Effects Of Irrigation Methods On Humus And Its Components Of Facilities Soil

Soil samples at the depth of 0-80 cm were collected in the same greenhouse where an irrigation experiment of tomato cultivation had been conducted for 13 years.Facilities soil humus components and different combined humus in different irrigation methods which included furrow irrigation,drip irrigation and subsurface irrigation were estimated.In order to provide a theoretical basis for the rational management of water supply in greenhouse vegetable cultivation,effects of irrigation methods on quantity and quality of soil humus of facilities soil were explored.Facility ’vegetable cultivation irrigation experiment was carried out in the experiment site of Shenyang Agricultural University.There were three irrigation treatments,furrow irrigation,drip irrigation and subsurface irrigation.The upper and lower limits of irrigation control were the same,6kPa and 40kPa,respectively.The wet ratio of the wet layer is 1,0.5 and 0.5,respectively.Drip irrigation and furrow irrigation methods were the same as the local production.Subsurface irrigation of porous plastic pipe was buried at the depth of 30cm.Conventional methods were used to determine the separation of soil humus components and combined humus.The main results are as follows:Firstly,soil humus fractions and SOC under three irrigation treatments at the depth of 0-50cm decreased linearly with soil depth,while the variation at the depth of 50-80 cm was small.The results showed that the effect of irrigation on soil humus were mainly within at the depth of 0-50cm.Secondly,there were significant differences in the content and component of soil humus in different irrigation treatments at the same depth;For soil humus components(humic acid,fluvic acid and humin),drip irrigation had the highest soil humus content,whilst furrow irrigation had the intermediate one,and subsurface irrigation had the lowest at the depth of 0-20cm.And at the depth of 20-80cm,’ soil humus components were in the order of subsurface irrigation>drip irrigation>furrow irrigation.Compared with subsurface irrigation treatment,surface soil humus components(humic acid,fluvic acid and humin)of drip irrigation were higher,and decreased more quickly with the increasing soil depth.Profile distribution of soil humus components under furrow irrigation were similar with drip irrigation,and the contents were generally lower than drip irrigation and subsurface irrigation.Thirdly,according to HA/FA and optical properties(△logK),the molecular structure complexity and the molecular weight of humus in the three irrigation treatments tended to increase with the increasing soil depth.Compared with drip irrigation and subsurface irrigation,soil humus molecular structure of furrow irrigation is more complex at the depth of 0-80cm.Fourthly,the composition and combined forms of soil humus had a significant or extremely significant relationship with the main soil fertility indexes such as SOC,total nitrogen and total phosphorus.The results showed that the content of humus and the complexity of its molecular structure had an important influence on soil fertility.Overall,drip irrigation had a better effect on humus than furrow irrigation and subsurface irrigation;and the SOC in drip irrigation treatment at the depthe of 0-20cm depth could be maintained at a high level in greenhouse vegetable cultivation,and the combined forms and components of humus were higher than furrow irrigation and subsurface irrigation.This is beneficial to the nutrient supply and soil quality improvement in protected vegetable cultivation.