Effect of combined fertilization of zinc, boron and molybdenum on agronomic traits and yield of Angelica dahurica

Objectives In Suining City, the genuine producing area of Angelica dahurica, the soils are defficient in available zinc, molybdenum and extremely defficient in boron, which is considered as one of the key factor to limit the production of Angelica dahurica. This experiment aimed to search the effect of combined application of zinc (Zn), boron (B) and molybdenum (Mo) fertilizers and work out an optimum micronutrient solution for A. dahurica growing in Suining areas.

Methods A field experiment with quadratic orthogonal rotation combination design was conducted in the purple soil of Suining, Sichuan Province. The mixed solutions of Zn, B and Mo fertilizers were foliar sprayed for 3 times before the vigorous growth period of A. dahurica. The agronomic traits and yield were measured after harvest in July 2015. The function models of three factors (Zn, B, Mo) on agronomic traits and yields of A. dahurica were established with the DPS software. The significance of the regression coefficient and regression equation was tested using F test. The effects of trace element fertilizers on drying rate, root density, root volume, root length, root diameter and yield of A. dahurica were analyzed using the regression equation model. The statistical frequency method and gray related degree-DTOPSIS method were applied to get the optimal fertilization program.

Results The application of Zn, B and Mo fertilizers significantly influenced the agronomic traits and yield of A. dahurica, and there were significant synergistic and antagonistic effects between the factors. Univariate analysis showed that the single factor impaction on root dry percentage, root volume, root length, root diameter and yield under the tested fertilization levels was Mo>Zn>B, and the effect on root density was B> Zn> Mo. Within the tested fertilizer ranges, Mo increased the root volume, reduced the root density, Zn increased the root diameter. Zn-B fertilizer, Zn-Mo fertilizer were antagonistic on yield, Zn-Mo fertilizer was antagonistic significantly on root volume, and Mo-B fertilizer was significantly antagonistic on root density. The optimal fertilization amount of Zn, B and Mo were 0.0305–0.0960 kg/hm², 1.0270–1.7928 kg/hm² and 0.1354–0.1774 kg/hm² based on the statistical frequency method. The production of A. dahurica achieved 44.4% more than control group when the application of Zn, B and Mo were 0.06 kg/hm², 2.28 kg/hm² and 0.17 kg/hm², introduced by the gray related degree-DTOPSIS method.

Conclusions Suitable combined application of Zn, B and Mo can significanty improve the yield of A. dahurica. The suitable combination ratio is very important for the good effects.