【作者】 罗珠珠；

【导师】 黄高宝； Guangdi Li；

【作者基本信息】 甘肃农业大学 ， 作物栽培学与耕作学， 2008， 博士

【摘要】 本研究依托澳大利亚国际农业研究中心(ACIAR)项目,于2001年开始在陇中黄土高原半干旱区的定西县李家堡乡实施了小麦→豌豆轮作系统下6种不同耕作方式的长期定位试验,旨在系统研究保护性耕作在黄土高原独特侵蚀环境下的适应性,特别是其对土壤质量和系统生产力的影响及其内在机理。6种耕作方式包括:传统耕作(T)、免耕(NT)、传统耕作秸秆还田(TS)、免耕秸秆覆盖(NTS)、传统耕作地膜覆盖(TP)和免耕地膜覆盖(NTP)。通过分析3个轮作周期不同耕作方式下土壤理化性质、生物性质和生产力对土壤质量的影响,阐明长期耕作过程中土壤质量的演变特征及其驱动因子,筛选出适宜于黄土高原半干旱区侵蚀环境下土壤质量评价的代表性指标;并综合前人的研究,结合区域特点,建立适宜于黄土高原半干旱区侵蚀环境的土壤质量评价模型。本研究得出以下主要结论:1)基于通用性和实用性原则,筛选了一些共性指标;基于有效性和敏感性原则,剔除了一些争议性指标;本着尽可能选择少量指标,尽可能运用复合指标的原则,结合黄土高原区域特点,增加了一些创新性二次指标;最后通过敏感性和判别分析,筛选出团粒结构、全氮、速效氮、有机质、蔗糖酶活性、产量、纯收益和产投比等8项因子,建立了土壤质量简化评价指标体系,涵盖了土壤物理、肥力、健康和生产力四个方面的性质。分别应用原始评价指标和简化评价指标两种评价体系,建立加权综合法和加乘法则两种模型,对研究区两种轮作序列6种不同耕作方式的土壤质量进行了综合评价,并对两种指标体系及两套评价方法进行了相关分析。结果表明,该研究建立的土壤质量简化指标体系具有较高的代表性,可用于黄土高原半干旱区土壤质量评价。2)免耕秸秆覆盖可以提高土壤质量。土壤质量综合指数排序为:P→W轮作序列,NTS＞TS=NTP＞NT＞T＞TP;W→P轮作序列,NTS＞TS＞NT＞NTP=T＞TP。免耕土壤避免了人为扰动,再加上进行秸秆覆盖,增加了土壤中的有机质含量,从而使得土壤结构得到了很大改善,增强了土壤蓄水纳墒能力,减少了水土流失,防止了土壤养分的流失,促进土壤生产力的提高;土壤产出能力提高,导致归还系统的有机物质也相应增加,加强了土壤生物的繁殖能力和活力;而土壤生物活动反过来又促进了良好土壤结构的形成和土壤肥力的进一步提高,形成了农田系统的良性循环,促进了土壤质量的提高。轮作序列间比较,土壤物理质量、肥力质量、土壤健康和综合质量各处理均表现为W→P轮作序列高于P→W轮作序列,而土壤生产力刚好相反,除NTS处理以外,其余处理均表现为P→W轮作序列高于W→P轮作序列。3)免耕秸秆覆盖可以改善土壤物理质量,土壤水分状况、结构性能和渗透性能共同决定着土壤物理质量的高低。土壤物理质量指数排序为:P→W轮作序列,NTS＞NTP＞NT＞TS＞T＞TP;W→P轮作序列,NTS＞NTP＞TS＞NT＞T(TP)＞TP(T)。NTS处理虽然容重(总孔隙度)和毛管孔隙无明显优势,但显著增加了水稳性团粒结构和非毛管孔隙度,促进了土壤水分的入渗,使得累积径流量和总侵蚀量降低。虽然不同处理间休闲期0-200cm土壤贮水量和生育期作物有效水含量差异不明显,但NTS处理在表层0-10cm体现了较好的抑蒸保墒作用,相对于传统耕作T最多可以提高56%。而且,NTS处理提高了生育期作物蒸腾耗水和棵间蒸发的的比例。不同年份小麦平均水分利用率NTS处理略低于TP(0.6%),但比T、NT、TS、NTP提高15.6%、16.7%、12.6%、0.8%;不同年份豌豆平均水分利用率NTS比T、NT、TS、TP、NTP提高15.8%、17.3%、10.3%、5.4%、9.2%。可见,NTS处理免耕的同时进行了秸秆覆盖,形成了良好的土壤结构,改善了土壤渗透性能,降低了地表径流,提高了土壤表层水分和水分利用效率,促进了土壤物理质量的提高。4)秸秆还田可以提高土壤肥力质量,农田养分平衡的盈亏是土壤养分水平消长的根本原因,决定了土壤肥力的发展方向;而土壤pH值虽不能直接表明土壤中某种养分的含量,但其通过影响土壤营养元素的转化方向、转化过程、形态及其有效性,间接影响着土壤肥力质量。土壤肥力质量指数排序为:P→W轮作序列NTS＞TS＞NTP＞NT＞T＞TP;W→P轮作序列,土壤肥力质量指数排序NTS＞TS＞NT＞NTP＞TP＞T。与试验初期相比,各处理耕层0-30cm土壤有机质、全氮和全磷均有所增加,且以NTS和TS增长幅度较大;耕层0-30cm全钾NTS和TS处理表现为增加,其余处理表现下降趋势。耕层0-30cm速效氮和速效磷均有所增加,但速效磷以NTS增长幅度最大,而速效氮却以NTS增长幅度最小;耕层0-30cm速效钾表现为下降趋势,但以TS和NTS减幅较小。从养分循环角度来分析,每经过一个循环过程都会导致养分的损失,作物的收获携出了大量的N、P、K养分,其中籽实是N、P养分输出的主要组织部分,而这部分养分是不能通过直接归还来补充的;K主要是通过秸秆输出的,但是秸秆作为有效资源,它可以经过还田循环利用。因此,在黄土高原雨养农作系统中,配施N、P肥的同时,尽可能的将秸秆归还农田,对促进和维持土壤养分平衡,提高土壤肥力质量具有重要意义。5)免耕可以提高土壤健康水平,水解酶活性与过氧化氢酶活性共同构成了影响土壤健康水平的主导因子。土壤健康指数排序为:P→W轮作序列,NTS→NTP→NT→TS→TP→T;W→P轮作序列,NTS＞NTP＞NT＞TS＞TP＞T。无论覆盖与否,也无论覆盖何种材料,两种轮作序列下免耕处理(NT,NTS,NTP)耕层0-30cm土壤过氧化氢酶活性和三种水解酶活性均明显高于翻耕处理(T,TS,TP)。两种轮作序列下NTS处理虽然微生物数量均处于中等水平,并不是土壤健康的优势因子,但由营养因素主要制约的活跃微生物数量高,促进了土壤中营养物质的循环,使其土壤健康水平依然很高。这也从另一侧面反映,土壤微生物数量并不是影响土壤健康的主导因素。6)免耕可以提高土壤生产力,产量、产投比和纯收益共同构成了影响土壤生产力的主导因子。生产力指数排序为:P→W轮作序列,TP＞NTS＞NT＞TP＞T＞TS;W→P轮作序列,NTS＞NT＞NTP＞T＞TS(TP)＞TP(TS)。6年间NTS处理小麦平均产量为2029.64Kg/ha,比T、NT、TS、TP、NTP提高了18.10%、26.21%、13.15%、2.34%、2.38%;NTS处理豌豆平均产量为1381.48Kg/ha,比T、NT、TS、TP、NTP提高了20.25%、30.33%、15.83%、8.82%、10.39%。这归功于NTS处理改善了土壤结构性和渗透性能,并提高了土壤水分和肥力状况,最终体现为作物产量显著提高。6年间NT处理平均纯收益为1692.44￥/ha,比T、TS、NTS、TP、NTP增加了37.52%、194.58%、9.02%、86.79%、13.99%;平均产投比为2.98,比T、TS、NTS、TP、NTP提高了0.61倍、1.28倍、0.52倍、1.10倍、0.52倍。这主要是因为NT不仅消除了作物收获后的耕作投入,而且也不需要进行秸秆和地膜投入,使得得纯收益和产投比均较高。更多还原

