Productivity of two stevia varieties under reduced irrigation and fertilization inputs

A 3-year field study was conducted in central Greece to determine the productivity of two stevia [(Stevia rebaudiana (Bertoni) Bertoni] varieties (‘Morita’ and ‘Candy-stevia’) under normal and reduced irrigation (100% and 75% of the evapotranspiration) and fertilization [1:0.8:1.1 or 1:0.4:0.8 N:P:K ratio in the first year and only N fertilization (100% or 74% of the recommended rate) in the second and third years] inputs. Averaged across years, stevia cv. Morita achieved greater dry leaf yield (3.48 t ha^?1) than the cv. Candy-stevia (2.85 t ha^?1). Irrigation and fertilization inputs did not significantly affect stevia cv. Morita dry leaf and steviol glycosides (stevioside plus rebaudioside-A) yields; however, decreasing irrigation and fertilization caused slight reduction of cv. Candy-stevia yields. In cv. Morita leaves, the concentrations of stevioside and rebaudioside-A ranged from 5.97% to 7.78% and 3.73% to 4.79%, respectively, while the corresponding concentrations in cv. Candy-stevia leaves were 8.21–9.36% and 3.89–6.33%. Conclusively, both stevia varieties could achieve satisfactory dry leaf biomass and steviol glycosides yield, even when grown under reduced irrigation (at 75% of evapotranspiration) and reduced N fertilization (74% of the recommended rate). Thus, stevia could represent an alternative crop to tobacco in the Mediterranean conditions.     

Effects of shade regimes and planting geometry on growth,yield and quality of the natural sweetener plant stevia (Stevia rebaudiana Bertoni) in north-western Himalaya

During 2008 and 2009, field experiments were conducted at the research farm of CSIR-Institute of Himalayan Bioresource Technology, Palampur, India to assess the effect of shade levels (no shade, 25% shade, 50% shade, 75% shade) and plant geometry levels [30 × 15 cm (north–south, N–S), 45 × 10 cm (N–S), 30 × 15 cm (east–west, E–W) and 45 × 10 cm (E–W)] on the growth, yield and quality of stevia. Plant development was fastest in controls and slowest in stevia plants growing at minimum light (75% shade). These plants showed delayed bud formation and flowering. Significantly, higher dry leaf yield was recorded when the crop was grown under 25% shading than under 50 and 75% shade. Total steviol glycosides content decreased with increasing shade levels. All shade levels resulted in the same leaf-to-stem ratio, which was significantly higher than that obtained under ambient light. Plant geometry significantly affected the number of leaves and leaf dry weight plant^–1. During both years, dry leaf weight was highest in the wider row spacing (45 × 10 cm) than in the narrow row spacing (30 × 15 cm). Stevia spaced at 30 × 15 cm in an E–W direction recorded significantly higher total steviol glycosides at 2 months after transplanting (MAT).     

Crop Productivity,Steviol Glycoside Yield,Nutrient Concentration and Uptake of Stevia rebaudiana Bert. under Mediterranean Field Conditions

Stevia rebaudiana Bertoni (Asteraceae Family), characterized by a high content of steviol glycosides (SG) in its leaves, represents an interesting source of non-sucrose and no-calorie sweeteners. Stevia, which is native to Paraguay, is a relatively new crop for the Mediterranean region, where it is grown as an annual or poly-annual crop. In order to assess the crop’s environmental requirements, productive performance and nutrient uptakes, a two-year field experiment was carried out in north-eastern Italy, where the species had never previously been cultivated. The aim was to evaluate the effects of important pre-harvest factors, such as cultivation site, harvest time and their reciprocal interaction, on productivity, leaf SG yield and nutrient requirements. Results showed that the timing of the harvest and the pedo-climatic conditions of the cultivation sites had a significant effect on the main biometric traits, total and leaf dry yield, SG production, macronutrient concentration and uptake.     

The effect of different nitrogen levels on yield and quality of stevia (Stevia rebaudiana bert.)

