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1.
为烤烟合理施用氮肥和土壤改良提供理论和技术依据,采用田间试验研究氮肥与土壤改良剂配施对烤烟产量、产值、上等烟比例、叶片氮磷钾含量、品质指标含量和土壤氮、磷、钾含量的影响。结果表明,随着施氮量增加,不施土壤改良剂和施用土壤改良剂的烟叶产量和产值均随着施氮量的增加而增加;烟叶均价和上等烟比例呈抛物线变化趋势,分别在施氮45.0、67.5 kg/hm2时最高;相同施氮量,施用土壤改良剂的烤烟产量和产值均高于不施土壤改良剂的,但施氮量超过67.5 kg/hm2时,会降低烤烟的均价和上等烟比例。在圆顶期和成熟期,随着施氮量增加,不施土壤改良剂和施用土壤改良剂的烤烟叶片含氮量、含磷量、含钾量均呈增加趋势;相同施氮量,相比不施土壤改良剂的,增施土壤改良剂的烤烟叶片含氮量、含磷量、含钾量均明显提高,中部叶和上部叶氯离子含量降低,土壤速效氮、磷、钾含量有所提高。本试验条件下,施氮量在67.5~90.0 kg/hm2,配施土壤改良剂30.0 kg/hm2时,土壤供肥能力强,烟叶品质好,烤烟的产量和产值均较高,分别为2487~2588 kg/hm2、43538~44202元/hm2。  相似文献   

2.
减量施氮对带状套作大豆土壤通气环境及结瘤固氮的影响   总被引:1,自引:0,他引:1  
为研究种植模式和施氮量对大豆土壤通气环境及结瘤固氮的影响,本研究采用二因素裂区试验设计,主区为种植模式:大豆单作(SS)、玉米/大豆带状套作(MS),副区为不同施氮量:不施氮(NN:0 kg hm-2)、减量施氮(RN:45kghm-2)和常量施氮(CN:60kghm-2),监测了大豆生育期内土壤的O2含量和土壤呼吸速率的动态变化规律,分析了各处理的土壤水稳性团聚体、容重和孔隙度差异,探讨了大豆生育期内结瘤量、固氮能力的变化特征。2年数据结果表明,与单作大豆相比,带状套作大豆可提高土壤O2含量、>2 mm粒径团聚体的百分含量、显著增加土壤孔隙度、显著增强后期土壤呼吸的速率,显著降低<1mm粒径团聚体百分含量与土壤孔隙度;R5期根瘤干重差异不显著,但结瘤数量显著增加39.9%,固氮酶活性与固氮潜力也在此时显著高于单作大豆。各施氮量间,土壤O2含量、0.25~1.00mm粒径的百分含量、带状套作大豆的土壤呼吸速率以RN处理最高,施氮能降低<0...  相似文献   

3.
不同尿素施肥水平对北方混播草坪中土壤各形态氮的影响   总被引:2,自引:0,他引:2  
本文的目的是为了研究北京地区冷季型草坪合理的施肥制度,了解尿素施用对混播草坪土壤中各形态氮的影响。通过土壤渗滤水采集装置试验,研究尿素施用对草地早熟禾和高羊茅的混播草坪的生长情况和对土壤当中各形态氮素含量的影响。尿素施用共分为,低氮(年施氮量为10g m-2,相当于尿素 25g m-2)、中氮(年施氮量为25g m-2,相当于尿素62.5g m-2)、高氮(年施氮量为40g m-2,相当于尿素100g m-2)三个施肥水平。各处理中的尿素分别在春季和秋季平均施用。结果表明: 本试验中最佳施肥量是:年施尿素62.5g m-2(相当于氮量为25g m-2),在该水平下,草坪草能迅速吸收氮素,促进草坪植物生长; 试验还得出,施用尿素的水平与实验后土壤中全氮、铵态氮、硝态氮和碱解氮含量并不呈正相关。  相似文献   

