南方低产黄泥田与高产灰泥田基础地力的差异

【目的】黄泥田为南方红黄壤区广泛分布的低产田。定量评价黄泥田基础地力,明确与高产灰泥田水稻氮磷钾养分吸收利用的差异,可为黄泥田改良及水稻施肥提供依据。【方法】采集福建省20个县的典型黄泥田0—20cm土壤,同时采集与其邻近且由同一微地貌单元发育的高产灰泥田土壤,进行了水稻盆栽试验。试验设施肥(每盆N0.60g、P2O50.24g、K2O0.42g)和不施肥两个处理。氮肥采用15N丰度10%的尿素,磷肥用磷酸二氢钙,钾肥用氯化钾。水稻品种为‘中浙优1号’,采用移栽种植,每盆种植两穴。收获后,调查籽粒产量,采集土壤和植株样品,植株分地上部和根部,分析了生物量、氮磷钾含量,土壤分析了全氮含量。植株与土壤同位素氮用ZHT-03质谱仪测定15N%丰度。计算了土壤基础地力与水稻养分吸收、累积及肥料利用率。【结果】黄泥田的基础地力经济产量、基础地力地上部生物产量较灰泥田分别低26.9%与23.5%,相应的基础地力贡献率分别低14.1与9.7个百分点。基础地力贡献率(经济产量)与土壤有机质含量呈极显著正相关,与土壤容重呈极显著负相关。不论施肥与否,黄泥田水稻有效穗数均显著低于灰泥田,且不施肥水稻有效穗数与土壤有机质含量呈极显著正相关,而与土壤容重呈极显著负相关。施肥条件下,黄泥田水稻成熟期籽粒、茎叶和根系氮、磷、钾素含量均低于灰泥田,其中3个部位磷素含量较灰泥田分别低9.6%、38.4%和46.3%,差异均显著,黄泥田水稻籽粒和茎叶的钾素含量较灰泥田分别低10.8%和18.5%,差异均显著。施肥下黄泥田水稻成熟期籽粒、茎叶的氮素吸收量较灰泥田分别低10.8%和17.3%,磷素吸收量分别低12.5%和46.2%,钾素吸收量分别低16.6%和28.5%,差异均显著。等量施肥条件下,黄泥田的水稻氮肥利用率较灰泥田低4.6个百分点,但土壤氮肥残留率增加3.0个百分点。【结论】以高产灰泥田为标准,黄泥田基础地力具有20%以上的产量提升潜力。土壤有机质与容重是影响基础地力贡献率与有效穗的重要肥力因子。黄泥田水稻氮肥利用率显著低于灰泥田,但土壤氮素残留率较高。提高有机质、降低土壤容重是提升基础地力的主攻方向。     

不同土壤水势与氮素营养对杂交水稻生理特性和产量的影响

以超级杂交水稻“两优培九”为试验材料,研究了不同土壤水势和氮素营养对其生理特性和产量及氮肥利用率的影响。结果表明, 1）同一土壤水势下,植株地上部分干重与总干重随氮肥水平的提高而提高,而根冠比则降低。2）在同一氮肥水平下,叶片净光合速率、叶绿素a和叶绿素b及其总含量、SPAD值及叶片水势随着土壤水势的降低而降低,而叶绿素a/b、丙二醛的含量和过氧化物酶的活性随之而增加;同一土壤水势下,叶绿素a和叶绿素b及其总含量、SPAD值均随氮肥水平的提高而提高,而叶片水势、叶绿素a/b和丙二醛的含量随之降低。3）在同一氮肥水平下,水稻产量随土壤水势的降低而降低;土壤轻度干旱时,水稻产量高低顺序为高氮中氮低氮;而当土壤水分充足或土壤重度干旱时,则表现为中氮高氮低氮。随着土壤水势的降低,中、高氮处理的氮肥农学利用率降低。试验结果还表明,225 kg/hm2施氮水平在0 kPa土壤水势下有明显的增产效果,过度增施氮肥并不利于水稻增产与氮肥利用率的提高。     

Effect of biochar applied with plant growth-promoting rhizobacteria (PGPR) on soil microbial community composition and nitrogen utilization in tomato