In the present work, the efficiency of different nitrogen doses (0, 50, 100, 150, and 200 kg ha^?1) on growth, yield, and quality of stevia (Stevia rebaudiana Bert.) was investigated in 2011–2013. The study was conducted in Antalya located in the Mediterranean Region of Turkey. Terra rossa type soil (LVx, FAO) characteristics of the experimental field were clay loam, with high amounts of lime (33,9%) and slightly alkaline (pH 7.7). The experiment was carried out in randomized block design with four replications. All the results were summarized as mean of three years. The highest fresh and dry biomass yields (26.75 t ha^?1 and 7.5 ha^?1, respectively) were obtained from 150 kg ha^?1 N dose and followed by 100 kg ha^?1 N dose (26.29 t ha^?1 and 7.24 ha^?1, respectively). Whereas the highest fresh and dry leaf yields (13.27 t ha^?1 and 3.82 t ha^?1, respectively) were realized in 100 kg ha^?1 N dose. Actually, all nitrogen doses gave higher biomass and leaf yields compared to the control. On the hand, major steviol glycosides (stevioside and rebaudioside A) in the leaf were not influenced by nitrogen levels. In conclusion, 100 kg ha^?1 N dose was found to be suitable for cultivation of stevia under field conditions.     

Response of sunflower hybrids to nitrogen application grown under different agro-environments

A wide gap exists between production and consumption of vegetable oils in Pakistan. Thereby, a significant proportion (2.28 million tons) of vegetable oils is being imported at the cost of 2257 million US$. Therefore, the present study was conducted to quantify the comparative performance of various sunflower hybrids as influenced by various levels of nitrogen (N) fertilizer under different agro-environments. The experimental treatments consisted of three sunflower hybrids (Hysun33, Hysun38, and Pioneer-64A93) and five levels of N fertilizer (0, 60, 120, 180, 240 kg N ha^?1), arranged in a randomized complete block design in a split plot with four replications. The field trials were conducted for two consecutive crop seasons under three different agro-ecologies (arid, semi-arid, and sub-humid) in the province of Punjab, Pakistan. The results of the study demonstrated that the productivity of sunflower hybrids varied greatly in response to N fertilization and different ecologies. Maximum achene yield of 3177 kg ha^?1 was harvested under sub-humid environment, followed by the semi-arid one. Among the hybrids, Hysun38 excelled the other two hybrids with a production of 3083 kg ha^?1 and 41% oil contents. Generally, the productivity of hybrids increased with the increasing doses of N fertilizer. Maximum achene yield was obtained by addition of 180 kg N ha^?1. The findings of the study revealed that yield potential of Hysun-38 could be exploited by addition of N fertilizer at the rate of 180 kg N ha^?1 under sub-humid environment.     

施氮量对枣棉间作棉花干物质积累，产量与品质的影响

研究了枣棉间作下棉花干物质积累与产量品质对不同施氮量的响应机制,确定枣棉间作的合理施氮量,为果棉间套作立体种植模式的合理氮肥运筹,提高棉花产量与品质提供理论依据。以在南疆的主栽棉花品种中棉所49为材料,研究了4个氮素水平（N 0、 150、 450 和750 kg/hm2）下棉花干物质的积累和产量的差异。结果表明,不同施氮量下棉花干物质累积存在显著差异,氮素缺乏或过量均影响其干物质在不同生育时期的累积量,使产量降低。施氮量对棉花品质也有显著影响,合理的氮肥用量不但能提高棉花单株结铃数和单铃重,从而提高产量,而且可使其有较好的整齐度,棉纤维长度,比强度和马克隆值。因此,在枣棉间作条件下,施氮量为N 450 kg/hm2 时棉花的干物质积累量较高,增产效果显著,品质较好。     

氮肥运筹对晚稻产量和氮素利用率的影响

用杂交水稻中优679为试验材料,研究氮肥运筹对晚稻产量和氮素利用率的影响。结果表明,在目标产量7 500 kg/hm2,总施氮量150 kg/hm2条件下氮肥运筹不同处理中,以基蘖肥∶穗肥=6∶4且基肥采用碳铵深施方式,其实际产量、齐穗后干物质生产量、成熟期干物质积累量、氮素利用率等均为最高。     

