【作者】 王小春；

【导师】 杨文钰；

【作者基本信息】 四川农业大学 ， 作物栽培学与耕作学， 2013， 博士

【摘要】 本研究于2008～2011年在大田试验条件下,以代表性玉米杂交种川单418为材料,在四川两个玉米主产区—川中丘区射洪县和川西山区雅安市对比研究了玉/豆和玉/薯模式中土壤肥力变化规律及玉米养分吸收利用特性、玉米生长和产量差异,两种模式下不同施氮量和氮肥运筹方式对玉米产量、氮素利用特征的影响及其生理机制,主要研究结果如下：1、两种模式下土壤养分变化规律及玉米产量和养分吸收差异经过一年种植后,不同作物带耕层土壤养分含量差异达显著水平,大豆带残留的硝态氮、速效氮、速效钾均显著高于甘薯带,而铵态氮和速效磷甘薯带较大豆带高,两种套作体系中玉米带耕层土壤养分含量差异不显著；第二、三年分带轮作,玉米分别以大豆和甘薯为前茬,由于大豆带和甘薯带土壤养分差异,使玉米氮和钾素吸收积累玉/豆模式显著高于玉/薯模式,磷的吸收积累则相反,不同作物带经玉米轮作后耕层土壤养分含量差异减小,主要表现在玉米对硝态氮、速效氮、磷等养分的均衡吸收上。两种套作模式经过一年种植后,玉/豆模式下玉米产量高于玉/薯模式,但差异未达显著水平；第二、三年分带轮作后,玉/豆模式下玉米产量显著高于玉/薯模式,两年平均分别高出679.5kg/hm2和839.1kg/hm2,增产9.4%和12.6%,穗粒数显著增加是增产的主要原因。2、两种模式下玉米氮肥运筹效应差异两种种植模式不同的施氮量和氮肥运筹处理对玉米的产量影响均达显著水平,且交互效应显著。玉/豆模式下,施氮量雅安试验点以N180处理产量较高,显著高于其它处理,射洪试验点以N180处理最高,但与N270处理差异不显著,玉/薯模式下,以N270处理产量最高。氮肥运筹试验中得出：两种模式中氮肥均以每公顷施纯氮180～270公斤,玉/豆模式中以“30%底肥+20%拔节肥+50%攻苞肥”氮肥运筹方式玉米产量最高,为7710.67kg/hm2,而玉/薯模式以“底肥和穗肥各一半”的氮肥运筹方式玉米产量可达6648.42kg/hm2。玉/豆模式下玉米粗蛋白和赖氨酸显著高于玉/薯模式,玉米籽粒粗脂肪和粗淀粉含量有玉/薯模式高于玉/豆模式的变化趋势,但差异不显著。随施氮量增加两种模式下粗蛋白含量均显著增加,在N360处理达最高,赖氨酸含量0～270kg/hm2之间随施氮量增加,显著提高,360kg/hm2处理赖氨酸反而降低,粗淀粉含量随施氮量提高,均显著下降。施氮时期对两种模式下粗蛋白和赖氨酸的含量的影响均表现为：氮肥后移>氮肥前移>底追均等,且各处理间差异达显著水平,表明增施拔节肥有利于粗蛋白的积累,且多次施肥的提高效果更好。3、两种模式下氮肥对玉米形态指标的影响两种种植模式下施氮量、氮肥运筹方式对玉米形态指标的影响存在显著或极显著的互作作用。在玉米生长前期,中高氮水平均抑制了两种模式下玉米的生长,中期随玉米需氮量的增加,中氮水平显现优势,玉/豆模式中以“N180,30%底肥+20拔节肥+50%攻苞肥”处理株高、茎粗,叶面积指数、SPAD值和干物质量均较高,玉/薯模式中以“N270,50%底肥+50%攻苞肥”处理较高,N360处理反而抑制了玉米生长,氮肥前移的运筹方式,灌浆期缺氮,叶面积指数和SPAD下降较快,不利于产量形成,而在两模式适宜的施氮水平和氮肥运筹方式下,叶面积和SPAD值的下降速率减缓,防止叶片衰老。4、两种模式下氮肥对玉米光合特性及干物质积累分配的影响两个试验点连续二年的研究结果表明,种植模式、施氮量和氮肥运筹方式对玉米各时期穗位叶光合速率、气孔导度、PS Ⅱ最大光化学效率、有效光化学量子产量的影响差异达显著水平。玉/豆模式下玉米在吐丝期和灌浆期穗位叶的净光合速率、气孔导度均比玉/薯高,且到灌浆期的下降率低于玉/薯模式,在此模式下,全生育期施纯氮90～180kg/hm2,采用“30%底肥+20%拔节肥+50%攻苞肥”施肥方式,还能显著提高玉米穗位叶PS Ⅱ最大光化学效率和有效光化学量子产量,有利于灌浆期玉米光合能力的提高和光合产物的积累,同时提高了干物质最大增长速率和平均增长速率,延长了灌浆持续天数,确保适当增加穗长,提高每穗粒数,进而显著提高群体库容量,提高玉米的增产潜能。玉/薯模式下全生育期施纯氮180～270kg/hm2,采用“50%底肥+50%攻苞肥的施肥方式”相对同种模式下其它处理,也具有较明显的优势。氮肥前移处理,吐丝期光合特性的各指标值均较高,但到灌浆期下降速率均较快,氮素胁迫,PS Ⅱ最大光化学效率和有效光化学量子产量值较低,玉米生长后期叶片的光合生产能力减弱,不利于光合产物积累。5、两种模式下氮肥对玉米氮素代谢、吸收利用和土壤硝态氮积累的影响及相互关系种植模式、施氮量和氮肥运筹对玉米各生育时期氮代谢酶活性及氮素吸收利用、土层硝态氮的积累均有显著效应,玉/豆模式中玉米各生育阶段积累氮素均显著高于玉/薯模式,同时提高了氮素收获指数和氮素利用效率,玉/豆模式中玉米成熟期籽粒有47.29%～55.48%来自开花前贮存在营养器官中的氮素,有44.52%～52.71%来自花后同化,而玉/薯模式中玉米成熟期籽粒有51.88%～61.75%来自花前积累,38.25%～48.12%来自花后同化,玉米收获后玉/豆模式下硝态氮的积累量显著高于玉/薯模式,且主要集中在0-60cm土层,60-120cm的土层中玉/薯模式略高于玉/豆模式。合理的氮肥用量和氮肥施用时期能有效提高氮素吸收利用,促进氮素代谢,减轻硝态氮的淋溶损失,两种模式下180～270kg/hm2施氮处理相对于其他施氮水平有助于抽雄期至成熟期玉米吸氮量的增加,提高氮素农艺生产效率,而且玉/豆模式与氮肥后移,玉/薯模式中与底追均等的氮肥运筹方式结合,能达到提高氮代谢酶活性、提高氮肥利用效率的目的,两种模式下氮肥前移处理均显著降低土层中硝态氮的积累量,但由于玉米前期需肥量少,残留在土壤中的硝态氮大部分发生了氮淋溶损失和反硝化作用,随水淋溶到了60cm以下,造成了氮的损失。硝态氮的积累随施氮量的增加显著提高,且过高的氮肥用量和氮肥前移施肥方式,不利于两种模式下玉米生长后期穗位叶硝酸还原酶(NR)、谷氨酞胺合成酶(GS)和蔗糖磷酸合成酶(SPS)活性的提高,还会导致氮效率的下降。更多还原

【Abstract】 From year2008to2011, typical maize hybrid chuandan418was used to study the regulation of soil fertility variation and characteristics of nutrient absorption, utilization, dynamic growth and yield differences of maize under maize/soybean and maize/sweet potato relay intercropping systems in two main maize producing areas in Sichuan, Shehong in the middle and Ya’an in the west, and the effects of nitrogen fertilizer application and nitrogen strategies on the yield, nitrogen absorption, utilization and their mechanism of maize under two systems were e studied under field experiment. The main results were as follows:1. Regulation of soil fertility variation and differences