Accumulation of Reserve Compounds in Common Bean Seeds under Drought Stress

To investigate the seed protein and major mineral nutrient (Fe, Zn, P, and N) contents and their accumulation procedure in the seeds of common bean (Phaseolus vulgaris L.), a biennial experiment was conducted under two contrasting moisture regimes (normal irrigation and water deficit). Seed reserves of eight genotypes (WA4502-1, WA4531-17, Akhtar, D81083, AND1007, KS21486, MCD4011, and COS16) were investigated at four stages of seed filling period (SFP). Split-plot experiments were performed as randomized complete block design with four replications. The results showed significant differences in the evaluated characteristics in both factors, the genotypes and the moisture regimes. Fe content of the seeds was affected the most by drought stress and reduced in all stages, while seed nitrogen and protein contents were affected the least under stress condition. The percentages of reductions due to water deficit were higher in stage 1 for Fe, stage 2 for Zn, and stage 4 for P and N. In the stage 3, minerals had the least changes. Nitrogen content of the seeds at mid-stages of SFP increased slightly under drought stress. Drought stress also caused 39–69% reductions in the grain yield of the genotypes. Under drought stress condition, the concentrations of Fe and N in the white bean seeds were less than that of the red and the Chitti genotypes. However, the seed P contents of the white bean seeds were higher than that of the other genotypes.     

新垦灰钙土蚕豆/玉米间作系统土壤活性有机碳、氮的时空变异研究

以宁夏新垦的淡灰钙土为对象,研究了蚕豆/玉米间作系统不同施氮水平下土壤活性有机碳、氮的时空变异特征。结果表明:新垦淡灰钙土土壤微生物量碳、氮(SMBC、SMBN)及可溶性有机碳、氮(SOC、SON)等活性有机碳、氮含量较低;随着施氮量的增加土壤SMBC含量显著增加;玉米收获期土壤SMBC、SMBN含量显著高于蚕豆收获期;土壤SMBC、SMBN含量空间变异为:蚕豆行间(F-F)含量最高,玉米行(M)、玉米行间(M-M)最低。与不施氮相比,施氮显著提高了蚕豆收获期土壤SOC、SON含量,而玉米收获期各施氮水平间土壤SOC和SON含量无明显差异;土壤SOC、SON的空间变异为:玉米行间>蚕豆行间、蚕豆行(F)、蚕豆与玉米行间(F-M)>玉米行。玉米收获期土壤SMBC及SMBN含量的显著增加,说明土壤微生物对矿质氮的固持对于新垦土壤肥力的提高具有重要作用。     

Wheat Grain Nitrogen Uptake,as Affected by Soil Total and Mineral Nitrogen,for the Determination of Optimum Nitrogen Fertilizer Rates for Wheat Production

Determination of appropriate nitrogen (N) fertilization for wheat (Triticum aestivum L.) production with respect to the available resources can result in the enhanced efficiency of agricultural systems and ecosystem health. Hence, a 3-year field experiment was conducted to determine (1) the effects of soil total N and soil mineral N (including nitrate, NO₃-N, and ammonium, NH₄-N) measured at seeding and postseeding for wet and dry soil samples at 0- to-30 cm and 0- to 60-cm depths on wheat grain N uptake and (2) the regression equations that can best explain the variation in wheat grain N uptake by N fertilizer and soil total and mineral N. Determination of wheat grain N uptake as affected by soil NO₃-N in areas with reasonable amounts of organic matter can also be used as a very useful tool for determination of appropriate N fertilization, which is of great agricultural and environmental implications.     