【Abstract】 In 2001,Gansu Agricultural University started a long-term conservation tillage project,funded by Australian Centre for International Agricultural Research,at Lijiabu Village,Dingxi,Gansu Province.The overall aim of the project was to study the effects of conservation tillage on crop productivity and soil quality,the adaptation of conservation tillage in the Loess Plateau where soil is prone to severe erosion,and its underlying mechanisms.The PhD project was part of this long-term project.There were six treatments with two tillage systems and three ground covers,namely conventional tillage (T),no-till without stubble retention(NT),conventional tillage with stubble incorporated (TS),no-till with stubble retention(NTS),conventional tillage with plastic film mulch(TP) and no-till with plastic film mulch(NTP).The experiment was fully-phased with two rotation sequences.Phase 1 started with field pea followed by spring wheat(P→W) whereas phase 2 started with spring wheat followed by field pea(W→P).The objectives of this thesis are:1) to quantitatively analyze effects of soil chemical,physical and biological properties on soil quality and productivity under different tillage systems and the driving factors for the changes of soil quality under tillage in a long-term,2) to select the best soil quality assessment indicators,and 3) to establish soil quality assessment models that are suitable for the erodible environment of semi-arid region on the Loess Plateau.The key results from the study are summarized as follows:1) The study selected 8 most sensitive indicators out of 29 assessment indictors that are used to evaluate soil physical quality,soil fertility,soil health and land productivity in the semi-arid region in the Loess Plateau.These 8 indicators were water stable aggregates,organic matter,total nitrogen,available nitrogen,invertase activities,grain yield,net income,ratio of output and input.The integrated assessment models established using the addition and multiplication method and weighted integrated method for soil quality assessed under different tillage systems,and the results from two assessment systems were similar and highly correlated.This showed that these 8 indicators could provide the best fit for the actual situation in the western Loess Plateau. 