氮肥施用对直播冬油菜产量及氮肥利用率的影响

为探明安徽省直播冬油菜种植中适宜的氮肥用量、氮肥种类和施氮方式,通过田间小区试验,研究尿素不同用量及等氮量尿素和控释尿素不同施用方式对直播冬油菜产量、氮肥累积量及氮肥利用率的影响。结果表明：施氮水平和施氮方式对直播冬油菜产量具有显著影响,成株率与产量之间呈显著正相关,施氮量180 kg N·hm^-2条件下,尿素分次施用处理（N180）和控释尿素一次性施用处理（CRU180）在生育中后期能有效提高直播冬油菜密度。施氮量240 kg N·hm^-2、尿素分次施用处理（N240）角壳和茎秆氮素累积量分配比例增加,籽粒分配比例减少,氮肥表观利用率、氮肥农学效率、氮肥生理效率和氮肥偏生产力显著降低,籽粒产量不增反降,较CRU180和N180分别降低2.87%和9.67%。各施氮处理中,N180处理产量最高,较其他施氮处理显著增产7.53%~82.15%。施氮量180 kg N·hm^-2条件下,相比尿素一次性施用处理（U180）,CRU180和N180显著增产8.53%和16.69%,籽粒氮素累积量显著增加8.80%和16.02%,氮肥表观利用率显著增加11.68%和14.30%,氮素农学效率显著增加12.53%和24.46%,氮素生理效率增加0.74%和9.13%,氮肥偏生产力显著增加8.59%和16.76%。综合本试验直播冬油菜产量、氮素累积量和氮肥利用率结果来看,合理的氮肥用量和氮肥品种可以有效增加直播冬油菜的成株率和氮素累积量,进而增加产量、提高氮肥利用率。安徽省直播冬油菜施氮量180 kg N·hm^-2,尿素分次施用和控释尿素一次性施用,均能达到产量和氮肥利用率的双向提升。考虑到直播冬油菜轻简化发展大趋势,建议采用控释尿素一次性基施。     

施肥对菜地土壤、蔬菜、径流中δ15N组成的影响

为了解施肥对蔬菜地土壤、蔬菜和地表水体中δ¹⁵N丰度的影响,选择2012至2018内施用不同肥料的28块蔬菜地（包括13块施用化肥蔬菜地、8块施用畜禽粪蔬菜地和7块施用商品有机肥加化肥蔬菜地）,采样分析表层土壤、蔬菜地上部分和地下部分及地表径流样的δ¹⁵N丰度。结果表明：施肥种类对土壤、蔬菜和地表径流中δ¹⁵N丰度均可产生显著影响,其丰度值由高至低依次为：畜禽肥>商品有机肥加化肥>化肥。蔬菜和地表水与土壤之间的δ¹⁵N丰度存在正相关。分析认为,蔬菜产品中氮同位素组成可以作为鉴定有机蔬菜的辅助依据,地表水体中δ¹⁵N丰度可作为水体中氮素污染源的指标。     

Increase in yield and nitrogen use efficiency of double rice with long-term application of controlled-release urea

Controlled-release urea(CRU) has better characteristics than conventional urea for synchronizing nitrogen(N) release with plant uptake. Understanding the effects of CRU on crop yield and N use efficiency(NUE) has long been the key to evaluate the performance of CRU. A long-term experiment over five consecutive years was conducted in Changsha, Hunan Province, China, to investigate the effects of polyethylene-coated urea with a 90-d release period on the yield and NUE of double rice(early and late...     

