我国大豆的生物固氮潜力研究

【目的】根瘤菌与大豆共生结瘤固氮是大豆的重要氮素来源之一,而我国在大豆生产中普遍过量使用化学氮肥,不仅增加了生产成本,而且严重抑制了大豆的生物固氮效率。因此在生产中充分发挥生物固氮作用、 合理施用化学氮肥、 降低大豆生产成本是我国发展大豆产业的重要措施,本文对我国大豆主产区生物固氮潜力及其分布特征进行了研究,旨在了解不施氮肥条件下不同大豆产区生物固氮的最大供氮能力,为大豆的合理施肥和充分发挥生物固氮作用提供理论依据。【方法】采用15N自然丰度法,在2011年和2012年测定了在不施用氮肥条件下我国4个大豆主产区包括黑河、 大庆、 长春、 铁岭、 济宁、 延安、 南宁等7个试验点在内的大豆生物固氮效率、 生物固氮量及其对产量的贡献。15N自然丰度法的原理是利用非固氮参照作物从土壤中吸收的15N丰度高于固氮植物,根据两者的15N自然丰度差异估算出固氮植物的生物固氮率。所选的非固氮参照作物必须同大豆生长季一致,并且各试验点选用同一种非固氮植物以保证各地数据的可比性。通过查阅文献,有研究使用玉米作为参照作物,并且符合上述要求,因此本研究选择玉米作为非固氮参照作物。【结果】在不施氮肥条件下,我国大豆在正常降水年份的生物固氮效率为47%～70%,其中铁岭最高为60%～70%,黑河最低为47%～54%;大豆的生物固氮量在N 92～150 kg/hm2之间变化,其中籽粒中的生物固氮量占总固氮量的65%～81%,生物固氮量最高的试验点为长春,最低的试验点为延安;生物固氮对产量的贡献在1039～1867 kg/hm2之间,其中最高的试验点为长春,最低的试验点为延安;在延安试验点苗期～开花期极度干旱的2011年,大豆缺水严重抑制了根瘤菌的数量和固氮酶的活性,其生物固氮效率、 固氮量及对产量的贡献均达极低水平,分别为15%和N 24 kg/hm2和245 kg/hm2。【结论】我国大豆不同主产区的生物固氮潜力存在较大差异,并且具有明显的分布规律。生物固氮效率以温带的铁岭为最高,向北至寒温带的黑河、 向南到亚热带的南宁均呈现逐渐降低的趋势。受种植密度等因素的影响,大豆生物固氮量及其对产量贡献的分布规律与生物固氮效率不完全一致,其中东北地区最高,其次是济宁和南宁,延安最低。     

土壤水蚀分布式预报模型研究述评

随着对土壤水蚀形成过程及其模拟研究的深入,侵蚀预报模型已由经验模型、物理过程模型向分布式模型发展。重点介绍了几种国外具有代表性的分布式水蚀模型,并对国内土壤水蚀分布式模型的研究现状进行了评价,指出了目前我国模型研究中存在的问题,以及建立我国土壤侵蚀预报模型所必须开展的研究工作和需要解决的科学问题。     

大豆在利用不同氮源时对土壤磷形态和有效性的影响

通过盆栽培养方法,在土壤中可利用磷基本耗竭条件下,研究供给两种不同氮源的大豆对土壤中有机和无机磷的利用和形态转化的影响。结果表明,生物固氮处理大豆吸收的总磷量比尿素处理多58.0%,而对磷素的利用效率仅下降了3.3%。无论供给哪种形态氮源,种植大豆后土壤中各形态无机磷含量总体表现为O-P>Al-P>Fe-P>Ca10-P>Ca8-P>Ca2-P,有机磷的含量表现为:中等活性有机磷(MLOP)>高稳性有机磷(HROP)>中稳性有机磷(MROP)>活性有机磷(LOP)。生物固氮处理,Al-P和O-P成为维持大豆生长的主要磷源,而尿素处理只有O-P。生物固氮处理主要是促进土壤中的MLOP和MROP矿化分解,分别减少了29.48 mg/kg和14.16 mg/kg;尿素处理土壤中的MROP和HROP转化的程度较大,分别减少了12.47 mg/kg和3.68 mg/kg。比较而言,尿素处理的大豆从土壤中获得有机磷的能力不及生物固氮处理。     

