Effects Of Different Oilseed Flax Rotation On The Soil Nutrient, Biological Characteristics And Crop Yield

Oilseed flax is one of the important oil and economic crops in the northern of China.With the increasing of the oil price,continuous cropping oilseed flax widely occured,which seriously affects the yield and quality of the sesame oil and retarding the healthy development of the flax industry.At the same time,the continuous cropping of oilseed flax also leads to a large amount of soil nutrient consumption and the soil disease is aggravated.And these threatened the health of the soil.In order to improve the sustainable ability of farmland production and the healthy development of flax industry,it is very important to study the reasonable rotation system for oilseed flax production.A long-term fixed-site experiment was conducted in 2013 at the oil station of Dingxi Academy of Agricultural Sciences with 13 different rotation modes were set up:continuous cropping oilseed flax,Flax-wheat-potato-flax?FWPF?,wheat-potato-flax-flax?WPFF?,potato-flax-Jax-barley?PFFW?,flax-Jax-wheat-Potato?FFWP?,Wheat flax-potato-flax?WFPF?,flax-potato-flax-wheat?FPFW?,potato flax-wheat flax?PFWF?,flax-wheat-flax-Potato?FWFP?,wheat-potato-wheat-flax?WPWF?,potato-wheat-flax-wheat?PWFW?,wheat-flax-wheat potato?WFWP?and flax-wheat-potato-Wheat?FWPF?.The aim of this study was to realize the effects of frequency and rotation patterns of flax on soil nutrients,biological characteristics and yield of crops,and to reveal their response mechanism to different rotation patterns.The main results obtained are as follows:1.The rotation of flax with wheat and potato increased soil organic carbon,total nitrogen and available phosphorus in 0⁶0cm soil layer,but significantly decreased the total phosphorus content of this soil layer.Compared with pre-rotation and continuous cropping oilseed flax,the soil organic carbon content in the soil layer of 0⁶0cm soil was increased by 23.69%and 19.94%in rotation systems,respectively,and the WPWF treatment in the 25%flax system was significantl.Compared with the rotation and fallow,continuous cropping significantly reduced the total nitrogen content in0⁶0cm soil layer,its total nitrogen decomposition rate was up to 0.91 Mg hm_-² year^-1,at the same time,the content of ammonium nitrogen in this soil layer was increased,and the content of nitrate nitrogen below the 60cm was obviously reduced.The total nitrogen decomposition rate of 0⁶0cm soil layer in the flax rotation was 73.04%and 103.43%lower than that of continuous cropping and fallow.At the same time,the content of ammonium nitrogen in each soil layer was reduced and the content of nitrate nitrogen below 60cm was increased.Compared with continuous cropping and leisure,flax rotation significantly reduced the total phosphorus content in 0³0cm soil,and increased the content of available phosphorus in this soil layer,especially PFFW treatment in the 50%flax system.2.Oilseed flax with wheat and potato rotation can improve soil urease and catalase activity in0¹0cm soil layer,increase microbial biomass carbon and microbial entropy in 0³0cm soil layer soil,but obviously reduce microbial biomass nitrogen content.Compared with the pre-rotation,fallow and continuous cropping oilseed flax,the soil urease activity in 0¹0cm soil was increased by 437.65%,682.86%and 34.27%respectively,by crop rotation,especially in the 25%flax rotation system,and the urease activity in the 10³0cm soil layer of the oilseed flax continuous cropping was the highest,which was 581.04%and 59.95%higher than that of the pre-rotation and fallow.The activity of catalase in 0¹0cm soil layer of oilseed flax rotation is significantly higher than that of fallow and flax continuous cropping,especially for the PWFW mode in 25%flax rotation system.The soil microbial biomass carbon in the 0³0cm soil layer in oilseed flax rotation systems was obviously increased by 12.38%⁷0.46%than that of fallow and continuous cropping oilseed flax,and the microbial biomass entropy of the soil layer was obviously improved,and the FPFW mode in the 50%flax rotation system was prominent.Compared with the rotation and fallow,the continuous cropping of oilseed flax obviously improved the soil microbial nitrogen content of the0³0cm soil layer,and obviously reduced the carbon and nitrogen ratio of soil microbial biomass.3.In all soil samples,the total number of Proteobacteria,Actinomycetes,Anhydride,Acidobacteria,Gemmatimonadetes and Pseudomonas Bacteroidetes gate in the 25 doors of soil bacteria was 88.90%of the total sequence and became the dominant population.The diversity of soil bacteria could be significantly improved by crop rotation and continuous cropping oilseed flax,and with the advance of the year,the abundance of Kaistobacter,Skermanella and Methylobacterium