Sources,Rates and Time of Nitrogen Application on Maize Crops under No-Tillage System

Quantitatively, nitrogen (N) is the foremost nutrient for maize crops (Zea mays L.), but the N source to increase the grain productivity still needs more investigation. Thus, the aim of this experiment was to study sources, rates and time of N application on the crop yield and agronomic characteristics of the maize under no-tillage system. The experiment was carried out during two growing seasons on an Oxisol under the factorial 5 × 3 × 3 scheme with five N rates (0, 50, 100, 150, and 200 kg ha^?1) and three sources (ammonium-sulfate-nitrate as inhibitor of the nitrification (ASN+I), ammonium sulfate (AS) and urea); we applied them two times with four replicates: first time at the sowing or later under side dressing when the plants had the six leaves stage. In the first year, the sources of N had no influence on the number of grain line /ear (NGLE), grain number/line (GNL), total number of grain/ear (TNFE), biomass of 100 grain, plant height (PH), height of the first ear insertion (AFEI) and stalk diameter, in contrast with the foliar N content and the crop yield. Early fertilization with N at the sowing time can afford applications as well as the total side dressing. The increase of the rates had positive influence on the N foliar content, plant height and 100 grains biomass. The highest productivities were found with rates above the threshold of 150 kg ha^?1, no matter the sources and the fertilization time.     

长期不同施肥潮土活性有机氮库组分与酶活性对外源牛粪的响应

【目的】研究不同施肥制度下潮土中活性有机氮库及酶活性对新添加有机物料的响应机制,可深入理解不同施肥制度培肥土壤、提高土壤基础地力的机理。【方法】供试土壤采集于从1986年开始的长期定位试验处理,包括CK (不施肥)、OF (常量有机肥)、CF (常量化肥)、OCF (常量有机无机配施) 4个处理。通过室内恒温培养试验,研究添加等氮量牛粪后长期不同施肥潮土有机氮库组分(微生物量氮、可溶性有机氮和颗粒有机氮)含量及土壤酶(α-葡萄糖苷酶、β-葡萄糖苷酶、β-木糖苷酶、纤维二糖水解酶、磷酸酶、过氧化物酶和酚氧化酶)活性的变化特征。【结果】首先,无论添加牛粪与否,土壤全氮、可溶性有机氮和颗粒有机氮含量均随培养时间呈上升趋势或与初始时期差异不显著;添加牛粪的长期不施肥与施化肥处理土壤微生物量氮含量显著低于相同处理不添加牛粪的土壤微生物量氮含量。其次,培养结束后,添加牛粪增加了长期不同施肥潮土全氮、可溶性有机氮和颗粒有机氮含量,分别提高了5.43%~15.49%、5.83%~69.42%及9.75%~42.29%,却降低了土壤微生物量氮含量16.91%~62.10%。另外,施肥、添加牛粪及其交互作用对土壤酶活性具有显著影响(P <0.05);无论添加牛粪与否,不同施肥处理土壤氧化酶(过氧化物酶和酚氧化酶)活性显著低于不施肥处理,不同施肥处理的土壤水解酶活性却呈现不同的变化趋势。不添加牛粪情况下,长期施肥显著提高了除β-葡萄糖苷酶以外的土壤水解酶活性;其中与长期不施肥处理相比,长期施用化肥土壤β-木糖苷酶和β-纤维素酶分别提高了208.74%和180.75%。添加牛粪情况下长期施用有机肥土壤β-葡萄糖苷酶和β-纤维素酶比不施肥分别提高了201.40%和308.04%;冗余分析(redundancy analysis,RDA)显示,添加与不添加牛粪条件下土壤酶活性的关键环境驱动因子不同,在不添加牛粪时为可溶性有机氮,添加后其关键驱动因子为全氮和可溶性有机氮。【结论】不同施肥制度下土壤微生物量氮、可溶性有机氮、颗粒有机氮与土壤全氮之间呈显著正相关;室内好气培养条件下,添加牛粪显著提高了长期不同施肥潮土的全氮、可溶性有机氮、颗粒有机氮含量,却显著降低了土壤微生物量氮含量;不同施肥制度下土壤酶活性差异显著,牛粪的添加改变了影响长期不同施肥潮土酶活性的关键环境因子。     