小麦白粉病发生气象条件和气象预报研究进展

基于已有成果,采用影响事实检测法,系统分析和汇总气象条件对小麦白粉病影响的规律,对气象因子在国内小麦白粉病预报中的应用进行综述,指出当前研究存在的问题,并对未来发展进行展望.已有研究表明,夏季气温偏低对白粉病病菌的越夏有利;秋冬季及早春气温偏高或阴雨日偏多利于病情发展,但雨水过多且集中则不利于病害发展;冬小麦生长中后期高温干旱会抑制病情发展;日照少则利于白粉病流行;病菌借助大气环流完成异地传播.关于气象因子对小麦白粉病影响的研究多基于田间观测,通过与气象资料对比分析,建立小麦白粉病发生发展与各气象因子及因子组合间的定量关系.有关小麦白粉病的气象预报分定性和定量两大类:定性预报一般采用指标预测法;定量预报以数理统计方法应用为多,人工神经网络法、模糊数学法和灰色系统理论也有应用.目前国内小麦白粉病预报研究中尚存在数据资料有限、指标选择不当、模拟方法仅限于黑箱和灰箱模型、研究结果地域性强、实用性较差等问题.机理模型的研究极少,未来亟待开展.     

土壤侵蚀中吸附态磷流失研究现状与展望

吸附态磷流失是土壤侵蚀的结果之一,不仅造成土壤肥力流失,还是导致水环境恶化的重要因子.吸附态磷流失是非点源污染计算的重要组成部分,通过土壤侵蚀研究吸附态磷流失是目前普遍采用的方法.总结了国内外关于吸附态磷流失的研究现状,分析了我国当前土壤侵蚀中吸附态磷流失研究中存在的问题,认为中国土壤侵蚀中吸附态磷流失研究还不能满足实践应用的要求.因此一方面需要增加实验数量,加强实验深度,坚持连续监测的工作,深入了解吸附态磷流失的机理;另一方面应积极构建适合国情的模型,构建基础信息数据库,开展国外模型在国内的适用性、差异性研究.     

结合Sentinel-2影像和特征优选模型提取大豆种植区

准确获取大豆的空间分布对于产量估计、灾害预警和农业政策调整具有重要意义,目前针对种植结构复杂地区所开展的大豆遥感识别研究鲜有报道。该研究以安徽省北部平原的典型大豆产区——龙山、青疃镇为研究区,基于Sentinel-2数据提出一种分层逐级提取策略的大豆识别方法。该方法首先构建决策树筛选规则,剔除研究区内非农田地物,获得田间植被的总体分布;然后生成19个候选特征因子,包括分辨率小于等于20 m的10个波段反射率以及9个植被指数。在典型地物类型样本的支持下,将ReliefF特征权重评估算法与随机森林(RandomForest,RF),BP神经网络(Back-Propagation Neural Network,BPNN)和支持向量机(Support Vector Machine, SVM)相结合,分别构建ReliefF-RF、ReliefF-BPNN、ReliefF-SVM三种组合模型筛选出对于大豆识别最有效的特征,并基于布设在研究区内6个样方(大小为1 km×1 km)的无人机影像提取得到的大豆分布来评估3种模型在大豆制图中的表现。结果表明,ReliefF-RF模型表现最佳,基于该模型筛选出7个优选特征因子,大豆制图的总体精度介于85.92%～91.91%,Kappa系数在0.72～0.81之间,各个样方的提取效果均优于其他两种模型。此外,基于优选特征达到的提取精度明显高于原始波段反射率,虽然略低于全部19个特征的结果,但是数据量降低了63.16%。该研究可以为农田景观破碎、种植结构复杂地区的大豆种植区提取相关研究提供有价值的参考和借鉴。     