of maize yield and nutrient uptake in two relay intercropping systemsAfter a year of planting, there was significant differences in soil fertility contents of cultivate layer in different crop strips. The residuals of nitrate nitrogen, available nitrogen and available potassium in the soybean strip were significantly higher than those in the sweet potato strip, however, the residuals of ammonium nitrogen and available phosphorus in the sweet potato strip were higher than those in the soybean strip, and soil fertility contents of cultivate layer in maize strip were of no significance in the two relay intercropping systems. After two or three-year’s strip rotation, the differences of nutrient absorption were great as the preceding crops were soybean or sweet potato, and the accumulation of nitrogen and potassium were higher in maize/soybean than that in maize/sweet potato, while the accumulation of phosphorus was opposite. There was a decreasing in soil fertility content of cultivate layer after crop rotation with maize. The results showed that maize had a better equilibrium effect on nutrient absorption, which would mainly be nitrate nitrogen, available nitrogen and phosphorus.Maize yield in maize/soybean was higher than that in maize/sweet potato with no significant difference after one year planting. This indicated that interspecies reciprocity benefited to maize yield production, but the yield-increasing effect were not significant. After two or three-year’s strip rotation, the maize yield of maize/soybean was considerably higher than that of maize/sweet potato. The two year’s productions were more than those of the previous year with679.5kg/ha and839.1kg/ha on average and with the increases of9.4%and12.6%in the two experimental sites, which reflected a more significant productivity in Shehong than that in Ya’an, the increased productivity may mainly due to the significantly increasing of kernels per ear in Shehong.2. The differences of N Management effects in two relay intercropping systems Two-year’s results in the two experimental sites showed that planting patterns, nitrogen application rates, and nitrogen strategies all had an significant effect on maize yield and there was a significant interactions among them. The results demonstrated that maize yield in maize/soybean was higher than that of maize/sweet potato significantly. In maize/soybean intercropping system; maize yield at treatment N180was significantly higher than other treatments in Ya’an, but that in Shehong was of no significance. In maize/sweet potato intercropping system, maize yield under treatment N270was the highest. Based on the appropriate nitrogen application level established at the previous year, the experiment focused on nitrogen strategies was conducted in Shehong from year2010to2011. The results showed that the two relay intercropping systems both achieved high yield when the nitrogen application amount was between180and270kg/ha, the maize yield in maize/soybean was highest, reaching7710.67kg/ha with the assigning proportion (basic N:jointing N:huge bellbottom N)3:2:5, but maize yield was highest in maize/sweet potato when the assigning proportion was5:0:5, and it reached6648.42kg/hm2.The content of crude protein and lysine were significantly higher in maize/soybean than those in