有机肥等氮替代化肥对玉米产量和氮素吸收利用效率的影响

有机肥替施部分化肥是实现我国化肥零增长并保持作物高产稳产的重要途径之一。以等养分条件为基础,研究不同比例有机肥等氮替代基施化肥对玉米产量以及氮素吸收利用的影响,为云南红壤坡耕地有机肥的合理利用及玉米施肥结构的调整提供科学依据。通过田间小区试验,分别设置不施肥处理(CK)、施用100%化肥处理(NPK)及4个基施有机肥等氮替代化肥处理,替代率分别为10%(T₁),20%(T₂),30%(T₃),40%(T₄),分析玉米产量、吸氮量以及氮肥利用率等指标在不同施肥处理下的变化情况。结果表明:与NPK处理相比,不同比例有机肥替代化肥的处理能在一定程度上提高玉米籽粒、秸秆生物量,玉米籽粒产量提高达6.07%～19.53%,秸秆生物量提高达2.16%～21.76%,且有机肥替代30%的化肥处理下的玉米籽粒产量和秸秆生物量最高,分别达到7 653 kg/hm²,16 530 kg/hm²,较其他施肥处理有一定的显著性; 有机肥替代化肥的处理均提高了玉米籽粒和秸秆的吸氮量,各施肥处理下的玉米地上部氮素平均积累量从大到小依次为T₃(292 kg/hm²)>T₂(248 kg/hm²)>T₁(212 kg/hm²)>T₄(203 kg/hm²)>NPK(176 kg/hm²)>CK(52 kg/hm²),T₃处理较NPK,T₁,T₂,T₄处理下的玉米地上部分吸氮量分别提高了39.90%,27.37%,15.01%,30.38%; 与NPK处理相比,有机肥替代化肥的处理均提高了氮肥偏生产力、氮肥贡献率、氮肥表观利用率、氮肥的农学利用率,提高比例分别为5.00%～21.80%,2.44%～9.48%,20.48%～94.02%,7.54%～32.86%,且T₃处理下的各氮素利用率指标均显著高于其他施肥处理。综上,有机肥与化肥配施可提高玉米的籽粒产量和生物产量,且提高玉米的吸氮量及氮素利用效率,且以有机肥等氮替代30%基施化肥的配施效果最好,可作为云南红壤坡耕地玉米增产和氮肥增效的合理施肥模式。     

苜蓿对旱地土壤有机碳氮变化的驱动作用

根据旱地长期定位试验和分离土壤有机质中微粒有机质及矿物结合有机质的方法,研究了长期生长苜蓿对土壤有机碳、全氮变化的驱动作用。结果表明:不施肥条件下,苜蓿地土壤有机碳、全氮的含量比裸地土壤中的含量明显增加,土壤有机碳和氮库中的微粒有机碳、氮的含量没有显著增加,而增加的有机碳、氮主要分布在矿物结合有机碳、氮组分中。在施用有机肥及氮、磷化肥条件下,苜蓿地土壤有机碳和全氮的含量显著地提高,增加的有机碳、氮几乎平均地分布在微粒有机碳、氮和矿物结合有机碳、氮组分中。由此表明,保持适宜的苜蓿生产力并采用合理的施肥措施,长期生长苜蓿能够有效地驱动土壤固定有机碳和氮素,从而保持和提高土壤肥力。     