4.
本研究于2015—2019年以晋杂34、辽杂27、晋饲2号、晋糯3号和汾酒粱1号为研究对象,设0(N0)、75(N75)、150(N150)、225(N225)、300(N300)、450 kg hm^-2(N450)6个氮素水平,调查其对产量性状、淀粉含量和土壤硝态氮以及氮素利用特性指标的影响,以探讨高粱合理的氮素施用方案。结果表明,高粱的产量、穗粒数及植株地上部氮素累积量,随施氮水平的增加呈先增加后趋于稳定的趋势,其中以N75处理增幅最大,较N0处理最大增幅分别可达23.68%、48.05%和51.86%;籽粒淀粉含量、5年叠加氮肥利用率、5年叠加氮肥农学效率和氮素5年叠加表观回收率随施氮水平的增加都存在不同程度的降低,其中N75处理下5年叠加氮肥利用率为63.01%,较N150处理提高了76.91%;籽粒淀粉产量则随施氮水平的增加呈先增加后降低的趋势。连续施氮4~5年后,施氮量≥225 kg hm^-2,残留的硝态氮在60~200 cm土层逐年累积,且在0~200 cm土层存在明显的累积峰,硝态氮淋失风险加剧。施氮量75~150 kg hm^-2之间,在满足高粱植株基本生长需求的同时,可以弥补了土壤氮库的消耗,有效降低了土壤硝态氮的淋失,亦有利于高粱产量和籽粒淀粉产量的形成。  相似文献   

5.
The transporting unit is one of the indispensable facilities in the biomass pyrolytic liquefaction system and the continuous and steady transporting characteristic is the key to ensure the process of biomass pyrolytic liquefaction.This paper introduces one biomass transporting system adopted in the experiment;taking sawdust,paddy shell, wheat hull and corn grain with different grain diameters as the representative materials,the influence law of various factors on transportation capacity is studied in this paper.The research results obtained can offer an important reference for realizing a continuous and reliable biomass pyrolytic liquefaction process.  相似文献   

6.
To determine a suitable nitrogen fertilizer application rate, an experiment was conducted using Jinza 34, Liaoza 27, Jinsi 2, Jinnuo 3, and Fenjiuliang 1 with six nitrogen (N) fertilization levels, including 0 (N0), 75 (N75), 150 (N150), 225 (N225), 300 (N300), and 450 kg hm-2 (N450). The effects of long-term nitrogen fertilization with different levels on sorghum grain yield, nitrogen use characteristics and soil nitrate nitrogen distribution were investigated. The grain yield, grain number and N accumulation of sorghum increased initially and then tended to be stabile with the increase of nitrogen fertilizer application. Among them, the maximum increase of sorghum under N75 treatment compared with that under N0 treatment was 23.68%, 48.05%, and 51.86%, respectively. With the increase of nitrogen fertilizer application, the grain starch content decreased, while the grain starch yield increased firstly and then decreased. Nitrogen apparent recovery rate, nitrogen fertilizer agronomic efficiency and nitrogen use efficiency which were accumulated for five years were reduced significantly with the increase of nitrogen fertilizer application. Compared with the N150 treatment, nitrogen use efficiency accumulated for five years under N75 treatment, which was 63.01%, was increased by 76.91%. When nitrogen fertilizer application was beyond 225 kg hm-2, after four to five years later, nitrate nitrogen residue was increased rapidly in the 60-200 cm soil layer year by year, NO3--N accumulation peaks distributed in the 0-200 cm soil layer and the risk of nitrate nitrogen leaching was increased. In view of the yield, starch yield, nitrogen utilization and environmental benefit, the reasonable nitrogen fertilizer application for sorghum was between 75 kg hm-2 and 150 kg hm-2.  相似文献   

7.
采用活性炭涂层改性悬浮填料,在连续曝气的条件下,考察了SBBR反应器脱氮性能。结果表明,SBBR反应器表现出良好的同步硝化反硝化(SND)脱氮性能,对NH3-N和TN的去除率分别为80.7%和63.1%。典型周期内反应器同步硝化反硝化率可达82.7%。单因素试验发现,脱氮率随着曝气时间t的增加而增加,随着溶解氧质量浓度ρDO和填料投加量δ增大而先增大后减小。同时,以溶解氧质量浓度、填料投加量和曝气时间为考察因素,脱氮率为评价指标,采用响应曲面法建立了二次多元回归模型。通过模型求解得出最佳工况:溶解氧浓度为2.37 mg/L,填料投加量为40.10%,曝气时间为5.17 h,此时,脱氮率得到最大值为69.28%。验证试验表明,回归模型的预测值与实测值偏差率为1.57%。  相似文献   

