Responses of chlorophyll fluorescence and nitrogen level of Leymus chinensis seedling to changes of soil moisture and temperature

Controlled experiment of Leymus chinensis seedlings grown in the environmental growth chambers at 3 soil moisture levels and 3 temperature levels was conducted in order to improve the understanding how leaf photosynthetic parameters will respond to climatic change. The results indicated that soil drought and high temperature decreased the photochemical efficiency of photosystem(F v/F m), the overall photochemical quantum yield of PSII(yield), the coefficient of photochemical fluorescence quenching(q\-P), but increased the coefficient of non-photochemical fluorescence quenching(q\-N). Severe soil drought would decrease F v/F m and yield by 3.12% and 37.04% under 26℃ condition, respectively, and 6.60% and 73.33% under 32℃ condition, respectively, suggesting that higher temperature may enhance the negative effects of soil drought. All the soil drought treatments resulted in the decline in leaf nitrogen content. There was no significant effect of temperature on leaf nitrogen level, but higher temperature significantly reduced the root nitrogen content and the ratio of root nitrogen to leaf nitrogen, indicating the different strategies of adaptation to soil drought and temperature. It was also implied that higher temperature would enhance the effect of soil drought on leaf photosynthetic capacity, decrease the adaptability of Leymus chinensis to drought.

Evaluating the Impact of Different Tillage Regimes and Nitrogen Levels on Yield and Yield Components of Maize (Zea mays L.)

A field study to evaluate the impact of different tillage regimes and nitrogen levels on yield and yield components of maize (Zea mays L.), was conducted during autumn 2014 at Students Farm, Department of Agronomy, University of Agriculture, Faisalabad. The experiment was laid out in RCBD (Randomized Complete Block Design), with split plot arrangement having three replications. The experiment was comprised of three tillage regimes (Minimum, Conventional and Deep) and three nitrogen levels viz: 100, 200 and 300 kg•ha-1. Urea was used as a source of nitrogen, sulphate of potash as a source of potassium and triple super phosphate as a source of phosphorous. The amount of phosphorous and potash was constant in all the treatments i.e. 125 kg•ha-1 and 100 kg•ha-1 respectively. Results of present study are summarized as yield parameters are significantly affected by different nitrogen levels and tillage regimes. Maximum number of plants at harvest (7.93), number of grain rows per cob (17.70), number of grains per row (34.31), number of grains per cob (678.58), and cob weight (187.50 g) were observed in deep tillage at 200 kg•ha-1 nitrogen application. 1000-grain weight (275.52 g), biological yield (15.66 t•ha-1), grain yield (6.16 t•ha-1) and dried stalk yield (9.91 t•ha-1) were observed maximum in deep tillage at 200 kg•ha-1 nitrogen application. Harvest index significantly affected by tillage regimes and maximum harvest index (39.58%) were recorded in deep tillage which was statistically at par with conventional tillage (38.83%). It was concluded that higher grain yield of maize can be obtained by deep tillage with the application of 200 kg•ha-1 nitrogen application under the prevailing conditions of Faisalabad.

Research on Glutamate Dehydrogenase Activity in Sugar Beet (Beta vulgaris L) under Different Nitrogen Levels

The experiment of Glutamate Dehydrogenase (GDH) activity in various plant parts under different nitrogen levels in frame culture during the whole period of growth was carried out on campus of Northeast Agricltural University in 1993. The result showed that GDH activity in leaf blades under four nitrogen applied levels rose rapidly to the acme from the seedling to foliage rapid growth stage, then diminished rapidly to the lower level at the latter stage of foliage rapid growth. This level was kept to harvest. GDH activity in roots at each growth stage under all nitrogen levels exhibited little disparity and did not show ostensible regularity of changes. GDH activity in leaf blades was stimulated with nitrogen, however, it reduced with nitrogen fertilizer applying further. GDH activity in leaf blades was the biggest compared with crowns, petioles and roots, which suggested that it could represent the highest enzyme activityof the whole plant.