夏闲期复播绿肥对旱地麦田土壤团聚体碳氮含量的影响

为探究不同绿肥品种翻压条件下晋南旱地麦田土壤团聚体稳定性以及有机碳(SOC)和全氮(TN)在不同粒径团聚体的分布特征,深入了解不同种类绿肥的增碳保氮机制。已连续3年(2018—2021年)不同绿肥品种(对照休闲、大豆、绿豆、油葵、玉米)翻压还田后冬小麦收获期0-10,10-20,20-30 cm土壤为研究对象,采用湿筛法进行土壤粒径分级,并分析粗大团聚体(>2 mm)、细大团聚体(0.25~2 mm)、微团聚体(0.053~0.25 mm)和粉黏粒组分(<0.053 mm)中SOC和TN含量,测算团聚体的构成与稳定性(R_0.25,>0.25 mm团聚体含量;MWD,平均重量直径;GMD,几何平均直径),并测定各粒径团聚体SOC和TN及其对土壤总有机碳和总氮的贡献率。结果表明:不同绿肥处理下旱地麦田土壤团聚体质量占比均以细大团聚体0.25~2 mm为主(占22.77%~39.71%)。复播绿肥显著增加0-30 cm土层>2 mm粒径团聚体质量占比,以大豆绿肥增加最明显,0.25~2,0.053~0.25 mm粒径团聚体质量占比降低,对<0.053 mm粉黏粒的影响不明显;大豆绿肥对各土层R_0.25、MWD和GMD值提高作用明显。大豆和玉米对0-30 cm各土层土壤总有机碳含量具有显著提高作用,分别提高27.83%和25.71%。大豆绿肥进一步提高土壤各粒径团聚体有机碳含量。复播绿肥降低土壤全氮含量,大豆绿肥处理的降低程度最小,且对<0.053 mm粉黏粒全氮含量具有增加作用。0.25~2,>2 mm大团聚体对0-10 cm土层土壤有机碳和全氮的贡献率最高;复播绿肥提升土壤碳氮比(平均21.39),较对照休闲(平均13.71)提高7.68,其中玉米提升效果最佳,大豆次之。综合土壤增碳固氮效果,连续3年翻压大豆绿肥可有效提高旱地麦田土壤团聚体稳定性,提升土壤肥力。     

Differences in Response to Iron Deficiency Among Some Lines of Common Bean

Abstract

Five dry bean cultivars (Coco blanc, Striker, ARA14, SVM29‐21, and BAT477) were evaluated for their resistance to iron deficiency on the basis of chlorosis symptoms, plant growth, capacity to acidify the external medium and the root‐associated Fe³⁺‐reduction activity. Plants were grown in nutrient solution supplied or not with iron, 45 µM Fe(III)EDTA. For all cultivars, plants subjected to iron starvation exhibited Fe‐chlorosis. These symptoms were more severe and more precocious in BAT477 and Coco blanc than in the others cultivars. An important acidification of the culture medium was observed between the 4th and the 8th days of iron starvation in Striker, SVM29‐21 and, particularly, ARA14 plants. However, all Fe‐sufficient plants increased the nutrient solution pH. This capacity of acidification appeared more clearly when protons extrusion was measured in 10 mM KCl + 1 mM CaCl₂. The above genotypic differences were maintained: ARA14 showed the higher acidification followed by Coco blanc and BAT477. Iron deficiency led also to an increase of the root‐associated Fe(III)‐reductase activity in all lines. However, genotypic differences were observed: Striker shows the highest capacity of iron reduction under Fe deficiency condition.     

Case Study of the Effects of Irrigation and Nitrogen Fertilization on Active and Reserve Soil Acidity

Excessive soil acidity and low soil pH may liberate plant toxic levels of manganese and aluminum from soil minerals, and interfere with nitrogen and phosphorus availability. Active soil acidity is measured as soil pH and reacts quickly in the soil-plant system. Potential or reserve acidity is inactive in the soil, and acts as a source of replenishment for active acidity. Studies to determine the effect of ammoniacal-nitrogen fertilizer treatments and irrigation methods on plant growth and development of cotton, and changes in soil properties were conducted. Nitrogen treatments ranged from 0 to 168.0 kg N/ha in 33.6-kg N/ha increments. Soil samples from each N-treatment from both irrigation blocks were analyzed for active and potential acidity. Irrigation water high in Na⁺, Ca²⁺, and HCO^3? tended to raise soil pH. Under dry land conditions ammonical N-fertilizer lowered soil pH. Reserve acidity was larger under dry land conditions than under furrow irrigation. No significant differences in reserve soil acidity were observed under furrow irrigation, or under dry land conditions. Calcium, Na⁺, and HCO^3? content of the irrigation water were driving forces to reduce both active and potential soil acidity. Fertilization with ammoniacal-nitrogen sources was the driving force in increasing active and potential soil acidity.     