8.
氮肥施用量对机插优质晚稻产量和稻米品质的影响   总被引:5,自引:0,他引:5  
本试验为筛选适合优质丰产机插晚稻的最佳氮肥用量,以优质双季晚稻泰优398、黄华占、天优华占、美香新占4个品种为试验材料,在机插条件下设0、135、180、255 kg hm–2四个施氮水平,测定产量构成及稻米品质指标。结果表明,适当增施氮肥可增加优质双季晚稻产量,施氮量为180kghm–2时产量最高。除黄华占的整精米率外,施氮量为180 kg hm–2时各品种的糙米率、精米率和整精米率最高。随施氮量的增加,机插优质双季晚稻的垩白粒率和垩白度降低,米粒长宽比变大,蛋白质含量和胶稠度均增加,直链淀粉含量减少;峰值黏度、热浆黏度、崩解值、最终黏度逐渐下降,消减值增加,糊化温度呈上升趋势。适当增施氮肥可改善机插优质晚稻加工品质、外观品质、蒸煮和营养品质,但RVA特性有变劣趋势。180 kg hm–2的施氮量可使机插优质双季晚稻优质和高产达到较好的协调统一。  相似文献   

9.
《Agricultural Wastes》1981,3(3):179-189
This research was undertaken to determine guidelines for combining dairy manure and field crop residues for maximum methane production per volume of anaerobic digester. The parameter investigated for establishing the proper mixture was the nonlignin-carbon to nitrogen ratio. Six 4·4 litre laboratory digesters, with operating volumes of 3·4 litre, were tested for 18 months with dairy cow manure combined with either barley straw, rice hulls or rice straw in three separate six-month phases. Non-lignin-carbon to nitrogen ratios of the various feed mixtures ranged between 12·3 and 40. Results indicate that methane production from fresh dairy manure can be enhanced by addition of chopped field crop residues. The maximum performance occurs when the non-lignin-carbon to nitrogen ratio of these feed mixtures is between 25 and 32. The non-lignin-carbon to nitrogen ratios for various other agricultural residues were also determined.  相似文献   

10.
滴灌玉米临界氮稀释曲线与氮素营养诊断研究   总被引:4,自引:0,他引:4  
旨在建立宁夏引黄灌区滴灌玉米临界氮稀释曲线模型,探讨氮营养指数(NNI)用于实时诊断和评价玉米氮素营养状况的可行性,为实现滴灌玉米合理施用氮肥提供理论依据。以天赐19为试验材料,采用滴灌水肥一体化技术,设6个氮肥水平,利用2年定位试验构建并验证了临界氮稀释曲线模型。结果表明:(1)在一定范围内,滴灌玉米干物质积累量随施氮水平的提高而增加,根据方差分析结果,将玉米各生育时期的地上部生物量分为限氮和非限氮2类;(2)滴灌玉米植株氮浓度均随着施氮量的增加而提高,但随生育期的推进和地上部干物质量的增加,玉米植株氮浓度均呈下降趋势;(3)滴灌玉米临界氮浓度(Nc)、最大氮浓度(Nmax)和最小氮浓度(Nmin)稀释模型与地上部干物质累积量之间均呈现幂函数关系,其决定系数R2分别为0.982、0.907、0.918,利用均方根误差(RMSE)和标准化均方根误差(n–RMSE)的验证表明,该模型稳定性好,误差范围小;(4)氮素营养指数模型(NNI)可衡量滴灌玉米氮素营养状况,滴灌水肥一体化条件下,宁夏引黄灌区玉米以270kghm–2为最佳施氮量;(5)根据模型推算,NNI与相对吸氮量(RNupt)、...  相似文献   

11.
长期定位施肥对夏玉米氮代谢的影响   总被引:5,自引:1,他引:4  
基于 30年的长期定位试验, 研究了长期定位施肥对夏玉米氮代谢的影响。随施肥量增加,氮代谢旺盛,吐丝后穗位叶NR活性高,其中M2N2处理NR活性平均比对照提高了4.0%,其次是M2N1、N2PK、M1N2,分别比对照提高了3.7%、3.4%、3.1%。穗位叶的游离氨基酸和蛋白质含量也表现为与NR活性类似的趋势。M2N2处理游离氨基酸和蛋白质含量与对照比较差异显著。分别比对照提高了19.6%和22.2%。其次M2N1、N2PK、M1N2处理。游离氨基酸含量分别比对照提高了17.9%、16.7%、和15.4%。蛋白质含量分别比对照提高了18.5%、18.4%和17.9%。有机肥氮肥配施处理,穗位叶NR活性在籽粒形成期间维持高活性时间长,穗位叶中的可溶性蛋白含量高。氮磷钾肥配施处理穗位叶NR活性、可溶性蛋白含量显著高于氮磷、氮钾处理。  相似文献   

