【作者】 苏伟；

【导师】 鲁剑巍；

【作者基本信息】 华中农业大学 ， 植物营养学， 2014， 博士

【摘要】 长江中下游地区油菜产量的提高往往受到季节性干旱、冬季低温以及土壤肥力较低等因素的限制。与此同时,在这一地区高强度的水稻种植每年会产生大量的水稻秸秆,由于缺乏合理的利用方式,相当数量的秸秆被直接焚烧于田间,导致了严重的环境污染和资源浪费。考虑到秸秆还田在改善土壤环境和培肥土壤方面的优势,在油菜季推行水稻秸秆还田不仅有可能提高油菜的产量,也可以合理的利用过剩的水稻秸秆,从而起到一举两得的效果。本研究利用盆栽试验、大田试验和长期定位试验,比较了不同稻草还田方式下油菜季土壤水热状况的差异,探讨了不同稻草还田方式对油菜生长、产量及氮利用的影响,分析了水稻—油菜轮作系统长期秸秆还田后土壤肥力及作物生产力的变化,以评估水稻秸秆还田的综合效应以及对油菜生产的影响,从而为水稻秸秆还田在油菜季的合理运用提供参考。主要的研究结果如下：1.稻草还田改善了土壤的水分状况,整个油菜生育期稻草翻压处理和覆盖处理0-30cm的土壤储水量平均分别较不还田处理提高了4.8%和9.8%。稻草覆盖显著降低了油菜越冬期0-10cm土层土壤温度的日变化幅度,保温效果明显。与覆盖还田相比,稻草翻压还田对土壤温度的调节作用相对较弱,较明显的土壤温度改变仅出现在5-10cm土层。盆栽和大田试验的结果均表明稻草还田不利于油菜出苗,无论稻草以何种方式还田,油菜的出苗率和群体数量均有一定程度的降低,其中覆盖还田条件下,降低的幅度更大。尽管如此,稻草还田还是改善了油菜的生长,稻草翻压还田在整个生育期显著增加了油菜的干物质积累量,而稻草覆盖还田在薹期之前也明显的促进了油菜的干物质积累,但在薹期之后这种正效应有逐渐减弱的趋势。分析土壤氨挥发和无机氮储量的结果发现,薹期追施氮肥之后,稻草覆盖导致了土壤氨挥发量的急剧增加,而相应的土壤无机氮储量则较稻草不还田处理显著降低。根据这一结果推测由薹肥氮损失加剧导致的氮供应不足可能是薹期之后稻草覆盖正效应下降的主要原因。从产量结果来看,稻草翻压增产效果明显,而稻草覆盖对油菜产量也有一定的正效应,但效应的大小在不同年份间有所不同,在干旱年份(2010-2011),稻草覆盖的增产效果明显,而在降水相对正常的年份(2011-2012),稻草覆盖的增产未达到显著性水平。以上结果说明覆盖和翻压在油菜季均是可行的稻草还田方式,但稻草覆盖条件下油菜的田间管理需要做出一定的调整,增加播种量和改变追肥方式均十分必要。2.田间条件下,设置0、3750、7500和15000kg/hm2四个还田量水平初步评估油菜季适宜的稻草覆盖量。从产量结果来看稻草覆盖可明显增加油菜的产量,平均的增产幅度达到16.0%。3个稻草用量处理中,以覆盖量为3750kgha-1的处理产量最高,随着覆盖量的进一步增加产量略有降低,但差异不大。以此作为判断依据同时兼顾操作方便的原则,在实际生产中应当推荐7500kg/hm2的覆盖量,相当于前季稻草全量还田。在稻草覆盖还田条件下研究了增加播种量对油菜出苗及产量的影响,结果表明增加播种量显著增加了油菜的群体数量,当播种量达到原播种量的1.6倍时,有效密度可增加51.2%。产量结果表明相同播种量的条件下,稻草覆盖明显增加了油菜的产量,而覆盖条件下增加播种量又可使油菜产量有进一步的提升,说明增加播种量是充分发挥稻草覆盖增产效应的有效措施。3.在双季稻-油菜轮作系统中,连续的秸秆覆盖还田可以提高作物的产量,早稻、晚稻、油菜3种作物中以油菜的增产效应最为明显,5年平均的增产幅度可达14.2%。连续秸秆覆盖还田增加了早稻、晚稻和油菜的养分吸收量,氮、磷、钾养分相对增加幅度的顺序为钾>氮>磷。养分内部利用效率的结果表明,秸秆覆盖对早稻、晚稻和油菜氮和磷的内部利用效率影响较小,但导致了作物钾内部利用效率的明显降低。从养分平衡的结果来看,秸秆还田后,各季作物的氮钾盈余均在秸秆不还田基础上有所提升,特别是钾的提升幅度很大,而磷盈余的变化则相对较小。在试验初期土壤全氮含量受秸秆还田的影响较小,但随着还田年限的增加,土壤全氮含量增加明显。秸秆还田对土壤速效磷的影响不明显,但从还田初期开始就显著提高了土壤速效钾的含量,整个试验期间(2007-2012),土壤速效钾含量平均比不还田处理增加了29.0%,差异显著。秸秆还田导致了土壤有机碳含量的增加,特别是在免耕条件下,增加幅度更为明显。以上结果说明连续的秸秆覆盖还田是双季稻-油菜轮作系统中提高土壤肥力增加作物产量特别是油菜产量的有效途径。更多还原

