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1.
[目的]以优质常规稻桂香3号为材料,研究不同施氮水平对其产量和氮素积累与分配特点及氮肥利用率的影响.[方法]田间试验设置5个施氮水平,分别为0、120、150、180和210 kg/ha,测定不同施氮水平下,桂香3号作晚稻种植的产量及其构成、氮素积累与分配比例和氮肥利用率.[结果]桂香3号产量随施氮量的增加而增加,施氮量超过150 kg/ha后产量下降;施氮量主要影响桂香3号的单位面积有效穗数和每穗粒数,对结实率和千粒重影响差异不显著;桂香3号氮素吸收量随施氮量的增加而增加,但氮肥施用过高不利于后期氮素向穗部分配;氮肥偏生产力(NPFP)、氮收获指数(NHI)和氮素籽粒生产效率(NUEg)均随施氮量的升高而下降,但施氮过高或过低均不利于氮肥农学利用率(NAE)、生理利用率(NPE)和吸收利用率(NRE)的增加.[结论]优质常规稻桂香3号适宜施氮量为150kg/ha,其产量最高,达7374.1 kg/ha; NAE、NPE和NRE也均达最大值,分别为15.9 kg/kg、43.8 kg/kg和36.3%.  相似文献   

2.
[目的]研究不同施氮水平对杂交水稻品种良丰优339群体结构、产量及氮素利用率的影响,为良丰优339栽培调控和群体控制提供依据.[方法]采用随机区组设计,设6个不同氮肥施用量处理(0、90、135、180、225、270kg/ha),调查良丰优339茎蘖动态变化、产量及其结构因子和氮素利用率.[结果]施氮量为90和135 kg/ha时对茎蘖动态控制较合理,氮肥偏生产力(NPFP)、氮素农学利用率(NAE)、氮素生理利用率(NPE)和氮素吸收利用率(NAE)均达到较高水平.在较低施氮水平下,有效穗数随施氮水平的提高而显著增加;在较高施氮水平下,结实率随着施氮水平提高而下降.[结论]良丰优339在低氮条件下即可获得良好的群体结构、产量和较高的氮素利用率,其适宜施氮量为90~135 kg/ha.  相似文献   

3.
[目的]探明施氮量和机插密度对钵苗机插水稻氮素利用率及产量的影响,为在钵苗机插水稻生产中选择适宜的施氮量和机插密度提供理论依据.[方法]在大田试验条件下,采用裂区设计,设3种机插密度水平(21.65万、16.84万和12.63万穴/ha)和4种施氮量水平(0、75、150和225 kg/ha),测定不同机插密度和施氮量下钵苗机插水稻的产量及其构成、干物质积累量、主要生育时期各器官氮积累量,并计算氮素利用率.[结果]随施氮量的增加,百千克籽粒需氮量呈逐渐上升趋势,而氮肥吸收利用率、氮肥生理利用率、氮肥偏生产力、氮素籽粒生产效率及氮素干物质生产效率均呈下降趋势,产量呈先升高后降低的变化趋势.随机插密度的降低,氮肥农学利用率、氮肥生理利用率、氮肥偏生产力、氮素籽粒生产效率及氮素干物质生产效率均呈降低趋势,产量也呈先升高后降低的变化趋势.施氮量和机插密度互作对成穗率、有效穗数、每穗总粒数、氮肥吸收利用率、氮肥农学利用率、氮肥生理利用率、氮肥偏生产力、氮素籽粒生产效率和氮素干物质生产效率的影响达极显著水平(P<0.01),但对产量无显著影响(P>0.05).[结论]在贵州喀斯特地貌地区实施钵苗机插水稻的适宜机插密度和氮肥施用量分别为16.84万穴/ha和150 kg/ha,水稻产量为9208.83 kg/ha.回归分析结果表明,获得最高产量的施氮量和机插密度分别为145.63 kg/ha和18.18万穴/ha,水稻产量为9024.771 kg/ha.  相似文献   