Liquid nitrogen level meter for high-temperature superconductor (HTS)

Many kinds of high temperature superconductor (HTS) power machines such as HTS cable,HTS fault current limiter and HTS magnet are cooled by liquid nitrogen.The level of liquid nitrogen should be monitored and controlled to ensure the thermal stability and the dielectric strength as well.To measure the level,capacitance method and differential pressure method are usually used.However,each method has installation difficulties and measurement errors for unsteady state operation with varying system pressure.A new liquid level meter using a 2G HTS conductor is described,which has similar structure with the liquid helium level meter with NbTi filament.The level meter is fabricated with a parallel connected heater,which helps the separation of the superconducting region and normal region,considering the critical temperature,large heat capacity of conductor and cooling characteristics.The level of liquid nitrogen can be obtained from the measured voltage signal along the 2G HTS conductor.Design,fabrication and test results of the new liquid nitrogen level meter are presented.

Studies on Glutamine Synthetase Activity in Sugar Beet （BetavulgarisL．） under Different Levels of Nitrogen

It was shown from the experiment that glutamine synthetase activity (GSA) in both leaf blades and roots under different nitrogen levels rose rapidly to reach its peak from seedling stage to foliage rapid growth stage and declined to its lowest level at the latter stage of root rapid growth, and then increased slightly. GSA in leaf blades had positive correlation with nitrogen level during the whole period of growth. GSA in roots showed the same tendency as it in leaf blades at the early middle stage of growth, but at the latter stage of growth, no positive correlation was established. GSA in leaf blades was the strongest compared with crowns, petioles and roots, and could represent the highest enzyme activity of the whole plant. GSA had quadratic curvilinear correlation with root yield and sugar production. GSA in leaf blades had significant positive correlation with α-NH2-N at the foliage rapid growth stage.

Research on Glutamate Synthase Activity in Sugar Beet(Beta Vulgaris L.)under Different Levels of Nitrogen

The experiment of glutamate synthase activity (GOGATA) in both leaf blades and roots under different nitrogen levels was carried out at Northeast Agricultural University in 1993. The result showed that GOGATA rose rapidly to reach its peak from seedling stage to foliage rapid growth stage, and then declined gradually. GOGATA was enhanced with increasing nitrogen levels and had significant positive correlation with nitrogen levels at the middle stage of growth GOGATA in leaf blades was the strongest compared with crowns, petioles and roots, thus, it could represent the highest enzyme activity of the whole plant. GOGATA had quadratic curvilinear correlation with root yield and sugar production. GOGATA in leaf blades had significant positive correlation with α-NH 2-N at the foliage rapid growth stage while GOGATA in roots existed this relation at the latter stage of growth. GOGATA in roots had significant negative correlation with sugar content at harvest.

Effects of Nitrogen Application Levels on Ammonia Volatilization and Nitrogen Utilization during Rice Growing Season

We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4＋-N in surface water, loss of ammonia through volatilization from paddy fields, rice production, nitrogen-use efficiency, and nitrogen content in the soil profile. The concentration of NH4＋-N in surface water and the amount of ammonia lost through volatilization increased with increasing nitrogen application level, and peaked at 1-3 d after nitrogen application. Less ammonia was lost via volatilization from clay soil than from sandy soil. The amounts of ammonia lost via volatilization after nitrogen application differed depending on the stage when it was applied, from the highest loss to the lowest： N application to promote tillering 〉 the first N topdressing to promote panicle initiation （applied at the last 4-leaf stage） 〉 basal fertilizer 〉 the second N topdressing to promote panicle initiation （applied at the last 2-leaf stage）. The total loss of ammonia via volatilization from clay soil was 10.49-87.06 kg/hm2, equivalent to 10.92%-21.76% of the nitrogen applied. The total loss of ammonia via volatilization from sandy soil was 11.32-102.43 kg/hm2, equivalent to 11.32%-25.61 % of the nitrogen applied. The amount of ammonia lost via volatilization and the concentration of NH4＋-N in surface water peaked simultaneously after nitrogen application; both showed maxima at the tillering stage with the ratio between them ranging from 23.76% to 33.65%. With the increase in nitrogen application level, rice production and nitrogen accumulation in plants increased, but nitrogen-use efficiency decreased. Rice production and nitrogen accumulation in plants were slightly higher in clay soil than in sandy soil. In the soil, the nitrogen content was the lowest at a depth of 40-50 cm. In any specific soil layer, the soil nitrogen content increased with increasing nitrogen application level, and the soil nitrogen content was higher in clay soil than in sandy soil. In terms of ammonia volatilization, the amount of ammonia lost via volatilization increased markedly when the nitrogen application level exceeded 250 kg/hm2 in the rice growing season. However, for rice production, a suitable nitrogen application level is approximately 300 kg/hm2. Therefore, taking the needs for high crop yields and environmental protection into account, the appropriate nitrogen application level was 250-300 kg/hm2 in these conditions.