High quality and high efficiency fertilization of rice

正Rice (Oryza sativa L.), one essential staple cereal, feeds over 60%of the world’s population (FAO 2020). As the global population grows, improving rice yield becomes an effective strategy to achieve food security (Deng et al. 2019).The use of chemical fertilizer, especially N fertilizer,has historically played a critical role in the growth of rice yield (Zhang et al. 2015; Wood et al. 2020). However,     

Reducing nitrogen fertilization of intensive kiwifruit orchards decreases nitrate accumulation in soil without compromising crop production

Excessive nitrogen(N) fertilization of high value horticultural crops is a common problem that not only increases the cost to farmers, but also negatively affects crop growth and the environment. A three-year field experiment was conducted in an intensive kiwifruit orchard in Shaanxi Province, China to compare the effects of reduced N fertilization applied as urea(U), and controlled release urea(CRU) on the N nutrition of kiwi vines, fruit yield and quality, and nitrate-N accumulation in the soil profile. The three treatments included a conventional N application rate(CF-U, 900 kg N ha~(–1) yr~(–1) as urea), two reduced N fertilization treatments where the amount of N fertilizer applied as U and CRU was reduced by 25% in 2013 and 2014, and by 45% in 2015. The 25 and 45% reduced N treatments had no adverse effects on the N concentrations in leaves and pruning branches and the fruit yield and quality of kiwi vines. However, they significantly enhanced the partial factor productivity of applied N(PFPN) and the economic benefits, and reduced nitrate accumulation in the 0–200 cm soil profile. The same benefits of reduced N fertilization were observed for both the U and CRU treatments, but the CRU treatment had the added benefit of decreasing the loss of nitrate through leaching. We concluded that the current level of N fertilization in kiwi orchards is very excessive, and reducing the N fertilizer rate by 25–45% could not only guarantee fruit yield, but also reduce N accumulation and loss.     

NITROGEN USE AND MANAGEMENT IN ORCHARDS AND VEGETABLE FIELDS IN CHINA: CHALLENGES AND SOLUTIONS

China is the largest producer and consumer of fruits and vegetables in the world. Although the annual planting areas of orchards and vegetable fields(OVF) account for 20% of total croplands, they consume more than 30% of the mineral nitrogen fertilizers in China and have become hotspots of reactive N emissions. Excess N fertilization has not only reduced the N use efficiency(NUE) and quality of grown fruits and vegetables but has also led to soil acidification, biodiversity loss and climate chan...     

施肥方式对黄土高原旱作春玉米农田土壤氨挥发的影响

【目的】通过两年田间氨挥发测定,研究不同施氮量和不同施氮方式对黄土高原旱作春玉米农田土壤氨挥发的影响。【方法】 该试验采用裂区试验设计,主处理设置0、180、300 kg·hm^-2 3个氮肥用量,同一施氮量下副区分尿素一次性基施（UR）、尿素分次施用（URT）（基肥40%,十叶期追肥60%）以及尿素与控释尿素掺混一次性基施（CRU）3种施氮方式,采用海绵吸收通气法进行原位测定。【结果】 （1）对于施基肥后的氨挥发速率,3种施肥方式均出现挥发峰值,且UR处理的氨挥发峰值高于另外两种施肥方式,特别是在高施氮量的情况下;对于追肥后的氨挥发,只有URT处理出现峰值,且高于基肥后的挥发峰值。（2）氨挥发累积量随着施氮量的增加而增加。在同等施氮量处理下,URT处理氨挥发累积量最高（2.88—36.84 kg·hm^-2）,且主要集中在追肥期（占整个生育期的72.2%—90.4%）;其次是UR处理（1.08—10.07 kg·hm^-2）;CRU处理氨挥发累积量最低（0.96—5.69 kg·hm^-2）。（3）施氮量和施肥方式对氨挥发量的交互作用极显著,氨挥发的年间差异主要是受到施肥后的降雨影响。【结论】 对于西北旱作覆膜春玉米,尿素与控释尿素掺混一次性施用方式（CRU）既能减少追肥人工投入,又能减低氨挥发损失,可作为该区域值得推广的绿色施肥方式。     

Effects of mechanized deep placement of nitrogen fertilizer rate and type on rice yield and nitrogen use efficiency in Chuanxi Plain,China