4.
《吉林农业科学》2014,(5):48-52
以辽北地区水稻品种铁粳9号为试材,分析了水稻产量及氮素利用率对氮素调控的响应。结果表明:同一基蘖穗肥比例下,随施氮量增加,有效穗数增加,千粒重降低,总吸氮量提高,氮素生理利用率和氮素收获指数降低,氮素回收率以中氮水平居高;同一施氮量下,前氮后移有利于提高有效穗数、千粒重和产量,总吸氮量、氮素回收率和氮素收获指数增加,氮素生理利用率降低;施氮量210 kg/hm2、基肥∶蘖肥∶穗肥为4∶3∶3是最佳氮素调控模式,其产量达到最高为9494.8 kg/hm2,较其他施氮处理提高0.6%~10.6%;适宜施氮量和前氮后移,能够协调产量构成因素,增加产量,提高氮素利用效率,降本增效。  相似文献   

5.
[目的]研究施氮量对油菜(Brassica napus L.)氮素吸收与利用的影响,为稻茬直播油菜精确定量施用氮肥提供理论和实践依据。[方法]以甘蓝型双低油菜品种扬油6号为材料,测定不同施氮处理(0、45、90、135、180、225、270、315和360 kg/hm2)初花期和成熟期各器官干重和氮素含量。[结果]油菜氮素吸收量和氮素利用率随施氮量的增加均呈先增加后减少的趋势,满足二次曲线关系。当施氮量低于110 kg/hm2时,随着施氮量的增加油菜对氮素的吸收量和利用率都呈增加的趋势;当施氮量在110~315 kg/hm2时,随着施氮量的增加氮吸收量仍呈增加的趋势,但氮素利用率已呈下降的趋势;当氮施用量超过315 kg/hm2时,随施氮量的增加二者均呈下降趋势。籽粒产量与施氮量之间呈二次曲线关系,获得最高产量的施氮量为278 kg/hm2。施氮量为278 kg/hm2时的氮素吸收量和利用率分别为209.90 kg/hm2和20.01 g(籽粒)/g(N),与最大氮素吸收量211.78 kg/hm2和最高氮素利用率20.88 g(籽粒)/g(N)相比,获得最高产量时的氮素吸收量和氮素利用率分别下降0.89%和4.17%。[结论]油菜达到最大氮素吸收量和最大氮素利用率的施氮量分别为315和110 kg/hm2。施氮量为278 kg/hm2能较好地协调油菜对氮素吸收和利用的关系并取得最高的籽粒产量。  相似文献   

6.
[目的]研究氮素用量、运筹对钵形毯状秧苗机插水稻产量和氮肥吸收利用的影响。[方法]以中熟中粳品种连粳7号为供试材料,研究氮素用量、运筹对钵形毯状秧苗机插水稻产量结构、茎蘖动态、叶绿素含量和氮素吸收利用等的影响。[结果]施氮量为300 kg/hm2时,产量最高(11 023.80 kg/hm~2),并能获得较高的出糙率、谷草比和氮肥吸收利用率,过低施氮量处理不能获得高产,过高施氮量处理的氮素吸收利用率显著下降。[结论]钵形毯状秧苗机插连粳7号,在基蘖肥∶穗肥=6.5∶3.5、施氮量为300 kg/hm2时产量和氮素吸收利用率最佳。  相似文献   

7.
施氮量对不同品种滴灌棉花氮素利用率及产量的影响   总被引:1,自引:1,他引:0  
【目的】研究不同施氮量对不同品种滴灌棉花的氮素利用率及产量的影响,为种植棉花高效合理的施用氮肥和高产量提供理论参考。【方法】供试棉花品种为新陆早50号、新陆早58号、鲁棉研24号,施氮量水平为0、120、240、360 kg/hm2纯氮。【结果】不同品种棉花吐絮期的各器官氮素分配比从大到小分别为:纤维+种子>叶片>铃壳>茎秆;不同施氮处理对不同品种棉花的平均氮累积量为N3>N2>N1>N0,不同品种氮累积量为新陆早58号>新陆早50号>鲁棉研24号;新陆早50号和鲁棉研24号在施氮量240 kg/hm2、新陆早58号在施氮量360 kg/hm2时的氮素利用率和产量达到最优,在获得高产的同时氮素达到有效的利用。【结论】3个品种中以新陆早58号的氮素分配率、氮累积量、生物量和产量达最高,鲁棉研24号的氮素利用率高于另外2个品种;滴灌棉花在360 kg/hm2处理下的生物量、氮素累积量和籽棉产量最高。  相似文献   

