黄淮海棉区钾肥效应研究

1988～1990年在黄淮海棉区三种不同地力含钾水平的土壤基础上连续施用钾肥,皮棉产量与钾肥用量的回归效应方程分别为:在速效钾含量小于100mg/kg 以下的棉田上,Y=783.6+0.755X(r=0.9886~(**));速效钾含量中等(100～120mg/kg)棉田上,Y=1005.5+0.8829X—0.0014X~2(回归 F=66.32~(**));速效钾含量为150mg/kg 棉田上,Y=1281.9+1.465X—0.005X~2(二次回归 F=22.5~*)。钾肥施用时期,在钾肥量少的情况下,一次施用以基肥和蕾肥效果较好;在钾肥量足的情况下,二次施用以基肥+蕾肥各半效果较好。同时钾肥能提高单铃重和衣分,并改善纤维品质,促进氮的吸收利用、叶绿素的合成和提高棉株抗旱性。     

江苏滨海盐碱地麦后直播棉氮、磷、钾肥料优化配比研究

【目的】建立江苏省滨海盐碱地麦后直播棉合理的施肥技术体系。【方法】2017―2018年在江苏省滨海棉田,以中棉所50为材料,采用正交设计,研究了不同氮、磷、钾肥配施量对棉花生物量、养分累积与利用及产量的影响。【结果】氮、磷、钾肥3因子对棉株地上部和生殖器官生物量、棉株地上部氮和钾素累积量及皮棉产量的影响均为氮肥磷肥钾肥。施N 150～225 kg·hm~(-2)、P_2O_5 75 kg·hm~(-2)下棉株地上部和生殖器官生物量、氮和钾累积量及皮棉产量较高。钾肥因子对生殖器官生物量和皮棉产量影响不显著。钾肥因子对氮、钾素利用效率的影响大于氮肥和磷肥,氮肥因子对磷素利用效率的影响大于磷肥和钾肥,施K_2O 75～150 kg·hm~(-2)氮、钾素利用效率较高、施氮225 kg·hm~(-2)磷素利用效率较高。土壤碱解氮、速效磷、速效钾含量较高棉田的氮、磷(P_2O_5)、钾(K_2O)肥配施量分别为225 kg·hm~(-2)、75 kg·hm~(-2)和150～225 kg·hm~(-2)。相关分析表明,皮棉产量与棉株氮、钾素累积量显著正相关。【结论】长江流域棉区滨海盐碱地麦后直播棉利于产量和养分利用效率提高的最佳氮、磷(P2O5)、钾(K_2O)肥配施量分别为225 kg·hm~(-2)、75 kg·hm~(-2)、75 kg·hm~(-2)。     

江苏滨海盐碱地麦后直播棉氮、磷、钾肥料优化配比研究

【目的】建立江苏省滨海盐碱地麦后直播棉合理的施肥技术体系。【方法】2017―2018年在江苏省滨海棉田,以中棉所50为材料,采用正交设计,研究了不同氮、磷、钾肥配施量对棉花生物量、养分累积与利用及产量的影响。【结果】氮、磷、钾肥3因子对棉株地上部和生殖器官生物量、棉株地上部氮和钾素累积量及皮棉产量的影响均为氮肥>磷肥>钾肥。施N 150~225 kg·hm-2、P2O575 kg·hm-2下棉株地上部和生殖器官生物量、氮和钾累积量及皮棉产量较高。钾肥因子对生殖器官生物量和皮棉产量影响不显著。钾肥因子对氮、钾素利用效率的影响大于氮肥和磷肥,氮肥因子对磷素利用效率的影响大于磷肥和钾肥,施K2O 75~150 kg·hm-2氮、钾素利用效率较高、施氮225 kg·hm-2磷素利用效率较高。土壤碱解氮、速效磷、速效钾含量较高棉田的氮、磷(P2O5)、钾(K2O)肥配施量分别为225 kg·hm-2、75 kg·hm-2和150~225 kg·hm-2。相关分析表明,皮棉产量与棉株氮、钾素累积量显著正相关。【结论】长江流域棉区滨海盐碱地麦后直播棉利于产量和养分利用效率提高的最佳氮、磷(P2O5)、钾(K2O)肥配施量分别为225 kg·hm-2、75 kg·hm-2、75 kg·hm-2。     

