Effects Of Potato-faba Bean Intercropping System On Soil Respiration And Bacterial Communities Under Different Cultivation Measures

As an important farmland management method,minimum tillage and no-tillage farming measures and intercropping planting patterns can not only improve soil properties and explore soil production potential,but also have an important impact on the composition and diversity of soil bacteria.This study took the potato intercropping broad bean system under different tillage measures as the research object,and set up a random block experiment with two factors of different tillage measures and intercropping patterns.The different tillage measures were no-tillage(NT),deep tillage 30 cm(CT)and rotary tillage(RT);different intercropping modes are potato monocropping(P),potato and broad bean intercropping(?),broad bean monocropping(B),a total of nine treatments.The effects of tillage measures and planting methods on soil physical and chemical properties,soil enzyme activity,soil bacterial composition and diversity,soil respiration rate and crop yield were studied.The main conclusions are as follows:(1)Farming measures combined with planting methods have different effects on the physical and chemical properties of the 0-40 cm soil layer.Through the analysis of the interaction,it can be known that tillage and planting have relatively significant effects on the physical and chemical properties of the soil.NTI treatment is the better measure and is more conducive to improve physical and chemical properties of soil.The soil total nitrogen content,nitrate nitrogen content,ammonium nitrogen content,pH,available phosphorus content,organic carbon content,soil aggregates and organic carbon content of soil aggregates under different treatments in the three growth periods of potato all vary with the soil.The deepening of the layers shows a gradual downward trend as a whole.In each treatment,the soil temperature in the 10 cm soil layer showed a gradual decline with the growth period,and the soil moisture in the 7 cm soil layer had a maximum during the tuber expansion period.On the whole,the contents of total nitrogen,ammonium nitrogen,nitrate nitrogen,and organic carbon in the soil under NTI treatment increased by 9.14%-24.79%?2.70%-37.14%?0.77%-1.01%?5.42%-36.43%respectively compared with other treatments.(2)Farming measures combined with planting methods have different effects on soil enzyme activities in the 0-40 cm soil layer,and the interaction of the two has a significant impact on soil enzyme activities.During the three growth periods of potato,the activities of the four soil enzymes under different treatments all showed a gradual decline with the deepening of the soil layer.The soil urease activity,soil invertase activity,and soil phosphatase activity under no-tillage and rotary tillage measures increased,but the catalase activity decreased.Similarly,compared with single cropping,intercropping treatment increased the soil Urease activity,soil invertase activity and soil phosphatase activity.(3)The interaction between farming measures and planting methods significantly affected the soil respiration rate during the three growth periods of potato.The soil respiration rate of most treatments(except CTB)showed a single-peak curve that first increased and then decreased.Compared with other treatments,the soil respiration rate and soil CO2 cumulative emissions of NTI treatment were reduced by 57.97%?70.90%and 56.16%?73.49%,respectively,indicating that the combination of no-tillage and intercropping had the most significant effect in increasing soil carbon sinks.(4)Through the analysis of the Alpha diversity index,it can be concluded that compared with deep tillage,no tillage measures can increase the bacterial diversity index of soil bacteria,while the intercropping treatment does not significantly promote the bacterial diversity index,even Lower than single processing.Heat map cluster analysis and NMDS analysis also show that farming and planting can affect the bacterial community structure in the soil.216 genera of bacteria were detected in soil samples.The top 20 genera and taxa with abundance greater than 1%in different treatments were similar,and Subgroup₆ had the highest relative species abundance,accounting for 12.12%to 19.30%.PCA analysis shows that environmental factors can explain the difference in flora composition at 63.91%.(5)Tillage and planting measures significantly affected potato yield.Potato yields were highest under RTP and NTP treatments,which were 29.9%and 19.3%higher than RTI and NTI,respectively.There was no significant difference in broad bean yield among the various treatments.The land equivalent ratios of the three farming treatments are all greater than 1,which has obvious advantages of intercropping.The land equivalent ratio under deep tillage measures is the highest.The results of this experiment initially reveal the effects of potato intercropping with broad bean system on soil properties,soil respiration and bacterial community under different tillage measures in the western Loess Plateau,and clarify that the combination of less no-tillage and intercropping has a more significant effect on soil properties,which is conducive to the enhancement of soil nutrient content and related enzyme activities;at the same time,it is conducive to increasing soil carbon sink,improving soil bacterial diversity index and creating a suitable microenvironment for crop growth.