Plant growth-promoting rhizobacteria (PGPR) represent an important microbial community group and have beneficial effects on plant growth and development. A pot experiment was conducted to study the effect of biochar applied with PGPR on the soil microbial community composition and nitrogen use efficiency (NUE) of tomato, which could provide a theoretical basis for rational fertilization. Six treatments were designed: no nitrogen (N), PGPR, or biochar control (CK); biochar without N or PGPR (BCK); N without PGPR or biochar (U); N and PGPR without biochar (UP); N and biochar without PGPR (UB); and N, PGPR, and biochar (UBP). The tomato yield in the UP treatment was 9.09% lower than that in the U treatment, whereas that in the UB treatment was 19.93% higher than that in the U treatment. The tomato yield in the UBP treatment was 32.45%, 45.69%, and 10.44% higher than those in the U, UP, and UB treatments, respectively. Biochar combined with PGPR increased the relative abundance of Nitrospira and Bradyrhizobium in the soil. At the tomato maturity stage, the soil NO₃^--N content in the UBP treatment was 87.12%, 88.12%, and 31.04% higher than those in the U, UP, and UB treatments, respectively. The NUE in the UP treatment was 4.03% lower than that in the U treatment, and that in the UBP treatment was 13.63%, 17.66%, and 10.77% higher than those in the U, UP, and UB treatments, respectively. This study showed that biochar combined with PGPR can improve soil microbial community structure and increase the NUE of tomato.     

氮肥优化管理协同实现水稻高产和氮肥高效

【目的】 研究不同氮肥管理方式对水稻生长、氮累积分配和产量的影响,为通过氮肥优化管理提高水稻产量和氮肥利用率提供理论依据。 【方法】 以江苏省如皋市农业科学研究所的长期定位田间试验（2008 年至今）为研究平台,以江苏省沿江及苏南地区主推水稻品种‘镇稻 11 号’为供试材料,设 3 种氮肥管理模式,即:不施氮肥对照（CK）、农民习惯施氮（N 350 kg/hm2,氮肥运筹为基肥∶分蘖肥∶促花肥 = 4:4:2,FFP）和氮肥优化管理（氮肥运筹为基肥∶分蘖肥∶促花肥:保花肥 = 4:2:2:2,OPTs）,其中氮肥优化管理包括优化施氮处理（N 240 kg/hm2,OPT）、优化替氮处理（OPT 施氮基础上,有机肥氮替代 20% 化肥氮,OPT1）和优化减氮再替氮处理（OPT 施氮基础上,先减氮 20% 再用有机肥氮替代 20%化肥氮,OPT2）,通过在水稻最大分蘖期、拔节期、开花期和成熟期采集地上部植株样品,分析生物量、产量、氮累积和氮转运及其相互关系的差异。 【结果】 OPTs 处理较 FFP 处理平均增产 8.4%,其原因是提高了水稻花后的氮累积和生物量,进而提高了水稻的穗粒数、结实率和千粒重。水稻氮累积和转运的结果表明,FFP 处理主要是通过增加花后植株体内氮转运来提高籽粒氮累积,而 OPTs 处理则主要是通过提高花后水稻植株氮累积来增加籽粒氮累积。同时,水稻氮肥利用率随施氮量的增加而降低,与 FFP 处理相比,OPTs 处理的氮肥偏生产力（PFP_N）、氮肥农学效率（AE_N）和氮肥回收效率（RE_N）分别平均提高 99.4%、137.6% 和 70.0%;且优化替氮处理（OPT1）在稳定增产的基础上仍可进一步提高水稻的氮肥利用率。另外,分析不同氮肥管理模式对水稻的产量贡献阶段可知,相较于 FFP 处理与 CK 处理间的氮肥低产低效阶段,氮肥优化管理则可实现从 FFP 提升到 OPTs 的高产高效阶段。 【结论】 利用氮肥总量控制、分期调控和适量有机替代的氮肥优化管理措施,可协同实现水稻高产和氮肥高效。      