花铃期棉田速效养分时空变异特征及对棉花产量品质的影响

试验于2004年在河南安阳(黄河流域黄淮棉区)和江苏南京(长江流域下游棉区)大田进行。氮素设0、120、240、360和480 kg hm^-2(分别用N0、N1、N2、N3、N4表示) 5个水平, 磷、钾施用量分别为185 kg hm^-2和118 kg hm^-2, 研究花铃期棉田土壤速效养分时间、空间变异特征及对棉花产量品质的影响。结果表明, 随着生育进程, 两试点N0处理0~60 cm土壤各层碱解氮呈先降低后升高的趋势, 其他4个处理先呈现下降趋势, 棉田追肥后, 含量明显增加, 之后明显降低, 吐絮后又开始回升; 两试点速效磷、速效钾含量均表现为先降低后升高的趋势。0~60 cm土壤各层速效养分含量随深度的增加呈下降的趋势。相同土层碱解氮、速效磷含量随距棉株水平距离的增加, 南京N1、N2、N3、N4处理呈下降趋势, N0处理水平变异特征不明显; 南京碱解氮含量时空变异较安阳显著, 安阳速效磷含量时空变异较南京显著。南京0~60 cm、安阳20~60 cm土层速效钾含量表现为随距棉株水平距离的增加均呈下降趋势, 而安阳0~20 cm呈现相反趋势。安阳、南京分别以360 kg hm^-2和240 kg hm^-2施氮水平棉花产量构成相对合理、皮棉产量最高、纤维长度和比强度较优。因此, 不同生态区应根据花铃期棉田速效养分时空变异特征, 确定适宜施肥量, 提高棉花产量品质。     

新疆棉田土壤速效养分的时空变异特征研究

研究了新疆南疆荒漠绿州棉田皮棉产量1991kg·hm2水平下,2月15日至11月15日内,0～100cm土层土壤碱解氮、速效磷、速效钾的时空分布,0～40cm土层土壤碱解氮和速效钾含量分布特征趋势一致,由2月中旬-6月中旬逐渐升高,到5月中旬-6月中旬时达最大值,进入7月份后,均呈陡然下降特点,9月份开始回升;40cm以下各层土壤碱解氮和速效钾含量变化波动较小;土壤速效磷的时空变异特征,4月和5月,0～60cm土壤中的速效磷呈匀速上升,7月中旬达高峰,但20～60cm土层速效磷含量开始急速下降,9月中旬降至最低点。耕层土壤速效磷含量在27.1～34.3mg·kg1波动变化,变幅较小。     

磷肥种类和用量对土壤磷素有效性和棉花产量的影响

田间试验研究了两种磷肥不同用量对土壤磷素、棉花全生育期磷素的有效性以及棉花产量的影响。结果表明:增施磷肥能增加棉田土壤速效磷、全磷含量、磷素活化系数以及棉花产量,土壤速效磷和磷素活化系数平均比对照处理增加302%和180%。同时,也能增加棉花对磷素的吸收和干物质的积累。但过量施用磷肥并不能显著增加棉花产量、吸磷量和干物质积累量。棉花对磷素的吸收和干物质积累以施磷量150kg.hm-2最优。两种磷肥比较显示,重过磷酸钙对棉田速效磷含量和磷素活化系数的贡献高于磷酸二铵,分别比磷酸二铵高244%和325%。     

土壤肥力差异对冀中南山前平原与低平原夏玉米产量的影响

评价区域土壤基础肥力差异、明确土壤肥力对作物产量的影响,对农田土壤培肥和优化养分管理具有重要意义。本研究利用2005—2013年在冀中南山前平原和低平原区开展的967组“3414”夏玉米田间试验,系统分析了河北冀中南山前平原与低平原基础地力差异对玉米产量的影响。结果表明：冀中南山前平原土壤有机质、全氮和有效磷均高于低平原,速效钾含量略低于低平原;山前平原玉米基础产量6133 kg/hm²,高于低平原的5815 kg/hm²。基础地力贡献率分别为71.2%和69.0%;山前平原在不施肥条件下获得高产的土壤有机质、全氮、有效磷和速效钾最小值分别为14.9 g/kg、1.07 g/kg、19.1 mg/kg和127 mg/kg,低平原则为16.0 g/kg、0.76 g/kg、18.8 mg/kg和106 mg/kg。影响山前平原玉米基础产量的主要肥力因子是土壤速效钾和有效磷含量,影响程度分别为38.6%和24.8%;影响低平原玉米基础产量的主要因子是土壤有机质和有效磷含量,影响程度分别为45.0%和32.2%。本研究表明,山前平原土壤培肥要以稳定和提高土壤速效钾和有效磷含量为主攻方向,低平原则要以提高土壤有机质和有效磷含量为目标。     

