增氧对提高蔬菜磷利用率及缓解淹水胁迫的作用及机理研究

Some problems like high phosphorus (especially organic phosphorus) surplus in soil and low phosphorus fertilizer utilization efficiency by excessive input of phosphorus fertilizer (especially manure) in vegetable cultivation and the financial loss caused by waterlogging stress during the summer rainy season in Taihu Basin should be solved urgently. More and more pot and field experiments showed that oxygen irrigation could significantly improve crop yield and phosphorus uptake and utilization. Previous studies usually focused on the effects of oxygen irrigation on agronomic traits such as yield etc., but the mechanisms of yield and phosphorus-use-efficiency enhancements, as well as phosphorus transformation process have not been illuminated. Oxygen irrigation required specialized oxygen manufacture equipment and affected by the field topography, and the source of irrigation water was difficult to control. Oxygen fertilizer application as one of methods for rhizosphere regulation is intend to use in this project to resolve the problems existed in vegetable production, such as obvious spatial mismatch in vegetable root architecture and available phosphorus distribution, as well as the flooding stress in summer. The rhizobox is to be used to divide the rhizosphere soil from bulk soil and the oxygen and pH microelectrodes are to be used to provide data “in situ”. The effects of oxygen fertilizer application on promoting rapid growth of vegetable root and increase of root activity, as well as mineralization of soil organic phosphorus would be quantified. The mechanisms of vegetable yield and phosphorus-use-efficiency enhancement, as well as the timeliness of flooding-stress alleviation would be simultaneously clarified. The importance of oxygen in the vegetable field is to be focused on in this project, and mechanism of “reduction application and efficient utilization of phosphorus fertilizer” would be presented. It also provides new insights into alleviating hazard of agricultural non-point source pollution in vegetable field via “improving of phosphorus uptake by aeration”, and promotion of vegetable phosphorus use efficiency by reasonable regulation of phosphorus fertilizer application.

目前蔬菜地磷肥（尤其是有机肥）过量投入，导致土壤大量磷（有机磷）累积以及蔬菜磷素利用率低，同时太湖流域夏季易受涝害等问题亟需解决。大量盆栽及田间试验结果表明，增氧灌溉可显著提高作物产量及磷素吸收利用。以往的研究多关注于增氧灌溉对产量等农艺性状的影响，但对其增产增效机理及对土壤磷转化影响并未涉及。增氧灌溉需要专用的制氧设备，同时受到地势等影响，且灌溉水源存在不易控性等不利因素。本项目拟通过根际增施氧肥的调控手段解决蔬菜根系与根际磷供应存在的空间错位问题，以及淹水胁迫等实际生产中存在的问题。利用根际培养箱及氧电极原位测定等技术定量化增施氧肥促进根系早发、刺激根系生长，增强根系活力以及加速有机磷矿化，阐明蔬菜增产及磷增效机理，以及氧肥对缓解淹水胁迫的时效性。本项目以氧气为切入点，为探寻蔬菜地“减磷增效”机理带来新的视角，通过“以氧促磷”来减少磷肥投入带来的面源污染问题及合理施肥提供新的思路。

目前蔬菜地磷肥（尤其是有机肥）过量投入，导致土壤大量磷（有机磷）累积以及蔬菜磷素利用率低。以往研究表明增氧灌溉可显著提高作物产量及磷素吸收利用，但其增产增效机理及对土壤磷转化的影响是未知的。本项目拟通过根际增施氧肥（过氧化脲）的调控手段解决增氧灌溉投入高且受地形影响较大等问题，同时阐明蔬菜增产及磷增效机理。研究结果表明，尽管菜地是旱地土壤，且磷肥施用量较高，但蔬菜根际仍存在“氧亏缺”与“磷亏缺”的双亏现象。根际增氧可以显著改善根际氧环境，缓解根际“氧亏缺”现象。根际增氧通过减少土壤对磷的吸附、增加对磷的解吸以及提高有机磷矿化从而提高根际土壤磷的有效性，缓解根际“磷亏缺”现象。根际适度增氧可以显著增加根长、根体积及提高根系活力，但持续高氧浓度会抑制蔬菜根系发育进而造成减产。综合考虑产量及环境效应，追施时以30%过氧化脲替代尿素（即15%氮来源于过氧化脲）为最佳的“磷氧”配比，且理论上可减少28.8%的磷肥施用量。土壤低氧胁迫模拟试验结果表明，低氧处理下蔬菜根系变短、变粗，产量显著下降。生长中期增氧显著增加CAT酶活性，降低MDA含量，降低根系细胞受低氧引起的氧化胁迫伤害程度从而促进根系发育，同时增氧通过提高土壤磷酸酶活性增加根际生物有效磷的浓度，促进蔬菜在低氧胁迫下的生长以及对磷的吸收利用。本项目以氧气为切入点，为探寻蔬菜地“减磷增效”机理带来新的视角，通过“以氧促磷”来减少磷肥投入带来的面源污染问题及合理施肥提供新的思路。