设施土壤有机氮组分及番茄产量对水氮调控的响应

【目的】酸解铵态氮和酸解氨基酸氮是土壤有机氮的主要组分,可表征土壤的供氮能力,并在氮素矿化、固定、迁移以及为植物生长供氮过程中起到至关重要的作用。研究水、氮调控下设施土壤有机氮组分和番茄产量的相互关系,为评价设施土壤肥力变化和制定科学合理的水、氮管理措施提供科学依据。【方法】田间定位试验在沈阳农业大学的温室内进行了5年,供试作物为番茄,栽培垄上覆盖薄膜,打孔移栽番茄幼苗,膜下滴灌。定位试验三个氮肥处理为施N75、300、525kg/hm^2,记为N1、N2和N3;三个灌水量为25、35和45kPa灌水下限(灌水始点土壤水吸力),记为W1、W2和W3,共9个肥水处理组合。在试验第五年番茄生长期(2016年4—8月)调查了番茄产量及其构成,在休闲期(2016年9月)测定0—10、10—20和20—30cm土层土壤有机氮组分、有机碳和全氮含量。【结果】9个处理中,土壤全氮、有机碳和除酸解氨基糖氮外的有机氮组分含量均随土层深度的增加而降低,且0—10、10—20和20—30cm土层间含量差异显著(P<0.05)。三个土层中酸解总氮占土壤全氮的66.0%、64.6%和55.2%,是土壤有机氮的主要存在形态。土壤酸解总氮中各组分含量及其所占比例的大小顺序为酸解氨基酸氮、酸解铵态氮>酸解未知态氮>酸解氨基糖氮。灌水下限和施氮量对番茄产量及单果重的影响均达极显著水平(P<0.01),水氮交互效应也达显著水平(P<0.05)。休闲期土壤酸解铵态氮与番茄产量间显著负相关(P<0.05)。番茄产量W1N2(25kPa+N300kg/hm^2)、W2N1(35kPa+N75kg/hm^2)和W1N1(25kPa+75kg/hm^2)处理间差异不显著。【结论】灌水和施氮量及其交互效应对各土层土壤全氮、酸解总氮、酸解铵态氮和酸解氨基酸氮的影响均达到极显著水平(P<0.01),而对土壤有机碳的影响不显著(P>0.05)。相同施氮量下,0—30cm土层酸解铵态氮和0—20cm土层酸解氨基酸氮含量均在土壤水吸力维持在35~6kPa范围内达最高值,此土壤水分含量下的0—20cm土层酸解氨基酸氮含量在施N75kg/hm^2时达到最大值。从节水减氮和番茄产量的角度考虑,控制土壤水吸力不低于35kPa、每季随水施N75kg/hm^2为供试番茄生产条件下最佳的水、氮组合量。     

Effect of copper and nitrogen nutrients on diosgenin production in fenugreek

Different amounts of nitrogen (N) and copper (Cu) in the forms of urea and copper sulfate (CuSO₄·5H₂O) were applied and their effects on diosgenin production and dry matter yield in fenugreek were investigated under farm cultivation conditions. High-performance liquid chromatography (HPLC) was employed to analyze diosgenin content. Diosgenin contents were measured in 25, 45 and 65 day-old leaves and in leaves at flowering stage and in fruits. The maximum diosgenin content was obtained in 45 day-old leaves. The results showed that simultaneous addition of Cu and N and the level of supply had significant effects on diosgenin production in leaves, fruits and dry matter yield. Simultaneous use of urea (100 kg ha^?1) and copper sulfate (30 kg ha^?1) increased diosgenin production and dry matter yield in 45 day-old leaves for 7.72 and 1.32 times, respectively, compared to unfertilized control group. But, the use of higher amounts of urea and copper showed a decrease in diosgenin production.     

