四川省夏玉米机械粒收适宜品种筛选与影响因素分析

为筛选适宜四川机械粒收夏玉米品种,明确玉米机械粒收质量影响因素,2017—2019年在四川省中江县开展了夏玉米机械粒收品种筛选试验研究,对参试28个玉米品种、98个品次机械粒收质量、籽粒含水率和产量数据进行分析。结果表明,玉米籽粒破碎率和落穗损失率高是四川夏玉米机械粒收存在的主要问题。夏玉米机械粒收籽粒破碎率平均为5.63%,杂质率平均为2.39%,落穗损失率平均为4.12%,籽粒总损失率平均为4.76%,其中落穗损失占籽粒总损失的86.55%。籽粒含水率与籽粒破碎率、杂质率、落粒损失率呈显著正相关,而与落穗损失率、籽粒总损失率相关不显著。收获时较高的籽粒含水率是导致籽粒破碎率高的主要原因,适当推迟收获时间可有效降低籽粒含水率,进而降低机械粒收籽粒破碎率。种植行距与收获机械行距不匹配导致错行收获是落穗损失率高的主要原因,保证收获机对行收获可显著降低落穗损失率,进而降低籽粒总损失率。本研究以玉米产量和机收时籽粒含水率为指标,筛选出产量高、籽粒含水率低的‘仲玉3号’‘渝单30’‘正红6号’‘延科288’ 4个玉米品种,可作为四川省夏玉米适宜机械粒收的品种。     

基于X-ray μCT技术的玉米籽粒结构特征的粒位效应分析

玉米籽粒因其在果穗上着生位置不同存在较大差异,明确籽粒结构特征的粒位效应为玉米的消费、加工和播种质量等玉米产量和品质性状的评价提供参考。该研究以3个不同籽粒类型的玉米品种登海618(DH618)、KX3564和先玉335(XY335)为材料,利用X射线计算机断层(X-ray micro-computed tomography,X-ray μCT)技术扫描测试样本,通过图像滤波、阈值分割等图像分析方法重建籽粒3维结构,获取玉米果穗不同粒位籽粒的胚、胚乳、皮下空腔、胚空腔、硬质胚乳、粉质胚乳、胚乳空腔等结构参数。数据分析表明,籽粒不同结构指标在果穗上呈现不同的变化规律,从基部到顶部(不考虑果穗两端的极端籽粒),胚、胚乳及硬质胚乳体积线性下降,各指标在果穗上的变化范围分别为15.82～33.36、180.15～296.50及87.13～166.00 mm~3;胚乳空腔皮下空腔胚空腔,果穗中部籽粒的空腔较小且稳定,3个品种表现一致;胚与胚乳的比值在粒位间基本稳定,粉质胚乳体积、硬质胚乳与粉质胚乳的比值从基部至顶部逐渐减小,但不同指标的变化斜率存在差异。3个供试品种的籽粒结构参数不同:DH618果穗不同部位籽粒胚与胚乳的比值大于KX3564和XY335,XY335籽粒硬质胚乳与粉质胚乳的比值大于DH618和KX3564。在籽粒空腔方面,KX3564皮下空腔的比例较高,而XY335胚乳空腔的比例较高。3个品种胚、胚乳、皮下空腔体积在玉米籽粒中的比例平均分别为9.27%、89.87%、0.86%。X-ray μCT扫描技术为玉米籽粒性状的研究提供新的方法与思路,明确果穗籽粒结构的粒位效应有利于全面地掌握玉米果穗上籽粒的性状特征,为玉米的生产、加工及品种改良等提供借鉴。     