12.
The MecaNiCAL model of carbon and nitrogen partitioning over a period of regrowth for a mean grass plant as described in Part 1 was fitted and evaluated against data from an experiment under controlled conditions with contrasting light and nitrogen nutrition. In the first investigation, the rate of nitrogen uptake was imposed to limit the compensation of errors between process. The root:shoot ratio was simulated well, with a good estimation of the nitrogen allocation to shoots. Some underestimation of the root weight after the cut and the final shoot weight under the low nitrogen treatment were consequences of both the lack of remobilisation and the high priority given to shoots. The good agreement obtained with the expected trend in simulations conducted with the simple nitrogen aborption submodel in extended conditions (contrasting initial content of nitrogen substrate and temperature change in regrowth) ensures the general consistency of the model in the limit of its area of validity. Partitioning to shoots and forage production seem to be sensitive mainly to the size of the carbohydrate substrate pool and its availibility, particularly under conditions of low light. Estimating the initial carbohydrate substrate pool by biochemical analysis may improve the accuracy of the model. Compared with more simple assumptions of partitioning, MecaNiCAL shows a higher level of agreement with the partitioning response to a wide range of environmental conditions. A simple assumption relating partitioning to plant nitrogen content does not seem to be sufficient to simulate the decrease in the root:shoot ratio observed under conditions of low light. Nevertheless, more data from experiments conducted under a wider range of contrasting conditions are required to estimate the validity of MecaNiCAL attached to the nitrogen absorption submodel and the advantage of its more complex assumptions with even greater accuracy.  相似文献   

13.
田间开放式增温对东北水稻氮素利用的影响   总被引:1,自引:0,他引:1  
东北地区是全球气候变暖趋势最为显著的地区之一,研究预期增温对东北水稻氮素吸收利用的影响,可为区域水稻可持续生产与氮肥优化管理提供借鉴。本研究于2019—2020年在黑龙江省哈尔滨市设置田间开放式增温(free air temperature increase,FATI)系统,大田与盆栽试验相结合,采用15N同位素示踪技术,模拟预期增温(+1.5℃)对水稻产量、氮素利用以及氮肥去向的影响。结果表明,增温促进了水稻地上部干物质积累,与对照相比,大田与盆栽的水稻产量2年平均分别提高10.4%和10.8%;增温显著提高了水稻氮素吸收总量,与对照相比,2年平均增幅达21.3%,但增温处理的氮素籽粒利用效率呈降低趋势;增温处理下水稻从肥料中吸收的氮素显著下降,但从土壤中吸收的氮素显著增加31.1%,导致氮肥回收率降低12.5%,而氮肥损失率增加14.2%。总体来看,增温有增加水稻籽粒产量的趋势,但降低了水稻对肥料氮的吸收比例,导致氮素利用效率降低,氮肥损失率显著增加。在气候变暖背景下,建议合理增加水稻移栽密度,以充分利用温度升高对水稻产量的正向效应,适当减少氮肥施用量、优化氮肥运筹管理,提高水稻氮...  相似文献   

14.
以业已完成深度重测序的134份水稻地方种质资源为材料,在大田栽培条件下按不施氮(N0),施96kg hm^–2纯氮(N1)和施192kg hm^–2纯氮(N2)3种氮肥水平,检测了分蘖盛期植株的钾含量、植株干重和钾积累。结果表明,水稻钾含量、植株干重和钾积累在N0、N1、N2三种氮肥处理下均呈正态分布,表型变异丰富。植株干重和钾积累与施氮量呈极显著正相关,钾含量与施氮量相关性不显著;钾含量与植株干重呈负相关,钾含量与钾积累相关性不显著,而植株干重与钾积累呈极显著正相关。在3个施氮水平下,籼稻的钾含量极显著低于粳稻,籼稻的干重和钾积累都极显著高于粳稻。全基因组关联分析发现,在3个氮肥水平下检测到12个显著相关位点,其中钾积累、钾含量和植株干重的显著相关位点分别有2、5和5个。在N1水平下,位于第6染色体上与钾含量相关的SNP(Chr6_1,524,776)的显著性峰候选区包含与钾离子转运蛋白互作的RUPO基因。根据钾含量的差异,鉴定出3个钾含量与低氮响应有关的SNP位点,1个位点与高氮响应有关,而位于第10染色体上的显著性位点Chr10_2,822,026对低氮和高氮均有响应,该区域的4个候选基因的表达在不同氮水平间存在差异。  相似文献   

