| In the long-term tobacco planting production process,in order to pursue higher tobacco leaf yield and economic benefits,over-fertilized and mono-cropped are adopted.Although this kind of measure could increase leaf yield,it is accompanied by the continuous decline of soil fertility and the increasing amount of fertilizer per unit area,thus forming a vicious circle between soil quality and tobacco farmers.In order to find out the impact of these management measures on soil structure and soil carbon and nitrogen,the long-term positioning test field of Yuxi Research and Test Base,Yunnan Province,was established in 1998,this experiment mainly studied:(1)different cultivation methods(tobacco mono-cropped,tobacco-rice rotation)and different fertilization management(0,75 and 112 kg N/ha and 60 kg N/ha + manure)for water-stable aggregates and soil organic carbon(SOC)),total soil nitrogen(TSN)content and the quality of tobacco production;(2)75 kg of pure nitrogen per hectare(Kg N / ha)fertilizer application conditions of tobacco rotation,tobacco-rice rotation two cultivation methods for different soil layers(0-10 cm,10-20cm)seasonal changes in soil physical and chemical properties in 2016 and 2017 for two consecutive years;(3)long-term continuous cropping under different fertilizer types(fertilizer,organic fertilizer)on soil physical and chemical properties in different soil layers in 2016-2017 Seasonal changes.The main findings are as follows:1.Two cultivation methods(tobacco mono-cropped,tobacco-rice rotation),four fertilization levels(0,75 and 112 kg N / ha and 60 kg N / ha + manure),after 18 years of continuous treatment,different cultivation methods,Fertilization amount and manure have a great influence on SOC and TSN in the agglomerates and aggregates of tobacco planting soil.Compared with continuous cropping and long-term application of fertilizers,rotation and application of manure can effectively increase the ratio of large particle size(> 250 μm)and geometric mean diameter(GDM)in soil aggregates,Reducing the proportion of micro aggregates and clays(< 250 m).At the same time,increasing the size of aggregate components and increase the content of SOC and TSN.2.Large aggregates(> 250 um)are greatly affected by tillage patterns and irrigation.Compared with tobacco mono-cropped,tobacco-rice rotation treatment can significantly improve soil structure,Meanwhile the contents of SOC and TSN in micro aggregates,clay(< 53 um)and soil organic carbon stocks(SOCS)in surface soil were also increased.In 10-20 cm layer,large aggregates proportion and stability is much more better than 0-10 cm.Thus,Agricultural measures such as rotation and irrigation have significant effects on the proportion of large aggregates and their internal carbon and nitrogen contents.Compared with tobacco mono-cropping,tobacco-rice rotation contributes to the rapid recovery and relative stability of the proportion of large aggregates.3.With the change of season,BD,MWD,GMD showed a wave-like periodic trend,while the proportion of large and small aggregates varied significantly with the season in the 10-20 cm layer compared with 0-10 cm layer.Due to the development of tillage and irrigation activities,the proportion of small aggregates increased and the proportion of micro aggregates decreased.The proportion of large aggregates and small aggregates in organic fertilizer treatment was significantly higher than that in inorganic fertilizer treatment,but the proportion of micro aggregates and clay was lower.Due to the influence of precipitation,on the one hand,the seasonal variation of large aggregates organic carbon content in surface soil in 2017 is greater than that in 2016,on the other hand,the leaching and denitrification of nitrogen in soil are enhanced,and the total nitrogen in soil decreases greatly from August to September 2017.Because the soil organic carbon pool is relatively stable,it is less affected by water.Therefore,tillage and irrigation can reduce the proportion of large aggregates,but the application of organic fertilizer can help the aggregation of large aggregates and improve soil structure.To sum up: In the two-year dynamic research process,tobacco-rice rotation can effectively improve soil physical and chemical properties,promote the formation of large aggregates,and increase soil organic carbon and TSN content.The application of organic fertilizer is beneficial to the aggregation of micro aggregates.The transformation of the body increases the SOC and TSN content in soils and aggregates of different particle sizes.With the extension of sampling time,tobacco-rice rotation and manure treatments maintains the relative stability of total SOC and SOCS in large and small agglomerates,providing a stable and stable soil environment for crop production. |
PDF Full Text Request