This paper investigates the yield and nitrogen use efficiency (NUE) of machine-transplanted rice cultivated using mechanized deep placement of N fertilizer in the rice–wheat rotation region of Chuanxi Plain, China. It provides theoretical support for N-saving and improves quality and production efficiency of machine-transplanted rice. Using a single-factor complete randomized block design in field experiments in 2018 and 2019, seven N-fertilization treatments were applied, with the fertilizer being surface broadcast and/or mechanically placed beside the seedlings at (5.5±0.5) cm soil depth when transplanting. The treatments were: N0, no N fertilizer; U1, 180 kg N ha^–1 as urea, surface broadcast manually before transplanting; U2, 108 kg N ha^–1 as urea, surface broadcast manually before transplanting, and 72 kg N ha^–1 as urea surface broadcast manually on the 10th d after transplanting, which is not only the local common fertilization method, but also the reference treatment; UD, 180 kg N ha^–1 as urea, mechanically deep-placed when transplanting; M1, 81.6 kg N ha^–1 as urea and 38.4 kg N ha^–1 as controlled-release urea (CRU), mechanically deep-placed when transplanting; M2, 102 kg N ha^–1 as urea and 48 kg N ha^–1 as CRU, mechanically deep-placed when transplanting; M3, 122.4 kg N ha^–1 as urea and 57.6 kg N ha^–1 as CRU, mechanically deep-placed when transplanting. The effects of the N fertilizer treatments on rice yield and NUE were consistent in the 2 yr. With a N application rate of 180 kg ha^–1, compared with U2, the N recovery efficiency (NRE), N agronomic use efficiency (NAE) and yield under the UD treatment were 20.6, 3.5 and 1.1% higher in 2018, and 4.6, 1.7 and 1.2% higher in 2019, respectively. Compared with urea alone (U1, U2 or UD), the NRE, NAE and yield achieved by M3 (combined application of urea and controlled-release urea) were higher by 9.2–73.3%, 18.6–61.5% and 6.5–16.5% (2018), and 22.2–65.2%, 25.6–75.0% and 5.9–13.9% (2019), respectively. Compared with M3, the lower-N treatments M1 and M2 significantly increased NRE by 4.0–7.8% in 2018 and 3.1–4.3% in 2019, respectively. Compared with urea surface application (U1 or U2), the yield under the M2 treatment was higher by 4.3–12.9% in 2018 and 3.6–10.1% in 2019, respectively. Compared with U2, the NRE and NAE under the M2 treatment was higher by 36.9 and 36.3% in 2018, and 33.2 and 37.4% in 2019, mainly because of higher N uptake. There was no significant difference in the concentration of nitrate in the top 0–20 cm soil under U1, U2 and M2 treatments during the full heading and maturity stages. During the full heading stage, U2 produced the highest concentration of nitrite in 0–20 cm and 20–40 cm soil among the N fertilizer treatments. In conclusion, mechanized deep placement of mixed urea and controlled-release urea (M2) at transplanting is a highly-efficient cultivation technology that enables increased yield of machine-transplanted rice and improved NUE, while reducing the amount of N-fertilization applied.     

控释尿素一次性施用的玉米减氮增效研究

基于田间小区试验,在常规施氮（U100,普通尿素,施氮量250 kg/hm²）基础上,设置普通尿素、控释尿素减量20%（U80和C80）和40%处理（U60和C60）,通过测定玉米产量及产量构成、氮素吸收和利用效率,结合土壤养分动态和植株光合特征与氮同化关键酶活性,评价控释尿素在玉米减氮增效中的作用。结果表明,氮肥减量20%时玉米产量和氮肥利用率都达到常规施氮水平,其中C80比U80增产14.5%;氮肥减量40%后产量有所降低,减产原因主要是百粒质量降低7.0%~9.5%。与U100相比,减氮20%的光合特征,土壤硝铵态氮水平,谷氨酸脱氢酶（NADH-GDH）、谷草转氨酶（GOT）和谷氨酰胺合成酶（GS）的活性均未显著下降,其中C80的净光合速率和光合氮利用效率比U100显著提高15.0%和24.8%,且C80较U80在提高氮素吸收总量、氮利用率、收获指数、光合氮利用率、酶活性和维持籽粒百粒质量方面更具优势。减氮40%后,U60的酶活性和光合特征与U100相比平均降低31.5%和27.6%,而C60的光合氮利用效率达到常规施氮水平。可见,氮肥减量20%时可以有效维持玉米产量,其中控释尿素一次性施用效果更佳,值得推广应用。     