密度与地膜覆盖对旱塬幼龄果园中大豆综合生产力的影响

本研究从籽粒产量兼顾蛋白品质、生物固氮及氮素副产物——秸秆氮和秸秆的角度综合评估了密度与地膜覆盖及其配合对黄土旱塬幼龄苹果园中大豆生产力的影响,旨在确定大豆最优综合生产力下合适群体密度和地膜覆盖的管理措施。2018—2019年连续两年试验设置3种大豆种植密度(高密度:24×10~4株·hm~(–2);中密度:16×104株·hm~(–2);低密度:10×104株·hm~(–2))和两种覆盖方式(覆膜与不覆膜)的完全组合处理,调查了不同处理下大豆籽粒产量及蛋白质含量、生物固氮率、器官干物质量及氮素分配等指标。结果表明,密度是大豆籽粒产量和蛋白产量的主控因子,中密度和低密度下2指标表现相似,2种密度平均的籽粒产量和蛋白产量分别较高密度下显著增加23.8%和24.5%(P0.05)。覆膜能够增加大豆籽粒蛋白质含量(3种密度平均增加9.6%),在与中、低密度配合下有利于根瘤固氮与地上协同互作,显著增加群体秸秆干物质量和秸秆吸氮量且不显著降低籽粒产量,从而提高对大豆干物质量、吸氮量和生物固氮量的贡献。与不覆膜相比,中、低密度下覆膜的秸秆干物质量分别增加1.76 t·hm~(–2)、1.81 t·hm~(–2),对各自大豆干物质量提高的贡献率为98%、102%;秸秆吸氮量分别增加39.50 kg·hm~(–2)、33.70 kg·hm~(–2),对各自大豆吸氮量提高的贡献率为79%、58%;秸秆中生物固氮量分别增加32.42 kg·hm~(–2)、25.41 kg·hm~(–2),对各自大豆生物固氮量提高的贡献率为67%、59%。最终,中密度覆膜实现了大豆籽粒产量3.55 t·hm~(–2)及蛋白产量1.27 t·hm~(–2)、生物固氮量256.80 kg·hm~(–2)、秸秆氮量134.87 kg·hm~(–2)和秸秆干物质量6.84 t·hm~(–2)各指标均较优的综合生产力,且相对不覆膜有较高的籽粒蛋白品质。在旱塬幼龄苹果园中,较高密度下覆膜既保证了大豆籽粒较多、较优产出,还可收获更多秸秆与秸秆氮,可为以节肥减排和稳产增产为目的的农田可持续集约化生产补充一定养分来源。     

大豆在利用不同氮源时对土壤磷形态和有效性的影响

通过盆栽培养方法,在土壤中可利用磷基本耗竭条件下,研究供给两种不同氮源的大豆对土壤中有机和无机磷的利用和形态转化的影响。结果表明,生物固氮处理大豆吸收的总磷量比尿素处理多58．0％,而对磷素的利用效率仅下降了3．3％。无论供给哪种形态氮源,种植大豆后土壤中各形态无机磷含量总体表现为O-P〉Al—P〉Fe—P〉Ca10-P〉Cas—P〉Ca2—P,有机磷的含量表现为：中等活性有机磷（MLOP）〉高稳性有机磷（HROP）〉中稳性有机磷（MROP）〉活性有机磷（LOP）。生物固氮处理,Al—P和0一P成为维持大豆生长的主要磷源,而尿素处理只有O-P。生物固氮处理主要是促进土壤中的MLOP和MROP矿化分解,分别减少了29．48mg／kg和14．16mg／kg;尿素处理土壤中的MROP和HROP转化的程度较大,分别减少了12．47mg／kg和3．68mg／kg。比较而言,尿素处理的大豆从土壤中获得有机磷的能力不及生物固氮处理。     

