【作者】 肖焱波；

【导师】 张福锁；

【作者基本信息】 中国农业大学 ， 植物营养学， 2003， 博士

【摘要】 间套作是集约化农业生产地区普遍采用的一种种植方式，其目的是在有限的时间和有限的土地面积上收获到两种以上作物的经济产量，降低逆境和市场风险，在解决当前人口和资源环境间的矛盾方面具有重要的现实意义。其中豆科／禾本科间作在我国传统农业中提供粮食和维持氮素平衡起重要作用。鉴于国内以往对间作的研究主要集中在间作产量优势方面，而种间根系相互作用影响养分资源竞争的研究较少，本研究在对小麦／大豆、小麦／蚕豆这两种间作体系中养分特别是氮营养竞争和相互促进作用研究的基础上，应用根系分隔技术、同位素示踪土壤标记和叶柄注射技术等，探讨了小麦／蚕豆间作体系中氮素利用的种间促进作用和豆科作物固定的氮向非豆科作物的转移等，旨在深入了解豆科／禾本科作物间根系相互作用提高氮素利用效率的实质，为优化间作体系，提高间作体系生产力和资源利用效率提高科学依据。 获得的主要结论如下： 1．在小麦／蚕豆和小麦／大豆间作体系中，小麦始终处于竞争优势，而大豆处于竞争弱势，蚕豆在间作中未受显著影响；物种间的相互作用在小麦／大豆体系中以竞争作用为主，小麦／蚕豆体系中以促进作用为主，根系在尼龙网分隔和不分隔时明显促进了种间对氮和磷的吸收。 2．接种试验表明不同根瘤菌菌株在小麦／蚕豆间作体系中对作物的生物量有显著影响。当小麦、蚕豆单独生长时（完全分隔），所有根瘤菌菌株对蚕豆的生长都有明显的促进作用，此时蚕豆的生物量在接种NM353、LN732和LN566比不接种分别增加32％、13％和22％；当两种作物根系完全相互作用时（不分隔），蚕豆生物量以接种NM353最高，比接种LN732、LN566和不接种高15％、29％和15％，此时接种NM353的小麦生物量在所有接种处理中也最高，分别比接种LN732、LN566和不接种高15％、22％、12％；施氮情况下接种NM353在根系不分隔处理中重现了促进蚕豆和小麦生长的结果，此时还降低了土壤硝态氮残留。 3．在小麦／蚕豆间作体系中通过根系分隔和标记¹⁵N的试验表明：小麦相对于蚕豆对土壤和肥料氮的依赖更强，蚕豆则更依赖于大气固氮。在根系完全分隔、尼龙网分隔和根系不分隔中小麦对¹⁵N的回收率分别为58％、73％和52％，而蚕豆则分别为30％、20％和3％。小麦对肥料氮的竞争促进了蚕豆固氮增加，在根系完全分隔、尼龙网分隔和根系不分隔时蚕豆来源于固氮的百分数（％Ndfa）分别为58％、80％和91％，因此小麦／蚕豆中存在对氮的互补利用，该体系中氮营养竞争和促进作用同时存在。在小麦／蚕豆间作体系中应用叶柄注射¹⁵N和土壤标记稀释法都表明蚕豆固氮向间作小麦发生了转移，转移的量相当于蚕豆总吸N量的5％。更多还原

【Abstract】 Intercropping, a widely accepted practice in many labor-intensive cultivation countries, with the aim of harvesting at least two crops in one field during a certain period, could be an alternative agronomical measure to counter the contradict between the ever increasing population pressure and the shortage of resources due to its lower risk against unpredictable climate change and unsteady market, and due to its higher efficient resources utilization as well. Legumes and cereals intercropping is one of the most common practices for enhancing grain yield per unit land area and played a crucial role in Chinese traditional agriculture. The yield advantage in these intercropping systems has been well documented during the past decades. However, the effect of interspecific roots interaction on nutrients competition and facilitation was not studied so well. There were some information on economical N use in legumes and cereal intercropping. Nevertheless, the key mechanism supporting the phenomenon was nothing but assumption. Moreover, the work on nitrogen transfer characterized with intercropping practiced in China was not well studied yet. Thus, research on nitrogen facilitation between intercropped legumes and cereal has to be implemented. The aim of our present work was to compare the nutrient competition and facilitation in wheat-soybean and wheat-fababean intercropping systems, and the emphasis was put on nitrogen facilitation and nitrogen transfer in wheat-fababean intercropping. The hypothesis supporting the experiment reported were as the following: the nodule of intercropped legume developed from infection of microbe in the rhizosphere into host roots, which then fixed N2. The fixed nitrogen can be acquired by the companion crop and succeeding crop via direct or indirect nitrogen release in different forms, and N transfer can be determined by injecting 15N into the petiole of fababean, and by measuring 15N abundance in wheat and fababean; Moreover, the symbiotic nitrogen fixation of legume can be enhanced by the nitrogen competition from the associated non-legume.Roots barriers technique was then used to compare the difference in nutrient use between intercropped wheat-fababean and wheat-soybean; Nitrogen isotope dilution method combined with root barriers technique was applied to study the difference between wheat and fababean in the nitrogen source utilization, and the interspecific competition and facilitation for nutrients were analyzed within the root barriers; To estimate the nitrogen transfer, 15N was injected into the petiole of fababean, and !>N can be determined in the associate wheat. The results were as the following:1. Wheat was the dominating crop in aspects of both the growth and nutrients competition either in wheat-fababean or in wheat-soybean system due to its stronger competition, and the growth of soybean but not fababean was suppressed by wheat; the interspecific competition was obvious in wheat-soybean but both the interspecific facilitation of nitrogen and phosphorus was obvious in wheat-fababean.2. The effects of rhizobial strains on the intercropped fababean and wheat differed from strain to strain. All the strains used enhanced the growth of fababean with the solid barrier. Compared with no inoculating, the biomass of fababean inoculated with NM353, LN732 and LN566 was improved by 32%, 13% and 22%, respectively. However, the effects of rhizobial strains varied in nutrient competition as with mesh barrier and without barrier. Rhizobial strain NM353 was the best one in enhancing both the growth of fababean and the associated wheat. The biomass of fababean inoculated with NM353 was the highest, which was increased by 15%, 29% and 15% over that inoculated with LN 732, LN566 and non-inoculants, respectively. In the meanwhile, the biomass of wheat was increased 15%, 22% and 12%. When no barrier was used, nitrate remained in the soil was the lowest among the three root barriers patterns, a promising way for future field study with respect to economic nitrogen use and environ更多还原