2) Soil quality can be improved by NTS.The order of integrated soil quality index(ISQI) from high to low was NTS,TS,NTP,NT,T and TP in P→W rotation,and NTS,TS, NT,NTP,T and TP in W→P rotation.No-tillage and stubble retention,in general,can improve soil structure,reduce soil and water erosion and soil nutrient loss,and hence increase crop productivity.This will,in turn,increase organic material returned back to soil,ensuring the high reproduction and activity of soil organisms.Accordingly,soil biological activity is conducive to improvement of soil structure and soil fertilizer.As a result,the healthy farmland ecosystem is built,thus inducing improved soil quality. Moreover,soil physical quality,fertilizer quality,soil health and integrated soil quality in W→P rotation were higher than that in P→W rotation.On the contrary,Soil productivity in W→P rotation was lower than that in P→W rotation.4) Soil physical quality can be improved by NTS.Soil water,soil structure and water infiltration rather than soil temperature were the dominant indictors for soil physical quality.The order of soil physical quality index(SPQI) from high to low was NTS,NTP, NT,TS,T and TP in P→W rotations,while the order of SPQI was NTS,NTP,TS,NT, TP and T in W→P rotation.This indicated that NTS have the strongest effect on soil physical quality.There is no big difference among different treatments’ bulk density and total porosity,but Non-capillary porosity and aggregates under NTS was greatly improved,enhancing soil infiltration and reducing runoff and sediment.Surface soil water content under no-till with stubble retention was greatly improved up to 56% compare to conventional tillage,although there is no big difference among different treatments’ water storage at 0-200cm.The average WUE of field pea under NTS cross years was 15.8%,17.3%,10.3%,5.4%and 9.2%higher than that of T,NT,TS,TP,an NTP,respectively.The average WUE of spring wheat under NTS cross years was 0.6% lower than that of TP,and 15.6%,16,7%,12.6%and 0.8%higher than that of T,NT,TS and NTP,respectively.Improved soil structure arised from no-tillage and stubble retention can enhance water infiltration,reduce runoff and increase topsoil water content,hence improve soil physical quality.4) Soil fertilizer quality can be improved by the two stubble retention systems.The balance of soil nutrients determined the direction of soil fertility.The order of soil fertilizer quality index(SFQI) from high to low was:NTS,TS,NTP,NT,T and TP in P→W rotation,and NTS,TS,NT,NTP,TP and T in W→P rotation.In comparison with the baseline soil fertility before experiment started,total and available N and P increased for all the treatments,especially on the NTS and TS treatments.Potassium, however,decreased for all the treatments except for NTS and TS treatments.This indicated that the NTS and TS treatment can replenish the soil nutrient pool via stubble retention or stubble incorporation.Soil nitrogen,phosphor and potassium decreased due to harvesting products.Output of soil potassium removed out of cropland with crop straw,which can be returned back to soil by organic material recycling.The output of soil nitrogen and phosphor