Development of a LC-MS/MS method for the analysis of enniatins and beauvericin in whole fresh and ensiled maize

A LC-MS/MS method for the detection of beauvericin and the four enniatins A, A1, B, and B1 in maize and maize silage was developed. The method uses direct injection of maize extracts without any tedious and laborious cleanup procedures. The limit of quantification was determined at 13 ng g(-1) for beauvericin and at 17, 34, 24, and 26 ng g(-1) for enniatins A, A1, B, and B1, respectively. The method was used in surveys of the compounds in fresh maize samples collected at harvest in 2005 and 2006. All samples had the same distribution of the enniatins: B > B1 > A1 > A. Enniatin B was present in 90% of the samples in 2005 and in 100% in 2006 at levels up to 489 and 2598 ng g(-1), respectively. Beauvericin contamination was more frequently detected in 2006 than in 2005 (89 and 10%, respectively) and in higher amounts (988 and 71 ng g(-1), respectively). The occurrence of beauvericin and the four enniatins was examined in 3-month-old maize silage stacks from 20 different farms. As observed in fresh maize, enniatin B was the most abundant compound in ensiled maize and was found from 19 stacks at levels up to 218 ng g(-1). The stability of enniatin B in maize silage was assessed by analyzing samples from 10 of the silage stacks taken after 3, 7, and 11 months of ensiling. Enniatin B could be detected at all locations after 11 months and appeared to be stable during ensiling.     

基于高光谱成像技术的青贮玉米饲料pH值无损检测

为实现青贮玉米饲料pH值的快速、无损检测,该研究采用高光谱成像技术建立不同品质青贮玉米饲料pH值的定量检测模型。采集青贮玉米饲料样本936～2 539 nm的平均光谱,采用6种预处理方法对青贮玉米饲料平均光谱进行处理,通过建立偏最小二乘回归（partial least squares regression,PLSR）模型得出多元散射校正（multiplicative scatter correction,MSC）和卷积平滑（savitzky-golay,SG）两种预处理方法效果较好,使用竞争性自适应重加权算法（competitive adaptive reweighted sampling,CARS）、变量组合集群分析算法（variable combination population analysis,VCPA）以及迭代保留信息变量（iteratively retains informative variables,IRIV）算法对经MSC和SG卷积平滑预处理光谱进行特征波长提取,利用PLSR和极限学习机（extreme learning machines,ELM）分别建立饲料全波段、特征波长的pH值预测模型。MSC-CARS-PLSR为最优算法组合,其校正集决定系数为0.926 2,均方根误差为0.421 3,预测集决定系数为0.917 0,均方根误差为0.426 6。研究结果表明,结合PLSR模型可以实现对青贮玉米饲料pH值的准确预测,可为青贮玉米饲料pH值提供一种可靠且有效的无损检测新方法。     

不同施氮水平下青贮玉米农田土壤酶活性时空分布特征

【目的】研究氮肥施用下青贮玉米田土壤酶活性时空变化特征,为内蒙古中部青贮玉米高产高效栽培提供理论依据。【方法】以“种星青饲1号”为供试材料,设置0(N0)、120 (N8)、180(N12)、240(N16)、300(N20)和360(N24) kg hm^-26个氮肥梯度,系统分析2018～2019年不同处理青贮玉米田土壤酶活性在5个生育期和0～40 cm土体的时空变化特征,并探究了青贮玉米产量对施氮水平的响应。【结果】青贮玉米田土壤酶活性在不同施氮处理、生育期于0～40 cm土体中存在显著差异(P <0.05),随着玉米生育期的延长,青贮玉米田土壤酶活性呈“抛物线”型变化,大喇叭口期-抽雄期最高。相比0～20 cm土层,较深的土层增加了过氧化氢酶(CAT)活性的同时降低了脲酶(UA)活性。增施氮肥有效促进蔗糖酶(IA)、碱性磷酸酶(APA)、脲酶活性及玉米产量的增加,且施氮量为240 kg hm^-2(N16)时集中呈现出酶活性及产量峰值。2018年与2019年N16处理玉米生物鲜重分别较其他处理高出了8.07%～65.88%和7.11...     

基于改进离散粒子群算法的青贮玉米原料含水率高光谱检测

快速、无损和准确检测青贮玉米原料含水率,对确保青贮玉米发酵品质、推动青贮产业健康快速发展有重要现实意义。为探究高光谱技术在青贮玉米原料含水率检测方面的可行性,研究通过高光谱成像系统获取青贮玉米原料高光谱图像并利用烘箱加热法测定实际含水率。在粒子更新方式和惯性权重2个方面对传统离散粒子群算法(discretebinary particle swarm optimization,DBPSO)进行优化,提出基于改进型离散粒子群算法(modified discrete binary particle swarm optimization,MDBPSO)的特征波段优选方法,并利用相关系数分析法(correlation coefficient,CC)、DBPSO和MDBPSO法提取原料含水率高光谱特征变量,基于全波段反射光谱(total spectral reflectance,TSR)和特征波段反射光谱建立青贮玉米原料含水率预测模型。结果表明,MDBPSO优选特征波段适应度函数的收敛精度和收敛效率较DBPSO法均有明显改善,最优适应度值由0.761 6提高至0.812 3,函数收敛迭代次数由280次降低至79次。MDBPSO-PLSR预测模型的建模精度和预测精度均高于CC-PLSR、DBPSO-PLSR和TSR-PLSR预测模型,其校正集决定系数Rc2和均方根误差RMSEC(root mean square error of calibration)分别为0.81和0.032,预测集决定系数Rp2和均方根误差RMSEP(root mean square error of prediction)分别为0.80和0.045。该研究表明,利用高光谱图像技术检测青贮玉米原料含水率具有较高的精度,研究可为后续开发青贮玉米原料水分快速检测仪器提供借鉴方法。     