不同施肥方式对超高产夏玉米叶绿素荧光特性及产量性状的影响

通过田间试验,研究了不同施肥方式下超高产夏玉米叶片叶绿素荧光参数、SOD活性、细胞膜稳定性及产量性状。结果表明,“种沟施肥+拔节期追氮+大喇叭口期追氮”有利于提高玉米叶片的PSⅡ原初光化学效率（Fv/Fm） 、PSⅡ量子效率（ΦPSII）和光化学猝灭系数（qP）, 降低非光化学猝灭系数（NPQ）。“种沟施肥+拔节期追氮+大喇叭口期追氮”和控释肥这两种施肥方式对提高叶片叶绿素含量和SOD活性,降低MDA含量和相对电导率的效果较好。控释肥对提高玉米子粒千粒重的效应较大,“种沟施肥+拔节期追氮+大喇叭口期追氮”显著提高玉米子粒产量。为了获得高产,应采用种沟施肥+拔节期追氮+大喇叭口期追氮的施肥方式,而控释肥则有利于简化施肥作业,提高劳动效率。     

Effect of N and P fertilization on yield and quality of Kochia grown in the greenhouse

Abstract

The use of kochia (Kochia scoparia (L.) Schrad.) as a forage crop has recently generated considerable interest, but little is known about how fertilization affects yield and quality. Two greenhouse experiments were conducted; the first with a clay loam soil and 0, 67 and 135 kg P/ha, and the second with a sandy loam soil and extremely high rates of P, which were 0, 4.5, 9.0, 13.5 and 17.9 ton P/ha. Both had 0, 84, 168 and 252 kg N/ha in a complete factorial with the P levels. In the first experiment, dry matter yield, root dry matter yield and flowering percentage increased linearly with N, while Ca, P and oxalate percentage decreased quadratically with N. Oxalate levels were low with a mean of 1.98%. Phosphorus levels affected only P percentage, which increased quadratically with P level. No interactions were observed between N and P in the first experiment.

In the second experiment, the high levels of P increased dry matter yield, crude protein and oxalate percentages, especially at low N levels. For these three parameters, there was an interaction between N and P. Phosphorus percentage increased guadra‐tically with P level up to 2.85% P, but decreased quadratically with N level. No interaction between N and P was observed for P percentage. Phosphorus levels reduced Ca percentage, but N had no effect. Oxalate levels were higher in the second experiment, with a mean of 5.23%, which might cause toxicity problems to livestock.     

底肥分层条施提高冬小麦干物质积累及产量

【目的】探讨底肥按比例分层条施对冬小麦群体动态变化、干物质积累与分配及籽粒产量的调节作用,为创建合理的耕层供肥条件提供理论依据。【方法】于2014～2015年和2015～2016年冬小麦生长季,在大田条件下,设置5种底肥施用方式:不施底肥 (T1);底肥单层条施在地表下8、16和24 cm (T2、T3和T4);底肥按1∶2∶3分为三份,分别施在地表下8、16和24 cm土层 (T5)。各处理均于拔节期随灌溉水追施氮肥,施肥量一致。调查了小麦关键生育期的生长和发育状况以及养分利用率。【结果】底肥单层条施时,在一定范围内随施肥深度增加,冬小麦分蘖和成穗数减少,但穗粒数显著增加,开花后干物质同化量提高,成熟期单茎干物质在各器官中的分配量增加,尽管开花后营养器官贮存的干物质向籽粒中的转移再分配受到抑制,但籽粒产量仍有一定程度的提高。与T4相比,T5的穗粒数和千粒重无明显变化,但植株分蘖和成穗数显著提高,开花后单位面积干物质积累量和籽粒产量均显著增加。【结论】通过优化养分在耕层土壤的分布,调节各生育阶段的养分供给,进而协调开花后干物质同化与营养器官临时贮存干物质再分配,及穗数与穗粒重之间的关系,在增加穗数的同时仍保持较高的穗粒数和千粒重,是底肥按比例分层条施实现冬小麦高产的重要原因。     