黄河三角洲盐渍土棉花施用氮、磷、钾肥的效应研究

为探讨盐渍土抗虫棉施用氮(N)、磷(P)、钾(K)肥的效应及其营养生理机制,指导滨海盐渍土抗虫棉合理施肥,在黄河三角洲盐渍土低、中、高盐棉田种植转Bt基因抗虫棉鲁棉研28,研究N、P、K肥配合施用对其养分吸收利用、Na+吸收积累、光合速率、干物质积累和产量的影响。结果表明,N、P肥配合,尤其是N、P、K肥配合施用显著增加了低、中、高盐田棉花的N、P、K养分吸收量,减少了Na+吸收积累量。低、中、高盐田棉花的N、P、K养分农学利用效率均以N、P、K配施的处理较高,氮养分农学利用效率分别为0.20、1.95和2.07kg皮棉kg-1N,磷养分农学利用效率分别为0.87、8.35和8.71kg皮棉kg-1P,钾养分农学利用效率分别为0.26、2.89和3.77kg皮棉kg-1K。N、P、K肥配合施用还维持了较高的棉株叶面积、叶绿素含量和净光合速率。低、中、高盐田棉花的生物产量和皮棉产量也均以N、P、K配施的处理较高,皮棉产量分别增产2.53%、28.67%和30.47%。中、高盐棉田的施肥效应明显好于低盐棉田。表明根据盐碱程度分类合理施肥是减轻盐渍土营养障碍、改善棉花营养、提高养分农学利用效率和棉花产量的有效途径。     

棉田套作冬绿肥促进棉花增产的机理研究

为了研究华北地区棉田种植越冬绿肥对土壤肥力及棉花生长的影响,利用棉田冬季空闲的时间和空间,秋季套种冬绿肥作物二月兰和毛叶苕子,翌年4月中旬种植棉花时结合整地翻压还田作肥料。结果表明,种植翻压绿肥3年后,耕层0~20 cm土壤真菌、细菌、放线菌数量均有大幅度增加,土壤转化酶活性都有较大提高;土壤有机质由8.65~8.74 g/kg上升到11.08 g/kg以上,作物必需的大量元素N、P、K也有所增加,土壤全N增加44%~50%;速效磷由6.79~7.01 mg/kg增加到12.80 mg/kg以上;速效钾增加6.04%以上;棉花叶片叶绿素含量(SPAD值)明显增加;成桃数显著高于不翻压绿肥处理;籽棉产量增加7.03%~7.68%。棉田套种绿肥并翻压还田不仅提升了土壤肥力,而且增加了棉花产量,具有重要的推广应用价值。     

钾肥对棉花产量的影响及最佳施用量研究

为了明确钾肥对黄淮海地区抗虫棉和常规棉的产量及其构成因素的影响以及该地区的最佳钾肥施用量,在山东省夏津县、河北省吴桥县进行了大田试验。结果表明,钾肥可以显著提高棉花产量,吴桥和夏津的增产幅度分别达到20.4%、6.4%;钾肥主要增加上部(≥10)果枝和外围节位(≥3节位)的成铃数和铃重;转基因抗虫棉品种和常规品种对钾肥的反应在本试验条件下没有显著差异。当土壤速效钾含量为100~130 mg.kg-1时,黄淮海地区棉田比较适宜的氯化钾施用量为150 kg.hm-2左右。     

氮素对滨海盐土棉花产量、品质及生物量的影响

为研究不同施氮量对滨海盐土花后棉株生物量、生物量累积特征及其与产量、品质的关系,于2010年和2012年在江苏滨海盐土设置了氮肥水平试验。结果表明:在0~600 kg·hm-2范围内施氮量越大棉株总生物量累积越多,而皮棉产量2010年和2012年分别在施氮375 kg·hm-2和300 kg·hm-2时达到最大;成铃数在施氮300~375 kg·hm-2范围内达到最大;铃重和衣分随施氮量增加而增加,达到最大值后(≥300 kg·hm-2)差异不显著。在300~375 kg·hm-2施氮量范围内纤维比强度最高;高氮有利于上部、顶部果枝纤维长度、比强度、伸长率的提高和马克隆值的优化,但显著降低中下部果枝棉纤维比强度,导致中部纤维马克隆值变劣、下部果枝纤维伸长率下降,说明高氮对中下部果枝棉纤维品质的形成利弊各半,适量高氮可提高上部及顶部果枝产量、品质。在滨海盐土条件下,利于产量、品质及氮素利用效率提高的适宜施氮量为375 kg·hm-2。     