葡聚糖改性尿素对冬小麦产量和肥料氮去向的影响

【目的】糖类物质具有调控氮素转化和作物生长的作用，目前尚不明确不同聚合度糖类物质与尿素反应对尿素氮肥利用、作物生长的影响及机理。通过将不同聚合度葡萄糖（葡聚糖）与¹⁵N尿素熔融制备葡聚糖改性尿素，分析葡聚糖改性尿素的结构变化与小麦产量和氮素吸收利用的关系，以期为葡聚糖在提高尿素氮肥利用效率中的应用提供科学依据。【方法】采用¹⁵N示踪技术，供试作物为冬小麦（济麦22），将葡萄糖（单体）、麦芽糖（2聚）、低聚麦芽糖（≈5聚）和聚葡萄糖（≈20聚）按1%添加量加入到熔融¹⁵N尿素（丰度为10.19%）中，制得葡聚糖改性尿素（葡萄糖、麦芽糖、低聚麦芽糖、聚葡萄糖改性尿素分别由GU、MU、OU和PU表示），以不同聚合度葡萄糖改性尿素和普通尿素（U）为供试肥料，运用田间土柱栽培试验研究葡聚糖改性尿素对小麦生长及肥料氮去向的影响。利用傅里叶红外变换（FTIR）光谱和¹³C核磁共振（¹³C NMR）波谱特征探究葡萄糖聚合度及其改性尿素的结构变化，并揭示其与小麦产量、氮肥利用的关系。【结果】（1）与U相比，葡聚糖改性尿素的FTIR谱图在3 343和1 601 cm^-1处的伯酰胺振动强度减弱，¹³C NMR波谱在158—171 ppm处检测到一个新的化学位移峰，是葡聚糖的醛基与尿素的胺基发生席夫碱反应，生成含C=N物质的标志。（2）与U相比，不同聚合度葡萄糖改性尿素（GU、MU、OU、PU）增加了小麦产量，分别较U提高了1.9%、9.2%、10.3%和12.3%，主要通过增加小麦穗数和穗粒数实现增产。（3）与U相比，不同聚合度葡萄糖改性尿素的小麦籽粒总氮吸收量和肥料氮吸收量分别提高了8.7%—20.0%和6.1%—13.9%；MU、OU和PU处理的氮素吸收量均高于GU。（4）与U相比，不同聚合度葡萄糖改性尿素的¹⁵N利用率提高了2.0—6.1个百分点，肥料氮残留率提高了1.3—4.9个百分点，肥料氮损失率显著降低6.9—7.4个百分点。（5）相关性分析结果表明，小麦产量与葡萄糖聚合度呈显著正相关关系，而与席夫碱含量呈显著负相关；利用一元二次方程可显著拟合席夫碱含量与小麦产量和¹⁵N利用率的关系，葡萄糖聚合度5—8时，小麦产量和肥料氮利用率最高。【结论】与普通尿素相比，不同聚合度葡萄糖改性尿素可以增加小麦产量，促进氮素的吸收利用，提高肥料氮残留量，减少尿素氮肥损失。一定范围内，随着葡聚糖聚合度的增加，小麦产量和肥料氮吸收量逐渐增加，土壤中肥料氮残留量逐渐降低。葡萄糖聚合度为5—8，其对尿素改性增效的效果最佳。     