粉粒状农用产品混合式自动定量包装研究

为了改善目前大量多品种各种规格粉粒状农用产品自动定量性能，提高自动定量速度和准确度，该文在分析了目前粉粒状农用产品自动定量包装基础上，提出了一种混合式自动定量包装新方法，研究了实现混合式自动定量包装的工艺流程、称重原理及方法和给料器数字控制方法，并对混合式自动定量包装系统工作性能作对比实验研究。实验结果表明，混合式自动定量包装能适应不同产品、不同规格、不同工作环境，适应性强，工作稳定可靠，在定量速度和准确度方面，满足了大量粉粒状农用产品自动定量包装要求，是一种实用、具有应用推广价值的新方法。     

植物根系吸收磷的机理模型验证研究

本文通过不同土壤条件下幼稚苗磷吸收实测值与机理模型预测值的比较,检验了几种养分吸收机理模型对玉米与大豆幼苗磷吸收的预测能力,同时探讨了影响几种养分吸收机理模型预测能力的主要因素。研究结果表明:供试四种机理模型均能较好地反映玉米与大豆幼苗的磷吸收变化情况;四种机理模型中,以建立于解析解基础上的 Ｓ Ｃ 模型的预测能力最低,两种数值解模型的预测能力相当,而以考虑了根毛作用的 Ｃ２ 模型的预测能力最强;影响机理模型预测能力的重要因素是土壤供磷与含水量水平、土壤供 Ｎ 形态、土壤性质及土壤供 Ｃａ 水平或pH值。土壤养分与水分胁迫、土壤质地粘重、土壤施 NH4+-N及酸性土壤施用石灰等条件均会使数值解机理模型的磷吸收预测能力降低,其原因可归结于这几种土壤条件均能诱导或加强幼苗根系吸收磷的某种主动适应机制,而这种机制并未考虑在养分吸收机理模型之中。     

Impact of pyrochar and hydrochar on soybean (Glycine max L.) root nodulation and biological nitrogen fixation

The aim of this study was to identify effects of carbonized organic material (“biochar”) on soybean growth, root nodulation and biological nitrogen fixation, and to elucidate possible underlying mechanisms. Soybean (Glycine max L.) was grown in four arable soils amended with carbonized organic material produced from wood or maize as feedstocks, by pyrolysis (“pyrochar”) or hydrothermal carbonization (“hydrochar”). Nodulation by Bradyrhizobium , biological nitrogen fixation (BNF) assessed by ¹⁵N techniques, plant growth, nutrient uptake and changes in chemical soil properties after soil amendment were determined. Data were analyzed by means of a three way ANOVA on the factors soil, carbonization technique and feedstock. It turned out that soybean root nodulation and BNF was influenced by the carbonization technique used to prepare the soil amendment. Hydrochar, in average and across all soils, increased nodule dry matter and BNF by factors of 3.4 and 2.3, respectively, considerably more than pyrochar, which led to 1.8 and 1.2 fold increases, respectively. Nodule dry matter and BNF correlated positively with available soil sulfur and negatively with available soil nitrogen. Hydrochars provided more available sulfur than pyrochars, and hydrochars caused a decrease in nitrogen availability in the soil solution, thereby exerting a positive influence on nodulation and BNF. Pyrochar amendment increased soil pH but had no effect on nodulation and BNF. Plant growth was affected by the soil and by the feedstock used for the “biochar”, and increased slightly more in treatments with pyrochar and hydrochar made from maize, which was richer in nitrogen and potassium. The results show that carbonized organic materials, and specifically hydrochar, have the capacity to increase BNF in soils. We suggest that this enhancement in BNF in response to soil amendments with carbonized organic materials is due to an increase in available sulfur and a reduction of available soil nitrogen.     