8.
不同施氮量对棉花产量、养分吸收及氮素利用的影响   总被引:2,自引:0,他引:2  
【目的】覆膜滴灌条件下,研究不同施氮量对棉花产量、养分吸收和氮素利用的影响,为棉花生产合理施氮提供科学依据。【方法】试验于2017~2019年设在新疆阿瓦提县,共5个施氮水平(0、110、220、330、440 kg/hm2),于棉花吐絮期采集植株样品,测定棉花产量、生物量、养分吸收和氮素利用。【结果】当施氮量在0~220 kg/hm2时,棉花产量、生物量和产值随着施氮量的增加显著增加,棉花对氮、磷、钾的吸收也显著增加,当施氮量大于220 kg/hm2时影响不显著。棉花氮素偏生产力和农学效率随施氮量增加显著降低。当施氮量大于220 kg/hm2时,氮素表观利用率显著降低,氮素贡献率差异不显著。【结论】当施氮量在0~220 kg/hm2时,随着施氮量的增加,棉花产量、生物量、产值和氮、磷、钾养分的吸收显著增加,当施氮量大于220 kg/hm2时,氮素表观利用率显著降低。综合棉花产量、经济效益、养分吸收和氮素利用,供试棉田推荐施氮量为220 kg/hm2。当施氮量为220 kg/hm2时,形成100 kg籽棉,需吸收N 4.25 kg、P2O5 1.14 kg、K2O 3.61kg。  相似文献   

9.
[目的]为了确定膜下滴灌马铃薯生产中适宜的种植密度和合理施氮量,提高氮素利用效率和块茎产量及品质,为膜下滴灌马铃薯生产提供理论和技术指导.[方法]以紫花白为试验材料,设54 000、65 550、77 100株/hm23个密度以及0、142.5、285.0、427.5纯Nkg/hm24种施氮量,采用裂区设计.[结果]在膜下滴灌种植模式下,马铃薯氮素累积吸收量均随着施氮量和种植密度的增加而提高;增加施氮量,AE、RE、PFP均呈现逐渐降低趋势;而适度提高种植密度,RE、AE、PEP均有一定程度的提高;马铃薯块茎产量、淀粉产量与施氮量、氮素累积吸收量和氮素吸收利用率之间存在0.01水平显著的正相关.协同提高氮素累积吸收量和吸收利用率是决定马铃薯块茎产量的关键.[结论]适度提高种植密度且增加施氮量有利于膜下滴灌马铃薯对氮素的吸收量、利用效率,进而有利于提高块茎产量和淀粉产量.在该试验条件下,适宜的种植密度与施氮量组合以77 100或65 550株/hm2、施氮量285 kg/hm2为宜.  相似文献   

10.
在大田条件下,以"汕优63"为对照,研究不同施氮量(0kg/hm2、100kg/hm2、200kg/hm2、300kg/hm2)对两系法亚种间杂交稻"两优培九"产量及氮素吸收利用特性的影响。结果表明,两优培九的吸氮量和干物质积累量随施氮量的增加而增加;籽粒产量和氮素利用率在1hm2施200kg氮时最高,高氮处理(1hm2施300kg氮)时反而降低;在相同施氮水平下,两优培九的籽粒产量、吸氮量、干物质积累量以及氮素利用率均高于汕优63。  相似文献   

11.
在已确定棉花施氮总量的基础上,2011年进一步进行了不同施氮时期对陆地棉叶片光合特性和产量构成因素的研究。研究结果表明:在播前施150 kg·hm-2基肥和花铃期施150 kg·hm-2追肥的N3处理功能叶片的SPAD值和净光合速率在花铃期以后均处于较高水平,而叶面积指数则表现为蕾期和花铃期各追施150 kg·hm-2氮肥的N4处理自花铃期保持最高水平,其次为N3处理。N3处理抑制蕾铃的脱落,其蕾铃脱落率分别比N2、N4处理低48.98%和44.44%。各处理皮棉产量以N3处理最高,达1324.7 kg·hm-2,比施肥各处理的平均产量高出14.9%。  相似文献   