氮肥减量施生物炭对水稻产量和养分利用的影响

为解决水稻生产过度依赖化肥及其环境和高效利用问题,探讨贵州黄壤稻田科学施用生物炭。在贵州省思南县典型黄壤稻田开展氮肥不减量(T0)和氮肥减10%施2.5 t/hm²(T1),氮肥减20%施5.0 t/hm²(T2),氮肥减30%施7.5 t/hm²(T3),氮肥减40%施10.0 t/hm²生物炭(T4)和不施肥对照(CK)共6个处理3次重复田间小区随机区组试验,研究了氮肥减量施生物炭对水稻产量、产量构成和氮磷钾养分吸收利用的影响。结果表明,氮肥减量施生物炭显著影响贵州黄壤稻田水稻产量、产量构成、地上部氮磷钾积累量和利用效率。水稻产量和氮磷钾积累量随氮肥减量和生物炭用量增加先增大后减小。2019年、2020年和2021年水稻实际产量和理论产量均分别以T2、T3和T2最高,较T0分别显著增产16.04%,17.94%和14.73%以及55.72%,64.08%和118.91%,水稻籽粒N、P₂O₅和K₂O积累量、偏生产力、农学效率、表观利用率和收获指数均较高,是较好的氮肥减量施生物炭处理。产量—施生物炭量回归方程和极值分析表明,2019年、2020年和2021年氮肥分别减量21.76%,24.60%和19.00%(即32.64,36.90,28.50 kg/hm²)施生物炭量5.44,6.15,4.75 t/hm²时水稻产量最高(分别为7.80,8.57,8.03 t/hm²),较T0分别增产22.52%,18.78%和13.74%。氮肥减量施生物炭显著提高氮磷钾化肥利用率,但导致化肥+生物炭磷和钾利用率降低,因此,贵州黄壤稻田施生物炭时应氮磷钾化肥同步减量,降低比例以氮磷钾减量19.00%~24.60%,施生物炭5.00~6.25 t/hm²为宜。研究结果对指导贵州黄壤稻田氮磷钾化肥减量和施生物炭具有重要指导意义。     

Comparisons of Yield,Water Use Efficiency,and Soil Microbial Biomass as Affected by the System of Rice Intensification

To compare the effects of the system of rice intensification (SRI) on yield, water use efficiency, and microbial biomass in associated rice soils, a field experiment was conducted in 2004 at the Agriculture Experimental Farm of Zhejiang University in Zhejiang Province, China. The treatments evaluated were traditional flooding (TF) vs. SRI cultivation methods. Grain yield in the SRI treatment was 26.4% greater than that in the TF treatment, reducing water use by 461.5 mm. Compared to TF, SRI increased water use efficiency by 91.3% and irrigation water use efficiency by 194.9%. Soil microbial indicators during the rice‐growing season also diverged between TF and SRI. Microbial biomass C (MBC) was in the range of 101–196 mg kg^?1 for TF vs. 113–224 mg kg^?1 for SRI; microbial biomass N (MBN) was in the range of 14–33 mg kg^?1 for TF vs. 28–53 mg kg^?1 in SRI. Compared to TF, SRI significantly increased both MBC and MBN, regardless of sampling date.     

秸秆还田下氮肥运筹对白土田水稻产量和氮吸收利用的影响

【目的】研究小麦秸秆直接还田条件下不同氮肥基追比例运筹方式对白土稻田水稻产量和氮素吸收利用的影响, 为华中低产白土稻田水稻合理施肥提供科学依据。【方法】设置2种小麦秸秆还田量(0和3000 kg/hm2)及3种氮肥基肥-分蘖肥-穗肥施用比例(80-0-20、 60-20-20 和40-30-30)和不施氮的对照, 共7个处理, 分别为N80-0-20、 N60-20-20、 N40-30-30、 N80-0-20+S、 N60-20-20+S、 N40-30-30+S和CK。水稻收获期采集代表性样品考察水稻产量结构性状, 同时测定水稻籽粒和秸秆产量, 分析籽粒和秸秆氮素含量, 计算水稻氮素吸收量和氮肥利用效率。【结果】基肥-分蘖肥-穗肥施用比例60-20-20的处理水稻籽粒产量最高, 两年试验较不施分蘖肥的对照分别增产9.4%~12.9%和7.4%~8.9%。实施小麦秸秆直接还田后, 水稻籽粒产量较不施秸秆的对照分别提高10.2%~23.4%和0.8%~5.5%。不施秸秆条件下, 基-蘖-穗肥施用比例60-20-20的处理水稻籽粒含氮量最高, 较不施氮的对照提高11.3%, 而秸秆含N量随中后期追肥比例的加大而提高。秸秆还田条件下, 氮肥后移能明显提高水稻籽粒和秸秆含氮量。水稻籽粒氮素吸收量, 基-蘖-穗肥比例60-20-20处理最多, 2011年较对照N80-0-20分别增加13.7%和24.8%, 2012年提高14.5%和9.2%; 秸秆氮素积累量则随中后期追肥用量的增加而增多, 基-蘖-穗肥比例40-30-30处理最多。不施秸秆条件下, 基-蘖-穗肥比例60-20-20的处理氮素干物质生产效率、 氮素稻谷生产效率、 氮收获指数均最高, 百公斤籽粒吸氮量最低。秸秆还田条件下, 氮素干物质生产效率和氮素稻谷生产效率均随中后期追肥量的增加而下降, 而百公斤籽粒吸氮量则最高。氮素农学效率、 氮肥回收利用率和偏生产力也是60-20-20比例的处理最高, 较对照N80-0-20农学效率分别提高4.90和2.44 kg籽粒/kg N, 氮肥利用率提高7.82和21.29个百分点, 偏生产力提高4.90和2.44个百分点。【结论】综合水稻产量、 氮素吸收量以及氮肥利用效率, 安徽省江淮丘陵低产白土地区, 小麦秸秆直接还田条件下, 单季中稻氮肥的基肥-分蘖肥-穗肥施用比例, 以60-20-20运筹方式较为适宜。     

