Effects Of Soil Acidification On Nutrient Leaching,Microbial Diversity And Citrus Growth

compatibly cultivated on acidic soil.The acidification of citrus orchards soil is going to be an increasingly serious problem due to the environmental problems and agricultural culture and restricts its yield and quality.This study was based on the investigation results of soil acidification status and influencing factors of typical citrus orchards in Fujian Province.The effects of soil acidification on the leaching loss of nutrients,microbial diversity and physiological metabolism of citrus plants were established by indoor simulated leaching and pot experiment.Finally,layering soil column test was used to preliminarily explored to the effect of improving different layers soil acidity on citrus growth and the efficiency of different modifiers.The main reults are as follows:1.Strongly acidic soil with p H lower than 4.5 which was accounted for 67.71%among 319 honey pomelo?Citrus grandis?orchards in Pinghe County,and the acidification of sublayer was more serious than the bottom layer.The soil p H of the 32 poonkan?Citrus reticulata?orchards in Yongchun Country ranged from 3.14 to 5.4,with an average of 4.26,that of 68.75%orchards was lower than 4.5.Soil p H showed extremely significantly positive correlation with soil base saturation and the content of soil exchangeable calcium and magnesium while exchangeable hydrogen and aluminum were opposite.The degree of soil acidification went up with the increase in planting years,soil alkali nitrogen content,nitrogen fertilizer application rate and content of soil available sulfur.These indicated that acidificationwould not only reduce soil fertility resulting in the deficiency of soil calcium and magnesiumbut also aggravate by planting years and the content of soil nitrogen and sulfur.2.As results of soil acidification,the leaching loss of ammonium nitrogen was risen and nitrate nitrogen declinde,but the total amount of nitrogen leaching loss was not significantly affected.It also reducedthe maximum phosphorus uptake?Qm?and increased the amounts of readily desorbable phosphorus?RDP?and the desorption rate,enhaning the risk of phosphorus release.Meanwhile,it caused extremely significant promotion in the leaching loss amount of soluble total phosphorus,soluble orthophosphate and organic phosphorus by increasing the ratio of unstable phosphorus?H₂O-P,Na HCO₃-P?and declining stable phosphorus?HCl-P,Residual-P?.Besides,soil acidification also promoted the leaching loss of potassium and magnesium.3.The high-throughput sequencing result showed that soil acidification reduced the abundance and diversity of soil bacterial and fungal communities,among which the abundance of harmful bacteria increased but the abundance of beneficial bacteria including Dyella,Flavobacterium,Streptomyces etc.decreased;Soil acidification also reduced in the fungal community abundance,among which the abundance of Penicillium and Chaetomium decreased,and the difference in abundance of Fusarium slowed down.4.The observed lower assimilation rate of CO₂ and higher concentration of intercellular CO₂ in citrus leaves resulted by soil acidification indicated that the decrease of CO₂ assimilation might be due to non-stomatal factors.The decrease of photosynthesis was probably related to the decrease of chlorophyll content and light use enficiency,the impaired PS?electron transport chain and the metabolic disorder brought about the increase of reactive oxygen species.5.According to the results of acidity improvement on different soil layers show that the acidity improvement of 0-20 cm soil layer played an important role in root growth,and that of 0-40 cm soil layer could promote the growth of citrus seedlings more effectively.The p H of the surface soil could significantly go up by different modifiers,especially potassium carbonate type compound fertilizer which could not only effected on 0-15 cm soil layer,but also apparently to 15-40 cm,and the effect of continuous application is significantly enhanced.In summary,the soil acidification is aggravating which has caused more loss of soil nutrient loss,change of microbial diversity and community structureand inhibition of plant growth in the major production area of Citrus.The modification of acidity in 0-20 cm and0-40 cm soil layers could effectively improve the growth of citrus and the potassium carbonate type compound fertilizer performed the best improved effect.