12.
棉铃对位叶氮浓度与纤维品质指标的关系   总被引:7,自引:2,他引:5  
 【目的】研究棉铃对位叶氮浓度与纤维品质指标的关系,为不同开花期棉铃纤维品质形成的氮素营养监测提供理论依据。【方法】在大田栽培条件下,以高品质棉(科棉1号)和常规棉(美棉33B)品种为材料,分别于江苏南京(118°50′E,32°02′N,长江流域下游棉区)和江苏徐州(117°11′E,34°15′N,黄河流域黄淮棉区)设置不同氮素水平(低氮:0 kgN?hm-2;中氮:240 kgN?hm-2;高氮:480 kgN?hm-2)试验,研究棉铃对位叶比叶重(LMA)、氮浓度(单位干重氮含量,NM;单位叶面积氮含量,NA)对氮素水平的响应,并初步探索了棉铃对位叶NA与纤维品质指标的关系。【结果】(1)棉铃对位叶NA蕴含了NM和LMA的双重信息,具有对氮素水平及开花期均较为敏感的特性,在氮素处理间差异性达显著水平,随开花期的推迟呈现出逐步上升趋势。(2)随着棉铃对位叶NA平均值的增加,棉纤维品质关键指标(纤维长度、比强度、马克隆值、整齐度)的变化趋势均为开口向下的抛物线型。(3)低氮与中氮处理间棉铃对位叶NA平均值的差距随着开花期的推迟逐渐扩大,而高氮与中氮处理间的差距逐渐缩小,相应氮素处理间纤维比强度和马克隆值的差距亦呈现出同样的变化趋势。【结论】棉铃对位叶NA与棉纤维品质指标的关系密切,可作为今后从氮素营养角度实时监测预报棉纤维品质优劣的一个重要生理指标。  相似文献   

13.
为研究种植密度与施氮量对机采棉冠层叶面积指数、透光率和果枝长度等的影响,采用裂区试验设计,主区设2个种植密度D18(18万株/hm~2)和D24(24万株/hm~2),副区设4个施氮量N0(0kg/hm~2)、N170(170kg/hm~2)、N320(320kg/hm~2)和N470(470kg/hm~2)。结果表明,同一施氮量下,随种植密度增大,单株结铃数、单铃重与衣分减小,冠层上、中和下部叶面积指数增大,冠层上、中和下部果枝长度呈先降后增的趋势,冠层开度降低,冠层上、中和下部单铃重逐渐降低。同一种植密度下,当种植密度为D18时,随施氮量的增加,单株结铃数、单铃重、衣分、籽棉产量、皮棉产量、DIFN、冠层上、中和下部叶面积指数及果枝长度均呈上升趋势,表现为N470N320N170N0,种植密度D24条件下呈先升后降的趋势,表现为N320N470N170N0。D24N320处理虽然较最高籽棉产量略低,但差异不显著,其增产率及氮肥农学利用效率最高,在减少氮肥投入量的同时也减轻了由此产生的环境污染。因此,当种植密度为24万株/hm~2、施氮量为320kg/hm~2是本试验条件下最理想的种植密度与施氮量。  相似文献   

14.
Excessive nitrogen(N) fertilization with a high basal N ratio in wheat can result in lower N use efficiency(NUE) and has led to environmental problems in the Yangtze River Basin, China. However, wheat requires less N fertilizer at seedling growth stage, and its basal N fertilizer utilization efficiency is relatively low; therefore, reducing the N application rate at the seedling stage and postponing the N fertilization period may be effective for reducing N application and increasing wheat yield and NUE. A 4-year field experiment was conducted with two cultivars under four N rates(240 kg N ha–1(N240), 180 kg N ha–1(N180), 150 kg N ha–1(N150), and 0 kg N ha–1(N0)) and three basal N application stages(seeding(L0), fourleaf stage(L4), and six-leaf stage(L6)) to investigate the effects of reducing the basal N application rate and postponing the basal N fertilization period on grain yield, NUE, and N balance in a soil-wheat system. There was no significant difference in grain yield between the N180 L4 and N240 L0(control) treatments, and the maximum N recovery efficiency and N agronomy efficiency were observed in the N180 L4 treatment. Grain yield and NUE were the highest in the L4 treatment. The leaf area index, flag leaf photosynthesis rate, flag leaf nitrate reductase and glutamine synthase activities, dry matter accumulation, and N uptake post-jointing under N180 L4 did not differ significantly from those under N240 L0. Reduced N application decreased the inorganic N content in the 0–60-cm soil layer, and the inorganic N content of the L6 treatment was higher than those of the L0 and L4 treatments at the same N level. Surplus N was low under the reduced N rates and delayed basal N application treatments. Therefore, postponing and reducing basal N fertilization could maintain a high yield and improve NUE by improving the photosynthetic production capacity, promoting N uptake and assimilation, and reducing surplus N in soil-wheat systems.  相似文献   