Seasonal Dynamics of Nitrogen and Phosphorus in Water and Sediment of A Multi-level Ditch System in Sanjiang Plain,Northeast China

The multi-level ditch system developed in the Sanjiang Plain,Northeast China has sped up water drainage process hence transferred more pollutants from farmlands into the rivers of this region.Understanding the seasonal dynamics of nitrogen (N) and phosphorus (P) transportation in the ditch system and the role of different ditch size is thus crucial for water pollution control of the rivers in the Sanjiang Plain.In this study,an investigation was conducted in the Nongjiang watershed of the Sanjiang Plain to study the nutrient variation and the correlation between water and sediments in the ditch system in terms of ditch level.Water and sediments samples were collected in each ditch level in growing season at regular intervals (once per month),and TN,NO 3--N,NH 4+-N,TP,and PO 4 3--P were analyzed.The results show that nutrient contents in water were higher in June and July,especially in July,the contents of TN and TP were 3.21mg/L and 0.84mg/L in field ditch,4.04mg/L and 1.06mg/L in lateral ditch,2.46mg/L and 0.70mg/L in branch ditch,1.92mg/L and 0.63mg/L in main ditch,respectively.In August and September,the nutrient contents in the water were relatively lower.The peak value of nutrient in ditch water had been moving from the field ditch to the main ditch over time,showing a remarkable impact of ditch system on river water environment.The nutrient transfer in ditch sediments could only be found in rainfall season.Nutrient contents in ditch sediment had effect on that in ditch water,but nutrients in ditch water and sediments had different origination.Ditch management in terms of the key fac-tors is hence very important for protecting river water environment.

Effects of Nitrogen Top-dressing Levels on Carbon-nitrogen Metabolism and Yield of Desmodium styracifoliumon

In order to research effects of the nitrogen top-dressing levels on carbon-nitrogen metabolism and yield of Desmodium styracifolium, a field experiment was conducted on the research farm of Guangxi University in 2007. Some physiological indexes and yield ofD. styracifolium were compared among five nitrogen top-dressing levels （0, 37.5, 75.0, 112.5 and 150.0 kg N. hm-2）. Results showed that the nitrogen top-dressing could significantly increase the contents of chlorophyll, soluble protein, sucrose and nitrogen as well as nitrate reducase activity. However, there were no significant differences in most of these indexes under high nitrogen levels. Consistently, there was no significant difference in yield among nitrogen top-dressing levels of 75 kg N.hm-2, 112.5 kg N. hm-2 and 150 kg N-hm-2. Therefore, the optimum nitrogen top-dressing level ofD. styracifolium was 75 kg N. hm-2.