秸秆还田下氮肥管理对低中产田水稻产量和氮素吸收利用影响的研究

探究氮肥运筹管理对湖北中低产田水稻产量及氮素利用率的影响,为中低产田水稻生产提供合理的施肥技术措施。本研究在秸秆还田和总氮（180 kg/hm2）控制的条件下,以水稻两优培九为材料,研究不同基、 蘖、 穗氮肥配比对中低产田水稻产量及其构成因子、不同时期叶片SPAD值、 氮含量、 地上部氮素累积量及其氮利用效率的影响。结果表明, 在2011年和2012年两年大田试验的4个基、 蘖、 穗氮肥配比处理中,各试验点水稻产量均以40-30-30的处理最高, 其中在田块A与田块C中比80-0-20处理增产15.9%和8.6%,在田块B与田块D中比60-20-20处理增产6.7%和5.5%。同时40-30-30处理的氮素收获指数（NHI）和氮肥偏生产力（PFPN）也最高,优化基、 蘖、 穗肥比可以提高氮素收获指数（NHI）和氮肥偏生产力（PFPN）。综上研究结果,各中低产田中不同基、 蘖、 穗氮肥配比处理的水稻产量依次为40-30-3050-20-3060-20-2080-0-20,结合产量构成因子、SPAD值、氮肥利用率等因素综合考虑,40-30-30是湖北中低产水稻田氮肥配比的合理运筹模式。     

Analysis of soil fertility and optimal nitrogen application of brown earth (luvisols) in China

The excessive application of nitrogen (N) has caused a series of environmental problems. Brown earth (BE) is one of the main soil types in China, and the specific soil-forming conditions make it high risk of nutrient leaching. Determining the soil fertility of BE and optimal N application rates for main crops’ production is important to reduce nitrogen leaching. Based on China's second national soil survey, the basic fertility level of BE was defined, and the effects of four N management methods [one-time base fertilizer (BF), topdressing (TF), combined organic fertilizer (OF) and controlled-release fertilizer (CF)] on maize and wheat yield and N efficiency were analysed. The study found that except for lower phosphorus content (level 4), the soil fertility of BE was at a moderate level (level 3). Compared with no N application, these four N management methods significantly increased the maize and wheat yield and showed the trend of OF > CF > TF > BF; TF, CF and OF significantly increased the N efficiency comparison with BF. The optimal N application rates for wheat and maize were 129–174 kg ha⁻¹ and 170–235 kg ha⁻¹, respectively, when considering the win–win of yield and N efficiency. N fertilizer reduction in BE needs to be further strengthened, and the specific N application rates to achieve profit maximization should be adjusted depending on environmental factors.     