山西省春玉米机械粒收质量及其影响因素分析

开展玉米机械粒收质量及其影响因素研究,对推动山西省玉米机械粒收发展,提升玉米产业核心竞争力有重要意义。本文以5个前期试验筛选的适宜机械粒收品种为材料,设置6个收获时期,在同一地块采用同一台机械与同一位农机手操作收获,研究不同收获期对机械粒收质量与产量的影响。研究表明,籽粒含水率随着收获时期的延迟降低;籽粒破碎率与机收落粒率随着收获时期延迟前期快速降低后期趋于稳定略有升高;杂质率随着收获时期的延迟逐步降低最后趋于稳定;落穗损失率随着收获时期的延迟升高。10月15日收获比9月24日收获平均增产11.9%。高的籽粒破碎率是限制山西省春玉米机械粒收的主要因素。籽粒含水率与破碎率模型为y=0.03x~2-1.224x+16.78 (R~2=0.802**)。当籽粒含水率为20.4%时,籽粒破碎率最低。籽粒含水率在15.6%～25.2%区间收获,破碎率能够达到≤5%的国家标准。在山西省春玉米区选择适宜机械粒收品种,收获时间推迟到10月15日,可达到理想粒收质量并增产。‘长单511’‘迪卡159’和‘长单716’在粒收质量与产量方面均表现优秀,可作为山西省春玉米区机械粒收品种推广应用。     

基于扩散理论的华北春玉米生理成熟后籽粒脱水过程分析

玉米机收籽粒可以显著提高玉米的生产效率,是玉米生产的发展方向。生理成熟后的籽粒含水率是决定机收质量的关键,受品种、密度和气候等多种因素影响。准确估算生理成熟后玉米籽粒含水率,进而分析其主要影响因素,最终确定玉米收获时间和筛选适宜机收的品种,对玉米主产区华北的春玉米籽粒机收发展具有重要意义。因此,于2017年和2018年在河北省泊头、南大港、玉田和山西榆次进行了两年田间春玉米试验,每年设置7个共性品种,每个品种3个密度,对生理成熟后籽粒含水率、品种性状、气象和管理要素进行了监测,并利用基于扩散理论考虑空气温湿度的脱水模型对籽粒含水率进行了模拟,进而计算脱水曲线下的面积(AUDDC),用以筛选脱水优异的玉米品种。结果表明,基于扩散理论的籽粒脱水模型对玉米生理成熟后籽粒含水率的模拟效果较好;年份、地点和品种对生理成熟时籽粒含水率(M_0)和水分扩散速率(k)具有显著影响,密度对脱水参数影响不显著。逐步线性回归分析得到灌浆期参考作物蒸发蒸腾量(ET_0)、最高气温和灌水量对M_0具有显著的正效应,生理成熟后30 d内ET0和灌浆中后期降雨对k具有显著的正效应,全生育期降雨对k具有显著的负效应。品种性状中对M_0影响最大的为苞叶层数(正效应),对k影响最大的为叶片数(负效应)。通过模型计算得到,生理成熟后10d华北地区春玉米籽粒含水率可以下降到28%,籽粒含水率下降到25%的概率为50%。由模型计算得到各品种生理成熟后10 d内的AUDDC,与AUDDC平均值比较发现‘京农科728’‘张1453’‘华农887’‘广德5’和‘金科玉3306’为脱水表现优异的品种。     

玉米机械粒收籽粒含杂率与穗轴特性关系分析

明确玉米机械粒收籽粒含杂率及其与穗轴特性的关系,对于实现高质量粒收,推动玉米机械粒收技术发展具有重要意义。该研究于2018—2020年在四川中江同一地块,采用同一机械、操作人员进行分期收获试验,调查籽粒含杂率、各杂质组分绝对含量、穗轴弯曲强度和含水率,探讨各收获期杂质组分和穗轴特性变化规律,以期明确籽粒含杂率与穗轴特性的关系。结果显示,随收获期推迟,籽粒含杂率、杂质中穗轴绝对含量和穗轴含水率显著降低,穗轴弯曲强度先升高后降低。不同收获期穗轴均是主要的杂质成分,比例达32%～79%,平均为51.45%。籽粒含杂率与穗轴弯曲强度和穗轴含水率关系分析结果显示,籽粒含杂率与穗轴弯曲强度不相关,与穗轴含水率呈指数关系(y=0.045 6e~(0.063 7x),R~2=0.774 7, n=75),玉米穗轴含水率降低至65.72%以下收获机械粒收籽粒含杂率可降至3%以下。进一步分析发现,在相同收获期或穗轴含水率相近时,籽粒含杂率与穗轴弯曲强度关系不大。穗轴作为玉米机械粒收主要的杂质成分,其含水率能很好解释籽粒含杂率的变化。生产上选择和选育玉米穗轴脱水快、含水率低或通过推迟收获期在玉米穗轴含水率较低时进行机械粒收,可显著降低机械粒收含杂率。     