Nitrogen Fertilizer and Its Residual Effect on Cotton Yield and Biomass Accumulation

[Objective] The optimum nitrogen rate of 300 kg·hm^－2 is well documented for cotton in the Yangtze River Valley, China. It can be reduced to 225 kg·hm^－2 without reducing yield in late sowing under high planting density. The aim of this study was to determine the possibility of further reducing the nitrogen application rate at the first flower stage, its residual effects and influence on cotton yield formation rule. [Method] A pot experiment was conducted with five nitrogen levels (120, 150, 180, 210 and 240 kg·hm^－2) in 2014, but only 180 kg·hm^－2(for studying nitrogen residual effect) in 2015, to study the cotton growth process, yield and its components and biomass accumulation. [Result] Nitrogen levels significantly affected the yield and biomass accumulation, but not the growth process and nitrogen residual effect. Maximum seed cotton yield (30.5 g·plant^－1), boll weight (3.8 g) and biomass accumulation, especially in the reproductive and vegetative organs, was recorded in the 180 kg·hm^－2 nitrogen treatment. In the rapid accumulation period, the proportion of biomass accumulation in the reproductive organs was the highest. [Conclusion] In a soil with medium fertility level, the application of 180 kg·hm^－2 nitrogen was optimal, because the strength of biomass accumulation in reproductive organs increased during the rapid accumulation period.     

氯甲基吡啶对滴灌棉花生物量、氮素吸收及氮肥利用率的影响

在田间滴灌条件下,采用单因素随机区组设计,设置CK(不施氮肥)、Urea(尿素)和Urea+Nitrapyrin(尿素+氯甲基吡啶)3个处理,重复4次,分别于2012和2013年研究了尿素添加硝化抑制剂氯甲基吡啶(Nitrapyrin)对棉花生物量、氮素吸收及氮肥利用率的影响。2年试验结果表明,尿素添加氯甲基吡啶随水滴施能增加棉株的生物量、吸氮量及产量,使植株地上部分的生物量和吸氮量较单施尿素分别提高4.1%~5.1%、4.3%~4.4%,皮棉产量提高4.1%~4.4%;其中,茎、叶、蕾花铃的生物量较单施尿素分别增加2.7%~4.5%、14.9%~16.2%和2.5%~3.9%,吸氮量则分别提高0.4%~1.1%、12.2%~16.3%以及2.9%~3.4%;氯甲基吡啶的添加能提高棉田氮肥利用率11.5%~12.5%。研究结果可为应用硝化抑制剂氯甲基吡啶促进滴灌农田氮肥高效利用提供理论依据。     

The Plant Architecture of Direct-Sowing Cotton Planted after Barley Harvested with High Yield and Centralized Boll-Setting

[Object] The study was conducted to investigate the plant architecture characteristic of direct sowing cotton planted after barely harvested with high yield and centralized boll-setting in the Yangtze River basin. [Method] In 2014, the cultivars Guoxin 12-1, Yijimian and Lumianyan 36 were used and the two conventional fertilizer (CF) application rates (namely pure nitrogen 45 kg·hm^－2, 150 kg·hm^－2) and Guoxin 12-1 was used in 2015. Two slow release fertilizer (SR) utilization rates (namely pure nitrogen 150 kg·hm^－2 and 225 kg·hm^－2) and two SR topdressing at different growth stages (namely 100% topdressing at seedling stage, 70% topdressing at seedling stage + 30% at flowing stage) were set with CF (pure nitrogen 150 kg·hm^－2) and no fertilizer treatment as the controls. [Result] While the pure nitrogen (CF) amount was 150 kg·hm^－2, the seed cotton yield of Guoxin 12-1 were 4 014.72 kg·hm^－2. In 2015, the seed cotton yield for the treatment, application SR (pure nitrogen 150 kg·hm^－2)and application ratios of seedling stage and flowering stage of 100% and 0, respectively, increased by 30.96%. The ratios of bolls setting from 08-15 to 08-30 to total bolls (RBT) for the two treatments were 31.8% and 26.1%, respectively. Then a significantly positive correlation between the seed cotton yield and RBT was found（r2014＝0.948^**, r2015＝0.976^**）. Based on the analysis of relationship between the plant architecture indexes and RBT, plant architecture characteristics of cotton population with high yield and centralized boll-setting was proposed. [Conclusion] These indexes would be used to supervise the cotton culture management to achieve high yield and centralized boll-setting for the direct sowing cotton planted after barely harvested.     