早稻施氮对连作晚稻产量和氮肥利用率及土壤有效氮含量的影响

于20022～005年,在湖南长沙采用连续定位试验,研究了早稻施氮对连作晚稻产量、氮肥利用率、土壤有效氮含量的影响。试验设早稻施氮/晚稻不施氮、早稻施氮/晚稻施氮、早稻不施氮/晚稻不施氮、早稻不施氮/晚稻施氮4个处理。结果表明,在连续4年早季施氮的条件下,连作晚稻施氮处理的平均产量为6.45.t/hm2,地上部干物质重12.13.t/hm2,氮素吸收量183.6.kg/hm2,分别比连作晚稻不施氮处理增加28.4%、35.1%和103.5%,均达到显著水平;在连续4年早季不施氮的条件下,连作晚稻施氮处理的平均产量为6.61.t/hm2,地上部干物质重12.14.t/hm2,氮素吸收量165.6.kg/hm2,分别比不施氮处理增加33.4%、37.6%和95.6%,均亦达到显著水平。连作晚稻在早季不施氮和早季施氮两种情况下氮肥利用率不同,前者的氮肥生理利用率显著高于后者,增幅为37.8%,两者的氮肥农学利用效率、吸收利用率差异不显著,但前者4年氮肥农学利用效率平均值比后者高18.1%,吸收利用率低6.8个百分点。早晚两季均不施氮小区土壤碱解氮含量均明显低于其他施氮小区,但没有出现随试验年度加长而连续下降的趋势;当早稻或晚稻其中有一季施用了氮肥,或者两季均施用了氮肥的小区,土壤碱解氮含量差异不显著。说明连作晚稻产量主要受当季施氮量的影响,而受早季施氮量的影响较小;早季不施氮小区的连作晚稻氮肥的农学利用效率、生理利用率比早季施氮小区高;在一定程度上降低稻田氮肥用量不会导致土壤背景氮含量的下降。     

晒田强度和穗期氮素运筹对不同氮效率水稻根系、叶片生长及产量的影响

为研究晒田强度和穗期氮素运筹对不同氮效率水稻生育中后期根系、叶片生长与产量形成的关系,以德香4103(氮高效品种)和宜香3724(氮低效品种)为材料,设置3种晒田强度:W_1,0—20cm土壤体积含水量为(53.60±5.00)%;W_2,0—20cm土壤体积含水量为(40.20±5.00)%;W_3,0—20cm土壤体积含水量为(26.80±5.00)%和3种穗期氮素运筹:N_1,晒田复水后第1天施用穗肥;N_2,晒田复水后第8天施用穗肥;N_3,晒田复水后第15天施用穗肥。测定水稻抽穗期和齐穗后15天的根系形态特征、根系干重、叶面积指数、剑叶光合速率、叶片干重、产量及产量构成。结果表明:(1)德香4103稻谷产量比宜香3724平均高11.57%。(2)两类品种的产量均与抽穗期LAI和叶片干重呈显著正相关,其中德香4103产量与抽穗期和齐穗后15天单株根重和根冠比呈显著正相关,宜香3724产量与抽穗期和齐穗后15天的单株根重呈显著正相关。(3)德香4103氮肥生理利用率与抽穗期单株根重和叶面积指数、齐穗后15天单株根长呈显著正相关,宜香3724氮肥生理利用率与齐穗后15天单株根重呈显著正相关。(4)W_1和W_2处理中,施氮处理N_2和N_3氮高效品种和氮低效品种抽穗期总根长和根表面积无显著差异,氮高效品种齐穗后15天的总根长小于氮低效品种;W_3处理中,N_1和N_2中抽穗期氮低效品种单株总根长和单株根表面积大于氮高效品种,氮高效品种和氮低效品种齐穗后15天根重和根冠比无显著差异。(5)氮低效品种成熟期的叶片干重和LAI均高于氮高效品种,抽穗期至成熟期氮高效品种的叶面积衰减率大于氮低效品种。(6)氮高效品种德香4103采用W_1N_3处理,能增加抽穗至成熟期总根长,降低叶面积衰减速率,提高抽穗后叶片光合速率,提高稻谷产量;而氮低效品种宜香3724以W_2N_2为最佳处理。综上所述,晒田程度和穗期氮素运筹能够显著影响不同氮效率水稻品种生育中后期的根系和叶片特征。通过优化晒田程度和穗期氮素运筹组合,为两类品种构建合理的根系指标和叶片体系,促进根系对氮素养分的吸收,提高灌浆结实期叶片物质生产和转运能力,最终提高稻谷产量。     

Combined effect of deficit irrigation and potassium fertilizer on physiological response,plant water status and yield of soybean in calcareous soil

