【作者】 肖剑英；

【导师】 谢德体； 张磊；

【作者基本信息】 西南农业大学 ， 土壤学， 2002， 硕士

【摘要】 免耕（no-tillage，NT，or zero-tillage，ZT）是指把土地耕作减少到最低限度的一种耕作方法，包括减少耕作强度和耕作次数。少耕、化学中耕、直播、无犁中耕、覆盖耕作、保护性耕作等都属于免耕措施，统称为免耕耕作制。 在我国，土地资源有限，特别是在耕地面积日益减少而且破坏和占用比较严重的情况下，开展土地资源的研究，在不破坏土地资源的前提下，使用有限的资源生产出尽可能多的产品，达到最佳的生态、经济和社会三大效益的统一。这样，实现农业的可持续发展，走生态农业之路就显得尤为必要了。 最早的免耕是在原始社会，那是在生产力极为低下、生产工具极为落后的情况下而被迫采取的一种耕作方式。近代的免耕始于20世纪30年代的美国，为了防治水土流失，防止风蚀和水蚀而发展起来的，到60年代，阿特拉津除草剂的发明利用，才使免（少）耕法得以成功应用和推广。以美国的覆盖式免耕为基础，世界上40多个国家如加拿大、澳大利亚、新西兰、日本、英国、法国、西班牙、巴西等都对少免耕法进行了研究，并取得了很大进展。 为了提高作物产量，我国从20世纪50年代开始进行少免耕法的研究，并且表现出从北方干旱半干旱的旱地到南方水田发展的趋势。试验发现：长期免耕，能改善土壤物理结构，增加土壤蓄水量、容重、土壤温度和水稳性团聚体，有利于土壤中各种养分的积累，特别是有机质积累很快，出现上高下低的分层现象，并相应增加作物产量。 纵观国内外的研究概况，对旱地的研究比较多，对水田的物理、化学和生物性状也有研究，但是，对稻田长期垄作免耕条件下的土壤微生物和肥力的关系的研究尚鲜见报道，因而着手于这方面的研究。 本文以长期垄作免耕试验田为研究对象，采用稀释平板计数法测定了土壤中主要的微生物细菌、真菌、自生固氮菌数量，用MPN（最大或然值法）测定纤维素分解菌的数量，采用氯仿熏蒸—淹水培养—纳氏比色法测定微生物生物量。测定土壤的基本养分状况全氮、全磷、全钾、速效氮、速效磷、速效钾、有机质、pH等采用常规分析法，对土壤可溶性碳的测定方法进行了多方面的探索，最后采用水提—H₂SO₄-Ag₂SO₄回流—FeSO₄滴定这一方法。 通过对12年免耕的稻田的土壤微生物和基本肥力特征研究，找出二者之间的关系，指出免耕耕作方式养分增加、肥力提高的主要原因是作物秸秆的加入以及免耕改变了土壤的水、热、气、肥条件，并因此而探索影响秸秆分解的因子，找出微生物种类和有机、无机肥料的更好搭配。 通过对长期免耕稻田的紫色土的定位试验地研究，得出如下结论： 1．稻田的长期垄作免耕，通过改变田间微地形和土壤的通气透水状况，而影响主要微生物如可培养细菌、真菌、纤维素分解菌、自生固氮菌等的数量和季节分布规律。 2．土壤中各种微生物的变化规律有差异，细菌、真菌、自生固氮菌表现出春冬季高，夏季和秋季低，而纤维素分解菌则是春秋季高，夏冬季低，出现上高下低的分层现象。但是，免耕垄作和厢作的变化较平稳，没有常规平作差异显著。 3．各处理的微生物生物氮呈现季节性变化，春季（4月15日）、夏末秋初（8月18日）和秋季（10月门日）数量较大，而夏季（7月 9日）和冬季（12月 20日）减少，免耕垄作和厢作的这一季节性变化规律尤为显著，生物量的这一规律，与国内外的研究报道一致。 4．经过12年的自然免耕，土壤的养分状况大为改善，一般都比试验前有增长，并且与微生物数量一样，表现出季节性和分层现象。全氮的增幅最大，将10月各处理的平均养分和12年前的同期养分相比，常规平作、冬水垄作、免耕垄作、免耕厢作和水旱轮作分别增加 89．70、157．2o、154．3O、157．2o、112．70，免耕垄作和免耕厢作的该季节平均增幅达 160．3％，聚土垄作（包括冬水垄作、兔耕垄作、免耕厢作）的平均增幅为 156．2％，有机质和速效氮也有同样的趋势；全磷和速效磷、全钾和速效钾随作物的种类、生长周期、水分和气温的变化而变化。纵观养分的变化规律，表明长期实行自然免耕的土壤，其养分表现出垄埂上层高于下层、聚土垄作高于其它处理的趋势。 5．微生物生物量与土壤有机质关系密切，相互促进，微生物越活跃，物质循环越快，有机质的积累也就越多。 6．土壤中的可溶性碳含量极少，存在季节性变化，春季表现出明显的数量优势，夏季和冬季、秋季和夏末秋初差异不明显，出现上高下低、免耕高于其余处理的规律。这与有机质的规律比较一致，表明土壤中的有机质与可溶性碳有密切关系。 7．通过几个月的盆钵试验发现：（）在秸秆分解过程中，土壤养分逐渐释放出来，全氮、全磷、全钾、速效氮、速效磷、速效钾、有机质等比试验前大幅增加，速效氮的增幅最大，pH也升高，土壤向中性和碱性方向发展。闪)在单独加入硫酸按时，全氮、全磷、全钾、速效钾、有机质变化不大，速效氮增加很多。在加硫酸铰的5个对比试验中，其增幅平均达 72石％，木霉比土著纤维素分解菌的增幅更大。（3）在单独加入自生固氮茵时，全氮、全磷、全钾、速效磷、更多还原