Mineral nitrogen impairs the biological nitrogen fixation in soybean of determinate and indeterminate growth types

Soybean (Glycine max Merrill) crop production in Brazil relies mainly on biological nitrogen fixation (BNF) for nitrogen (N) supply. Recent adoption of indeterminate growth-type genotypes has raised doubts on the need for supplemental mineral N that might negatively affect the BNF. We assessed the effects of mineral N on BNF attributes of soybean genotypes grown in central and southern Brazil. Genotypes were inoculated with Bradyrhizobium sp. and/or received mineral N in three sets of experiments. In the first set, two genotypes received increasing rates of mineral N in nutrient solution, which consistently reduced the BNF. In the second set, mineral N applied at sowing and/or topdressing reduced nodulation and ureides-N in determinate and indeterminate growth-type genotypes. In the third set, mineral N applied at R5.3 stage, foliar or as topdressing, did not increase grain yield in four field experiments. Mineral N impaired BNF irrespective of the growth type and had no effect on grain yield.     

Response of symbiotic and asymbiotic nitrogen-fixing microorganisms to nitrogen fertilizer application

Journal of Soils and Sediments - Biological nitrogen fixation (BNF) plays an important role in nitrogen cycling by transferring atmospheric dinitrogen to the soil. BNF is performed by symbiotic and...     

Glyphosate- and imazethapyr-induced effects on yield, nodule mass and biological nitrogen fixation in field-grown glyphosate-resistant soybean

Over half of the 21 Mha of soybean planted in Brazil is now transgenic glyphosate-resistant (GM_RR). A field experiment was carried out to investigate whether the application of glyphosate or imazethapyr to the GM_RR variety reduced the input of N₂ fixation (BNF). No effects on yield, total N accumulation, nodulation and BNF (δ¹⁵N) could be assigned to the genetic modification of the plant. Imazethapyr reduced soybean yield but had no significant effect on BNF. Even though yields were not affected by glyphosate, the significant reduction of nodule mass and BNF to the GM_RR suggests that the use of this herbicide could lead to an increased dependence on soil N and consequently an eventual decrease of SOM reserves.     

Nitrogen fixation potential in global chickpea mini-core collection

Biological nitrogen fixation (BNF) is a sustainable alternative for nitrogen supply to agriculture worldwide. One approach to increasing BNF in agriculture is to breed and use legumes with greater BNF capacity. To assess the capacity for BNF in chickpea (Cicer arietinum) global germplasm, a genetically diverse subset from the USDA global chickpea core collection was assayed for BNF potential. The greenhouse experiment assayed 39 global accessions and commercial cultivar UC-5, inoculated with Mesorhizobium ciceri. Plant height, branch number, nodule number, shoot weight, root weight, nodule weight, proportion of nitrogen fixed, and total nitrogen fixation were determined. All characteristics varied significantly among the accessions. Proportion of plant nitrogen fixed ranged from 47% to 78% and was correlated with shoot weight (r = 0.21, P < 0.01) and total plant weight (r = 0.20, P < 0.01), but not with nodule number or weight. Accession 254549 from Iraq produced the greatest total fixed nitrogen, more than any other accession and 121% more than that fixed by UC-5. The variation among BNF capacities of the accessions supports the preservation and use of global germplasm resources and suggests that nitrogen fixation in commercial chickpea varieties may be improved by introgressing positive alleles from the global chickpea germplasm collections.     

15N同位素稀释法研究固氮菌接种对甘蔗生物固氮的影响

利用15N同位素稀释法,研究接种固氮菌klebsiella L03对甘蔗品种B8和ROC22的生物固氮的影响。结果表明： B8的固氮百分率最高为3128%Ndfa,从苗期开始就显著高于ROC22,分蘖期和伸长初期的固氮量和固氮百分率与ROC22相比差异达到极显著水平。B8和ROC22的根、茎、叶都可发生固氮,以伸长初期（60d）叶片中的固氮能力最强。接种L03能显著提高B8和ROC22各器官的含氮量,其中对ROC22叶片和B8茎的含氮量提高作用最明显。不同甘蔗品种、相同品种的不同器官甚至相同器官的不同生长时期固氮作用有很大差异。     