maize/sweet potato, and those remained higher in Ya’an compared to Shehong; The content of crude fat and starch which were insignificantly higher in maize/sweet potato than those in maize/soybean remained higher in Shehong compared to Ya’an. With the increasing of nitrogen application level, the content of crude protein in both the relay intercropping systems increased significantly, and reached their peaks under treatment N360. The amount of lysine increased significantly with the increasing of nitrogen application when the amount of nitrogen was under270kg/ha, however, there was a decreasing trend under the treatment N360, while starch content decreased significantly with increasing of nitrogen fertilizer. The effects of different nitrogen assigning proportions on crude protein and lysine was significant, which indicated that increasing jointing nitrogen application increased crude protein and better effects were obtained by multiple fertilizing method.3. Effects of nitrogen fertilizer on the growing of maize in two relay intercropping systemsStudies found that different planting patterns with different nitrogen levels and nitrogen strategies affected the growth of maize, the accumulation and distribution of dry matters, reflecting significant or extremely significant interaction effects. In the early growth stage, medium-to-high nitrogen levels restrained maize growth. In the middle growth, medium nitrogen application level showed advantages. In maize/soybean intercropping system, plant height, stem diameter, LAI index and SPAD values inceased fastly under the treatment of N180, with30%basic N:20%jointing N:50%huge bellbottom N, however, those indexes were higher in maize/sweet potato relay intercropping when applied N270,50%basic N:50%huge bellbottom N. N360restrained maize growth; Those was mainly because forward nitrogen application led to nitrogen deficiency in Mid-grain-filling stage, decline of LAI index and SPAD values rapidly, which went against the formation of yield. As a result, slower deceasing of LAI index and SPAD values under two systems at suitable nitrogen application level and suitable nitrogen strategie would help to avoid the senescence of leaves.4. Effects of nitrogen fertilizer on maize photosynthesis and accumulation distribution of dry matter in the two relay intercropping systemsAfter successive years of research, results in two experimental sites were concluded that planting patterns, nitrogen application level and nitrogen strategies had a significant effect on photosynthetic rate, stomatal conductance, PS II maximum photochemical efficiency and EQY in every growth stage. The Pn and stomatal conductance of ear leaves in maize/soybean intercropping system were higher than that in maize/sweet potato intercropping system during silking stage and filling stage, but was decreased slowly in filling stage. Maize/soybean improved PS II maximum photochemical efficiency, EQY of ear leaves and the accumulation of photosynthetic products when nitrogen fertilizer was between90and180kg/ha and assigning proportion was30%basic N:20%jointing N:50%huge bellbottom N, meanwhile it helped increase dry matter output rate from leaves and stems to grains, avoiding the senescence of leaves, therefore, and the maximum speed of growth and average growth rate