【Abstract】 As a protective tillage ,No-tillage and ridge culture (NT) is a kind of culture mode to minimumize the land cultivating (including cultivating intensity and cultivating times).It means leaving the plant residue after harvesting. Under this principle, the NT system is also called limited tillage, zero-tillage, chimical-tillage, no-plowtillage, straight sowing, mulch-no-tillage and protective-tillage etc.In our country, the land is limited. The cultivated land is decreasing and is seriously occupied and destroyed. Study is in need for high production and the aim of best ecological, economical and social effects without destroying land resources. Therefore, it is necessary to carry out the sustainable development of agriculture and track a path to ecological agriculture.The first NT began in primitive society. It was a culture mode adopted under the condition of low productivity and poor tools. Recent No-tillage and ridge culture commenced in the United States in the 1930s. It was developed to prevent the erosion of water and soil and to avoid the wind and water erosion. Not until the atrazine herbicide was invented and successfully used in the 1960s was the NT technique succeeded and spread. Based on the mulch no-tillage of the United States, more than 40 countries, such as Canada, Australia, New Zealand, Japan, England, France, Spanish, Brazil, etc, were engaged in a study on the NT or ZT. and made a great achievement.The study of NT began in the 1950s in our country for high yield. The experiment indicated that long-term of NT could improve the soil’s physical structure and the soil’s sluice capacity, and could aggregate the accumulation of various nutrients in soil and increase plant yield.In research much importance was attached to the study of dry land and the physical, chemical and biologic properties of water land, but the relationship between soil microbes and soil fertility in the paddy field of long-term no-tillage and ridge culture was relatively ignored,so this experiment was conducted for further study. We mensurate the number of the primary soil microbes such as bacteria, fungi and azotobacter with diluting flat technique, and mensurate the number of cellulose decomposing bacteria with MPN technique, and mensurate the biological quantity of the soil microbes with the technique of chloroform suffocating-inundation culture-colour-compared. The normal analytic technique was adopted to mensurate the basical nutrients such as total N, total P, total K, available N, available P, available K, organic matter, pH and so on. Meanwhile, various techniques were employed to mensurate the soil dissoluble carbon, finally the technique of water saturating-H2SO4-AgSO4-Circumfluence-FeSO4 titration was used in this experiment.The basic fertility characteristics, and soil microbes and the relationship between them were investigated on paddy fields of purple soil, where no-tillage and ridge culture had been practiced for twelve years. The advantages and disadvantages were contrasted among five culture modes (conventional culture, no-tillage and fallow in winter, no tillage and ridge culture, no-tillage and box culture, and the rotation of paddy and upland). The main causes of more nutrient and higher output in NT were found in this experiment which was the more input of residue, and better match was explored for the reside decomposing among the microbial composition, organic or inorganic fertilizers.Though the study on the long-term of no-tillage and ridge culture in this dissertation, the research results are as follows:1) NT can change the wee terrain and change the conditions of air and water, which leads to the seasonal fluctuation of the main kinds of microbes such as bacterica, foungi, azotobacter and cellulose decomposing bacteria.2) There is difference between the laws of different kinds of microbes. The quantity of bacteria, fungi and azotobacter is high in spring and winter and low in summer and autumn while the quantity of cellulose decomposing bacteria is higher in spring and更多还原