Sesbania rostrata as a green manure for lowland rice: Growth,N2 fixation,Azorhizobium sp. inoculation,and effects on succeeding crop yields and nitrogen balance

Summary Root and stem nodulation, nitrogen fixation (acetylene-reducing activity), growth and N accumulation bySesbania rostrata as affected by season and inoculation were studied in a pot experiment. The effects ofS. rostrata as a green manure on succeeding wet-season and dry-season rice yields and total N balance were also studied.S. rostrata grown during the wet season showed better growth, nodulation, and greater acetylene-reducing activity than that grown during the dry season. Inoculation withAzorhizobium caulinodans ORS 571 StrSpc® (resistant to streptomycin and spectinomycin) on the stem alone or on both root and stem significantly increased N₂ fixation by the plants. Soil and seed inoculation yielded active root nodules under flooded conditions. Plants that were not inoculated on the stem did not develop stem nodules. The nitrogenase activity of the root nodules was greater than that of the stem nodules in about 50-day-oldS. rostrata. S. rostrata incorporation, irrespective of inoculation, significantly increased the grain yield and N uptake of the succeeding wet season and dry season rice crops. The inoculated treatments produced a significantly greater N gain (873 mg N pot^–1) than the noinoculation (712 mg N pot^–1) treatment. About 80% of the N gained was transferred to the succeeding rice crops and about 20% remained in the soil. The soil N in the flooded fallow-rice treatment significantly declined (–140 mg N pot^–1) but significantly increased in bothS. rostrata-rice treatments (159 and 151 mg N pot^–1 in uninoculated and inoculated treatments respectively). The N-balance data gave extrapolated values of N₂ fixed per hectare at about 303 kg N ha^–1 per two crops forS. rostrata (uninoculated)-rice and 383 forS. rostrata (inoculated)-rice.     

CO2浓度升高、氮与土壤水分对春小麦生长及干物质积累的效应

大型人工气候室条件下进行了350μmol/mol和700μmol/mol 2种CO_2浓度,湿润及干旱2种水分处理和0mg/kg_土、50mg/kg_土、100mg/kg_土、150mg/kg_土和200mg/kg_土5种N肥施用量试验结果表明,高CO_2浓度下春小麦分蘖并未增加,低N时分蘖明显降低,因而高CO_2浓度下春小麦分蘖必须补充足够N素。CO_2浓度增高下播后55d施用N肥,春小麦叶宽、叶面积指数均增加,而不施N肥叶宽、叶面积指数未增加。充足N肥和水分有利于促进春小麦叶片生长,明显提高叶面积和分蘖。CO_2浓度增高,春小麦地上部干物质量增加与N肥施用量有关,中N和高N处理地上部干物质量明显增加,而不施N和低N时则增加不明显。干旱条件且高CO_2浓度下地上部干物质量增幅低于湿润条件,因而CO_2浓度升高对N素和水分胁迫无明显补偿作用。且CO_2浓度升高其根干物质量和根冠比未增加,相反湿润条件下不施N处理根干物质量略有降低,而根冠比明显降低。     

Effects of Inoculation with Glomus mosseae in Conventionally Tilled and Nontilled Soils with Different Levels of Nitrogen Fertilization on Wheat Growth,Arbuscular Mycorrhizal Colonization,and Nitrogen Nutrition

Evaluation of the performance of inoculants in undisturbed and unsterilized soils, where diverse communities of microorganisms are present, is a necessary step before using arbuscular mycorrhizal fungi (AMF) in agricultural technology. The effects of inoculation with Glomus mosseae on arbuscular mycorrhizal colonization, growth, and nitrogen (N) uptake of wheat plants in unsterilized tilled and untilled soils from the Argentinean Pampas with different levels of N fertilization were assessed. The fertilization and inoculation effects depended on the tillage treatments. In no-tillage, the colonization was greater than in conventional tillage, but it was reduced by the N fertilization. In conventional tillage, the inoculation with G. mosseae increased colonization. Both conventional tillage and N fertilization promoted wheat root growth. Inoculation did not affect root growth but enhanced N concentration in roots when fertilizer was not applied.     