不同有机肥输入量对黑土密度分组中碳、氮分配的影响

为阐明不同有机肥施用量对黑土密度组分中碳、氮分配特征的影响,探讨合理调控土壤质量的施肥模式。以黑龙江省海伦国家野外科学观测研究站上进行了10年的田间定位试验土壤为研究对象,采用密度分组和腐殖质化学分组相结合的方法,探讨和分析不同有机肥施用量下土壤各密度组分中有机碳、氮的消长变化以及重组中腐殖物质的组成特征。结果表明:与试验初期相比,经过10年单施化肥处理,土壤总有机碳和全氮、各密度组分中有机碳氮以及腐殖物质各组分的含量均显著下降,而有机无机配施能够提升土壤总有机碳和全氮的含量水平,改善密度组分中有机碳氮的分配特征,土壤总有机碳、全氮和各密度组分中有机碳氮对不同有机肥施用量的响应有所差异。随着有机肥施用量的增加,土壤总有机碳和全氮的含量呈逐渐升高的趋势,二者与有机肥施用量之间达到极显著的线性相关(P<0.01);低量有机肥(7.5,15t/(hm2.a))配施化肥仅增加了土壤游离态轻组有机碳、氮的含量,并未造成闭蓄态轻组和重组中有机碳、氮的积累,而高量有机肥(22.5t/(hm2.a))配施化肥后,促进了土壤各密度组分中有机碳、氮的形成和积累;此外,低量有机肥有利于土壤富里酸的积累,高量有机肥有助于胡敏酸和胡敏素的积累,从而提高了土壤有机质的腐殖化程度,增强了土壤有机质的稳定性。在东北黑土区,加大有机肥的施用量是提高土壤肥力和土壤固碳能力的有效途径。     

不同猪粪施用量下红壤水稻土表层水氮磷动态

土表水中养分含量变化不仅是土壤养分状况的直接反映,也是土壤养分流失及其环境影响的间接测度。研究施肥条件下土表水中养分含量动态,可为优化施肥管理措施提供科学参考。本研究通过布设0~44.8 t/hm2共8个猪粪施用量梯度的水稻盆栽试验,通过定期采样监测,试图探明不同猪粪施用量水平下红壤水稻土表层水氮磷含量动态。结果表明:早稻季,表层水总磷、总氮、铵态氮和有机氮的平均含量分别为0.04~1.13、3.17~12.97、1.81~5.11和1.17~7.39 mg/L。晚稻季各养分平均含量水平升高,分别为0.13~7.98、3.17~25.57、1.21~10.41和1.87~15.35 mg/L,其中磷的累积效应最明显,较早稻季最大升高约6倍。各养分含量与猪粪施用量显著线性相关,当猪粪施用量≥11.2 t/hm2时,表层水养分浓度显著升高并于施肥后第4天和第14天出现养分释放高峰。与单施化肥相比,配施猪粪会使表层水养分形态以有机氮为主,最高可占总养分的66%,同时养分大量释放期延长一周。连续大量施用产生的累积效应表明该施肥制度将导致土壤保肥能力趋于饱和,养分流失风险激增,实际生产中应考虑用量和频率的叠加效应。     