15.
Excessive or insufficient application of fertilizer has raised broader concerns regarding soil and environmental degradation. One-time application of slow release fertilizer (SF) has been widely used to reduce yield gap with potential maize yield and improve nitrogen use efficiency (NUE). A 2-year field experiment (2018–2019) was conducted to evaluate the effects of SF rates from 0 to 405 kg N ha–1 (named F0, SF225, SF270, SF315, SF360, and SF405) and 405 kg N ha–1 of common fertilizer (CF405) on the grain yield, biomass and N accumulation, enzymatic activities related with carbon–nitrogen metabolism, NUE and economic analysis. Results indicated that the highest grain yields, NUEs and economic returns were achieved at SF360 in both varieties. The enzymatic activities related with carbon–nitrogen metabolism, pre- and post-silking accumulation of biomass and N increased with increasing SF rate, and they were the highest at SF360 and SF405. The grain yield at SF360 had no significant difference with that at SF405. However, the N partial factor productivity, N agronomic efficiency and N recovery efficiency at SF360 were 9.8, 6.6 and 8.9% higher than that at SF405. The results also indicated that the average grain yields, NUE and economic benefit at SF405 were 5.2, 12.3 and 18.1% higher than that at CF405. In conclusion, decreasing N rate from 405 kg ha–1 (CF) to 360 kg ha–1 (SF) could effectively reduce the yield gap between realized and potential maize yields. The N decreased by 11.1%, but the yield, NUE and economic benefit increased by 3.2, 22.2 and 17.5%, which created a simple, efficient and business-friendly system for spring maize production in Jiangsu Province, China.  相似文献   

16.
The aims of this research were to compare subsurface drip irrigation scheduling and nitrogen fertilization rates in cucumber, and evaluate yield and quality of cucumber fruit, water (WUE), irrigation water (IWUE), and nitrogen use (NUE) efficiencies in the solar greenhouse in Southwest China. The irrigation water amounts were determined based on the 20 cm diameter pan (Ep) placed over the crop canopy, and cucumber plant was subjected to three irrigation water levels (I1, 0.6 Ep; I2, 0.8 Ep; and I3, 1.0 Ep) in interaction with three nitrogen fertilization levels (N1,300 kg ha-1; N2, 450 kg ha-1; and N3, 600 kg ha-1). The results showed that the cucumber fruit yield increased with the improvement of irrigation water. Irrigation water increased yields by increasing the mean weight of the fruits, and also by increasing fruit number. But the highest values of IWUE and WUE were obtained from 12 treatment. NUE significantly decreased with the improvement of N application, but increased by irrigating more water. The quality of cucumber fruit decreased with the improvement irrigation water and nitrogen fertilization. In conclusion, the optimum irrigation level and nitrogen fertilizer application level for cucunber under subsurface drip irrigation in the solar greenhouse in Southwest China were 0.8 Ep and 450 and 600 kg ha-1, respectively.  相似文献   

17.
The effects of the basal and top-dressing nitrogen (N) on'N uptake and translocation, N utilization efficiency, grain yield and quality of medium-gluten winter wheat Yangmai 10 were studied from 2000 to 2002. The main results were as follows.Nitrogen content and nitrogen accumulation in plant at maturity increased with the amount of N application. Grain protein content and wet gluten content were significantly correlated with applied N. There was a significantly positive correlation between nitrogen accumulation before anthesis (NBA) and basal N fertilizer, and between nitrogen accumulation after anthesis (NAA) and top-dressing N. N accumulated in grains was significantly correlated to NBA, NAA and N translocation from vegetative organs after anthesis (NTVA). NBA was significantly correlated with N application, but NAA and NTVA had a quadratic curve correlation with applied N. N fertilizer use efficiency (NUE) had a quadratic curve correlation with applied N, and the NUE was high when basal and top-dressing N was equally applied. For the medium-gluten wheat Yangmai 10 under the same N application ratio, there was a N-regulating effect when the N application was less than 266.55 kg ha-1, a stagnation of yield and quality when N application ranged from 266.55 to 309.08 kg ha-1, and an excessive N application when the N application rate was greater than 309.08 kg ha-1. Under the conditions of this experiment, the precise N application is 220-270 kg ha-1 with basal and top-dressing N equally used when a grain yield of more than 6750kg ha-1, protein content higher than 12%, wet gluten content more than 30% and NUE greater than 40% could be obtained.  相似文献   