蕾期调亏灌溉对海岛棉棉铃发育及产量的影响

以新海24号、新海35号为材料,设置滴灌定额0 m3·hm-2(重度调亏,土壤含水量10%左右)、900 m3·hm-2(轻度调亏,土壤含水量16%左右)、1800 m3·hm-2(丰水,土壤含水量20%左右)3个处理,研究蕾期调亏灌溉对海岛棉棉铃发育及产量的影响。结果表明:0 m3·hm-2处理的铃直径、铃体积分别在花后10 d内、20 d内快速增大,铃重在花后30 d内增长速度较快;但铃直径、铃体积在开花后30 d,铃重在开花后50~60 d,均较900 m3·hm-2和1800 m3·hm-2处理显著下降。900 m3·hm-2处理的铃直径、铃体积及铃重均与1800 m3·hm-2处理无明显差异。皮棉产量以900 m3·hm-2处理最高,平均为2372.92 kg·hm-2,比1800 m3·hm-2和0 m3·hm-2分别高10.97%和41.78%。因此,海岛棉蕾期滴灌定额以900 m3·hm-2较为适宜。     

种植密度和缩节胺调控对麦后直播棉产量和冠层特征的影响

2013―2014年以早熟棉(中棉所50)为材料,采用裂区设计,在江苏省南京市研究了种植密度(7.50万、9.75万和12.00万株·hm~(-2))和缩节胺(DPC)调控(0,52.5和105.0 g·hm~(-2))对麦后直播棉产量和冠层特征的影响。结果表明:皮棉产量在不同种植密度下以12.00万株·hm~(-2)处理最低,在不同DPC用量水平下以0 g·hm~(-2)处理最低;种植密度与DPC调控存在互作效应,以种植密度9.75万株·hm~(-2)、DPC用量52.5~105 g·hm~(-2)处理产量较高,且产量构成中以铃数对产量的直接效应最大。对冠层特征影响表明,下部果枝夹角和长度随种植密度增加而降低,而中、上部果枝的夹角和长度、叶面积指数均以种植密度9.75万株·hm~(-2)处理较高;不同部位果枝夹角和长度、叶面积指数均随DPC用量增加而降低,而透光率则相反。相关分析表明,下部果枝夹角大、中部果枝较长及上部果枝夹角小且叶面积指数和透光率较高,有利于提高产量和霜前花率。综上,该棉区麦后直播棉种植密度9.75万株·hm~(-2)、DPC用量52.5~105 g·hm~(-2)(蕾期、开花期和打顶后用量比例为1∶2∶4),有利于改善棉花冠层特征,实现早熟高产。     

Response of Enzyme Activity of Soil to Urea Application Rate in a Cotton Field Trial

We studied the response of urease activity of soil in cotton field to different long-term urea (amide nitrogen) application (N application rates were 0, 90, 180, 270, 360, 450 kg·hm^－2), as well as responses of dehydrogenase and proteinase activity of soil at the harvest stage of cotton. The results showed that urease activity of soil increased with increased urea application rate, and urease activity at 0-20 cm soil depth were close to those at 20-40cm soil depth. In contrast, urease activity of soil greater than 40 cm soil depth decreased with increased soil depth. There was a significant positive correlation between urease activity and total N content, organic matter content, and available N content of soil. Dehydrogenase and proteinase activities increased with increased urea application rate (0-360 kg·hm^－2); however, at the urea application rate of 450 kg·hm^－2, dehydrogenase and proteinase activities declined. When the urea application rate was 270-360 kg ·hm^－2, urease, dehydrogenase and proteinase activities were much higher than those of the urea application rate less than 270 kg ·hm^－2, and there was no significant effect on urease, dehydrogenase and proteinase activities when urea application rate was 270-360 kg·hm^－2 in the cotton field.     