15.
稻麦两熟地区,旱直播水稻生产受前茬小麦收获、全量麦秸秆还田及耕整地质量不高等因素的影响,常采用迟播期、大播量、高基本苗和主茎成穗为主的“独秆”栽培模式,而配套该模式直播稻优质丰产的氮肥管理技术尚缺乏系统的研究。以优质食味粳稻南粳9108为材料,采用机械旱直播方式,基本苗为380×104 hm-2,设置不同叶龄期(六、七、八、九和十叶龄期)氮肥追施处理及氮肥追施用量(纯氮180 kg hm-2和225 kg hm-2)处理,以基本苗380×104 hm-2和300×104 hm-2的旱直播精确定量氮肥管理(纯氮270 kg hm-2,基肥︰分蘖肥︰穗肥=3.5︰3.5︰3.0)为对照,系统比较研究“独秆”栽培模式下,全程氮肥在分蘖中后期施用对旱直播水稻产量和品质的影响。结果表明,随追施叶龄的延后,水稻产量呈先增后降趋势,八叶期追施氮肥水稻产量显著高于其他处理,且追施量增加,水稻产量进一步提高。与2组对照相比,在纯氮180 kg hm-2,氮肥减量33.3%情况下,不施氮素基肥配合八叶期一次性追施氮肥,可显著提高水稻产量5.10%和8.65%;在纯氮225 kg hm-2,氮肥减量16.7%情况下,不施氮素基肥配合八叶期及7 d后二次追肥可显著提高水稻产量7.46%和11.09%。不施氮素基肥配合八叶期追施氮肥水稻产量提高的原因是,保障较大穗型的基础上增加有效穗数,显著提高群体颖花量,同时保持较高水平的结实率和千粒重。随追肥叶龄延后,水稻整精米率呈增加趋势,垩白度呈增大趋势,蛋白质含量增加,直链淀粉含量下降,食味值呈降低趋势。与2组对照相比,不施氮素基肥配合八叶期追施氮肥的水稻,加工品质提高,整精米率提高0.67%~2.23%;外观品质变好,垩白度降低3.6%~14.5%;营养品质提升,蛋白质含量增加3.03%~14.08%;蒸煮食味品质呈变优趋势,直链淀粉含量下降4.23%~10.95%;食味值无显著差异。综上所述,“独秆”栽培模式下基肥不施氮肥配合全程氮肥在分蘖中后期适宜叶龄施用可实现稻麦两熟地区旱直播稻迟播期、大播量和高基本苗生产方式的提质增产生产。  相似文献   

16.
节水减氮对土壤硝态氮分布和冬小麦水氮利用效率的影响   总被引:8,自引:0,他引:8  
针对当前关中平原冬小麦生产中氮肥投入过量、灌溉水资源不足的问题,研究节水减氮栽培模式下冬小麦籽粒产量、水氮利用及硝态氮淋失情况,能为确定冬小麦节水减肥环保增效的生产模式提供理论依据。于2017—2019年在陕西杨凌开展冬小麦节水减氮田间栽培试验,采用二因素裂区设计,施氮量为主处理,灌水量为副处理,设施氮量处理N300 (300 kg hm–2)、N225 (225 kg hm–2)、N150 (150 kg hm–2)、N75 (75 kg hm–2)、N0 (不施氮)和灌水量处理W2 (1200 m3 hm–2)、W1 (600 m3 hm–2)、W0 (0),分析小麦产量、水氮利用效率及土壤硝态氮淋失情况。结果表明,2017—2018年和2018—2019年小麦季灌水处理较不灌水处理分别增产14.88%~15.01%和4.11~4.16倍,但处理间差异不显著,而越冬期灌水600 m3 h...  相似文献   

