Mechanisms Research Of Aeration Influencing Phyllostachys Praecox Plantation Under The Organic Mulching Condition

Phyllostachys praecox is a kind of scattered bamboo cultivated for edible bamboo shoots and P.praecox has many characteristics like easy cultivation,high yield,shoot emerging early,and being highly palatable.As a high-efficiency cultivation technology for producing bamboo shoots early,the organic material mulching technique is widely used in P.praecox management.However,after several years of continuous mulching,the P.praecox bamboo will inevitably degrade with characteristics like bamboo aging,flowering,and the reduction of bamboo shoots,etc.Nowadays,the degradation condition of the mulching bamboo plantation is serious,which has negative impacts on the income of farmers.Based on the previous research,we found that the distribution of P.praecox rhizome in soil horizon raised significantly with the increase of mulching times.To prevent bamboo degradation,farmers usually increase the distribution depth of P.praecox rhizomes by covering the plantation soil with exotic soil.Thus,the bamboo rhizome up-floating induced by soil hypoxia may contribute to bamboo degradation.Soil aeration may play an important role in preventing the degradation of P.praecox under mulching conditions,which can promote sustainable management,but there is still a lack of relative research.Therefore,we hypothesized that soil hypoxia induced by organic mulching leads to the recession of the P.praecox plantation,and burring tubes methods were adopted to test the hypothesis and inhibit the degradation of the mulching bamboo plantation,the inner mechanism was also discussed.The P.praecox plantation was located in the Red Soil Ecological Experimental Station,Chinese Academy of Sciences,Yingtan City,Jiangxi Province.Chicken manure（fermentation layer）and rice husk（insulation layer）were applied as the mulching materials.A 3-years mulching study was conducted from 2019 to 2021.No chemical fertilizer was applied to all treatments before mulching in 2019.Chemical fertilizer was applied to all treatments before mulching in 2020 and 2021;the mulching period was from January to March;soil aeration was achieved by drilling soil and burying PVC tubes.A completely randomized block study design was adopted,including four treatments:mulching treatment without aeration（TM）;mulching+poor aeration treatment（TA1,aeration density is 1 aeration tube per square meter）;mulching+strong aeration treatment（TA2,aeration density is two tubes per square meter）;treatment with neither mulching nor aeration（CK）;each treatment contained 3replicates.After removing mulching materials in March,compound chemical fertilizer was applied to all treatments in May,September,and November.The four treatments shared the same management during the non-mulching period.Due to the COVID-19 in 2020,soil samples and plant tissues of P.praecox were collected dynamically during the mulching and non-mulching periods in 2019 and 2021.The dynamic changes of soil physicochemical properties,soil enzyme activities,soil microbial indexes,growth conditions,and physiological characteristics of P.praecox under the four different treatments were investigated.The main conclusions are listed as follows:1.Mulching without aeration treatment（TM）significantly decreased the soil oxygen（O₂）content when compared with the no mulching treatment（CK）.The poor aeration treatment（TA1）and strong aeration treatment（TA2）significantly increased the soil O₂ content when compared with TM.TA2 treatment had the best improvement of aeration among the three mulching treatments,which increased 18.45%-23.85%of the O₂ content and reduced the thermal insulation capacity and moisture retention when compared with those in TM treatment.In the process of mulching,mulching treatments significantly increased soil pH value compared with CK;aeration can further alleviate soil acidification.The soil acidification of P.praecox was mainly due to the application of the chemical fertilizer.When compared with TM treatment,TA2 treatment significantly increased the contents of soil organic matter（SOM）,total nitrogen（N,TN）,and total phosphorus（P,TP）contents.TA2 treatment also significantly improved the soil nutrient availability（nitrate nitrogen,available phosphorus and available potassium content）in the mulching process,which was conducive to the absorption and utilization of P.praecox.Mulching treatments significantly increased the soil carbon to nitrogen ratio（C/N）.The soil nitrogen-phosphorus ratio（N/P）of all the treatments was low,which indicated the soil P content is sufficient in the bamboo plantation.2.The activities of soil urease,acid phosphatase,catalase,invertase andβ-glucosidase had a strong annual variation and increased with the mulching time.The highest soil enzyme activities were observed in summer and the lowest was in winter.Soil pH is the dominant factor affecting soil enzyme activity in the later stage of mulching.In the mulching period,TM treatment