18.
[Objective] The historical evolution pattern of nitrogen(N), phosphorus(P)and potassium(K) fertilizer application rate and its effects on lint cotton yield were explored to provide the theoretical basis for reasonable fertilizer management strategy in the cotton planting region of the Yangtze River Valley. [Method] GGE biplot analysis method was adopted to analyze the correlation among N, P and K fertilizer application rate and lint cotton yield with the dataset of national cotton regional trials of the Yangtze River Valley during 1991-2013. The linear and nonlinear regression analysis method was used to reveal the evolution of the fertilizer applying patterns,and analyze the effects of N, P, K application rates on cotton lint yield. [Result] The application rates of N, P and K fertilizer presented highly significant positive correlation with lint cotton yield, among which the potassium fertilizer was the strongest relative factor with lint cotton yield, followed by phosphorus fertilizer, while nitrogen fertilizer was the weakest factor. The application rate of nitrogen fertilizer was related with the test year in the pattern of a quadratic function, while phosphate and potassium had progressive increase linear relation with the test year in the cotton planting region of the Yangtze River Valley. Meanwhile, cotton lint yield was in response to nitrogen fertilizer content increase with a quadratic parabola function, and increased with the applying phosphate fertilizer and potassium fertilizer content with linearly increasing function. [Conclusion] The increasing application amount of N, P and K fertilizer was generally beneficial to cotton yield improvements, however, exorbitant applying nitrogen fertilizer was unfavorable for cotton production, and a reasonable mixture formula of N, P and K fertilizer was better in terms of cotton yield-increasing effect.  相似文献   

19.
氮沉降对杉木人工林土壤有机碳和全氮的影响   总被引:9,自引:3,他引:9  
通过野外模拟试验,研究氮沉降增加对杉木人工林土壤有机碳、全氮及C/N比的影响。试验设计为4种处理,分别为N0(0 kg.hm-2.a-1)、N1(60 kg.hm-2.a-1)、N2(120 kg.hm-2.a-1)、N3(240 kg.hm-2.a-1),每处理重复3次。以尿素[CO(NH2)2]作为氮源,每月以溶液方式对林地进行喷施。通过2 a的处理后发现,随着氮沉降水平的增加,土壤有机碳呈下降趋势,而全氮含量则不断上升,致使土壤C/N比降低。  相似文献   

20.
[Objective] The historical evolution pattern of nitrogen(N), phosphorus(P)and potassium(K) fertilizer application rate and its effects on lint cotton yield were explored to provide the theoretical basis for reasonable fertilizer management strategy in the cotton planting region of the Yangtze River Valley. [Method] GGE biplot analysis method was adopted to analyze the correlation among N, P and K fertilizer application rate and lint cotton yield with the dataset of national cotton regional trials of the Yangtze River Valley during 1991-2013. The linear and nonlinear regression analysis method was used to reveal the evolution of the fertilizer applying patterns,and analyze the effects of N, P, K application rates on cotton lint yield. [Result] The application rates of N, P and K fertilizer presented highly significant positive correlation with lint cotton yield, among which the potassium fertilizer was the strongest relative factor with lint cotton yield, followed by phosphorus fertilizer, while nitrogen fertilizer was the weakest factor. The application rate of nitrogen fertilizer was related with the test year in the pattern of a quadratic function, while phosphate and potassium had progressive increase linear relation with the test year in the cotton planting region of the Yangtze River Valley. Meanwhile, cotton lint yield was in response to nitrogen fertilizer content increase with a quadratic parabola function, and increased with the applying phosphate fertilizer and potassium fertilizer content with linearly increasing function. [Conclusion] The increasing application amount of N, P and K fertilizer was generally beneficial to cotton yield improvements, however, exorbitant applying nitrogen fertilizer was unfavorable for cotton production, and a reasonable mixture formula of N, P and K fertilizer was better in terms of cotton yield-increasing effect.  相似文献   

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