控施氮肥与尿素配施对玉米生长、养分吸收及产量的影响

本文通过田间试验,研究几种控释肥与尿素的配施对玉米干物质积累、氮素吸收及产量的影响。结果表明,与不施氮处理(CK)相比,施用氮肥具有显著的增产效果,控释氮肥70%与普通尿素30%处理(CRU70%)的玉米产量显著高于普通尿素100%(CRU0%),增产6.0%,在成熟期,CRU70%处理的地上部干物质积累量和氮素积累量均显著高于CRU0%,处理CRU 70%的氮肥当季回收率,农学效率和偏生产力均显著高CRU 0%处理,分别提高20.8%、36.5%、6.1%。综合玉米产量、养分吸收利用及经济效益,控释氮肥70%与普通尿素30%配施可发挥两种氮肥的优势,获得显著的增产效果,提高经济效益。     

Substituting nitrogen and phosphorus fertilizer with optimal amount of crop straw improves rice grain yield,nutrient use efficiency and soil carbon sequestration

Crop straw return after harvest is considered an important way to achieve both agronomic and environmental benefits.  However, the appropriate amount of straw to substitute for fertilizer remains unclear.  A field experiment was performed from 2016 to 2018 to explore the effect of different amounts of straw to substitute for fertilizer on soil properties, soil organic carbon (SOC) storage, grain yield, yield components, nitrogen (N) use efficiency, phosphorus (P) use efficiency, N surplus, and P surplus after rice harvesting.  Relative to mineral fertilization alone, straw substitution at 5 t ha^–1 improved the number of spikelets per panicle, effective panicle, seed setting rate, 1 000-grain weight, and grain yield, and also increased the aboveground N and P uptake in rice.  Straw substitution exceeding 2.5 t ha^–1 increased the soil available N, P, and K concentrations as compared with mineral fertilization, and different amounts of straw substitution improved SOC storage compared with mineral fertilization.  Furthermore, straw substitution at 5 t ha^–1 decreased the N surplus and P surplus by up to 68.3 and 28.9%, respectively, compared to mineral fertilization.  Rice aboveground N and P uptake and soil properties together contributed 19.3% to the variation in rice grain yield and yield components.  Straw substitution at 5 t ha^–1, an optimal fertilization regime, improved soil properties, SOC storage, grain yield, yield components, N use efficiency (NUE), and P use efficiency (PUE) while simultaneously decreasing the risk of environmental contamination.     

Quantifying in situ N2 fluxes from an intensively managed calcareous soil using the 15N gas-flux method

Denitrification-induced nitrogen (N) losses from croplands may be greatly increased by intensive fertilization.  However, the accurate quantification of these losses is still challenging due to insufficient available in situ measurements of soil dinitrogen (N₂) emissions.  We carried out two one-week experiments in a maize–wheat cropping system with calcareous soil using the ¹⁵N gas-flux (¹⁵NGF) method to measure in situ N₂ fluxes following urea application.  Applications of ¹⁵N-labeled urea (99 atom%, 130–150 kg N ha⁻¹) were followed by irrigation on the 1st, 3rd, and 5th days after fertilization (DAF 1, 3, and 5, respectively).  The detection limits of the soil N₂ fluxes were 163–1 565, 81–485, and 54–281 μg N m⁻² h⁻¹ for the two-, four-, and six-hour static chamber enclosures, respectively.  The N₂ fluxes measured in 120 cases varied between 159 and 2 943 (811 on average) μg N m⁻² h⁻¹, which were higher than the detection limits, with the exception of only two cases.  The N₂ fluxes at DAF 3 were significantly higher (by nearly 80% (P<0.01)) than those at DAF 1 and 5 in the maize experiment, while there were no significant differences among the irrigation times in the wheat experiment.  The N₂ fluxes and the ratios of nitrous oxide (N₂O) to the N₂O plus N₂ fluxes following urea application to maize were approximately 65% and 11 times larger, respectively (P<0.01), than those following urea application to wheat.  Such differences could be mainly attributed to the higher soil water contents, temperatures, and availability of soil N substrates in the maize experiment than in the wheat experiment.  This study suggests that the ¹⁵NGF method is sensitive enough to measure in situ N₂ fluxes from intensively fertilized croplands with calcareous soils.     