头季稻氮肥运筹对再生稻干物质积累、产量及氮素利用率的影响

为探讨头季稻不同肥料运筹方式对再生稻产量和氮素利用率的影响,以杂交稻组合"Ⅱ优航2号"为材料,在头季施氮量225.00kg·hm-2的基础上,研究了不同基蘖穗肥氮素配比[3种基蘖肥与穗肥配比分别为8:2(N1)、7:3(N2)、6:4(N3)]头季稻-再生季稻氮素累积量、干物质生产、产量及氮素利用率的特性。结果表明:与N1、N2相比,头季成熟期N3处理氮素累积量分别增加9.26%、3.54%,头季齐穗期～头季成熟期N3处理氮素转移量分别增加21.47%、6.76%,整个生育期N3处理干物质净积累总量分别增加5.10%、4.78%。N3处理头季产量最高,达12431kg·hm-2,极显著高于N1、N2处理;氮肥利用率达46.44%,比N1、N2处理提高14.81%、5.43%;氮肥农学利用率达20.66kg·kg-1,比N1、N2处理提高14.97%、12.34%。研究结果还表明,头季不同基蘖穗肥氮素配比对再生稻再生季的影响不显著。     

Effects of changes in applied nitrogen concentrations on nodulation,nitrogen fixation and nitrogen accumulation during the soybean growth period

ABSTRACT

The specific mechanism by which nitrogen application affects nodulation and nitrogen fixation in legume crops remains uncertain. To further study the effects of nitrogen application on soybean nodulation and nitrogen accumulation, three consecutive tests were performed during the VC-V4, V4-R1 (10 days), and R1-R2 (10 days) growth periods of soybean. In a dual-root soybean system, seedlings on one side were watered with a nutrient solution containing NH₄⁺ or NO₃^? as the N source (N+ side), and those on the other side were watered with a nitrogen-free nutrient solution (N- side). During the VC-R2 period, on the N+ side, high nitrogen treatment inhibited nodule growth and nitrogenase activity (EC 1.18.6.1), and the inhibition was significantly increased with increasing high nitrogen supply time (10 days, 20 days). When the high nitrogen treatment time reached 20 days, the specific nitrogenase activity (C₂H₄ μmol^?1 g^?1 nodule dry mass h^?1) was similar to that in the low nitrogen treatment, indicating that the nitrogen fixation capacity per gram of dry mass nodules was almost the same. Therefore, it is assumed that long-term high nitrogen treatment mainly reduces nitrogen fixation by reducing the nodule number. The effect of nitrogen concentration on the roots on the N+ side was greater than that on the N- side. Taken together, these results indicate that nitrogen application affects a contact-dependent local inhibition of root nodule growth, nitrogenase activity, and nitrogen accumulation. The whole plant systematically regulates specific nitrogenase activity, and high nitrogen inhibition is recoverable.     

氮肥用量对滨海滩涂区甘薯干物质积累、氮素效率和钾钠吸收的影响

我国沿海滩涂种植能源作物甘薯有广阔的前景。为确定苏北滩涂区甘薯适宜施氮量,比较了6个施氮水平下甘薯的成活率(SR)、商品率(CR)、蔓薯比(V/T)、干物质积累(DMA)、氮素累积值(NAV)、氮利用效率(NUE)、氮收获指数(NHI)及钾钠吸收的差异。结果表明:(1)施氮量与甘薯地上部分DMA和NAV均呈极显著正相关(P<0.01,余同),对地下部分NAV影响较小(P>0.05)。(2)与不施氮比较,施氮60 kg(N)·hm-2对甘薯的V/T、SR、NUE和NHI均无显著影响。(3)甘薯的CR、地下部分和块根DMA以及理论产量(NAV×NUE×NHI)均以施氮60 kg(N)·hm-2显著高于其他处理。施氮量超过60 kg(N)·hm-2,施氮量与甘薯的V/T值呈极显著正相关,与SR、CR、NUE、NHI、地下部分和块根DMA均呈极显著负相关。(4)甘薯对钾钠的吸收量均随施氮量的增加而增加,二者呈极显著正相关。甘薯地上部分钾钠含量均在施氮量为60 kg(N)·hm-2时达到最高值。施氮量对钾钠含量比没有影响。因此,苏北滩涂区甘薯适宜施氮量为60 kg(N)·hm-2。     