A 2-year field experiment (2013 and 2014) was conducted in calcareous soil (CaCO₃ 19.2%), on soybean grown under three irrigation regimes 100%, 85% and 70% of crop evapotranspiration combined with three potassium (K₂O) levels (90, 120 and 150 kg ha^?1). The objective was to investigate the complementary properties of potassium fertilizer in improving soybean physiological response under water deficit. Plant water status (relative water content RWC, chlorophyll fluorescence F_v/F₀ and F_v/F_m), had been significantly affected by irrigation or/and potassium application. Potassium improved growth characteristics (i.e. shoot length, number, leaf area and dry weight of leaves) as well as physiochemical attributes (total soluble sugars, free proline and contents of N, P, K, Ca and Na). Yield and yield water use efficiency (Y-WUE) were significantly affected by irrigation and potassium treatments. Results indicated that potassium application of 150 and 120 kg ha^?1 significantly increased seed yield by 29.6% and 13.89%, respectively, compared with 90 kg ha^?1 as average for two seasons. It was concluded that application of higher levels of potassium fertilizer in arid environment improves plant water status as well as growth and yield of soybean under water stress.     

西南黄壤性水稻土长期不同施肥模式下作物产量及氮肥利用率演变特征

为了解西南黄壤性水稻土长期施肥效应,通过连续19年长期定位试验,分析了西南黄壤性水稻土单施化肥(NPK)、单施有机肥(M)、1/2有机肥和1/2化肥配施(0.5MNPK)、全量有机肥和全量化肥配施(MNPK)4种施肥模式对作物产量、氮肥利用率的影响及变化特征。结果表明:长期施用化肥或有机肥可显著增加作物产量,NPK、M、0.5MNPK、MNPK比CK分别显著增产56.2%、57.8%、65.0%、74.0%;各施肥处理氮肥偏生产力(PFP_N)、氮肥内部利用率(IE_N)、氮肥回收利用率(RE_N)、氮肥累积利用率(ARE_N)分别为10.9~20.7kg·kg~(-1)、44.7~53.8 kg·kg~(-1)、13.6%~19.6%、12.0%~16.9%,均以0.5MNPK最高,MNPK最低,高量氮肥施用导致氮肥利用率较低;长期单施化肥处理氮肥利用率随时间保持持平或呈下降趋势,施用有机肥的各处理氮肥利用率随时间呈显著上升趋势,尤其是氮肥累积利用率呈极显著上升趋势。长期施用有机肥尤其是有机无机配施作物产量稳定且氮肥利用率稳步提高。因此,常年高量施氮的黄壤性水稻土可适量减少氮肥用量,相应的进行有机无机肥料的合理配施是提高作物产量和肥料利用率的有效措施。     

Validation of the DNDC-Rice model by using CH4 and N2O flux data from rice cultivated in pots under alternate wetting and drying irrigation management

The DNDC (DeNitrification-DeComposition)-Rice model, one of the most advanced process-based models for the estimation of greenhouse gas emissions from paddy fields, has been discussed mostly in terms of the reproducibility of observed methane (CH₄) emissions from Japanese rice paddies, but the model has not yet been validated for tropical rice paddies under alternate wetting and drying (AWD) irrigation management, a water-saving technique. We validated the model by using CH₄ and nitrous oxide (N₂O) flux data from rice in pots cultivated under AWD irrigation management in a screen-house at the International Rice Research Institute (Los Baños, the Philippines). After minor modification and adjustment of the model to the experimental irrigation conditions, we calculated grain yield and straw production. The observed mean daily CH₄ fluxes from the continuous flooding (CF) and AWD pots were 4.49 and 1.22?kg?C?ha^?1?day^?1, respectively, and the observed mean daily N₂O fluxes from the pots were 0.105 and 34.1?g?N?ha^?1?day^?1, respectively. The root-mean-square errors, indicators of simulation error, of daily CH₄ fluxes from CF and AWD pots were calculated as 1.76 and 1.86?kg?C?ha^?1?day^?1, respectively, and those of daily N₂O fluxes were 2.23 and 124?g?N?ha^?1?day^?1, respectively. The simulated gross CH₄ emissions for CF and AWD from the puddling stage (2 days before transplanting) to harvest (97 days after transplanting) were 417 and 126?kg?C?ha^?1, respectively; these values were 9.8% lower and 0.76% higher, respectively, than the observed values. The simulated gross N₂O emissions during the same period were 0.0279 and 1.45?kg?N?ha^?1 for CF and AWD, respectively; these values were respectively 87% and 29% lower than the observed values. The observed total global warming potential (GWP) of AWD resulting from the CH₄ and N₂O emissions was approximately one-third of that in the CF treatment. The simulated GWPs of both CF and AWD were close to the observed values despite the discrepancy in N₂O emissions, because N₂O emissions contributed much less than CH₄ emissions to the total GWP. These results suggest that the DNDC-Rice model can be used to estimate CH₄ emission and total GWP from tropical paddy fields under both CF and AWD conditions.     

