【作者】 殷晓燕；

【导师】 沈其荣； 徐阳春；

【作者基本信息】 南京农业大学 ， 植物营养， 2004， 硕士

【摘要】 淡水资源的不足和大量耗竭将严重影响我国农业的可持续发展，因此，人们对消耗我国农业用水80％左右的传统水稻栽培提出了挑战，其中水稻旱作栽培作为一种有效的农业节水途径而受到越来越多的关注，而地膜覆盖旱种水稻和利用半腐解秸秆替代地膜的覆盖旱种水稻都受到了广泛的重视。目前旱作水稻的研究多采用育苗移栽后旱种的管理方式，这不仅耗时费力，而且与移栽水作水稻相比，旱作移栽还存在活棵所需时间长、成活率低等一系列问题。本试验采用旱直播地膜覆盖育苗技术，克服了上述缺陷，通过2001年和2002年的田间试验，研究了直播旱作（包括覆膜、覆草和裸地）水稻和常规水作水稻的生物学特征以及产量构成的差异，旨在探索旱作水稻的增产途径；同时通过田间¹⁵N微区试验和在相同条件下设立的无氮区试验，研究水稻在旱作和水作两种生态条件下对土壤氮素和肥料氮素吸收和利用的差异，为水稻旱作的进一步推广以及水稻旱作过程中的氮素养分管理技术提供理论依据。 研究结果表明，与常规水作水稻相比，不同地表覆盖的直播旱作水稻均有不同程度的减产，减产幅度介于2％-18％之间；旱作处理秸秆覆盖和地膜覆盖处理水稻产量分别比裸地处理高出8％和4％。不同处理之间水稻的收获指数没有明显差异，然而2002年旱种水稻栽种密度增加的前提下，收获指数下降明显。将课题组中在不同土壤条件下覆盖旱作处理水稻的产量进行比较发现，秸秆覆盖在轻度盐碱土上的增产效果明显，明显好于地膜覆盖处理。 对试验中不同处理水稻的生长发育特征及产量构成因素的研究表明，直播旱作水稻的生育期比常规水作水稻有所延长，推迟4-10天成熟。旱作水稻出叶缓慢，株高、叶长和叶宽均有所下降。就旱作后水稻的叶面积指数、地上部生物产量等群体指标而言，可以通过适当增加栽种密度有所提高，达到水作水稻的水平。对旱作水稻产量构成因素进行分析表明，旱作条件下有效穗数、结实率和千粒重都可能成为旱作水稻产量的主要限制性因子。我们认为，旱作水稻产量进一步提高的潜力在于在栽种密度、水分管理、氮肥施用量等多种因素中找到优化方案，从而使产量构成因素的三方面有效穗数、每穗粒数以及千粒重充分协调以达到增产的目的。 以相同条件下不施氮肥小区作为参照，对氮肥施用后旱作水稻生物产量、含氮量以及吸氮量增产效应的研究结果表明，旱作水稻氮肥的肥效明显低于传统水作处理。就氮肥表观利用效率而言，试验中旱作水稻对氮肥的吸收利用效率较低，介于15％-43％之间；水稻旱作后氮素生理利用率有所提高，介于27％-53％之间，尤其是半腐解秸秆覆盖旱作处理，2001年其氮肥生理利用率可高达52.7kg／kg N，与同条件下的水作稻相比，氮肥施用后在同样多吸收1kg氮素的情况可增产籽粒21.9kg。 对不同地表覆盖旱作水稻氮素吸收利用特征的研究表明，与水作水稻生育前不同地表覆盖直播旱作水稻的产量和氮素吸收利用特征期大量吸收氮素不同，直播旱作水稻较水作水稻更注重中后期对氮素养分的吸收，在生育后期氮素吸收速率呈上升趋势。旱作水稻中后期对氮素的吸收利用以土壤氮素为主;幼穗分化后水稻的土壤吸氮量占阶段吸氮总量的69.5%，比水作水稻多17.8%。早作条件下水稻当季吸收的氮素以土壤固有氮为主，而水作则更依赖于肥料氮的供给.旱作水稻在生育后期，从土壤中吸收的氮在一定程度上缓解了旱作水稻中后期的供氮问题. 以2002年为例，对早作水稻生育期内土壤矿质氮时空变化的规律进行研究表明，旱作水稻土壤中矿质氮以硝态氮为主，表层和亚表层硝态氮含量的变化受施肥和降雨的影响较大.基肥施用后，覆草处理氮素的生物固持现象明显，表层土壤矿质氮含量比裸地旱作处理下降了28 .3 kgNhm一，降低了矿质氮淋失的可能性。不同生育阶段土壤氮素表观盈余的计算结果表明，在旱作水稻旺盛生长的分集期和抽穗期旱作处理都表现出不同程度上的土壤氮素表观亏缺;然而就全生育期旱作各处理土壤氮素的盈余量而言，平均高达134魄Nhm一2，生育前期氮肥的大量投入是氮素盈余的主要原因。 综上所述，直播旱作水稻与水作水稻在氮素吸收利用特征方面存在着明显差异，因而在直播覆盖旱作水稻的氮肥管理中，应该注意区别于传统水作水稻注重基肥施用的施肥模式，坚持基肥少施，适度增加穗肥力度的氮肥施用原则，以实现增产增效的目的.更多还原

