Analysis of nutrient contents and microbial flora in the continuous cropping soil of strawberry in different regions of Jiangsu province

Abstract: 【Objective】In recent years, different levels of continuous cropping obstacles have occurred in strawberry production in China.Continuous cropping reduces the content of soil organic matter and leads to increasing shortage of trace elements.It may also cause imbalance of microbial structure in the soil.As a result, strawberry plants become susceptible to pests and diseases that cause huge losses for strawberry producers.In our study, soils of continuous cropping of strawberry were collected from Gangshang town, Shiliu town, and Baima town, which are the main strawberry producing areas in Jiangsu province.By investigating the nutrient contents and microflora status of the continuous cropping soils at different depths in these areas, we planned to analyze the effect of continuous cropping on strawberry plants, understand the mechanisms of continuous cropping obstacles, find countermeasures, as well as provide a theoretical basis for overcoming continuous cropping obstacles in strawberry.【Methods】Soil samples were collected from strawberry greenhouses in Gangshang town, Shiliu town, and Baima town in Jiangsu province at the end of May 2016, and these areas have been continuously cropping strawberries for more than seven years.The greenhouses at different locations in each region were used and the soils of 0 to 10 cm, 10 to 20 cm, and 20 to 30 cm in depths were collected using a five-point sampling method.The soil samples were divided into two equal parts, one of which was used to detect soil microorganisms, and the other was used to determine soil physical and chemical properties.On September 5 th of the same year, 20 strawberry plants were planted in continuous cropping soils collected from each area in a potted manner, and the non-continuous cropping soils in the same area were used as the experimental control.Three replicates were conducted in this experiment.On the 57 th day after planting (November 1 st) , the status of plant growth was investigated.【Results】The organic matter content (g · kg-1) of the surface soils (0 to 20 cm) in Gangshang town, Shiliu town, and Baima town was18.40±5.42, 18.26±1.28, and 28.63±8.04, respectively, and the organic matter in Gangshang town and Shiliu town is in shortage.As the depth of the soil increased, the organic matter content in Shiliu town and Baima town showed a decreasing trend, while it increased first and then decreased in Gangshang town.The content of available nitrogen (mg · kg-1) in the surface of Gangshang town, Shiliu town, and Baima town was 75.37±1.24, 81.25±3.09, and 113.75±14.21, respectively, and the available nitrogen in Gangshang town and Shiliu town is relatively in shortage, and the content of available nitrogen in Baima town is moderate.The available soil nitrogen in the three regions was mainly concentrated in the 0 to 20 cm soil layer, and the available nitrogen content in the deeper soil layer decreased by 33%-45%.The available manganese content (mg · kg^-1) in the surface of Gangshang town, Shiliu town, and Baima town was 3.76±0.56, 44.15±3.20, and 13.06±0.85, respectively, corresponding to lacking, abundant, and moderate, respectively.The boron concentration (mg · kg^-1) in continuous cropping soil in Gangshang town, Shiliu town, and Baima town was 0.63±0.27, 0.51±0.03 and 0.25±0.03, respectively.The soil boron was moderate in Gangshang town and Shiliu town, but lacking in Baima town.The contents of available potassium, phosphorus, magnesium, iron and zinc were very high in the three regions.The result of soil electrical conductivity (EC) showed that the continuous cropping soils in Gangshang town and Baima town had mild salinization, and the soils in Shiliu town had moderate salinization.Soils in Gangshang town and Shiliu town were neutral in pH, while soils in Baima town belonged to the slightly alkaline soil.As the depth of soil increased, the abundance of soil actinomycetes in Gangshang town, Shiliu town and Baima town showed a decreasing trend;the abundance of soil bacteria in Gangshang town and Shiliu town tended to decrease;while that in Baima town increased.Interestingly, with the deepening of the soils, the abundance of fungi in Gangshang town first decreased and then increased;that in the Shiliu town showed a decreasing trend, while soils in Baima town showed an increasing trend.【Conclusion】Continuous cropping results in the loss of soil nutrients and the imbalance of microbial community structure, which will have a significant impact on strawberry production.As long as possible, continuous cropping should be avoided in the production, and soil improvement should be conducted in time.