Utilization of BNF Technology Supplementing Urea N for Sustainable Rice Production

The critical nitrogen (N) requirement of rice crops for maximum yields is well known. To overcome acute N deficiency in rice soils as a result of an increasing yield per unit area in the past 50 years of almost three-fold, this element has been usually supplied to the rice crop as the chemical fertilizer ‘urea’. Unfortunately a substantial amount of the urea-N is lost through different mechanisms, causing environmental pollution problems. In principle, utilization of biological nitrogen fixation technology can supplement the use of urea-N, reducing the environmental problems to a considerable extent by improving nitrogen use efficiency. Different biological nitrogen fixation (BNF) systems have different potentials to provide an N supplement. It is necessary to design appropriate strategies to obtain more sustainable N supply to the rice crop. This paper reviews research to evaluate the potential of different BNF systems to supply N for the rice crop, assessing the current information.     

Nitrogen metabolism and seed composition as influenced by glyphosate application in glyphosate-resistant soybean

Previous research has demonstrated that glyphosate can affect nitrogen fixation or nitrogen assimilation in soybean. This 2-year field study investigated the effects of glyphosate application of 1.12 and 3.36 kg of ae ha(-1) on nitrogen metabolism and seed composition in glyphosate-resistant (GR) soybean. There was no effect of glyphosate application on nitrogen fixation as measured by acetylene reduction assay, soybean yield, or seed nitrogen content. However, there were significant effects of glyphosate application on nitrogen assimilation, as measured by in vivo nitrate reductase activity (NRA) in leaves, roots, and nodules, especially at high rate. Transiently lower leaf nitrogen or (15)N natural abundance in high glyphosate application soybean supports the inhibition of NRA. With the higher glyphosate application level protein was significantly higher (10.3%) in treated soybean compared to untreated soybean. Inversely, total oil and linolenic acid were lowest at the high glyphosate application rate, but oleic acid was greatest (22%) in treated soybean. These results suggest that nitrate assimilation in GR soybean was more affected than nitrogen fixation by glyphosate application and that glyphosate application may alter nitrogen and carbon metabolism.     

The amount,but not the proportion,of N2 fixation and transfers to neighboring plants varies across grassland soils

ABSTRACT

Biological nitrogen fixation (BNF) is an important nitrogen source for both N₂-fixers and their neighboring plants in natural and managed ecosystems. Biological N fixation can vary considerably depending on soil conditions, yet there is a lack of knowledge on the impact of varying soils on the contribution of N from N₂-fixers in mixed swards. In this study, the amount and proportion of BNF from red clover were assessed using three grassland soils. Three soil samples, Hallsworth (HH), Crediton (CN), and Halstow (HW) series, were collected from three grassland sites in Devon, UK. A pot experiment with ¹⁵N natural abundance was conducted to estimate BNF from red clover, and the proportion of N transferred from red clover to the non-N₂ fixing grass in a grass-clover system. The results showed that BNF in red clover sourced from atmosphere in the HH soil was 2.92 mg N plant^?1, which was significantly lower than that of the CN (6.18 mg N plant^?1) and HW (8.01 mg N plant^?1) soils. Nitrogen in grass sourced from BNF via belowground was 0.46 mg N plant^?1 in the HH soil, which was significantly greater than that in CN and HW soils. However, proportionally there were no significant differences in the percentage N content of both red clover and grass sourced from BNF via belowground among soils, at 65%, 67%, 65% and 35%, 27%, 31% in HH, CN, and HW, respectively. Our observations indicate that the amount of BNF by red clover varies among grassland soils, as does the amount of N sourced from BNF that is transferred to neighboring plants, which is linked to biomass production. Proportionally there was no difference among soils in N sourced from BNF in both the red clover plants and transferred to neighboring plants.