decreased year by year,and the Modestobacter,Leatzea and Leatzea increased year by year.The abundance of bacteria and Nitrospira increased year by year.Compared with rotation and fallow,continuous cropping oilseed flax significantly increased the abundance of Arthrobacter,Kaistobacter and Modestobacter.4.Different crop rotations had a greater influence on the soil fungal population structure,and the dominant population changed in rotation,continuous cropping and fallow systems.The abundances of harmful fungi were reduced by crop rotation.The abundances of various harmful fungi were obviously improved by the continuous cropping of oilseed flax,and the abundance of a few beneficial bacteria was also increased.The abundance of Plectosphaerell and Fusariu was increased by continuous cropping of flax and crop rotation,compared to pre-rotation.The abundance of Fusarium was significantly reduced in rotation and fallow,compared with the continuous cropping of oilseed flax,and the PFWF mode in the 50%flax rotation system decreased the maximum.Compared with the pre-rotation,the abundances of Geomyces?P<0.05?were significantly reduced by the crop rotation and continuous cropping of flax,and the decreaseing in the continuous cropping of flax was the most,and the decreaseing in FWPW of the 25%flax rotation system was the smallest.Compared with pre-rotation and fallow,the abundances of Plectosphaerell were increased by the rotation and continuous cropping of the flax,especially in the continuous cropping of the flax system,which was 244.82%and 7868.61%higher than that of pre-rotation and fallow.Compared with the continuous cropping of flax,the microbial abundance of Plectosphaerell was significantly reduced by rotation,and the maximum reduction was FWPF mode in the 50%flax rotation system?P<0.05?.Compared with the pre-rotation,fallow and crop rotation,the abundances of the harmful bacteria of Cylindrocarpon and Thanatephorus and Metarhizium?P<0.01?were significantly improved.5.The relationship between soil bacteria and soil physical and chemical properties and biological characteristics showed that the influence of oilseed flax continuous cropping on the number of Actinomycetes,Nitrospira,Aeromicrobium,Kribbella,and Cyanobacteria had a significant positive correlation with the total nitrogen content of soil.The total phosphorus content of soil was negatively correlated with Chloroflexi,and the total carbon content of soil was positively correlated with Nitrospira and Firmicutes.The effect of flax rotation on the abundance of Nitrospira was positively correlated with the total carbon content.The effect on the abundance of Arthrobacter,Nitrosovibrio and Flavisolibacter was positively correlated with the content of total phosphorus,nitrate and ammonium nitrogen content.The soil carbon and nitrogen ratio,microbial biomass carbon,urease and microbial entropy were significantly correlated with the Verrucomicrobia and Planctomycetes,and the soil microbial biomass nitrogen and catalase were negatively correlated with Proteobacteria,Gemmatimonadetes and Pseudomonas.6.The relationship between soil fungi and soil nutrients and biological characteristic showed that soil total phosphorus,total nitrogen,total carbon had a significangly positive correlation with Microdochium,Plectosphaerella,Psychrotolerant,Llyonectria and Fusarium.The effects of oilseed flax rotation on the Microdochium,Llyonectria,Fusarium,had relationship with soil carbon.The effects of continuous cropping of flax on the Microdochium,Plectosphaerella,Fusarium had higher correlation with soil total nitrogen.The abundance of Fusarium,Llyonectria,Stagonosporopsis had a high correlation with soil microbial carbon and nitrogen.Rhizoctonia had a significant positive correlation with the soil catalase.The effect of continuous cropping of flax on the number of deceased fungi is positively correlated with soil microbial biomass nitrogen content.7.Comapred with the wheat stubbkle,potato stubble can increase the yield of oilseed flax by an average of 16.92%.Compared with the potato stubble,wheat cropped on oilseed flax stubble can increase the production by 22.47%.The higher the frequency of oilseed flax,the greater the yield of wheat and potato.Oilseed flax rotation can increase the annual yield by 770.00⁹705.00 kg hm^-2year^-1,compared with continuous cropping of oilseed flax.The annual average yield of PFWF mode is the highest,which is increased by 1100⁹706 kg hm^-2 year^-1 compared with other treatments.Except for flax continuous cropping,the annual yield of FWFP is the lowest,which is reduced by32.18%⁸5.72%compared with other treatments.50%?I?the annual yield of flax is the highest,which is higher than that of continuous cropping of oilseed flax,50%?II?flax and 25%flax,than144.00³596.00 kg hm^-2 year^-1.