土壤中可溶性氮和pH对有机肥和化肥的短期响应

通过温室盆栽试验,施用猪粪堆肥(PC)、污泥堆肥(SC)、菜籽饼肥(CM)和无机化肥(IF)后,对土壤pH值和不同形态氮素的短期响应进行研究,探讨土壤可溶性无机氮、有机氮及土壤pH值之间的相互关系。结果表明,CM,PC和IF处理的pH值都呈现先快速下降后缓慢回升的趋势,但PC处理下降幅度较小;而SC处理和不施肥对照(CK)处理的pH值基本不变;不同施肥处理均提高了土壤中氮素水平,3种有机肥中以CM处理最显著地提高了土壤中总可溶性氮(TDN)、NH4+-N、NO3--N和可溶性有机氮(DON)浓度,PC处理的次之,SC处理的最弱,而IF处理与CM处理提高幅度相似。不同施肥处理中土壤可溶性氮表现出不同的短期响应,IF处理和CM处理的TDN分别经过11,13d的稳定期后迅速上升到一个较高的水平,至31d开始下降;PC处理和SC处理未出现突然升高的现象,而是前20d较稳定在一定的范围内波动,之后缓慢下降,总体与对照趋势一致。不同处理土壤中NH4+-N均呈下降趋势;IF处理、CM处理的NO3--N呈增加趋势,PC处理的呈先增加后降低趋势,而SC处理的呈缓慢下降趋势,结果说明不同有机肥在土壤中的转化存在明显的差异。相关性分析显示,CM处理、IF处理的土壤pH值与NH4+-N呈极显著正相关,而与NO3--N呈极显著负相关;除PC处理外,其他处理的DON含量与TDN具有显著正相关性,而PC处理的DON同时与NH4+-N、NO3--N呈显著负相关。     

不同比例有机肥替代化肥对水稻产量和氮素利用率的影响

在江西双季稻区进行30 a的田间定位试验,比较不施氮肥(CK)、施用化肥(NPK)、等养分条件下70%化肥配合施用30%有机肥(70F+30M)、50%化肥配合施用50%有机肥(50F+50M)、30%化肥配合施用70%有机肥(30F+70M)施肥条件下水稻产量、氮素吸收、氮素利用率的变化。结果表明:与等养分量NPK处理相比,有机无机肥配施处理能显著提高30 a双季稻平均产量(P<0.05),增产幅度在2.47%～5.73%,其中30F+70M处理产量最高,且不同比例有机无机肥配施处理之间有显著差异,30F+70M处理显著高于50F+50M处理(P<0.05)。在不同时间段,不同有机无机肥配施处理产量表现不同,低量有机肥配施处理在试验前期具有明显的增产优势,高量有机肥配施处理在试验中后期增产效果明显。与等养分量NPK处理相比,有机无机肥配施处理30 a平均吸氮量无显著差异,不同施肥处理每生产1 t籽粒对氮素的需求不同,有机无机肥配施处理(20.57～20.94 kg)低于NPK处理(21.77 kg),其中30F+70M、70F+30M处理具有较高的氮素生产效率。有机无机肥...     

长期施用化肥和有机肥下潮土干团聚体有机氮组分特征

依托中国科学院封丘农业生态实验站长期施肥试验,选取不施肥(CK)、单施化肥(NPK)、有机无机肥配施(1/2OM)、有机肥(OM)处理,对比研究27a连续施用化肥和有机肥对土壤机械稳定性团聚体及其有机氮组分的影响。结果表明,长期施用有机肥显著提高了耕层土壤中大于2 mm团聚体的比例,较CK提高了33%,较NPK增加了17%。施肥显著提高耕层团聚体中有机氮含量,以OM处理效果最明显,大于2 mm、2～0.25 mm、小于0.25 mm团聚体中酸解有机氮含量分别为776.4、837.7、625.3 mg·kg~(-1)。各团聚体中有机氮以酸解铵态氮为主,氨基糖态氮最少。长期单施化肥主要提高了大于2 mm团聚体中酸解铵态氮比例,施用有机肥提高了氨基酸态氮和酸解未知态氮含量及分配比例。长期施用有机肥使潮土结构明显改善,有利于耕层团聚体中全氮及有机氮各组分的积累,氨基酸态氮、氨基糖态氮、非酸解有机氮主要赋存于2～0.25 mm团聚体中,而酸解铵态氮和酸解未知态氮在大于2 mm团聚体中分布较多,有效地提高了土壤供氮能力。     