地膜覆盖与施肥对秸秆碳氮在土壤中固存的影响

[目的]作物秸秆不仅含有较高的有机碳,而且含有丰富的矿质营养元素.秸秆还田是东北黑土地区培肥土壤和农业可持续发展的重要技术措施.然而不同地膜覆盖(简称"覆膜")及施肥方式下秸秆碳(C)和氮(N)在土壤中的固持特征还不是很明确.本研究通过定量分析秸秆碳对土壤有机碳(SOC)和秸秆氮对土壤全氮(TN)的贡献,探讨不同覆膜和...     

Effects of Side Deep Fertilization on Yield Formation and Nitrogen Utilization of Mechanized Transplanting Rice

【Objective】Mechanized transplanting of rice with synchronous side deep application of fertilizer is a new and advanced technology that is still developing rapidly. In-depth studies on the effects of mechanized side deep placement of different types of nitrogen (N) fertilizer on the grain yield and N utilization efficiency of mechanized transplanted rice will be helpful for devising strategies to improve the mechanization of planting and fertilization, and to provide a theoretical basis for reducing costs and increasing fertilization efficiency in rice production. 【Method】Field experiments were conducted in 2017 and 2018 with a randomized complete block design, with five N fertilizer application treatments: N0-plots without N fertilizer; CUB-manual surface broadcast of urea (CU); CUM-mechanized side deep placement of CU; CRUB-manual surface broadcast of controlled release urea (CRU); and CRUM-mechanized side deep placement of CRU. The characteristics of matter production, as well as N uptake and distribution, N use efficiency, yield, and yield components of rice were determined. 【Result】Each N fertilizer application treatment had similar effects on yield formation and N use efficiency in the two years. Compared with the CU treatment, the CRU treatment significantly improved dry matter accumulation, N uptake, N utilization efficiency, and grain yield. The dry matter accumulation and N uptake at maturity, N recovery efficiency (NRE), N agronomy efficiency (NAE), and grain yield were higher in the CRU treatment than in the CU treatment by 3.22%, 17.50%, 46.00%, 17.79%, and 3.72%, respectively, in 2017; and by 8.77%, 13.27%, 32.07%, 12.74%, and 3.32%, respectively, in 2018. Compared with surface broadcasting, mechanized deep placement of N fertilizer, regardless of the type of N fertilizer, significantly enhanced N use efficiency, and increased NRE and NAE by 17.91%-43.14% and 19.61%-37.39% respectively, in 2017; and by 53.80%-54.10% and 21.11%-35.11%, respectively, in 2018. Compared with surface broadcasting, mechanized deep placement of N fertilizer (CU or CRU) increased the grain yields in 2017 and 2018 by 4.46%-6.95% and 5.55%-8.11%, respectively, because of increased numbers of effective panicles and spikelets. The N uptake in stems-sheaths and leaves and the apparent amount of N translocated in stems-sheaths and leaves (TNT) were significantly higher in the CRUM treatment than in any other N application treatments from the heading stage to the maturity stage. Compared with the other N fertilizer treatments, the CRUM treatment also increased N uptake, SPAD values, and total aboveground biomass at the panicle initiation stage and full heading stage. 【Conclusion】Mechanized side deep placement of controlled release urea is an efficient fertilization method to increase the grain yield and N use efficiency of mechanized transplanted rice.     