不同施氮水平下硅肥对谷子抗倒伏能力、产量和品质的影响

[目的]倒伏严重影响谷子产量和品质。探究不同施氮水平下硅肥提高谷子茎秆强度、产量及品质的作用,为谷子高产高效施肥提供技术方案。[方法]以晋谷21和张杂13为供试谷子品种,在山西太谷进行大田试验。在常规施氮量N_(1)(180 kg/hm^(2))和高施氮量N_(2)(450 kg/hm^(2))下,分别设置不施硅、施用硅酸钠(Si_(1),SiO_(2) 68.85 kg/hm^(2))和硅钙肥(Si_(2),SiO_(2) 67.2 kg/hm^(2)),共6个处理。在谷子成熟期测量其株高、抗倒伏能力相关指标、光合特性、产量和品质相关指标,并观察茎秆横切面显微结构。[结果]N_(1)水平下,施用硅肥降低了谷子基节长度,增加了茎粗、茎秆抗折力和穿刺力,晋谷21和张杂13两品种前五基节的节间长度分别降低了4.1%~30.1%和9.5%~11.5%,茎粗分别增加5.3%~19.4%和13.0%~34.1%;晋谷21抗倒性在N_(1)-Si_(1)处理较强,第一、第二基节抗倒伏指数较N_(1)-Si_0处理分别增加37.4%和35.8%,张杂13在N_(1)-Si_(2)处理时较强,第一、第二基节抗倒伏指数较N_(1)-Si_0处理分别增加136.0%和94.7%。N_(2)水平下,施用硅肥后晋谷21和张杂13前五基节的节间长度分别降低了9.6%~30.3%和10.6%~14.9%,茎粗分别增加了9.56%~23.9%和16.2%~31.0%,茎秆扁平度降低。硅钙肥对谷子茎秆强度影响大于硅酸钠,N_(2)-Si_(2)处理晋谷21的第二基节抗折力、穿刺力和抗倒伏指数比N_(2)-Si_0分别增加97.9%、77.6%和83.3%,张杂13的第一基节抗折力、穿刺力和抗倒伏指数比N_(2)-Si_0分别增加74.0%、66.8%和128%。施硅后谷子茎秆中机械组织增厚,维管束数量增多且排列均匀,向茎秆中心延伸,且在N_(2)水平下,硅钙肥作用效果优于硅酸钠。硅可促进谷子穗码发育,增加穗粗、穗粒数和千粒重,在高氮水平下硅钙肥处理使晋谷21和张杂13的产量分别增加23.8%和24.0%。施用硅肥能够提高谷子脂肪、蛋白质和氨基酸含量,在高氮水平下可以降低谷子直链淀粉/支链淀粉值。[结论]在高氮条件下,施用硅钙肥使谷子前五基节长度降低,茎粗增加,机械强度增加,进而提高抗倒伏能力;施用硅肥还可增加光合速率和蒸腾速率,促进物质积累和运输,增加产量,改善品质。

两种产量水平下超级杂交稻氮素吸收利用特性

探明不同产量水平下超级杂交稻的氮素吸收利用特性,可为我国西南稻区超级杂交稻高产栽培和育种提供理论和实践依据。以2个超级杂交稻品种(‘德优4727’‘泸优727’)和2个高产常规稻品种(‘金农丝苗’‘黄华占’)为材料,于2018—2020年在四川省德阳市(高产点)和泸州市(中产点)两个生态点进行大田和盆栽试验,研究两种产量水平下超级杂交稻氮素吸收、转运及利用效率的差异。结果表明:大田条件下不同生态点间超级杂交稻产量、氮素吸收积累利用特性差异显著。高产点超级杂交稻产量、氮肥偏生产力较中产点分别增加8.3%~23.2%、8.3%~23.1%。高产点超级杂交稻播种(SO)—幼穗分化(PI)、PI—齐穗(HD)阶段氮素吸收量和氮素吸收速率(除2018年幼穗分化—齐穗外)均高于中产点,HD—成熟(MA)阶段仍保持较高的氮素吸收量。高产点超级杂交稻成熟期氮素总吸收量较中产点增加15.6%~33.7%。尽管高产点超级杂交稻氮素收获指数较中产点平均增加4.6%(2018年除外),但成熟期仍有大量氮素滞留在超级杂交稻的秸秆中,造成高产点氮素籽粒生产效率较中产点平均减少11.3%。方差分析表明,盆栽条件下土壤、土壤×地点、土壤×品种互作对超级杂交稻产量、氮素吸收量、氮素籽粒生产效率影响不显著。高产点盆栽超级杂交稻产量、氮素吸收量、氮素籽粒生产效率变化趋势与大田试验相似。高产点SO—PI平均温度高于中产点,HD—MA平均温度低于中产点;高产点SO—PI、PI—HD和HD—MA太阳辐射积累量(除2018年PI-HD外)均高于中产点。相关分析表明,高产点籽粒产量与PI—HD氮素吸收量、氮素收获指数呈显著正相关;氮素籽粒生产效率与SO—PI的氮素吸收量和平均温度呈显著负相关。中产点籽粒产量与氮素籽粒生产效率、总吸氮量呈显著正相关;氮素籽粒生产效率与SO—PI和HD—MA的平均温度呈显著负相关。因此,不同产量水平超级杂交稻产量和氮素吸收利用特性差异主要与不同生育期内的平均温度和太阳辐射有关。