甘薯喷施烯效唑的适宜氮水平研究

【目的】 为获得甘薯最佳氮肥和烯效唑配施用量,比较了 6 个施氮水平下甘薯的干物质积累量 (DMA)、蔓薯比 (T/R)、各器官氮素含量、甘薯产量、氮素利用率及烯效唑贡献率 (UCR)的差异。探讨不同氮肥施用量下,叶面喷施烯效唑与济薯 22 生长及产量的关系。 【方法】 在山东平阴安城乡小官村开展甘薯氮肥田间试验,以不施肥为对照 (CK),设 6 个施氮量处理:0(N₀)、45 kg/hm2(N₁)、90 kg/hm2(N₂)、135 kg/hm2(N₃)、180 kg/hm2(N₄)、270 kg/hm2(N₅);每个水平设置喷施烯效唑 (N-U) 和不喷施两个处理,烯效唑喷施浓度为 25 mg/L。在移栽后 85 天、110 天和收获期,调查了甘薯的干物质积累量、氮素利用率和产量。 【结果】 1) 增施氮肥可明显增加甘薯地上部干物质积累量 (DMA)。喷施烯效唑施氮处理间,除 N₁-U 外,DMA 无明显差异,N₃-U、N₄-U 和 N₅-U 地上部 DMA 相对于氮处理显著降低,说明烯效唑喷施抑制了地上部分徒长;当施氮 量大于 90 kg/hm2 时,氮处理与 N-U 处理甘薯地下部 DMA 均明显降低,但 N-U 处理地下部 DMA 均高于氮处理,其中 N₁-U 和 N₂-U 与相对应N处理差异显著。2) 三个生育期的蔓薯比 (T/R),N-U 处理的值均有不同程度地下降,说明烯效唑可起到抑制地上部生长或促进地下部生长的作用。3) 喷施烯效唑提高了 85 天和 110 天甘薯蔓的氮含量,但对收获期影响不大;同一生育期内,氮处理与 N-U 处理块根氮含量曲线在 90 kg/hm2 附近出现交点,并随着生育期发展慢慢前移,表示可提高块根氮含量的最小施肥量为 90 kg/hm2。4) 氮 处理中产量最高为 N₁处理(N 45 kg/hm2),N-U 处理中产量最高为 N₂ (N 90 kg/hm2);当施氮量大于 90 kg/hm2 时,氮处理与 N-U 处理产量均显著降低;在同一氮水平下,喷施烯效唑可显著提高 CK-U 与 N₀-U 的产量。5) 氮处理中,氮肥贡献率 (FCR) 和农学效率 (AE) 随施氮量呈“V”型变化,N₁ 最高;喷施烯效唑使 N₂-U 处理的 FCR、AE 上升,其他处理均下降;偏生产力 (PFP) 随施氮量增加而降低,喷施烯效唑可使 N-U 处理 PFP 值上升;烯效唑对产量的贡献顺序为 N₂ > N₀ > CK > N₄ > N₃ > N₅ > N₁。 【结论】 氮肥施用量是影响甘薯产量的关键因素,本试验条件下,氮处理甘薯的最佳氮肥用量为 45 kg/hm2,N-U 处理甘薯的最佳氮肥用量为 90 kg/hm2,喷施烯效唑可提高甘薯产量,使地上、地下部协调生长。      

Response of mango tree nutritional status and biochemical constituents to boron and nitrogen fertilization

Abstract

A field experiment was conducted at Al Malak Valley Farm, El-Sharkeya Governorate-Egypt (30°–51° N; 32°–53° E) using 15 years old productive mango (Mangifera indica L.) trees cv. Zebda. The experiment was repeated for two successive seasons (2014/2015) and (2015/2016). The trees were planted 8×8 meters apart in sandy soil under drip irrigation system using the Nile water. Treatments included three concentrations of boron (0.0, 250, 500?mg L^?1) and three concentrations of nitrogen (1000, 1250, 1500?g nitrogen/tree/year). Boron was applied as foliar spray of boric acid and nitrogen was applied to the soil as ammonium sulfate. Treatments were arranged in a factorial Completely Randomized Block Design with three replicates for each treatment. Results show that boron application has improved mango tree nutritional status. Leaf nitrogen, phosphorus, potassium and boron concentrations significantly increased as the boron application rate increased. In addition, boron application resulted in significant increase in leaf total chlorophyll, total carbohydrates, total sugars, carbon/nitrogen (C/N) ratio and decrease in total phenol content. Boron showed higher impact than nitrogen on all tested parameters. The interaction treatment of 250?mg L^?1 boron and 1500?g/tree nitrogen proved to be the best treatment.     

