【作者】 刘开强；

【导师】 江立庚；

【作者基本信息】 广西大学 ， 作物栽培学与耕作学， 2008， 硕士

【摘要】 不同耕作制度下施入稻田中稻草的分解环境存在很大差异。在常规耕作条件（常耕）下,稻草一般在耕作时被埋入土中。而在免耕条件下,稻草只能施在稻田的表面。因此,不同的稻田耕作制度下,稻草的分解和养分释放存在较大的差异。为了探讨这种差异并阐明其对水稻氮素吸收与利用的影响,论文以籼型杂交水稻金优253为试验材料,于2006年和2007年分别进行大田和盆栽试验,对稻草在常耕和免耕条件下的分解和养分释放过程进行比较,并通过¹⁵N示踪测定和比较稻草氮素在不同耕作方式下的去向。论文还测定了不同耕作方式下水稻氮素吸收与利用效率,并分析了不同耕作方式下水稻氮素吸收、利用与稻草氮素释放特性间的关系。主要研究结果如下:稻草主要成份为半纤维素、纤维素和木质素,分别占稻草干重的41.42%、31.28%和6.20%。稻草还田后,稻草中半纤维素和纤维素残留量随稻草分解而迅速下降,还田25-40天后分解速率变慢,平均分解速率分别为0.35 g·d^-1和0.27 g·d^-1。木质素的分解速率较慢,平均分解速率为0.034 g·d^-1。耕作方式对稻草不同成份分解的影响是不同的,免耕条件下半纤维素、纤维素的分解速率较快,残留数量低。其中,2006年免耕条件下稻草半纤维素、纤维素的分解速率分别比常耕条件下的高2.93%和7.68%,最终残留率分别比常耕时低10.82%和32.48%。2007年免耕条件下稻草半纤维素、纤维素的分解速率分别比常耕高3.39%和2.92%,残留率分别低20.65%和22.92%。但是,在2006和2007年试验中,耕作方式都没有明显影响木质素的分解。稻草中的氮、磷、钾、硅等养分随稻草分解而释放,但不同养分释放的速率明显不同。稻草中的K在还田后的10天迅速释放,之后,其残留量仅在小范围内波动。氮在稻草还田后0-10天和40-70天时具有较高的释放速率,磷在稻草还田后0-10天释放速率较快。硅在稻草还田后25-40天释放速率最快。免耕条件下稻草氮、磷、硅等释放速率较常耕大,有利于稻草氮、磷、硅的释放,但钾素释放速率在不同耕作方式下差异不大。水稻的叶和茎的物质组成存在较大差异。与稻茎相比,稻叶的氮、硅和木质素含量较高,纤维素和钾的含量较低,而半纤维素和磷的含量比较接近。因此,叶和茎的分解及养分释放也存在明显的差异。总的趋势是,叶片中半纤维素和木质素的分解速率比茎快,纤维素、钾的分解速率较茎慢。半纤维素、纤维素、木质素和钾在稻草还田后0-15天具有较高的分解速率,氮和磷在还田后0-15天和30-45天,而硅则是在还田后的45-60天。残留在叶中的半纤维素、纤维素、木质素、氮素比率比茎部分别低41.43%、84.66%、23.26%和17.71%,磷、钾、硅的残留比率差异不大。稻草分解后释放氮素的20.91%被水稻吸收利用,31.85%残留在尚未分解的稻草中,29.55%残留在土壤中,4.13%随渗漏水损失,气体挥发等其他损失为13.56%。耕作方式对稻草氮素去向影响最大的是渗漏损失,免耕条件下氮素的渗漏损失成倍增加。其次是在稻草中的残留量,免耕条件下氮素在稻草中的残留量下降。免耕对稻草氮素的利用是不利的。但免耕条件下稻草氮素在土壤中的残留及气体损失等在不同年份间的结果不尽相同。将水稻植株积累的氮素分成土壤+肥料、稻草两个部分。研究发现,水稻从土壤和肥料中吸收的氮素比率为96.61%,从稻草中吸收的氮素占总吸收量的比率为3.39%。除2007年免耕水稻吸收稻草中氮素的数量和比率比常耕水稻略高外,免耕水稻从土壤+肥料、稻草中吸收的氮素的数量与比率及总的氮素吸收量均比常耕水稻的低,其中2006年免耕水稻氮素吸收量显著低于常耕水稻。这表明,免耕对水稻的氮素吸收能力有一定的影响,但不影响不同来源氮素的吸收比率。更多还原

【Abstract】 There would be a big difference of straw decomposition and nutrition release between no-tillage and conventional tillage.Therefore field and spot experiments were conducted to study the decomposition and release characters of incorporated straw under different tillage patters with Jinyou 253 in 2006 and 2007.At the same time,¹⁵N tracer method was used to quantify the fate of nitrogen from incorporated straw.The results were showed below:The main components of straw are semi-cellulose,cellulose,and lignin, with the contents of 41.42%,31.28%and 6.20%respectively.The residue of semi-cellulose and cellulose with the average decomposition rates of 0.35 g·d-1 and 0.27 g·d-1,decreased sharply from 0 to 10 days,and became gently from 25 to 40 days after retuming.The average decomposition rate of lignin was 0.034 g·d-1,which less than semi-cellulose and cellulose.Tillage patterns played different parts on the decomposition of different straw components.It had high decomposition rates and lower residue of semi-cellulose and cellulose under no-tillage,but it was not true for lignin.Potassium released quickly in the first 10 days after returning,and then became gently.Nitrogen showed a higher decomposition rate during 0 to 10 or 40 to 70 days after returning and 0 to 10 days for phosphorus,25 to 40 days for Si.It had higher decomposition rates of nitrogen,phosphorus and Si 0-100 days after returning under no-tillage patterns,except potassium.Leaf of rice straw contains more nitrogen,Si,lignin and less cellulose, potassium than stem.So there must be great difference between decomposition rates of leaf and stem.Results indicated that leaf had high decomposition rates of semi-cellulose,lignin,and lower decomposition rate of cellulose,potassium than stem.Also it had higher decomposition rates of semi-cellulose,cellulose,lignin from 0 to 15 days after returning and 0 to 15, 30 to 45 days for nitrogen and phosphorus,45 to 60 days for Si.The residue of semi-cellulose,cellulose,lignin and nitrogen in leaf were lower than stem by 41.43%,84.66%,23.26%and 17.71%respectively.It was found that 20.91%of nitrogen from incorporated straw were uptake by rice plant,31.85%remained in straw,29.55 resided in soil,4.13% washed away and 13.56%lost in other forms.The leakage loss was influenced greatly by tillage patterns and increased times under no-tillage. Nitrogen remained more in straw under no-tillage and it was disbennifit for nitrogen use from incorporated straw.But the residue in soil and the other loss were different from years. It was found that 96.61%of nitrogen,accumulated in rice plants,came from soil and fertilizer,and the other 3.39%from incorporated straw.The accumulations and rates of nitrogen from straw or soil and fertilizer were more under conventional tillage compared to no-tillage,especially in 2006, except the no-tillage treatment in 2007.It indicated that tillage pattern had certain influence on nitrogen absorption,however,no obvious influence on the rates of nitrogen from incorporated rice straw.更多还原