17.
马铃薯作为乌兰察布市主要农作物,连作障碍问题日益突出,已然影响产业可持续发展,减轻或消除连作障碍对马铃薯生产意义重大。以当地主栽品种“后期红”为试验材料,设置轮作、一年连作、二年连作等处理,从出苗后33天开始,每隔15d,测定叶片光合性能相关指标、土壤速效氮含量。结果表明,随着生育进程的推进,三种种植模式下的马铃薯叶面积指数LAI、相对叶绿素含量SPAD、光合速率Pn、蒸腾速率Tr等指标变化趋势相同;与对照轮作相比,二年连作会使马铃薯LAI、SPAD、Pn、Tr在某些生育期明显降低,而一年连作马铃薯的大部分指标无显著变化;二年连作土壤中的速效氮含量明显低于对照,一年连作与对照无明显差异;相关分析表明土壤速效氮含量与光合特性指标呈显著正相关。因此,适当增加马铃薯连作土壤中氮肥投入,尤其是中后期合理施肥,有助于提高光合特性。  相似文献   

18.
木醋液熏蒸对大棚土壤及西瓜生长的影响   总被引:1,自引:1,他引:0  
摘 要:木醋液是生物质热裂解过程中的烟气液化而形成的液体,作为土壤熏蒸剂的作用与效果目前还没有数据。本研究将不同量木醋液喷施于大棚土壤,并以溴甲烷为对照,观测其抑菌作用及其对西瓜生长的影响。结果表明:喷施750~3000 kg/hm2木醋液,土壤pH值降低了0.10~0.31个单位,矿质氮无显著的变化,可培养细菌、真菌和放线菌分别提高了101%~132%、38%~204%和10%~58%,而镰孢菌和疫霉菌分别降低了64%~316%和12%~38%。比起溴甲烷,木醋液尽管对土壤微生物区系的负面影响很小,但杀灭病原菌的作用不仅很微弱,且时效也很短;还可能抑制土壤有机氮矿化,降低土壤矿质氮含量,施用量过大会降低西瓜产量,显然,木醋液作为设施大棚土壤熏蒸剂的价值很低。  相似文献   

19.
Winter wheat (Triticum aestivum L.) represents almost 50% of total cereal production in the European Union, accounting for approximately 25% of total mineral nitrogen (N) fertilizer applied to all crops. Currently, several active optical sensor (AOS) based systems for optimizing variable N fertilization are commercially available for a variety of crops, including wheat. To ensure successful adoption of these systems, definitive measurable benefits must be demonstrated. Nitrogen management strategies developed based on small-scale plot research are not always meaningful for large-scale farm conditions. In 2010–2012 (5 site-years) on-farm study was implemented in northern Poland utilizing a strip-trial design. The objective was to evaluate the performance of AOS in combination with a built-in algorithm for variable N rate fertilization. In this study, the reference uniform N rates (farmer’s practice) were comparable to optimum variable N rate recommendations. Side-by-side comparisons of uniform and variable N application revealed inconsistent benefits in terms of grain yield, grain protein content (GPC), N use and N use efficiency (NUE). Anticipated yield increases and/or reduced N rates are typical drivers for AOS adoption. Significant yield increases are not easily attained on farms with winter wheat yields already close to maximum yield potential. Thus, sensor-based variable N rate recommendations for fields previously fertilized with relatively low uniform N rates would often entail more appropriate allocation (redistribution) of the same amount of total N. This would minimize N surplus in areas of lower productivity and to improve the sustainability of N management overall.  相似文献   

20.
施氮量对白肋烟生长发育及产量质量的影响   总被引:5,自引:2,他引:3  
为了降低白肋烟上部叶烟碱含量偏高问题,确定适宜的施氮量,通过田间试验,研究了云南宾川白肋烟主栽品种TN90在不同施氮水平条件下白肋烟的生长发育及产、质量的变化。结果表明:不同施氮量对烟株农艺性状、烟叶产量、产值、外观品质、化学成分均有显著影响。株高、茎围、单株叶面积随施氮量的增加而上升,产值、均价和上等烟比例在适宜的施氮下表现较好。农艺性状、经济性状、品质性状综合比较,在云南宾川白肋烟产区以施氮270kg/ hm2为宜。  相似文献   

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