increased, which also helped extend the grain-filing days. All of these benefited the improvement of photosynthetic capacity and the accumulation of photo synthate in Mid-grain-filling stage, ensured that ear length increased appropriately, kernels per ear also improved, and then the whole group storage capacity increased, maize yield potential improved. but for maize/sweet potato there was significant advantage when applied nitrogen fertilizer between180and270kg/ha at assigning proportion was50%basic N:50%huge bellbottom N At silking stage various photosynthetic characteristics indexes were higher when applied nitrogen forward, but was decreased faster at filling stage, because of nitrogen stress, PS II maximum photochemical efficiency and EQY were lower which was against the accumulation of photosynthetic products.5. Effects of nitrogen fertilizer on maize nitrogen metabolism, absorption, utilization and soil nitrate nitrogen accumulation and their interrelation.Plant patterns, nitrogen fertilizer levels and nitrogen application strategies had a significant effect on enzymes activity involved in Nitrogen metabolism, absorption, utilization and soil nitrate nitrogen accumulation. The nitrogen accumulation in maize/soybean was higher than that in maize/sweet potato significantly. N harvest index and N use efficiency were also improved. In maize/soybean intercropping system, there was47.29%to55.48%of nitrogen coming from nutritive organs before blooming,44.52%to52.71%coming from assimilation after flowering. In maize/sweet potato intercropping system, there was51.88%to61.75%of nitrogen coming from nutritive organs before blooming，38.25%to48.12%coming from assimilation after flowering. The accumulation of nitrate nitrogen after maize harvest in maize/soybean which was mainly concentrated from0to60cm layer was significantly higher than that in maize/sweet potato; however, it was slightly higher in maize/sweet potato than that in maize/soybean from60to120cm layer. Proper nitrogen application level and application time helped improve nitrogen absorption and utilization, and promote nitrogen metabolism, and reduce nitrate nitrogen loss effectively. The nitrogen absorption of maize and nitrogen agricultural production efficiency were increased applied180to270kg/ha nitrogen fertilizer to both planting patterns compared to other nitrogen application levels. Maize/soybean relay intercropping system along with3:2:5and maize/sweet potato relay intercropping system along with5:0:5could increase enzymes activity involved in N metabolism and nitrogen use efficiency.Forward nitrogen application would decrease the accumulation of nitrate nitrogen in soil under two systems was mainly due to less fertilizer requirement for maize in the early growing stage, most nitrogen lost caused by leaching which along with the way water flew to below60cm and denitrification, causing a great loss of nitrogen. The accumulation of nitrate nitrogen increased significantly with the increasing of nitrogen application level, especially excessive high level with forward nitrogen applied was not good for improving the activities of nitrate reductase (NR), glutamine synthetase(GS) and sucrose phosphate synthetase(SPS) during the later period of maize growth, and would reduce nitrogen use efficiency更多还原