage(September 3 rd) and fruit maturity stage(October 9 th).【Results】(1) The accumulation of dry matter in the whole growing stage was 23 133.65 kg∙hm-2, and the accumulation of dry matter in each growing stage was shown in the following order: color-turning stage > fruit swell stage > fruit maturity stage > flowering stage > leaf-extension stage > bud break stage, and the accumulation of dry matter in different types of organs was exhibited in the following order: root > stem > fruit > leaf.(2) During the whole growing stage, the nitrogen content of the root presented a V-shaped change, the nitrogen content of the stem presented a W-shaped change, and the nitrogen content of the leaf and fruit showed a downward trend.(3) During the whole growing stage, the phosphorus content change was as follows: leaf > fruit > root > stem, and the root, stem and leaf all showed a trend of“descending-ascending-descending,”and the phosphorus content in fruits gradually decreased.(4) During the whole growing stage, the order of potassium contents in different types of organs was basically shown as follows: leaf > fruit > stem > root.(5) During the whole growing stage, the accumulation of nitrogen was 197.08 kg∙hm-2, and the accumulation in different types of organs was in the following order: root > fruit > leaf > stem; The accumulation of phosphorus accounted for 26.37 kg∙hm-2, and the accumulation in different types of organs was shown in the following order: root > fruit >stem > leaf; The accumulation of potassium accounted for 146.80 kg∙hm-2, and the accumulation in different types of organs was shown in the following order: fruit > root > stem > leaf.(6) During the whole growing stage, the total demand for N, P2O5 and K2O was 563.03 kg∙hm-2, 241.60 kg∙hm-2 and 393.10 kg∙hm-2, respectively, with a ratio of 2.33:1.00:1.63. The total demand for N, P2O5 and K2O in the colorturning stage was the largest, which was 171.46 kg∙hm-2, 83.16 kg∙hm-2 and 168.36 kg∙hm-2,respectively, with a ratio of 2.06∶1.00∶2.02; The demand for N was high from bud break stage to flowering stage,and the demand for P2O5 and K2O increased gradually as the growing season progressed. After the fruit swell stage, the demand for N and K2O increased as the fruit matured.【Conclusion】The yield of‘Tongxinyuanzao'trees was 16 418.68 kg∙hm-2, the total demand for N, P2O5 and K2O was 563.03 kg∙hm-2, 241.60 kg∙hm-2 and 393.10 kg∙hm-2, respectively, with a ratio of 2.33:1.00:1.63; After bud break,attention should be paid to the application of nitrogen fertilizer. With the growing stage, the application of phosphorus and potassium fertilizer should gradually increase. After fruit set was completed, the application of nitrogen, phosphorus and potassium fertilizer should increase and the nitrogen, phosphorus and potassium fertilizer should be supplemented during the color-turning stage. In addition, it is necessary to pay attention to the application of potassium fertilizer, and supplement of the nitrogen and potassium fertilizers at the fruit maturity stage.