黄河流域棉区秸秆还田下机采棉的氮肥用量和利用率研究

提高种植密度、优化缩节胺(1,1-dimethyl-piperidinium chloride,DPC)化控技术是黄河流域棉区机采棉田的基本管理措施,秸秆还田则是实现农作物化肥零增长的技术途径之一。于2013―2014年在河北省河间市秸秆还田地块,研究了密度、DPC化控和氮(Nitrogen,N)肥用量对棉花产量及其构成因素、干物质和N的积累与分配以及N肥利用率的影响,其中2013年蕾期和花铃期降水量大,2014年比较干旱。研究结果表明,与低密度(6.75×10~4株·hm~(-2))相比,高密度处理(11.25×10~4株·hm~(-2))在干旱年份的籽棉产量和N肥偏生产力分别显著提高8.1%和7.4%,N回收率也显著增加25.5百分点,达到41.6%。与清水对照相比,DPC化控的籽棉产量、N肥偏生产力和农学效率在多雨年份分别显著提高39.2%、43.3%和212.8%,N回收率略增加但差异不显著。提高密度促进了干物质积累,但降低了多雨年份的收获指数;DPC化控的生物量较低,但在多雨和干旱年份均可提高收获指数。N肥用量对棉花产量的影响不显著,但表现出低N处理(105 kg·hm~(-2))的产量高于中N处理(210 kg·hm~(-2))和高N处理(315 kg·hm~(-2))的趋势。低N处理2年的N肥偏生产力分别为24.5 kg·kg~(-1)和54.4kg·kg~(-1),回收率分别为45.2%和41.0%,显著高于中N处理和高N处理。综上所述,增密和DPC化控相结合,有利于机采棉田干物质的积累及向产量器官的分配,有利于维持产量的稳定性;在秸秆还田条件下,棉田的适宜施N量可降至105 kg·hm~(-2)。     

Effects of Nitrogen Application Rates on Soil Nitrogen Content,Nutrient Uptake and Utilization of Cotton in Low Fertility Fields

[Objective] The effects of nitrogen (N) application rates on cotton yield, nutrient uptake and utilization rate, soil available N and urease activity were investigated in low-fertility cotton fields of the Yellow River Basin. [Methods] Six N application rate treatments, 0, 90, 180, 270, 360 and 450 kg·hm^－2 (N0, N90, N180, N270, N360 and N450, respectively), were established using cotton CCRI 79 in the field during 2016 and 2017. The cotton yield, dry matter quality, N, phosphorus and potassium accumulation levels, N use efficiency, 0–100-cm soil layer ammonium and nitrate N contents, 0–100-cm soil layer urease activity and other indicators were investigated. [Results] (1) Compared with N0, the N treatments significantly increased seed cotton yield, except the N90 treatment in 2016. Two years of N360 treatments significantly increased the number of bolls per cotton plant, while no significant differences were found among the seed cotton yields with other N treatments. The N application rates had no significant effect on lint percentage. (2) Compared with N0, N applications significantly increased the cotton dry matter accumulation. The accumulation of N, phosphorus and potassium in cotton increased along with the N application rates in the 90–360 kg·hm^－2 range. The levels of N, phosphorus and potassium in N450-treated cotton decreased compared with N360-treated cotton. As the N application rates increased, the N agronomic efficiency and N fertilizer partial productivity of cotton decreased. When the N application rates exceeded 360 kg·hm^－2, the N physiological efficiency began to decrease, but there were no significant differences among treatments. (3) The nitrate N contents in the 41–80-cm soil layers of the treatments, except for N90, significantly increased compared with N0. The nitrate N contents in the 41–80-cm soil layers of N270-, N360- and N450-treated cotton were significantly increased compared with those of N0, N90 and N180. However, N applications had no significant effects on the ammonium N contents in the soil. (4) The soil urease activities increased when N application rates were less than 360 kg·hm^－2, and then decreased when the N application rates were greater than 360 kg·hm^－2. [Conclusion] The optimum N application rate was 277.0 kg·hm^－2. When the N application rates were greater than 360 kg·hm^－2, the nitrate N contents in the soil increased. However, the nutrient accumulation levels and the N fertilization efficiencies decreased, and the soil urease activities were inhibited. No obvious increase in cotton yield was observed.