【Abstract】 Seasonal drought, low temperature in winter and low soil fertility are main limiting factors for winter oilseed rape production in the middle and lower basin of Yangtze River. Therefore, identifying management practices that modificate the soil micro-enviroment, meanwhile enhance soil fertility is desirable for winter oilseed rape in this region. On the other hand, intensive rice production in the region contributes to enormous amounts of rice straw every year. Because of having not found an alternative method to use the straw, formers just burn it, which causes the waste of resources and environmental pollutio. Considering the advantages of straw retaining in improving soil moisture, soil temperature as well as soil fertility, rice straw retaining in winter oilseed rape season may be a potential practice not only to improve the productivity of winter oilseed rape, but also to fully utilize rice straw. In this study, pot experiment, short-term field experiment and long-term field experiment were conducted to (1) evaluate the effects of rice straw retaining on soil water and soil temperature;(2) explore the influences of rice straw retaining on winter oilseed rape growth, yield and nitrogen use;(3) analyze the changes of soil fertility and crop productivity under the condition long-term straw retaining. Results from this study may provide some information that can be used to (1) determine whether rice straw retaining has the potential of improving the productivity of winter oilseed rape;(2) preliminarily judge whether winter oilseed rape requires different management practices under straw retaining. The main results were as follows.1. Straw retaining had significant effects on soil moisture at0-30cm depth. Both straw incorporation and straw mulching resulted in higher soil water content at all growth stages of winter oilseed rape. At seedling stage of winter oilseed rape, straw mulching significantly reduced diurnal fluctuations of soil temperature, but straw incorporation had no significant influence on soil temperature. The results of pot and field experiments showed that both straw incorporation and mulching reduced the emergence percentage of winter oilseed rape, however, the relative mangnitude of the decrease was much bigger when straw mulching was applied than when the straw incorporaction was applied. Straw incorporaction improved the dry matter accumulation of winter oilseed rape throughout the whole growth periods. While straw mulching also increased the dry matter accumulation of winter oilseed rape at all growth stages, nevertheless, the relative magnitude of the increase in dry matter accumulation of winter oilseed rape between the mulched and un-mulched treatments reduced after seedling stage. Straw mulching resulted in more topdressing N loss through ammonia volatilization and a significantly lower soil inorganic N content after seedling stage, which might be the main factor that was responsible for decreasing positive effects of straw mulching on oilseed rape growth after seedling stage. Straw incorporation significantly increased rapeseed yield, but the effect of straw mulching on winter oilseed rape yield varied depend on seasons. In drought season (2010-2011), the mulched treatment had significantly more seed than the un-mulched treatment, however, in relatively normal season (2011-2012), straw mulching merely resulted in an insignificant increase in rapeseed yield.2. Different straw-mulching rates treatments (0,3750,7500and15000kg/hm2) were arranged in a field experiment to preliminarily estimate proper straw-mulching rates for winter oilseed rape. The results showed that compared with no straw mulching, mulching could increase significantly the rapeseed yield by16.0%on average. While between the three mulching rates treatments, no significant difference in rapeseed yield was observed. According to this result, meanwhile give consideration of the fundamental of easy operation, the mulching rates of7500kg/hm was recommended in actual farming, this rate roughly corresponded to the amounts of pervious rice straw. The effect of different sowing rates on emergence and yield of winter oilseed rape was studied under the condition of straw mulching. The results showed that the increase in sowing rates had no significant influence on emergence percentage of winter oilseed rape, but it significantly increased the plant density and yield of winter oilseed rape, indicating that increasing the seeding rates was an effective practice to improve rapeseed yield when straw mulching was applied in winter oilseed rape production.3. In the double rice-winter oilseed rape cropping system, continuous straw mulching increased the crop yield, moreover, the yield response was more significant in winter oilseed rape season than in rice season. Similar to yield, nutrient uptake of early-season rice, late-season rice and winter oilseed rape were also improved by continuous straw mulching. Straw mulching resulted in significantly lower internal efficiency of potassium (K) both in rice season and winter oilseed rape season, but it had no significant influence on internal efficiency of nitrogen (N) and phosphorus (P). The results of system-level nutrient balance showed that significant positive N, P and K balances had occurred without straw mulching, when straw mulching was applied, N and K surplus of cropping system were furthermore intensified. At the initial stage of long-term field experiment, there was no significant difference in soil total N content between mulched and un-mulched treatments, but with prolongation of experimental years, a gradually significant increase effect of straw mulching on soil total N content was observed. Straw mulching had no sigficant influence on soil available P content, but it had significantly increased soil exchangeable K content since the beginning of experiment. Straw mulching also resulted in an increase in soil total organic C content, moreover, under the condition of no-till, this increase was more significant.更多还原