significantly increased soil urease activity when compared with CK,but aeration treatments had no significant effects on the urease activity when compared with TM treatment.There was a significant positive correlation between soil catalase activity and SOM content.Mulching treatments significantly improved soil catalase activity.3-years continuous mulching effectively improved the soil acid phosphatase activity.In the mulching period,soil invertase andβ-glucosidase activities followed the order of CK<TM<TA1<TA2.3.The contents of soil microbial carbon（MBC）and soil microbial nitrogen（MBN）also showed a strong annual variation,and increased with the increase of mulching time.The highest MBC and MBN were both observed in summer and the lowest of them were in winter.Mulching treatments（TM,TA1 and TA2）significantly increased soil MBC and MBN contents when compared with CK.Aeration had little effect on soil MBC and MBN contents when compared with TM treatment.The contents of MBC and MBN had a positive correlation with soil pH.Our results showed that continuous mulching without aeration was not conducive to soil bacterial diversity.In the later stage of mulching in 2021,TA2 significantly improved soil bacterialαdiversity index when compared with TM.This result indicated that strong aeration could significantly improve the soil bacterial diversity of P.praecox plantation.The soil bacterial community composition in the P.praecox plantation was significantly changed after3-years of mulching.At the later stage of mulching,the main dominant bacterial phyla were Proteobacteria,Acidobacteria and Chloroflexi,while the main dominant bacterial genera were Pseudomonas,Bradyrhizobium and Faecalibacterium.Principal Co-ordinates Analysis suggested that the bacterial community composition of TA2 and CK treatment clustered closely,but separated distinctly from TA1 and TM treatments.Mantel test showed that soil O₂ content is the main driving factor affecting bacterial community structure in the later stage of mulching.Structural Equation Model demonstrated that in the mulching process,aeration promoted soil nutrients mainly through the indirect path mediated by soil enzyme activities.The functional prediction based on Functional Annotation of Prokaryotic Taxa showed that TA2 treatment could promote soil C and N cycling and was conducive to the growth of P.praecox after3-years of mulching.However,long-term mulching without aeration may have a negative impact on the soil nutrient cycling of P.praecox plantation.4.Mulching significantly increased the yield and diameter at the breast height of P.praecox in 2019,especially TA2 treatment showed the best improvement.However,after3-years of mulching,the yield of P.praecox decreased significantly,especially the yield of TM treatment decreased by 35.49%compared with that in the first year’s mulching.TA2 could significantly increase the yield of P.praecox when compared with TM treatment,and effectively inhibit the degradation of P.praecox plantation.Continuous mulching（three years）without aeration increased the N/P ratio of P.praecox leaves,indicating that although soil P content was great,mulching without aeration would reduce P absorption of P.praecox,resulting in bamboo P deficiency.The rhizome buds of P.praecox decreased significantly with 3-years mulching,especially TM treatment decreased 81.90%rhizome buds.TM treatment significantly increased the up-floating of bamboo rhizome.TA2 alleviated the up-floating of the bamboo rhizomes,and significantly improved the diameter of the bamboo rhizome.After 3-years of mulching,TM treatment seriously limited the stomatal conductance and transpiration rate of the P.praecox leaves.TA2 treatment plays a vital role in improving the photosynthetic capacity of P.praecox under mulching conditions.The MDA content,antioxidant enzyme activity and anaerobic respiratory enzyme activity of TM treatment increased significantly compared with other treatments,indicating that mulching leads to the hypoxia stress of P.praecox.TA2increased soil oxygen content and effectively alleviated the hypoxia stress of P.praecox.In conclusion,the hypoxia stress of P.praecox rhizome is induced by mulching.Furthermore,3-years mulching had negative effects on the growth and development of the P.praecox rhizome.Continuous mulching significantly decreased soil bacterial diversity,thereby affecting soil enzyme activity and soil nutrient transformation,inducing bamboo rhizome up-floating,which negatively impacted the growth and production of P.praecox.Aeration treatment,especially the strong aeration treatment,alleviated the hypoxia of the P.praecox root system,enhanced the photosynthetic capacity of P.praecox,improved soil bacterial diversity and nutrient availability,and promoted the growth of P.praecox.The results of the current study can provide a theoretical basis for the degradation mechanism of P.praecox plantation,and provide reference and improvement measures for the sustainable management of P.praecox plantation.