Effect of nitrogen on yield,quality, and irrigation water use efficiency of drip fertigated grafted watermelon (Citrullus lanatus) grown on a calcareous soil

A two-year field experiment was conducted during the growing seasons 2016 and 2017 to investigate the response of drip fertigated watermelon to different rates of nitrogen (0, 10, 20, 30, and 40?g/m³ N) applied in the form of ammonium sulfate (AS). The combined effect of nitrogen (N) and sulfur (S) was investigated. Irrigation water use efficiency (IWUE) under the different N levels was, also, evaluated. N levels in the irrigation water induced a significant effect on yield parameters (total and commercial yields, dry matter yield, plant yield, and fruit number). Increasing the level of N also induced significant increases in fruit length and fruit fresh weight. IWUE was also significantly improved at high levels of N. Fertigation using modern techniques can be considered an efficient method in the delivery of N to the crop at N levels of 30–40?g/m³, as ammonium sulfate.     

Influence of integrated nutrient management (INM) on nutrient use efficiency,soil fertility and productivity of hybrid rice

A field experiment was conducted during the two consecutive kharif seasons of 2011 and 2012 on sandy-loam lateritic soil of Indian subtropics to investigate the impact of integrated nutrient management (INM) on crop productivity, nutrient use efficiency of applied nutrients and soil fertility in restoring sustainability with hybrid rice cultivation. Application of 50% recommended dose of fertilizer (RDF) + 50% recommended dose of nitrogen (RDN) through mustard oil cake (MOC) or 75% RDF + 25% RDN through MOC + biofertilizer recorded significantly higher grain and biomass yields, greater NPK removal and higher partial factor productivity of applied nutrient (PFPN) than those of the crop having 100% RDF, 100% RDN through MOC and 25% RDF + 75% RDN through MOC, which showed very poor performance. The former treatments also improved organic carbon and available NPK contents in soil in spite of greater removal of NPK by the crop. Results of study suggested integrated use of 50% RDF + 50% RDN through MOC or 75% RDF + 25% RDN through MOC + biofertilizer for increasing hybrid rice productivity, PFPN and improving soil fertility for sustainability.     

化肥减量配合紫云英还田对双季稻产量及氮肥利用率的影响

旨在明确化肥减量条件下不同紫云英还田量对亚热带双季稻区早、晚稻产量及氮肥利用率的影响。以双季稻种植模式为研究对象,设置2个不同的减肥量处理配施不同的紫云英还田量,观察紫云英连续还田下不同处理对双季稻产量和养分利用率的影响。结果表明:与常规施肥处理(100%F)相比,20%减肥量各处理的早稻产量均得到显著提高,增产幅度为5.0%～13.2%;40%减肥量条件下,配施15 000～22 500 kg/hm~2紫云英早稻产量不减产,而配施30 000～37 500 kg/hm~2紫云英后早稻产量有显著提高,增产幅度为5.4%～8.5%。各减肥配施紫云英处理的晚稻产量均随紫云英还田量的增加而升高(P0.05)。各减肥配施紫云英处理早稻化学氮肥的农学利用率、偏生产力及回收率均较常规施肥处理显著提高,但晚稻的氮肥利用率无显著差异。将紫云英还田输入的氮纳入总氮素投入后,早稻总氮素的农学利用率和回收率均随紫云英还田量的增加而降低;与100%F相比,各减肥配施紫云英处理的农学利用率未显著降低,但紫云英还田量达到37 500 kg/hm~2及以上时会导致早稻的氮素回收率显著降低。各紫云英还田处理土壤全氮含量均高于100%F(P0.05),且土壤速效氮含量均显著高于100%F处理(P0.05)。亚热带双季稻种植模式下,长期紫云英还田配合减量施肥对早、晚稻产量和氮肥利用率均产生正面效应,且能提高土壤有机质含量和全氮含量,土壤速效氮含量显著高于常规施肥处理。因此,适量紫云英还田配施化肥除可减少化肥用量外,也是亚热带双季稻区兼顾提升稻米产量和培肥土壤的有效技术。本试验条件下,化肥减量40%配合22 500～30 000 kg/hm~2紫云英的配比综合效果较好。     