春小麦光合生理和产量对干旱-复水的响应

为探究不同生育时期土壤干旱对不同抗旱性小麦品种光合生理特性和产量的影响,以抗旱性弱品种"新春22号(XC22)"和抗旱性强品种"新春6号(XC6)"为试验材料,在土柱栽培和大田条件下,分别设置常规灌溉(CK)、分蘖期轻度干旱(W1)、分蘖期中度干旱(W2)、拔节期轻度干旱(M1)和拔节期中度干旱(M2)5种处理,研究小麦叶片叶面积指数(LAI)、叶绿素含量、气体交换参数和叶绿素荧光参数及地上部干物质积累、穗重与产量的变化。结果表明:抗旱性弱品种"XC22"受水分胁迫影响更大,复水后恢复能力较弱,仅W1处理能恢复到与CK相等水平。同"XC22"相比,抗旱性强品种"XC6"在M1处理后,"补偿效应"表现更加明显,RuBPC酶活性、气体交换参数与叶绿素荧光参数均能在复水后快速恢复至CK水平,较其他处理恢复能力更强,乳熟期其净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)与叶绿素荧光参数的暗适应下最大荧光产量(Fm)、光适应下最大荧光产量(Fm'')、PSⅡ实际光合量子产量(ΦPSⅡ)、光化学淬灭系数(qp)较CK分别显著提高11.39%,7.50%,7.38%和7.86%,6.78%,17.24%,2.48%。轻度干旱处理并未减少小麦干物质积累和产量,反而有助于穗重的增加,且"XC6"在M1处理下,干物质积累、穗重与产量均显著高于CK。光合参数与产量的相关与通径分析表明,产量与Pn、Gs、Fm、Fm''、qp呈极显著正相关,且Pn在产量形成中的促进作用更大。春小麦花后光合生理特性的恢复与保持受拔节期水分胁迫影响更显著。在新疆滴灌模式下,生育前期轻度干旱胁迫,有利于抗旱性强品种小麦复水后光合性能改善,增加地上部干物质积累,促进光合产物向生殖器官的转运,有利于产量形成。     

施用有机肥条件下氮肥不同底追比对冬小麦干物质运转和籽粒产量的影响

以冬小麦品种‘临Y7287’为供试材料,秸秆还田条件下,研究了在等化肥施用量,额外增施生物有机肥,氮肥不同底追比对小麦生长发育、干物质运转和籽粒产量的影响。结果表明:与单施化肥相比,化肥与生物有机肥配施可显著提高冬小麦叶面积,提高灌浆期干物质累积量,促进干物质向籽粒转移,显著提高了千粒重、穗粒数和成穗数,从而提高了小麦产量。在配施生物有机肥4 500 kg·hm~(-2)条件下,以氮肥底追比为1∶1(即50%氮肥底施,50%氮肥拔节期追施)增产效果最好,较单施化肥成穗数提高了12.71%,穗粒数提高了4.93%,千粒重提高了6.42%,产量增加了11.27%。因此,推荐山西临汾盆地冬小麦施肥方案:以生物有机肥4 500 kg·hm~(-2)配施N 225 kg·hm~(-2),50%氮肥底施,50%拔节期追施较宜。     

