Effect Of Located Fertilization On Humus Component Contents And Optical Properties Of Aggregates In Plastic Shed Soil

With the rapid development of greenhouse vegetable production in China,at the same time,there are soil problems such as deterioration of soil structure,soil nutrient imbalance.How to improve or solve this problem through fertilization management is one of the important contents of current research.Therefore,this study a field location fertilization experiment was conducted in greenhouse growing tomato for seven consecutive years.There were four chemical fertilizer（N₀,N₁,N₂ and N₃）and four combined applications of chemical fertilizer with manure（M）（N₀M,N₁M,N₂M and N₃M）.Rate of N₀,N₁,N₂ and N₃ were 0,187.5,375.0,562.5 kg·hm^-2,respectively,and rate of manure was 75000 kg·hm^-2.Effects of chemical fertilizer and combined application of chemical fertilizer with manure on the content and optical properties of humus components in soil aggregates were studied.The main research conclusions are as follows:（1）Compared with same nitrogen application rate of chemical ferttilizer,combined application of chemical ferttilizer with manure promoted the transformation of silt-clay into micro-aggregates（0.053-0.25 mm）and macro-aggregates（>0.25 mm）,improved the stability of soil aggregates in the 0-20 cm soil layer.And significantly increased the contents of organic carbon and total nitrogen in macro-aggregates（>0.25 mm）and micro-aggregates（0.053-0.25mm）（P<0.05）,and increased the contents of soil organic carbon and total nitrogen（P<0.05）.In application of chemical fertilizer and combined applications of chemical fertilizer with manure treatments,the nitrogen application rate had no significant effect on soil organic carbon and total nitrogen contents,organic carbon and total nitrogen contents in macro-aggregates,micro-aggregates.（2）Compared with the application of chemical ferttilizer without nitrogen,chemical ferttilizer with nitrogen and combined application of chemical ferttilizer with manure improved the proportion of water-soluble organic carbon and total nitrogen in soil aggregates in the 0-10cm soil layer,but their contents in chemical ferttilizer was not significantly affected by nitrogen application rate.Compared with same nitrogen application rate of chemical ferttilize,combined application of chemical ferttilizer and organic fertilizer increased the contents of water-soluble organic carbon and total nitrogen in macro-aggregates.（3）Compared with same nitrogen application rate of chemical ferttilizer,combined application of chemical ferttilizer with manure reduced the proportion of carbon and nitrogen of fulvic acid and humic acid in soil aggregates in the 0-20 cm soil layer.In all treatments,fulvic acid carbon and nitrogen contents,and humic acid carbon content in soil aggregates in the 0-10 cm soil layer were higher than in the 10-20 cm soil layer.（4）Compared with same nitrogen application rate of chemical ferttilizer,combined application of chemical ferttilizer with manure increased contents and ratios of humin carbon and nitrogen in soil aggregates in the 0-10 cm soil layer.Their contents in soil macro-aggregates were significantly increased in the 10-20 cm soil layer.Overall,the combined application of chemical ferttilizer with manure promoted the transformation of fulvic acid and humic acid into humin in soil macro-aggregates in the 0-10 cm soil layer.（5）Compared with same nitrogen application rate of chemical ferttilizer,in 0-10 cm soil layer,the molecular structure of fulvic acid in soil macro-aggregates and micro-aggregates by N₀M and N₁M treatments tended to be simplified.The molecular structures of fulvic acid in soil micro-aggregates tended to be more complicated by N₃M treatment.The molecular structure of humic acid in soil micro-aggregates tended to be simplified by N₂M treatment,while the molecular structure of humic acid in soil silty clay tended to be more complicated.In conclusion,under the conditions of tomato cultivation in the greenhouse,combined application of chemical ferttilizer with manure for seven consecutive years not only promotes soil aggregate stability and its organic carbon total nitrogen contents in the 0-20 cm soil layer,but also improves quality of humus in soil aggregates,and the transformation of fulvic acid and humic acid into humin in soil macro-aggregates,further leads to fixed and stability of soil organic carbon（nitrogen）.