侧深施氮对机插水稻产量形成及氮素利用的影响

【目的】水稻机插同步侧深施肥是一项新兴的技术,正在迅速发展。深入探究不同类型氮肥机械侧深施用对机插水稻产量及氮素利用效率的影响,有利于提高水稻机械化种植水平,为机插水稻节本增效提供理论依据。【方法】2017年和2018年开展大田试验,采用完全随机区组试验设计,设置5种施氮处理,即不施氮肥（N0）、尿素撒施（CUB）、尿素机械侧深施（CUM）、控释尿素撒施（CRUB）和控释尿素机械侧深施（CRUM）,测定水稻物质生产特性、氮素积累分配、氮素利用效率、产量及产量构成因素。【结果】2年各施氮处理对水稻产量形成、氮素利用的影响基本一致。与尿素相比,控释尿素可以显著提高水稻干物质积累量、氮素积累量、氮肥利用率以及稻谷产量;2017年成熟期干物质积累量和氮素积累量、氮肥吸收利用率（NRE）、氮肥农学效率（NAE）和稻谷产量分别增加3.22%、17.50%、46.00%、17.79%和3.72%,2018年相应增幅分别为8.77%、13.27%、32.07%、12.74%和3.32%。与人工撒施相比,机械侧深施可以显著提高氮肥利用率,2017年NRE和NAE分别增加17.91%—43.14%和19.61%—37.39%;2018年NRE和NAE分别增加53.80%—54.10%和21.11%—35.11%。与人工撒施相比,机械侧深施肥处理的产量分别增加4.46%—6.95%（2017年）、5.55%—8.11%（2018年）;增产的主要原因是其具有更多有效穗数和颖花总量。齐穗至成熟期,CRUM处理茎叶鞘氮素积累量和茎叶氮素表观转移量（TNT）均显著高于其他施氮处理。此外,在穗分化期和齐穗期,相比其他施氮处理,CRUM处理的氮素积累量、SPAD值、干物质积累量均显著增加。【结论】控释尿素机械侧深施（CRUM）是一种能提高机插水稻产量和氮素利用的有效施肥方法。     

Symbiotic performance,shoot biomass and water-use efficiency of three groundnut (Arachis hypogaea L.) genotypes in response to phosphorus supply under field conditions in Ethiopia

Phosphorus is a key nutrient element involved in energy transfer for cellular metabolism, respiration and photosynthesis and its supply at low levels can affect legume nodulation, N₂ fixation, and C assimilation. A two-year field study was conducted in Ethiopia in 2012 and 2013 to evaluate the effects of P supply on growth, symbiotic N₂ nutrition, grain yield and water-use efficiency of three groundnut genotypes. Supplying P to the genotypes significantly increased their shoot biomass, symbiotic performance, grain yield, and C accumulation. There was, however, no effect on shoot δ¹³C values in either year. Compared to the zero-P control, supplying 40 kg·ha⁻¹ P markedly increased shoot biomass by 77% and 66% in 2012 and 2013, respectively. In both years, groundnut grain yields were much higher at 20 and 30 kg·ha⁻¹ P. Phosphorus supply markedly reduced shoot δ¹⁵N values and increased the %Ndfa and amount of N-fixed, indicating the direct involvement of P in promoting N₂ fixation in nodulated groundnut. The three genotypes differed significantly in δ¹⁵N, %Ndfa, N-fixed, grain yield, C concentration, and δ¹³C. The phosphorus × genotype interaction was also significant for shoot DM, N content, N-fixed and soil N uptake.     