【Abstract】 Shortage of water resource is one of the main inhibitors in development of sustainable agriculture. Since more than 80% of the freshwater used in agriculture finds its way in waterlogged rice soil, the traditional waterlogged way has been challenged by water-saving cultivation of rice crop. Thus, a novel cultivation system of rice crop in aerobic soil was found and it showed its great potential in water saving agriculture. In this system, about 90-100% of freshwater irrigated could be saved compared with waterlogged one.Rice seedlings are Usually transplanted to soil in this new cultivation system to ensure enough panicles per hectare. However, transplant would take more time and have less suviving rate of rice seedlings, compared with transplanted paddy rice. In our study, the method of direct-seedling was selected trying to overcome the disadvantages. The objective of the present study is to determine the effects of direct-seeding rice cultivated in aerobic soil with mulching on the rice growth and development, the yield formation and nitrogen uptake, so that we can provide a basis for nitrogen management practices for rice cultivation in aerobic soil condition.A two-year iield experiment was carried out in sandy loam soil in Yancheng, Jiangsu province (33 27’N, 120 11’E) in 2001 and 2002. There were three treatments in rice cultivation in aerobic soil, including the soil being covered with plastic film (PF), with rice straw (RS) and the soil without any mulching (B). The control for the experiment was the rice grown in waterlogged soil (W). The main field experiment, which was subdivided into one waterlogged area and one large aerobic area, was constructed in a one-factorial block design with three replications each treatment. The experimental block of waterlogged rice was separated from the aerobic block by a strong plastic foil vertically inserted into depth of 60 cm for hydrological isolation.After sowing, plastic film was used to cover all surface of aerobic treatments to ensure a better seedling emergence. At the 3-leaf stage, the plastic film was removed in RS and B treatments. The soil surface in RS treatment was then covered with semi-decomposed rice straw (about 6000 kg dry straw . hm-2). Two tensionmeters with tips at 18 cm depth were installed in each plot to indicate soil water content which was maintained round 75-90% of water holding capacity (WHC), that is to say, as soon as soil water content was lower than 75-90% of WHC, irrigation would be made immediately and then stopped when the water at the soil surface reached the expected values.15N sub-plots were laid out within each treatment and thus the application of225 kg N .hm-2 (15N-labeled urea with 2% 15N abundance ) was homogeneously added into soil by hand. Plant samples were taken in 15N sub-plots at four growth stages, such as maximum tillering, panicle initiation, heading and harvest of the rice plant. All the samples were dried at 70C for 72h after kept at 105C for 20 min to kill enzymes in the plants. Total plant N content and 15N abundance were determined with Delta C continuous flow mass spectrometer coupled to Carlo Erba elemental analyzer 1108 by Conflo II interface. Soil sampling at the depths of 0-20cm and 20-40cm from fields was done every two weeks during the experimental duration. The soil mineral N (including NO3--N and NH4+-N) was determined as follows: 0.01mol.L-1CaCl2 was used as extract on a horizontal shaker for Ih, and Nwm in the filtrate was analyzed using a flow-analyzer (CFAA3). At the same time the soil water content of each sample was determined by oven drying.The main results of this study are showing as follows. Grain yields of rice decreased slightly when cultivated in aerobic systems and the reduction rate ranged from 2%-18%. However, yields of upland rice plots covered with plastic film (PF) and straw mulch (RS) were 8% and 4% higher than that of upland rice without mulch (B). The havest index (HI) of rice crop had no significant differences between different treatments, and reduced when plant d更多还原