大白菜CHS基因鉴定及其在高氮水平下转录表达分析

为了探究高氮水平引起大白菜叶柄黑点症加剧的机制,通过对抗、感叶柄黑点症大白菜品系进行正常氮和高氮水平处理,处理前和处理后不同时间对叶柄取样并进行转录组测序,然后再对大白菜查尔酮合酶(chalcone synthetase,CHS)基因进行鉴定并分析不同的大白菜CHS基因在正常氮水平和高氮水平、抗性品系和感性品系之间的差异表达,结果表明,共鉴定到7个大白菜CHS基因,其中有3个(BrCHS1、BrCHS3及BrCHS4)在高氮水平下表达量比正常氮水平下高,且在高氮水平下感性品系表达量高于抗性品系。因此推测这3个大白菜CHS基因可能与大白菜叶柄黑点症的形成有关。研究结果为揭示大白菜叶柄黑点症发生机制奠定了基础。

不同施氮水平对黑钙土花生碳氮代谢相关酶活性、产量和品质的影响

为探讨黑钙土花生适宜施氮量,本研究以吉花25为试验材料,共设置6个氮肥水平,分别为施用纯氮0、112.5(传统施肥,N1)、90(减氮20%)、79.5(减氮30%)、159(增氮40%)、225 kg/hm^(2)(增氮100%),研究了氮肥对花生碳氮代谢相关酶的活性、产量和品质的影响。结果表明,施用氮肥会提高硝酸还原酶(NR)活性、谷氨酰胺合成酶(GS)活性和谷氨酸脱氢酶(GDH)活性、蔗糖合成酶(SS)和蔗糖磷酸合成酶(SPS)活性,但过量施用氮肥会抑制NR、GS、GDH、SS和SPS活性。各施氮处理产量均高于对照,在传统施肥的基础上减氮施肥20%(施氮量90 kg/hm^(2))时,花生产量最高,与对照相比增产9.21%,相较于传统施肥增产1.57%,说明减氮20%即可既满足花生生长发育的氮肥需求,同时又能保证叶片中碳氮代谢相关酶的活性,增强了花生对氮素的吸收与利用的能力,并通过降低单株秕果数和单株单果数,提高单株双果数、百果重和百仁重,最终提高花生产量。

施氮水平对不同切花菊品种生长及氮素累积和分配的影响

[目的]针对当前菊花生产中氮肥使用过量、氮效率低下和不同氮素营养特性菊花品种氮素吸收及分配规律不明等问题,本文研究不同施氮水平对不同切花菊生长、氮效率及氮素累积和分配的影响,以明确不同切花菊品种对氮素吸收利用特性,为切花菊的高效生产提供理论依据。[方法]以9个不同家系的切花菊品种为材料,测定了高氮(每株800 mg)、正常氮(每株400 mg)和低氮水平(每株50 mg)下,9个切花菊品种全生育期生长指标、氮效率指标和各部位氮素累积量。[结果]9个切花菊品种的株高、茎粗、叶干重、茎干重、根干重、总根长、一级分枝数、着花数等生长指标和根氮累积量、叶氮累积量、植株氮累积量等氮累积量指标均随氮水平的增加而增加,氮效率指标随氮水平的增加而降低;正常氮水平下,9个菊花品种的花干重、冠幅、花径和花氮累积量最高,花期最早。不同氮水平下,‘南农丽黄’在茎粗、各部位生物量、平均根直径、根体积、冠幅、花径、氮吸收效率、农艺氮效率、植株氮累积量和花氮累积量指标上显著高于其他品种(P<0.05);‘南农雪峰’和‘南农紫峰’的株高、茎粗、各部位生物量、冠幅、花径、氮吸收效率、农艺氮效率和植株氮累积量较其他品种低。苗期和生殖生长期间,9个菊花品种植株中叶氮累积量最高,茎次之,根最低;盛花期时,植株中叶和茎氮累积量比例显著下降,花器官的氮累积量显著高于其他器官。不同氮水平下,9个菊花品种的植株氮累积量与花干重、冠幅、花径、一级分枝数、着花数、花期呈显著正相关(0.39≤r≤0.83),花氮累积量与花干重、花期呈显著正相关(0.53≤r≤0.89)。[结论]高氮水平促进了菊花的营养生长,抑制了菊花的氮效率和品质形成,菊花的全生育期生长规律和氮素累积分配规律一致,植株氮累积量和花氮累积量对菊花开花品质的形成具关键作用。