京津冀地区密植高产宜机收籽粒春玉米品种筛选

机收籽粒可以显著提高玉米生产效率降低生产成本，但是目前京津冀地区适宜机收籽粒的玉米品种较少，品种筛选评价体系缺乏，阻碍了玉米籽粒机收的推广实行。针对这一问题，该研究开展了3 a春玉米品种和种植密度互作试验以及2 a玉米籽粒机收试验。根据宜机收籽粒品种要求、该地区气候和种植条件，设置宜机收性、高产稳产优质性和水分利用效率（Water Use Efficiency, WUE）高稳性3个一级评价指标。宜机收性下二级评价指标为籽粒破碎率、含杂率、总损失率和收获速率。籽粒破碎率和含杂率与籽粒含水率分别呈二次函数关系和指数关系，籽粒破碎率≤5%的籽粒含水率在3.6%～24.8%之间；当籽粒含水率≤26.99%时，含杂率≤3%的，因此将生理成熟后10 d的籽粒含水率≤25%作为籽粒破碎率和含杂率的三级评价指标。总损失率与籽粒含水率二次函数关系，与倒伏倒折率和穗位高标准差呈线性关系，因此将生理成熟后10 d的籽粒含水率（≤25%）、倒伏倒折率（≤5%）和穗位高标准差（≤5.93 cm）作为总损失率的三级评价指标。由于倒伏倒折率是影响收获速率的主要作物指标，因此将倒伏倒折率（≤5%）作为收获速率的三级评价指标。品种―种植密度互作试验的平均产量、WUE和穗粒腐病率分别为10 889.64 kg/hm2、2.28 kg/m3和1.75%，产量和WUE标准差平均值分别为1 776.79 kg/hm2和0.43 kg/m3，产量和WUE高稳系数平均值分别为0.53和0.46。通过相关性分析计算，种植密度增加15 000株/hm2条件下春玉米产量和WUE平均增加6.59%和11.89%，单株产量平均下降8.38%。据此得到高产稳产优质性和WUE高稳性下的二级评价指标及其判别标准。在确定各级评价指标及其判别标准的基础上，通过层次分析法和熵权法得到末级评价指标的组合权重，并将各评价指标的判别标准作为判别品种的指标值，避免单纯依靠排序确定品种优劣。通过综合性状评价筛选出豫丰98、豫单9953和金科玉3306为京津冀地区适宜籽粒机收的春玉米品种。分析发现该地区宜机收籽粒春玉米品种应具有籽粒脱水快、高产、稳产、增密增产、穗粒腐病率低、WUE高的特点。通过构建适宜的品种筛选体系，有利于玉米籽粒机收技术在京津冀地区推广，对其他地区密植高产宜机收籽粒玉米品种的筛选有一定的借鉴意义。     

陇东旱塬区宜机收玉米品种的性状指标综合评价

目前玉米生产机械化程度越来越高,玉米籽粒机收将是大势所趋,因此人们对玉米品种的选择也趋向于耐密植、抗倒伏和籽粒脱水快等优良性状。为了筛选出陇东旱塬区适宜的籽粒机收玉米品种,通过灰色关联度分析法对引进的17个玉米品种表型性状和籽粒机收适宜性进行综合评价。结果表明,和恒5266产量高,但是机收表现不理想;迪卡159、先丰9号、先玉1483、五谷737和新农育6003等5个品种综合表现良好,可以作为陇东旱塬区籽粒机收玉米品种贮备品种加以推广,尤其是五谷737产量高、抗性好、机收表现好,宜大力推广种植。     