叶面喷施锌、硼、锰肥对兰州百合干物质积累与分配的影响

采用田间试验方法,在坡耕地条件下研究了叶面喷施Zn、B、Mn3种微量元素肥对兰州百合干物质积累与分配及鳞茎产量的影响。结果表明,适宜浓度的Zn、B、Mn肥均能提高百合植株干物质的积累及分配效率,增加鳞茎产量;200mg·L-1的Zn、B、Mn肥处理对干物质积累的影响最为显著,分别较对照提高26.5%、31.8%和23.6%;Zn、B肥有利于光合物质向鳞茎转移分配,200mg·L-1的Zn、B肥处理收获期鳞茎所占干物质比率较对照分别提高4.16和2.44个百分点;喷施Mn肥处理鳞茎所占干物质比率较对照有所降低,降幅与喷施浓度呈正相关。200mg·L-1Zn、B肥和100mg·L-1Mn肥处理对百合鳞茎的增产作用显著。     

施氮量对黄河滩区棉花叶片生理特性、干物质积累及产量的影响

为探讨黄河滩地植棉适宜的施氮水平,以转双价（Bt Cry1A+CpTI）基因抗虫杂交棉品种中棉所72为试验材料,设置了N 0、 150、 300和450 kg/hm2 4个施氮水平,研究了施氮量对棉花叶片生理特性、 干物质积累及产量的影响。结果表明,随着施氮量的提高,棉花叶面积指数（LAI）,叶片叶绿素和全氮含量,谷氨酰胺合成酶（GS）和超氧化物歧化酶（SOD）活性呈增加的趋势,丙二醛（MDA）含量有下降趋势,进而延缓了叶片的衰老进程。在施氮量为N 300 kg/hm2 时,棉花干物质积累量较大,且分配到生殖器官的比例较高;施氮量过低时,干物质积累量较少;施氮量过高时,有利于营养器官生长,干物质积累量最大,但分配到生殖器官的比例较低。棉花施氮量为N 300 kg/hm2时籽棉产量最高,比不施氮（N 0）和施氮量为N 150 kg/hm2的处理分别增加15.29% 和9 .77%,差异达到显著水平;与施N 450 kg/hm2的处理产量差异不显著。因此,在土壤肥力较低且下层土质沙性较强的黄河滩地,棉花的适宜施氮量为300 kg/hm2。     

追施氮肥量对菘蓝根的外形品质、干物质积累及活性成分含量的影响

采用田间小区试验,设5个处理,氮肥用量分别为 225、 450、 675、 900、 1125 kg/hm2,每一个处理3个重复小区,研究不同追施氮肥量对菘蓝的光合参数、 根的外形品质、 干物质积累及活性成分含量的影响,探讨氮肥施用量对菘蓝植株地上部和地下部生长的生理影响,优选菘蓝最佳追施氮肥量。结果表明, 追施氮肥有利于提高菘蓝叶片的净光合速率、 气孔导度、 胞间CO2浓度、 蒸腾速率,可以显著增加菘蓝根主根直径和根长,有明显的壮根效应;而菘蓝总鲜重随着施氮量提高而增加,但超过 900 kg/hm2 后就不再增加;在450 kg/hm2下菘蓝根侧根数最少,低氮（225 kg/hm2）和高氮（900、 1125 kg/hm2）水平下菘蓝根侧根数增加过多,影响了菘蓝根药材外形品质;随着施氮量增加,地上部和地下部干物质积累先增加后下降,而根冠比不断下降,氮肥量为675 kg/hm2 时地上部干物质积累最大,氮肥量为900 kg/hm2 的地下部干物质积累最大,追施氮肥对地上部的促进效应明显高于地下部。施氮量增加,多糖含量先增加后下降,施氮量为 675 kg/hm2 时菘蓝根中多糖含量最高为158.383 mg/g,而(R,S)-告依春含量没有明显的变化规律,氮肥量为900 kg/hm2 时含量最高达到 0.5655 mg/g。为保证菘蓝根产量和药用品质适宜的追施氮肥量是675900 kg/hm2。