控温条件下秸秆腐解过程中黄泥田氮素转化及酸度对水肥耦合的应答

Nitrogen transformation and acidity remediation in responses to water-fertilizer coupling management during straw decomposition at fixed temperature in yellow-paddy field

【目的】在华中低产酸化黄泥田双季稻区,研究不同温度、水分条件及施肥对添加微生物促腐菌剂下秸秆腐解过程中土壤氮素转化和酸度矫治的影响。【方法】采用室内培养试验,于15℃和35℃条件下,设2个水分条件[40%和100%最大田间持水量(WHC)]及2种氮肥处理(尿素、猪粪),动态监测水稻秸秆腐解过程中土壤无机硝态氮(NO-3-N)、氨态氮(NH+4-N)和总水溶性氮(TDN)含量,以及土壤p H变化在105 d培养周期内的变化特征。【结果】温度与各形态氮含量及土壤p H间均缺乏相关性,不同温度下水分、氮肥类型对氮转化及p H影响大致相同;35℃和15℃条件下几乎整个培养周期内,各处理氨态氮含量表现为WHC40%+U>WHC40%+M>WHC100%+U>WHC100%+M,即尿素处理优于猪粪处理(P<0.01),不论添加何种氮素均表现为WHC40%>WHC100%(P<0.01);NO-3-N和TDN含量顺序为WHC100%+U>WHC100%+M>WHC40%+U>WHC40%+M,其中后二者NO-3-N含量无差异,WHC100%条件下NO-3-N和TDN含量均显著高于40%WHC(P<0.05);氮净矿化量为WHC40%+U>WHC100%+U,添加猪粪处理后在两水分条件下都为负值,表现生物固定,而净硝化强度为WHC100%+U>WHC100%+M,低水分含量的两氮肥添加均表现弱硝化;各处理至培养结束时土壤p H均大幅提升,p H值大小呈WHC40%+M>WHC40%+U>WHC100%+M>WHC100%+U,净变化值则分别为+0.35、+0.51、-0.61和+0.15,其中,WHC100%+M处理虽然最终表现有0.61单位降低,但在前期仍有大幅上升的现象。【结论】高温度、水分含量下,施尿素可因其短期内氮矿化与p H(高净氮矿化量、净硝化量、酸度提升)方面的优势而作为田间推荐的水肥耦合管理措施;微生物在氮素循环中对设定的温度条件有一定适应能力;相比于尿素在改变各种氮浓度和诱导p H变化方面的良好作用,猪粪从供氮时效方面讲,是一种可采用的但也相对难以利用的氮源。

Objectives]The imPacts of soi1 water content,ferti1ization incorPorated with addition of decay-faci1itating microbia1 inco1ua on the N transformation and soi1 acidity remediation were investigated in 1ow yie1d acidified ye11ow-Paddy soi1 in doub1e rice croPPing area,centra1 China.[Methods]An incubation exPeriment invo1ved by decay-faci1itating microorganisms was resPective1y Performed at 15℃ and 35℃ in 1aboratory for 105 days to eva1uate imPacts of soi1 water content[40% and 100% of water ho1ding caPacity( WHC)]and N ferti1izer&nbsp;(urea and manure). The soi1 inorganic nitrate( NO3--N),ammonium( NH4+-N)),tota1 disso1ved nitrogen ( TDN)and changes of PH were monitored Periodica11y.[Results]Data showed that water content and N ferti1izer exhibited simi1ar effects on N transformation and PH variance when soi1s were incubated by two kinds of temPeratures,35℃ and 15℃,and ammonium contents in soi1s were order1y c1assified into four 1eve1s by WHC40%+U > WHC40% +M > WHC100% +U > WHC100% +M across the entire incubation Period( P <0. 01 ) regard1ess of N ferti1izer,but the contents of nitrate and TDN in treatments were a11 in orders of WHC100% +U >WHC100% +M >WHC40% +U >WHC40% +M. The contents of nitrate and TDN reatments under WHC100%were increased significant1y comParing with those under WHC40%( P <0. 05 ),not difference existed between ferti1izer treatments. WHC40% +U showed higher net N minera1ization than WHC100% +U when manure was aPP1ied,suggesting that microbia1 immobi1ization occurred in soi1s. Additiona11y,net nitrification in WHC100% +U was higher than that in WHC100% +M,but treatments incubated under WHC40% show s1ight nitrification;PH va1ues are e1evated in near1y a11 the treatments fo11owing a sPecific trend of WHC40% +M >WHC40% +U >WHC100% +M >WHC100% +U,with net PH variation of +0. 35,+0. 51,-0. 61 and +0. 15,resPective1y. Obvious1y,a1though WHC100% +U 1eads to great increase in PH at initia1 stage,but decrease the PH by 0. 61 at the end of incubation. Higher temPerature,water content and urea aPP1ication shou1d be recommended as an effective fie1d management Practice for satisfactory N minera1ization and PH e1evation. Soi1 microorganisms have an adaPtation to temPerature for N minera1ization,the magnitude of C- and N- minera1ization main1y dePend on the avai1abi1ity of soi1 water and N resources. Manure is an aPP1icab1e choice desPite of suPP1ying 1ess N of various forms and weak affecting in PH f1uctuations.[Conclusions]An integrative manage Practice in maintaining caPacity of soi1 water content and increasing the efficiency of N ferti1izer shou1d be an effective Pathway during the Process of returning straws from ear1y rice and 1ate rice to fie1d at the 1ow yie1d Paddy soi1s in centra1 China.