is associated with grain seeds,which is removed from crop field forever.Therefore,stubble retention combined with nitrogen and phosphor fertilizer supply can replenish the soil nutrient pool in the loess plateau. Although soil pH value can not be used to directly indicate the level of soil nutrients,it is a useful indicator to indirectly show the soil fertilizer quality by influencing transformation,forms and availability of soil nutrients.On the contrary,the change of pH had an opposite trend to the change of soil nutrients under both rotation sequences. This suggested that although soil pH value can not be used to directly indicate the level of soil nutrients,it is a useful indicator to indirectly show the soil fertilizer quality by influencing transformation,forms and availability of soil nutrients.5) Soil health can be improved by the 3 no-till treatments.Soil catalase and hydrolases activities are the dominant factors to improve soil health.The soil health index(SHI) orders from high to low were:NTS,NTP,NT,TS,TP and T in both rotation sequences. Soil catalase and hydrolases activities in 0-30cm were higher on the no-till treatments (NT,NTS and NTP) than on the cultivation treatments(T,TS and TP) regardless cover or not,covered by stubble or plastic film mulch.This indicated that soil catalase and hydrolases activities are the dominant factors for the 3 no-till treatments(NTS,NTP, NT) to improve soil health.Relatively,microorganism amount is intermediate for the NTS treatment,but soil health index on NTS were higher than those on the other tillage systems.This showed that not all microorganisms but active microbiomass that can help maintain soil nutrient recycling and improve soil health,indicating microorganism amount is an unimportant factor for soil health.6) Soil productivity can be improved by the 3 no-till treatments.Grain yield,benefits and ratio of output and input were the dominant factors of soil productivity.The order of soil productivity index(SPI) from high to low was:NTP,NTS,NT,TP,T and TS in P→W rotation,and NTS,NT,NTP,TP,T,TS and TP in W→P rotation.NTS improved the rotation grain yield significantly while no-till without stubble retention had the worst grain yield compare to conventional tillage system.The average yield of spring wheat under NTS was 18.10%,26.21%,13.15%,2.34%and 2.38%higher than that under T,NT,TS,TP and NTP respectively.The average yield of field pea under NTS was 20.25%,30.33%,15.83%,8.82%and 10.39%higher than that under T,NT,TS, TP and NTP respectively.The average benefits of NT within 3 rotation cycles was 37.52%,194.58%,9.02%,86.79%and 13.99%higher than that of T,TS,NTS,TP and NTP respectively.The average ratio of output and input under NT within 3 rotation cycles was 0.61,1.28,0.52,1.10 and 0.52 times higher than that of T,TS,NTS,TP and NTP respectively.更多还原