黄淮海夏玉米机械化粒收质量及其主要影响因素

针对黄淮海夏玉米区机械粒收质量差及其主要影响因素不明确,该研究选择黄淮海夏玉米区2013-2019年机械粒收技术联合试验示范的1 250组测试样本进行籽粒含水率、破碎率、杂质率和损失率等粒收质量统计分析,结果表明,夏玉米机械粒收时籽粒含水率平均为27.38%,破碎率平均为9.29%,杂质率平均为1.68%,损失率平均为3.28%,籽粒含水率和破碎率明显高于全国平均值。从不同年份收获质量看,2018、2019年收获籽粒平均含水率下降至25.45%和25.05%,平均破碎率下降至9.07%和7.88%,虽仍然高出国家玉米机械收获规定的破碎率标准(≤5%)的要求,但收获质量已发生明显改善。破碎率与收获期籽粒含水率之间呈二次曲线关系,破碎率最低时籽粒含水率为21.08%。因此,破碎率高仍然是黄淮海夏玉米机械粒收存在的主要质量问题,而收获期籽粒含水率高是导致破碎率高、制约机械粒收的主要原因。针对黄淮海夏播区热量资源梯度分布差异较大,玉米收获季节窗口期短的特点,选择早熟、脱水快的品种,进行品种脱水与区域气候资源配置,进一步降低收获期籽粒含水率,规范宜机械粒收栽培技术以及收获机操作规程是破解黄淮海夏玉米粒收质量差的关键。     

陇东旱塬区机械粒收玉米新品种品质分析

为筛选出适合陇东旱塬区机械籽粒直收的优质丰产玉米新品种,采用DA7200型近红外品质分析仪对平凉市泾川县高平玉米籽粒机械直收试验的20个玉米品种的籽粒进行了蛋白质、脂肪和淀粉含量测定。结果表明,有13个品种的蛋白质、脂肪和淀粉含量都达到了国家级玉米品种审定标准,其中MC703、新玉108、瑞普909、联创825、先玉698、MC618和京科999在淀粉和蛋白质含量较高的同时,脂肪含量也比较高,淀粉、蛋白质和脂肪含量3个指标比国家级玉米品种审定标准分别高1.45%～3.33%、7.50%～21.25%和16.67～43.33%。结合产量和籽粒机械粒收指标数据,从参试品种中筛选出3个品质指标均较高且适宜旱塬区机械粒收的丰产优质玉米新品种是可行的。     

密度对春玉米生理成熟后倒伏变化的影响

晋中盆地热量资源丰富,后期可供春玉米立秆脱水时间充足,抗倒性是该区域实施春玉米机械粒收的关键因素。增密种植与立秆延期收获是机械粒收技术发展和推广的重要措施,而玉米生长后期倒伏是限制种植密度进一步提升的重要因素,如何合理选择种植密度同时兼顾高产和抗倒就成为该区域实施春玉米机械粒收技术面临的重要问题。为此于2017—2019年在山西省农业科学院东阳试验示范基地,以29个玉米主栽品种和已审定、待审定、有潜力的宜机收品种为材料,分析了春玉米3个种植密度(6.0万株·hm~(-2)、7.5万株·hm~(-2)和9.0万株·hm~(-2))下生理成熟后倒伏情况。结果表明,随着种植密度增加,春玉米生理成熟期平均倒折率分别为0.4%、1.2%和2.5%,生理成熟后平均倒折率呈显著(P0.05)增加,且每推迟10 d玉米倒折率分别平均增加0.2个、0.7个和1.5个百分点。根据拟合方程,以GB/T 21962—2008规定的玉米机械粒收条件倒折率小于5%为标准, 9.0万株·hm~(-2)仅可立秆至10月2日, 7.5万株·hm~(-2)和6.0万株·hm~(-2)可充分利用当地积温立秆脱水至11月。根据收获期产量和倒折率双向平均法, 3年都稳定表现出高产抗倒的品种为‘金科玉3306’(7.5万株·hm~(-2))、‘金科玉3306’(9.0万株·hm~(-2))、‘迪卡517’(7.5万株·hm~(-2))和‘华农887’(7.5万株·hm~(-2)),收获期平均产量为14 091.8kg·hm~(-2),平均倒折率为1.7%,可推荐为该区域春玉米适宜机械粒收的品种和密度。一般可根据降水年型、灌溉条件以及品种耐密性等,合理选择6.0万株·hm~(-2)或7.5万株·hm~(-2)两种种植密度,以实现高产抗倒,最终提高春玉米机械粒收产量和质量。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.