Effects of fertigation scheme on N uptake and N use efficiency in cotton

While fertigation can increase fertilizer use efficiency, there is an uncertainly as to whether the fertilizer should be introduced at the beginning of the irrigation or at the end, or introduced during irrigation. Our objective was to determine the effect of different fertigation schemes on nitrogen (N) uptake and N use efficiency (NUE) in cotton plants. A pot experiment was conducted under greenhouse conditions in year 2004 and 2005. According to the application timing of nitrogen (N) fertilizer solution and water (W) involved in an irrigation cycle, four nitrogen fertigation schemes [nitrogen applied at the beginning of the irrigation cycle (N-W), nitrogen applied at the end of the irrigation cycle (W-N), nitrogen applied in the middle of the irrigation cycle (W-N-W) and nitrogen applied throughout the irrigation cycle (N&W)] were employed in a completely randomized design with four replications. Cotton was grown in plastic containers with a volume of 84 l, which were filled with a clay loam soil and fertilized with 6.4 g of N per pot as unlabeled and 15N-labeled urea for 2004 and 2005, respectively. Plant total dry matter (DM) and N content in N-W was significantly higher than in N&W in both seasons, but these were not consistent for W-N and W-N-W treatments. In year 2005, a significantly higher nitrogen derived from fertilizer (NDFF) for the whole plant was found in W-N and N-W than that in W-N-W and N&W. Fertigation scheme had a consistent effect on total NUE: N-W had the highest NUE for the whole plant, but this was not significantly different from W-N. Treatments W-N and W-N-W had similar total NUE, and N&W had the lowest total NUE. After harvesting, the total residual fertilizer N in the soil was highest in W-N, lowest in N-W, but this was not significantly different from N&W and W-N-W treatments. Total residual NO3-N in the soil in N&W and W-N treatments was 20.7 and 21.2% higher than that in N W, respectively. The total 15 N recovery was not statistically significant between the four fertigation schemes. In this study, the fertigation scheme N-W (nitrogen applied at the beginning of an irrigation cycle) increased DM accumulation, N uptake and NUE of cotton. This study indicates that Nitrogen application at the beginning of an irrigation cycle has an advantage on N uptake and NUE of cotton. Therefore, NUE could be enhanced by optimizing fertilization schemes with drip irrigation.     

Strip deep rotary tillage combined with controlled-release urea improves the grain yield and nitrogen use efficiency of maize in the North China Plain

Inappropriate tillage practices and nitrogen(N) management have become seriously limitations for maize(Zea mays L.) yield and N use efficiency(NUE) in the North China Plain(NCP). In the current study, we examined the effects of strip deep rotary tillage(ST) combined with controlled-release(CR) urea on maize yield and NUE, and determined the physiological factors involved in yield formation and N accumulation during a 2-year field experiment. Compared with conventional rotary tillage(RT) and no-t...     

氮肥一次性基施对不同成穗方式下直播常规粳稻产量的影响

在江苏省稻麦两熟轮作地区,以南粳9108为材料,在控释氮肥配方（40 d释放期控释氮肥∶100 d释放期控释氮肥=1∶4）和速效氮肥的不同配比下,研究全程氮素一次性基施条件下控释氮肥施用比例对不同成穗方式下直播常规粳稻产量的影响。试验为裂区设计,主区设置3种不同基本苗处理,在成熟期调查其主茎占有效穗数的比例,以分别代表主茎为主成穗型、主茎分蘖并重成穗型和分蘖为主成穗型的3种水稻群体,控释氮肥配方和速效氮肥的不同配比为副区,分别为纯氮比5∶5、6∶4和7∶3。结果表明：不同成穗方式下直播常规粳稻达到高产时的适宜控释氮肥配方与速效氮肥的一次性基施配比存在差异,主茎为主成穗方式下,控释氮肥配方与速效氮肥以7∶3的纯氮比例配施时产量最高,产量为10.0 t·hm^-2,较5∶5和6∶4处理显著提高53%~7.5%;主茎分蘖并重型和分蘖为主成穗型两种成穗方式下,控释氮肥配方与速效氮肥以5∶5的纯氮比例配施时产量最高,分别为9.5、9.4 t·hm^-2,较其他处理显著提高9.2%~10.5%和9.3%~11.9%。在成穗方式间,以主茎为主成穗方式下的7∶3处理的产量最高,该处理在群体颖花量、生育后期光合势及阶段干物质积累等方面都具有显著优势。综上,不同直播稻成穗方式下基施适宜比例的控释氮肥均能获得较高的产量,适当增加基本苗以提高主茎占有效穗比例,以主茎成穗为主,配套控释氮肥配方和速效氮肥配比为7∶3的一次性基施氮肥技术有助于实现直播常规粳稻的高产。