Rate and timing of nitrogen application influence partial factor productivity and agronomic NUE of maize (Zea mays L) planted at low and high densities on calcareous soil in northwest Pakistan

Field experiments were conducted to investigate impact of nitrogen (N) rate and time (splits) on partial factor productivity (PFP) and agronomic N use efficiency (NUE_A) of maize (Zea mays L.) at the New Developmental Research Farm of The University of Agriculture Peshawar-Pakistan, during two consecutive years in summer 2002 and 2003 under low and high plant densities. The 2 × 3 × 6 factorial experiment having two plant densities (D₁ = 60,000 and D₂ = 100,000 plants ha^?1) and three N levels (N₁ = 60, N₂ = 120 and N₃ = 180 kg N ha^?1) as main plots, and six ways of N applications (viz. two equal, three equal, three unequal, four equal, five equal, and five unequal splits) as sub-plots. The results indicated that both PFP and NUE_A of maize were highest at high than at low plant density. Both PFP and NUE_A showed negative relationship with increase in N rate. The highest PFP and NUE_A were obtained when N was applied in five equal splits but these results were comparable with treatments receiving N in four equal and five unequal splits. These results suggest that application of N in four or five splits under high plant density increasing both PFP and NUE_A as well as grain yield of maize under calcareous soils in Northwest Pakistan.     

Effects of 10 years of conservation tillage on soil properties and productivity in the farming–pastoral ecotone of Inner Mongolia, China

Soil degradation and subsequent yield decline are the main factors limiting further development of agriculture on the farming–pastoral transition zone of China. A 10-year field experiment was conducted in Inner Mongolia to compare the long-term effects of no-tillage with straw cover (NT), subsoiling with straw cover (ST), rototilling with straw cover (RT) and traditional tillage (TT) using ploughs on soil properties and productivity in a spring wheat–oat cropping system. Long-term conservation tillage increased soil organic matter in the top 20 cm by 21.4%, total N by 31.8% and Olsen's P by 34.5% in the 0–5 cm layer compared to traditional tillage. Mean percentage of macro-aggregates (>0.25 mm, +20%) and macroporosity (>60 μm, +52.1%) also improved significantly in the 0–30 cm soil layer ( P  <   0.05). The largest yield improvements coupled with greatest water use efficiency (WUE) were achieved by no-tillage with straw cover. Ten-year mean crop yields increased by 14.0% and WUE improved by 13.5% compared to traditional tillage due to greater soil moisture and improved soil physical and chemical status. These improvements in soil properties and productivity are of considerable importance for the seriously degraded soils in semiarid Inner Mongolia, as well as for food security, sustainable agriculture and carbon storage in the farming–pasture transition regions of China.     

水氮供应对温室滴灌番茄水氮分布及利用效率的影响

为探讨温室番茄水肥一体化滴灌系统优化模式,通过温室番茄滴灌施肥试验,研究田间滴灌管布置方式、灌水量、施氮肥量这3个因素对土壤含水率、土壤硝态氮含量及水肥利用效率的影响。3种布置方式包括1管1行(T1)、1管2行(T2)和1管3行(T3);基于Penman-Monteith修正公式计算的潜在蒸散量(Potential Evapotranspiration,ET₀)设计灌水量,3种灌水量处理包括50%ET₀(W1)、70%ET₀(W2)和90%ET₀(W3);3种施氮肥量处理包括120(N1)、180(N2)和240 kg/hm²(N3)。采用正交试验设计,共9个处理。结果表明,不同管道布置方式土壤含水率分布趋势基本相同,土壤表层0～20 cm含水率较低,>20～40 cm土层深度土壤含水率分布较高,40 cm土层深度以下土壤含水率减小,且T1和T2布置方式较T3土壤含水率分布均匀。土壤硝态氮(NO₃-N)质量分数随土层深度的增加而减小,0～30 cm土...