大豆在不同铁水平下生理特性与品种耐性的关系

为了探明不同铁水平下大豆生理特性的变化与品种耐性的关系,以铁效率差异显著的铁高效(吉育99)和铁低效(吉育93)大豆品种为试材,采用水培方式,裂区设计,基因型为主区,铁处理为裂区,测定大豆抗氧化酶活性、叶绿素荧光参数、叶绿素相对值(SPAD)和干重,并通过典型性相关性分析、建立二次多项式逐步回归方程以及Logistic模型对测定指标进行分析。结果表明,铁胁迫条件下,大豆基因型、铁浓度,以及两者间的互作效应对大豆叶绿素荧光参数和抗氧化酶活性影响显著;铁高效品种的PSⅡ实际光化学量子效率(Phi PSⅡ)、电子传递速率(ETR)、暗适应下PSSⅡ的最大光化学效率(Fv/Fm)以及SOD、POD和CAT活性显著高于铁低效品种。典型性相关分析表明,过氧化氢清除能力与PSⅡ实际光化学效率显著相关。通过建立二次多项式逐步回归方程发现,2个品种的SPAD均与Fv/Fm呈正相关,干重与Phi PSⅡ呈正相关;铁高效品种的SPAD和干重均与Phi PSⅡ呈正相关,而铁低效品种SPAD和干重则与Fv/Fm呈正相关。Logistic模型分析表明,在低铁条件下,铁高效品种V和Vm均高于铁低效品种。综上,铁高效大豆品种在低铁条件下通过维持较高的CAT活性和Phi PSⅡ,避免膜质过氧化导致的光合能力下降,并通过提高V和Vm加快干物质的积累,增强对铁胁迫的耐性。本研究结果为大豆铁高效育种提供了一定的理论参考。     

Lettuce (Lactuca sativa L.) growth,yield and quality response to nitrogen fertilization in a non-circulating hydroponic system

The objective of this study was to determine the effect of nitrogen fertilization rate on growth and quality of leafy lettuce grown during the winter season in non-circulating hydroponic system. Plants were subjected to seven nitrogen (N) concentrations, i.e. 0, 30, 60, 90, 120, 150 and 180 mg L^?1 N using ammonium nitrate. Nitrogen treatments did not have a significant effect on leaf fresh and dry mass, root fresh and dry mass, number leaves and leaf area. Leaf ascorbic acid and total phenolic content, and antioxidant capacity peaked at 100 and 120 mg L^?1 N, whereas leaf chlorophyll concentration linearly increased with increasing N application. The results indicate that a solution N concentration of 100 and 120 mg L^?1 may be sufficient to improve growth, yield and quality parameters of leafy lettuce grown in non-circulating hydroponic system.     

施肥方式对滴灌加工番茄干物质积累、养分吸收和产量的影响

通过加工番茄大田试验,研究了不同施肥方式下,膜下滴灌加工番茄的干物质积累与养分吸收规律及产量构成。结果表明,在滴灌追施100%氮肥和初果期之后滴灌追施70%钾肥的基础上,基施65%磷肥和初果期之前滴灌追施35%磷肥(优化处理)比100%磷肥基施的加工番茄干物质增加11.51%,产量提高3.59%,氮、磷、钾肥的利用率分别增加了6.06、4.15和5.26个百分点。氮肥和磷肥在初果期之前滴灌追施,氮肥和钾肥在初果期之后滴灌追施的滴灌配方肥处理的产量显著低于优化处理,且优化处理的肥料效益也好于滴灌配方肥处理。加工番茄在初果期之前滴灌追施氮与磷,在初果期之后滴灌追施氮与钾可以提高加工番茄产量,增加肥料利用效率。     

温带牧草地牧草干物质量和N素产量的空间格局的时间稳定性

The objectives of the present study were to examine the spatial patterns of sward dry matter （DM） and nitrogen （N） yields in a grass silage field at first, second, and third cuts over a 3-year period; quantify their temporal stabilities with temporal stability maps; and assess the potential for site-specific management in each pasture-growing period using classified management maps. At cut 1, the spatial patterns of DM and N yields proved to be well defined and temporally stable and were likely to be due to differences in the net N mineralization rates across the field during spring. In contrast, at cut 2, the patterns of DM production were patchy and temporally unstable. It was concluded that, in principle, a simple site-specific approach to N fertilization would be possible in this field during spring at cut 1. At later harvests, the rationale for a site-specific approach to fertilizer management was less clear with logistics appearing to be more complex and less feasible.