Tissue Nitrogen as a Base for Recommendations of Additional Nitrogen to Spring Wheat in Southern Finland

Abstract

Nitrogen (N) deficiency has become more common in the traditional wheat cultivation areas of southern Finland as yield potentials have increased. Based on data for the period studied (1968-88) a grain protein concentration below 11.2% in spring wheat (Triticun aestivum L.) is an indicator of N deficiency. The mean of maximum grain yield obtained was 4655 kg ha^?1 when grain protein concentration exceeded 11.2%. The estimation of plant tissue N content could be an effective diagnostic tool for identifying N status in the early growth stages of spring wheat. To address the feasibility of this test, the present study was conducted in 1990-91 to determine the critical plant tissue N concentrations of three plant parts at the early double-ridge stage (Stage 2), at the stage when stigmatic branches of the carpel begin to form (Stage 7) and at pollination (Stage 10). Nitrogen was applied at rates of 0 and 110 kg N ha^?1 as granular ammonium nitrate and granular slow-release-nitrogen fertilizers to establish a wide range of plant tissue N levels, grain yields and grain protein concentrations. Critical plant N levels were calculated for the different plant parts using the Cate-Nelson procedure. From this study it can be concluded that the critical N level recommended for Stage 2 is 43 g of N kg^?1 dry matter of the whole plant. Critical N levels recommended for Stage 7 are 28 g of N kg^?1 dry matter of the whole plant, 30 g of N kg^?1 of the leaves and 13 mg total N in dry matter. Critical N levels recommended for Stage 10 are 12 g of N kg^?1 of the whole plant, 23 g of N kg^?1 of the leaves and 15 mg total N in dry matter.     

稻-麦轮作体系不同施肥模式对氮肥利用效率和土壤有效养分平衡的影响

土壤肥力和养分利用效率是保障可持续粮食生产的基础。通过田间试验研究了稻—麦轮作体系下不同施肥模式氮肥利用效率和土壤有效养分的变化,结果表明:在减少养分总投入量的条件下,有机肥部分替代化肥处理(RF-OM和RF-S处理)水稻地上部总生物量显著高于LRF处理(P<0.05),与FP处理差异不大;小麦秸秆生物量与FP和LRF处理差异均不显著,籽粒生物量及地上部总生物量与LRF处理相差不大。水稻收获期RF-OM处理地上部主要器官含氮量与LRF处理差异不显著,氮素积累总量显著高于LRF处理(P<0.05);小麦收获期RF-OM和RF-S处理秸秆、籽粒含氮量和氮素积累量与LRF处理均无显著差异。收获期RF-OM和RF-S处理水稻糙米和稻壳、小麦秸秆和籽粒含磷量及磷素积累量与FP和LRF处理差异都不大;水稻秸秆、稻壳及小麦秸秆含钾量和钾素积累量均显著高于FP和LRF处理(P<0.05)。有机肥部分替代化肥处理水稻、小麦氮肥农学利用率、氮肥表观回收率和氮肥偏生产力与FP和LRF处理相比均显著提高(P<0.05),氮素籽粒生产效率也高于FP和LRF处理,甚至达到显著水平(P<0.05)。试验表明,水稻、小麦收获期增钾处理(RF-OM和RF-S处理)土壤速效钾、缓效钾含量显著高于FP和LRF处理(P<0.05),水稻收获期土壤碱解氮和小麦收获期土壤有效磷含量与LRF处理差异不大,同时,经1个稻—麦轮作周期后,4个施肥处理土壤有效养分(碱解氮、有效磷、速效钾、缓效钾)含量均高于供试土壤。有机肥部分替代化肥能显著提高稻麦氮肥利用效率,有利于土壤有效养分平衡,并显著提高土壤速效钾和缓效钾养分含量,是适宜的稻麦化肥减量和稳产增效施用技术。     

