The Response Of Greenhouse Gas Emissions From Greenhouse Lettuce To Organic Fertilizer And Its Mechanism

Organic manure composting and lettuce-cultivated fertilization experiments were carried out in solar greenhouse,located in practical teaching & scientific research base on soil ecological environment in Liaocheng University.The greenhouse gases?GHGs?emission flux of ten fertilization treatments,such as decomposed cow manure?C?,chicken manure?H?,sheep manure?S?,cow manure and straw?CSt?,chicken manure and straw?HSt?,sheep manure and straw?SSt?,cow manure,chicken manure and straw?CHSt?,cow manure,sheep manure and straw?CSSt?,sheep manure,chicken manure and straw?SHSt?,cow manure,chicken manure,sheep manure and straw?CHSSt?were analyzed.The effects of the ten fertilization treatments mentioned above on soil physical & chemical properties,enzyme activity and GHGs emission were studied.The relevance of soil physical & chemical properties with soil enzyme activity was observed.The impacts of soil physical & chemical properties and soil enzyme activity on GHGs emission flux was discussed.The main research results were as follows:?1?GHGs emission trend and GWP under manure-composting treatmentsCH₄ and CO₂ emission flux of each treatment firstly increased and then declined with the time going on,and the maximum value appeared between the second and third week after the composting.The maximum value of N₂ O emission flux under C,H,CSt,HSt,CHSt treatments appeared among the fifth,sixth,and seventh week.However,which of S,SSt,CSSt,SHSt,CHSSt treatments appeared during the first and second week.The total CO₂ emission flux decreased in sequence of CHSt>HSt>SHSt>CHSSt>SSt>CSSt>CSt>H>S>C.The total CO₂ emission fluxes of all straw-adding treatments were significantly higher than that of H,S,C treatments.The total CH₄ emission fluxes decreased in order of H>C>CHSt>HSt>CHSSt>CSt>SHSt>S>CSSt>SSt.The total N₂ O emission flux decreased successively as CHSt>SHSt>HSt>S>CHSSt>CSSt>SSt>CSt>H>C.The GWP decreased according to CHSt>HSt>SHSt>CHSSt>CSSt>SSt>S>CSt>H>C.CO₂ and N₂ O emission was the main sources for GWP in the process of manure composting due to CO₂ and N₂ O emission amount accounted for more than 82%.?2?Influence of different fertilization treatments on soil physical & chemical propertiesManure fertilization increased soil content of organic matter,nitrogen,phosphorus and potassium.The incremental ranges of available phosphorus and potassium under the same fertilization treatment were much higher than that of total phosphorus and total potassium.Compared with CK,the increasing effect of soil pH and total nitrogenunder CSt treatment obviously ascended by 8.12%,6.07% respectively.The CHSSt treatment improved soil electrical conductivity obviously,but SHSt greatly reduced soil electrical conductivity.The soil electrical conductivity of CSt treatment decreased 8.63% than CK.Soil nitric nitrogen?NO3-N?contentof S,CHSSt,HSt,CHSt,CSSt,H,CSt,SHSt treatments increased by 221.78%,205.84%,137.53%,106.39%,69.23%,64.23%,5.00%,3.99% respectively compared with CK.?3?Effect of different fertilization treatments on soil enzyme activityManure fertilization increased soil protease,amylase,sucrase and nitrite reductase activity.Protease decreased in order of CSSt>CSt>C>HSt>S>SSt>CHSSt= H>CHSt>SHSt>CK.Amylase decreased in sequence of CSt>CHSSt>C>CHSt>HSt>S>CSSt>SSt>H=CK>SHSt.Sucrase decreased successively as CSt>CHSSt>CSSt>HSt>C>SSt>CHSt>CK>H>SHSt>S.Nitrite reductase decreased in turn of CHSSt>CSSt>SSt>C>HSt>S>CHSt>H>CSt>SHSt>CK.Protease,amylase,sucrase and nitrite reductase activity of CSt treatment were higher than CK.Manure fertilization decreased urease and nitrate reductase activity.Urease decreased as SSt>CK>H>C>HSt>CHSSt>CSSt>SHSt>CSt>CHSt>S.Nitrate reductase decreased as CHSSt>SHSt>CK>S>H>C>CSSt>CSt>SSt>CHSt>HSt.The correlative analysis of enzyme activity and physical & chemical properties showed that available potassium was significantly positive with protease and nitrite reductase activity.Organic matter and the effective phosphorus improved proteinase activity greatly.Total phosphorus extremely improved amylase activity.Electrical conductivity increased soil sucrase and nitrate reductase activity.Total nitrogen and total potassium obviously increased soil urease activity.Total potassium inhibited amylase,sucrase,nitrite reductase,nitrate reductase activity.NO3--N inhibited urease activity.?4?GHGs emission and GWP of different manure fertilization treatmentsIn early stage of manurefertilization,all fertilization treatments promoted N₂ O and CH₄ emission in lettuce-cultivated soil compared with CK.Among which,N₂ O emission flux of CHSSt was highest and CH₄ emission flux of S,CSt,CHSt,H,C was significantly higher than CK.The CO₂ emission flux decreased in sequence of CHSt>S>SHSt>SSt>CHSSt>CK>CSt>HSt>CSSt>C>H.In middle stage of manure fertilization,all manure fertilization treatments reduced N₂ O emission flux?except SHSt?;CH₄ emission flux decreased in order of SHSt>CHSSt>CK>SSt>C>CSSt>H>S>CHSt>HSt>CSt;CO₂ emission flux decreased in turn as SSt>S>SHSt>CK>CHSSt>C>CHSt>CSt>HSt>H>CSSt.In late stage of manure fertilization,N₂ O emission flux decreased in sequence of H > HSt> CHSSt > CK > S > CHSt > CSSt > SHSt > SSt > CSt >C;CH₄ emission flux of all fertilization treatments was lower than that of CK.CO₂ emission flux decreased successively as HSt>CSt>H>SHSt>CK>C>SSt>S>CHSSt>CHSt>CSSt.N₂O emission amount was positive during the whole fertilization process and it decreased successively as CHSSt>H>S>CHSt>SHSt>HSt>CSSt>CK>CSt>SSt>C.CO₂ emission amount decreased in order of HSt>CHSt>SHSt>S>SSt>CSt>CK>CHSSt>C>H>CSSt.CH₄ emission amount decreased in sequence of CK>H>CHSSt>C>CHSt>CSt>CSSt>SHSt>HSt>S>SSt.The sequence of GWP of each treatment was as same as CO₂ emission amount described above,which demonstrated that CO₂ emission amount made greater contribution than N₂ O and CH₄.?5?Analysis of the mechanism of soil greenhouse gases emissionSoil organic matter,total nitrogen,nitrate nitrogen and nitrite reductase,urease significantly promoted N₂ O emission.Soil organic matter and total nitrogen promoted CH₄ emission.pH and NO3--N inhibited CH₄ emission.Soil organic matter and sucrase promoted CO₂ emission.Protease inhibited CO₂ emission.?6?Optimization of organic manure composting and fertilization patternBased on the effects of each treatment on soil physical & chemical characteristics,soil enzyme activity and GHGs emission,in view of shortcoming of nitrogen loss under single livestock manure decomposition,and adverse impact on atmospheric pollution caused by straw burning,cattle and straw pattern decomposition style and fertilization pattern was recommended.