施氮水平对谷子干物质积累分配及氮素利用率的影响

为探明施氮水平对谷子干物质积累分配和氮素利用的影响,在西北半干旱雨养农业区,以常规种陇谷13号和杂交种张杂谷13号为试验材料,设置4个氮浓度梯度:0(N_(ck))、45(N_(低))、90(N_(中))、135(N_(高))kg/hm~2,测定2个品种在不同施氮水平下的产量、干物质积累、分配和氮素利用效率。结果表明,陇谷13号在N_(高)处理下,较N_(ck)处理花后干物质对籽粒贡献率提高32.5%、穗粒质量提高30.0%、株高提高14.5%、籽粒干物质积累量提高20.5%,产量增加11.1%;张杂谷13号在N_(中)处理下较N_(ck)处理花后干物质对籽粒贡献率提高21.0%、穗粒质量提高20.7%、籽粒干物质积累量提高21.5%、产量增加11.6%。陇谷13号在N_(中)处理下氮肥农学效率最高,为3.75 kg/kg;而张杂谷13号在N_(低)处理下氮肥农学效率最高,为9.57 kg/kg。在不同的施氮水平下,陇谷13号氮肥用量为135 kg/hm~2时产量最高,张杂谷13号氮肥用量为90 kg/hm~2时产量最高,表明杂交谷子品种更耐低氮环境,是化肥减氮生产中的优势品种类型。

不同施氮量对麻竹光合特性和氮代谢关键酶活性的影响

本试验以麻竹为材料,分别设置0 g/丛(N0,对照)、11.2 g/丛(N1)、13.5 g/丛(N2)、22.5 g/丛(N3)共4个施氮量水平,于盆栽条件下研究不同施氮量对笋期麻竹叶片光合特性、氮代谢关键酶活性及出笋数量的影响,并分析出笋数量与各出笋期叶片光合特性、氮代谢关键酶活性的相关性。结果表明,施用氮肥可显著增强笋期麻竹叶片光合特性、氮代谢关键酶活性,显著提高出笋数量。麻竹叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)活性及出笋数量均随施氮量的增加而增加,N3处理即施氮量为22.5 g/丛时各指标达到最大值,而胞间二氧化碳(Ci)则呈相反趋势。相关性分析表明,各出笋期叶片Pn、Gs、Tr和NR、GS、GOGAT活性与出笋数量呈极显著正相关关系。综上看出,施氮量22.5 g/丛(N3)能够更好地协调碳氮代谢水平,增强麻竹光合特性,提高氮代谢关键酶活性,增加麻竹出笋数量。

不同施氮水平对油莎豆农田土壤养分表观平衡和块茎产量的影响

研究不同施氮水平下沙质土壤油莎豆(Cyperus esculentus)土壤养分表观平衡及块茎产量,为沙质土壤油莎豆科学施氮提供理论依据。以油莎豆品种“中油莎1号”为研究对象,分别设置0 kg·hm^(-2)(N0)、75 kg·hm^(-2)(N1)、150 kg·hm^(-2)(N2)、225 kg·hm^(-2)(N3)4个施氮水平。分析4个施氮水平对油莎豆农艺性状、土壤表观养分平衡及块茎产量的影响。结果表明:随着施氮量增加,两地油莎豆茎蘖数、株高、单片叶面积等均有增加,但过高的施氮量会造成油莎豆地上部徒长,导致产量下降;施氮量为150 kg·hm^(-2)(N2),油莎豆最大根长、根体积等农艺性状最优,油莎豆整株干重及块茎产量均最高,块茎鲜产可达到9298.87~10336.06 kg·hm^(-2);两地氮素表观盈余率在0 kg·hm^(-2)(N0)和75 kg·hm^(-2)(N1)水平下均为负值,150 kg·hm^(-2)(N2)和225 kg·hm^(-2)(N3)水平下均为正值,表明两地氮素均在N2水平即施氮量为150 kg·hm^(-2)时达到氮素平衡状态。冗余分析也表明油莎豆茎蘖数、最大根长、根体积、氮携出量是驱动油莎豆干物质及块茎产量形成的主要因素。因此在北方沙质土壤条件下,N素施入量为150 kg·hm^(-2)时,可促进油莎豆对养分的吸收、维持土壤表观养分平衡,有利于油莎豆良好的生长发育和产量的提高。