Effects of humus content,farmyard manuring,and mineral‐N fertilization on yields and soil properties in a long‐term trial

Investigations carried out at Field F3 of the Halle long‐term fertilization trials using data from 1974 to 1983 showed that with adequate supply of mineral N‐fertilizer soil organic matter (SOM) had no significant effects of yield. Similarly enhanced SOM did not justify a reduction of mineral N (Stumpe et al., 2000). The studies presented here examine the effects of the SOM differences existing after the termination of those trials in 1986 up until 1997 (then mainly differences of hardly decomposable SOM) in comparison to farmyard manuring with enhanced mineral N application (3‐factor‐experiment). As with total SOM, hardly decomposable SOM did not directly affect yields. The effects of FYM treatment observed at lower mineral‐N levels were compensated for by enhanced mineral‐N supply. The direct effect of FYM (40 t ha^—1) corresponded to a mineral‐N supply of about 60 kg ha^—1 and the residual effect to about 20 kg ha^—1. The differences of the C‐content in the soil at the beginning of the present studies continued throughout the experimental period of 12 years. In addition, significant differentiation has been caused by FYM and N fertilization in comparison to unfertilized treatments. The major finding is that differences in SOM content do not lead to yield differences on physically good soils (chernozem‐like soils) if appropriate compensation by mineral‐N fertilization takes place.     

Potential of seed and root exudates of the common bean Phaseolus vulgaris L. for immediate induction of rhizobial chemotaxis and nod genes

Abstract

Immediate induction of rhizobial chemotaxis and nod genes by seed and root exudates of the common bean Phaseolus vulgaris L. was investigated. One hour after the onset of Rhizobium incubation in a culture medium composed of common bean exudates and soil extract, a large number of Rhizobium cells were attracted by the seed exudates of all the cultivars (cvs Hokkaikintoki, Himetebou and Kurodanekinugasa), while the media containing root exudates was not statistically different from the control. After 1 h of incubation, the nod genes were induced significantly by the seed exudates of Himetebou and Kurodanekinugasa. In contrast, the seed exudate of Hokkaikintoki and the root exudates of all the cultivars failed to exert a beneficial effect on the immediate induction of the nod genes. These results suggested that the seed exudates displayed a higher potential for immediate induction of rhizobial chemotaxis and nod genes than the root exudates, except for nod gene induction by the seed exudate of Hokkaikintoki.     

Nitrogen source and aluminum toxicity of two sorghum genotypes differing in aluminum susceptibility

After a 35 days growth on nutrient solutions with NO^‐ ₃ NH₄NO₃ and NH⁺ ₄ as nitrogen source (pH 4.2) dry matter yield of the sorghum genotype SC0283 was much less affected by Al (1.5 mg‐¹) than that of the genotype NB9040. With NO^‐ ₃ as the sole nitrogen source only growth of the NB9040 plants was significantly reduced. Since OH^‐ efflux, shoot Al content and concentrations of all major nutrients of both genotypes were almost equal, a higher sensitivity to Al may underlie the lower Al tolerance of the NB9040 genotype. In the presence of NH.‐N Al again lowered d.m. yield of the NB plants. With SCO283 significant Al effects on d.m. yield were observed only with NH₄NO₃. Aluminum drastically increased the amount of protons released per unit of root surface area, especially with the NB9040 line. This shift in proton flux density was partly the result of a decrease of the specific root surface area and partly due to enhanced excess of catlonic nutrients taken up. With NH₄NO₃‐fed plants the latter could almost completely be attributed to a changed N preference brought about by inhibited uptake of NO^‐ ₃ and a simultaneous enhanced NH, absorption. Although both proton efflux and NH⁺ ₄ preference of the NB plants were severely increased by Al, relative yields of this genotype were not lowered by NH⁺ _4. This can probably be explained by (1) the high NH, sensitivity of this cultivar through which Al effects can be masked and (2) the continuous adjustment of the solution pH through which rhizosphere conditions were prevented.