| Nitrogen directly affects the yield and quality of medicinal plants.Therefore,rational application of nitrogen fertilizer plays an important role in ensuring the safety and effectiveness of medicinal materials.The suitable habitat for the growth of Angelica sinensis is the high-altitude mountains above 2000 meters.Due to the problems of transportation and cost,farmers mainly apply inorganic fertilizer and rarely apply organic fertilizer.In the rainy season,the leaching loss of fertilizer on the hillside land is seriously,so the amount of fertilizer is used,the fertilizer utilization rate is very low,the soil ecology of field is deteriorating,and the yield and quality of A.sinensis is decreasing year by year.Attapulgite(ATP),as a potential soil ecological regulator,has shown many advantages in agricultural production.The advantages of nutrient comprehensiveness and diversity of organic fertilizer is very important for the quality of medicinal materials.Nitrogen reduction combined with organic fertilizer / attapulgite may be of great significance for the quality,efficiency and sustainable development of medicinal materials.Therefore,this paper carries out the effects of nitrogen reduction combined with organic fertilizer / Attapulgite on soil characteristics,A.sinensis growth,yield and quality of medicinal materials,puts forward the reasonable proportion of nitrogen reduction,and discusses the mechanism of nitrogen reduction combined with organic fertilizer / attapulgite in improving the yield and quality of A.sinensis.In 2019 and 2020,pot experiment and field experiment were carried out respectively in Danggui Road real estate area,Min County,Gansu Province.The pot experiment adopts a completely randomized design,with seven treatment groups,(1)N100(conventional nitrogen fertilizer dosage),(2)N75OA(conventional nitrogen fertilizer dosage reducted by 25% + ATP and organic fertilizer),(3)N50OA(conventional nitrogen fertilizer dosage reducted by 50% +ATP and organic fertilizer),(4)N25OA(conventional nitrogen fertilizer dosage reducted by 75%+ ATP and organic fertilizer),(5)N0(no nitrogen fertilizer,ATP and organic fertilizer),(6)CK(no fertilizer),(7)CKS(no fertilizer + sterilized soil),Treatments 1 ～ 5 were applied with the same amount of conventional phosphorus fertilizer and potassium fertilizer,and treatments 6 and7 were not applied with any fertilizer.The randomized block design was adopted in the field plot experiment.The amount of fertilization was the same as that in the pot experiment.Six treatment groups of 1 ～ 6 in pot experiment were set up.The main research results was as follows:1.Fertilization methods had no significant effect on plant height,but different fertilization methods had significant effects on plant width and stem diameter of A.sinensis.Compared with N100 group,nitrogen reduction combined with organic fertilizer / attapulgite could increase plant width and basal stem diameter of A.sinensis in root expansion stage(REP)and reduce plant width in dry matter accumulation stage(DAP).It is suggested that the slow-release effect and comprehensive effect of nitrogen reduction combined with organic fertilizer / attapulgite can fully ensure the nutritional demand of plant growth,make the plant enter the vigorous growth period earlier,and the structural carbohydrates produced from aboveground sources flow to underground roots earlier,resulting in the expansion of the pool,so as to promote the root growth and dry matter accumulation of A.sinensis.Therefore,the attapulgite / organic-inorganic combined application group had greater fresh weight per plant at harvest.2.The effect of nitrogen reduction combined with organic fertilizer / attapulgite on net photosynthetic rate(Pn)of leaves in leaf cluster stage(LCP)and DAP was not significant,but it could significantly increase REP Pn.It may be because nitrogen reduction combined with organic fertilizer / attapulgite improved soil physical,chemical and biological properties,and finally increasesd soil nutrient availability and available nutrient content,which promoted root development and nutrient absorption,so as to improve leaf nitrogen content,increase Pn and promote the healthy growth of A.sinensis plants.Compared with N100 group,nitrogen reduction combined with organic fertilizer / attapulgite group can improve REP soil respiration intensity(SR)and reduce harvest period of medicinal materials(MHP)SR.Pearson correlation analysis showed that REP Pn had a very significant positive correlation with REP SR,and REP Pn had a very significant positive correlation with the fresh weight of A.sinensis root of MHP,indicating that there had a strong photosynthetic source and respiratory flux during the vigorous growth period,which was of great significance to the increase of root weight of A.sinensis in the underground part during the harvest period.3.Compared with N100 group,nitrogen reduction combined with organic fertilizer /attapulgite group had greater fresh weight per plant.The average fresh weight per plant of A.sinensis in N50 OA,N75OA and N25 OA groups were 72.86 g,71.26 g and 66.36 g respectively,which were 1.44,1.41 and 1.32 times higher than that in N100 group.The surface of A.sinensis is dilute brown,flexible,and the section is yellow white.The cambium ring obviously separates the phloem and xylem,and the thickness ratio of phloem / xylem of lateral root(tail of A.sinensis)is significantly greater than that of body of A.sinensis and head of A.sinensis.Nitrogen reduction combined with organic fertilizer / attapulgite had a significant effect on the properties of A.sinensis,mainly manifested in the thickening of odor and the obvious increase of lateral roots.Compared with N100 group,the combined application of nitrogen fertilizer and OA could