聚天门冬氨酸和壳聚糖复配剂对谷子光合生理特性及产量的影响

为研究聚天门冬氨酸和壳聚糖复配剂(PAC)对不同施氮量下谷子叶片光合生理特性及产量的影响,于2021-2022年在中国农业科学院作物科学研究所公主岭试验站开展大田试验,以华优谷9号为材料,设置常规氮素(CN)和PAC配合氮素(PN)的不同施氮量(0、75、112.5、150、225和337.5 kg·hm^(-2))全基施处理。结果表明,随施氮量增加,谷子叶面积指数和干物质积累量呈升高趋势,功能叶叶绿素含量、净光合速率、核酮糖-1,5-二磷酸(RuBP)羧化酶活性、磷酸烯醇式丙酮酸(PEP)羧化酶活性和产量均呈先升高后降低趋势。在同一施氮量下,PN处理可以提高谷子叶面积指数、干物质积累量、功能叶叶绿素含量、RuBP羧化酶和PEP羧化酶活性以及花期和灌浆中期净光合速率。2021和2022年PN较CN处理谷子产量增幅分别为10.43%~16.17%和3.64%~23.60%,其增产效果在中、低氮水平(75、112.5、150 kg·hm^(-2))下更为显著。综上,PAC配合适量氮肥全基施可增强谷子叶片光合能力,提高谷子产量,可作为一项增产增效的生产技术应用于我国谷子生产。

不同蓝莓品种幼苗氮素利用效率和适宜施氮水平分析

为筛选蓝莓(Vaccinium spp.)氮高效品种及探究不同蓝莓品种幼苗的适宜施氮水平,本研究以长江流域4个蓝莓主栽品种‘莱格西’(‘Legacy’)、‘绿宝石’(‘Emerald’)、‘优瑞卡’(‘Eureka’)和‘蓝美1号’(‘Lanmei 1’)为实验材料,通过盆栽实验,设置不施氮(0.000 g·kg^(-1))、低氮(0.214 g·kg^(-1))、中氮(0.429 g·kg^(-1))和高氮(0.857 g·kg^(-1))4个处理,分析不同施氮水平下不同蓝莓品种幼苗农艺性状及氮素利用效率的差异。结果显示:‘莱格西’和‘绿宝石’属于低氮高效型,‘优瑞卡’属于中氮高效型,‘蓝美1号’属于氮高效型。随着施氮水平的提高,4个蓝莓品种幼苗的单株干质量增加量,株高,冠幅,基径,叶片叶绿素相对含量,根、茎、叶和单株氮素增加量,以及单株磷素增加量总体呈上升趋势;单株分枝数和单株钾素增加量呈先上升后趋于稳定的变化趋势;氮素效率、氮素吸收效率和氮素生理利用效率总体呈先上升后下降的变化趋势;根冠比则总体呈下降趋势。相关性分析结果显示:在不施氮和3个施氮水平下,蓝莓幼苗的氮素效率与单株干质量增加量、茎氮素增加量、单株氮素增加量、单株磷素增加量、单株钾素增加量、氮素吸收效率均呈显著(P<0.05)或极显著(P<0.01)正相关。综合分析结果表明:‘蓝美1号’为氮高效品种,可作为氮高效遗传改良种质资源;单株干质量增加量可作为蓝莓氮素利用效率评价的重要指标;氮高效品种‘蓝美1号’和中氮高效品种‘优瑞卡’幼苗的推荐施氮水平为0.429 g·kg^(-1),低氮高效品种‘莱格西’和‘绿宝石’幼苗的推荐施氮水平为0.214 g·kg^(-1)。

基于模型剪枝的棉花氮素营养水平诊断

确定棉花的氮素营养水平是实施精准施肥的先决条件和基础。近年来,深度学习逐渐应用于氮素营养水平诊断中,但该方法对高性能设备的依赖性较高,限制了其在资源受限边缘设备上的部署应用。针对这一问题,该研究提出一种基于树莓派4B的棉花氮素营养水平诊断方法。研究采用ResNet101网络构建诊断模型,并通过网络瘦身算法对模型进行剪枝优化,最终将剪枝比例为87%的模型部署在资源受限的树莓派4B上。试验结果表明:当剪枝比例达到87%时,模型精度损失2.55个百分点,同时剪枝后模型参数量、计算量和存储体积分别为4.37 M、1.05 G和16.65 MB,明显提高模型在计算能力有限设备上的推理速度,有助于快速、准确地评估田间棉花的氮素营养状况,从而实现对棉花的精准施肥,提高产量和质量。该研究不仅为实现棉花氮素营养水平的大面积快速诊断提供了技术参考,同时对于作物营养水平诊断的智能终端装备研发具有参考价值。