increase the contents of total volatile oil,total ferulic acid,ligustilide and other phthalides in A.sinensis.The activity determination results of different parts of A.sinensis showed that the contents of ferulic acid and phthalein volatile oil in tail of A.sinensis(lateral root)were the highest,followed by body of A.sinensis and head of A.sinensis.The results suggested that nitrogen reduction combined with organic fertilizer / attapulgite could change the morphology of A.sinensis and increase the number of lateral roots to a certain extent,so as to improve the content of active components and fresh weight of plant,so as to improve the quality of A.sinensis.4.Nitrogen reduction combined with organic fertilizer / attapulgite had a certain effect on the distribution of soil aggregate structure.Compared with N100,nitrogen reduction combined with organic fertilizer / attapulgite group could increase content of > 2.5 mm aggregates and decrease content of < 0.25 mm aggregates.The higher the aggregate content with particle size of0.25 ～ 5.00 mm,the greater the soil permeability,and the stronger the ability of soil to retain water and supply water required by plants.Therefore,nitrogen reduction combined with organic fertilizer / attapulgite can improve the structure and composition of soil aggregates.Nitrogen reduction combined with organic fertilizer / attapulgite could increase the contents of soil alkali hydrolyzable nitrogen,available phosphorus,available potassium and organic matter during the growth period of A.sinensis.Nitrogen reduction combined with organic fertilizer / attapulgite had different effects on 9 soil enzymes involved in soil C,N,P and s cycle.In general,nitrogen reduction combined with organic fertilizer / attapulgite can improve the activities ofβ-1,4-glucosidase,phosphomonoesterase and sulfatase,can reduced the activities ofβ-1,4-xylosidase,polyphenol oxidase and peroxidase.5.The rhizosphere soil of A.sinensis in seven treatment groups was sequenced to explore the effects of different fertilization modes on microbial diversity and community structure.Compared with CK,different fertilization modes can improve the richness and diversity of microbial community in Angelica rhizosphere soil.Compared with N100,the combined application of nitrogen fertilizer and OA reduced the richness of rhizosphere bacterial community of A.sinensis,but improved the diversity.Compared with CK,although the bacterial community richness of sterilization group(CKs)decreased significantly,the bacterial community diversity did not decrease significantly,suggesting that the formation of rhizosphere microbial community in the growth process of A.sinensis is a process of interaction and dynamic shaping between plant rhizosphere and soil environment.Principal coordinates and NMDS analysis showed that the combined application of inorganic nitrogen fertilizer and OA,inorganic nitrogen fertilizer and soil sterilization significantly affected the community structure of bacteria and fungi,while P fertilizer and K fertilizer had little effect.By analyzing the relative content changes of main phylum and genus among different groups and the redundancy analysis of phylum,soil enzyme and soil nutrient content,it shows that there is a close relationship between fertilization mode microorganism soil nutrient.6.In order to apply the potted research results to production practice,the effects of nitrogen reduction combined with organic fertilizer / attapulgite on the yield and active ingredient content of A.sinensis were studied.The results showed that the results of field experiment and pot experiment were basically the same.Compared with N100 group,the average yield of A.sinensis in N75 OA,N50OA and N25 OA groups increased by 41%,33% and 23% respectively.The contents of total ferulic acid and total volatile oil of phthalide were the highest in N75 OA and N50 OA groups,but there was no significant difference between the two groups,followed by N25 OA group.The organic-inorganic combined application group was higher than the inorganic nitrogen fertilizer group.In conclusion,on the one hand,nitrogen reduction combined with organic fertilizer /attapulgite has a slow-release effect on nutrients and improves fertilizer utilization.On the other hand,the combined application of inorganic organic fertilizer provides comprehensive nutrition for microorganisms,causes changes in microbial community structure and diversity and enrichment of functional microorganisms,promotes the secretion of more soil enzymes circulating C,N,P and S,strengthens the mineralization process of organic matter in soil and provides more available nutrients in soil,so as to promote root development and meristem more lateral roots.The root system transports more nutrient elements to the aboveground functional leaves of the plant,increases the content of nitrogen,phosphorus and other elements in the leaves,so as to make the leaves have higher photosynthetic efficiency,promote the construction of a larger reservoir,and finally lead to the growth of underground roots of A.sinensis,the increase of fresh weight of single root,the synthesis and accumulation of more total ferulic acid and volatile oil active substances in phloem,so as to improve the quality of A.sinensis.In short,the interaction and interaction between soil nutrients,microorganisms and plant roots cause the transformation and effectiveness of soil nutrients,and ultimately affect the growth of A.sinensis plants,the changes of root morphology and the synthesis and accumulation of active substances,which may be an important mechanism for nitrogen reduction combined with organic fertilizer /attapulgite to improve the yield and quality of A.sinensis. |
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