青贮玉米新品种引种试验初报

为筛选适宜临夏地区种植的优质高产青贮玉米品种,促进旱作生态区青贮玉米产业发展,在临夏县川塬灌区覆膜栽培条件下,对引进的13个青贮玉米新品种进行试验观察。结果表明,生物产量高于对照品种豫玉22号的品种共8个,其中铁研53、京九青贮16、大京九26较高,分别为123 297.8、121 464.4、119 172.6 kg/hm2,较对照品种豫玉22号分别增产14.47%、12.77%、10.64%;屯玉168、陇青贮1号、瑞青贮616、金穗1915、大唐8号分别为118 714.3、117 339.2、114 130.7、110 005.5、108 638.8 kg/hm2,较对照品种豫玉22号分别增产10.21%、8.94%、5.96%、2.13%、0.86%。依据青贮玉米品质分级标准,佳玉1017达到一级;屯玉168、陇青贮1号、金穗1915、京科627、登海3721、瑞青贮616达到二级。综合产量和品质因素,屯玉168、陇青贮1号、金穗1915、京九青贮16、大京九26、瑞青贮616适宜在临夏地区推广种植,铁研53作为高生物产量、佳玉1017作为高饲用品质推荐品种。     

Microwave-assisted extraction of bound phenolic acids in bran and flour fractions from sorghum and maize cultivars varying in hardness

To release bound phenolic acids, a microwave-assisted extraction procedure was applied to bran and flour fractions obtained from eight sorghum and eight maize cultivars varying in hardness. The procedure was followed by HPLC analysis, and the identities of phenolic acids were confirmed by MS/MS spectra. The extraction of sorghum and maize bound phenolic acids was done for 90 s in 2 M NaOH to release ferulic acid and p-coumaric acid from bran and flour. Two diferulic acids, 8-O-4'- and 8-5'-benzofuran form, were identified and quantitated in sorghum bran, and only the former was found in maize bran. The contents of ferulic acid and diferulic acids in sorghum bran were 416-827 and 25-179 μg/g, respectively, compared to 2193-4779 and 271-819 μg/g in maize. Phenolic acid levels of sorghum were similar between hard and soft cultivars, whereas those of maize differed significantly (p < 0.05) except for ferulic acid in flour. Sorghum phenolic acids were not correlated with grain hardness as measured using a tangential abrasive decortication device. Maize ferulic acid (r = -0.601, p < 0.01), p-coumaric acid (r = -0.668, p < 0.01), and 8-O-4'-diferulic acid (r = -0.629, p < 0.01) were significantly correlated with hardness.     

Liquid chromatographic determination of zearalenone and zearalenol in animal feeds and grains, using fluorescence detection

A liquid chromatographic (LC) method was developed for the determination of zearalenone and zearalenol in grains and mixed animal feeds. Samples are extracted with chloroform and purified by a base-acid liquid-liquid partition. Zearalenone and zearalenol are separated by reverse phase LC and determined by fluorescence detection, excitation wavelength 236 nm with a 418 nm cutoff filter. The method was applied to the determination of zearalenone and zearalenol in 395 survey samples of corn, oats, barley, sorghum, silage, and finished feeds. The limit of detection is 10 ng/g for both toxins. The range of naturally occurring toxins found was 10-4,000 ng/g. Average recoveries were 84% for zearlenone and 69% for zearalenol. Coefficients of variation were 24.6% for zearalenone and 30.8% for zearalenol for crop year 1980, and 28.3% for zearalenone and 22.0% for zearalenol for crop year 1981.     

Liquid chromatographic determination of fumonisins B1, B2, and B3 in corn silage

Corn silage was dried, ground, and then extracted with 0.1 M ethylenediaminetetraacetic acid. The filtrate was applied to a FumoniTest immunoaffinity column. Fumonisins were derivatized with naphthalene-2,3-dicarboxaldehyde, separated on a C(18) liquid chromatographic column, and detected by fluorescence. The detection limits for fumonisin B(1), fumonisin B(2), and fumonisin B(3) were 50, 25, and 25 ng/g of dried silage, respectively. Recoveries of fumonisin B(1), fumonisin B(2), and fumonisin B(3) from wet and dried corn silage spiked over the range of 100-5000 ng/g averaged 91-106%. The method was applied to corn silage samples collected from the midwestern area of the United States during 2001-2002. Of 89 corn silage samples, fumonisin B(1), fumonisin B(2), and fumonisin B(3) were found in 86 (97%), 64 (72%), and 51 (57%) of the samples. The mean positive levels of fumonisin B(1), fumonisin B(2), and fumonisin B(3) were 615, 93, and 51 ng/g, respectively, in dried silage. This suggests that fumonisins may be frequent low level contaminants in corn silage.     

菜籽蛋白加工废液中多酚和多糖同步提取工艺优化

为开发利用菜籽蛋白加工废液中的生理活性物质,该研究在单因素试验基础上,采用Box-Behnken响应面试验设计法,对菜籽蛋白加工废液中多酚和多糖提取工艺条件进行优化,同时探究两种物质的体外抗氧化活性。结果表明,影响菜籽蛋白加工废液中多酚和多糖得率的因素大小顺序为:乙醇体积分数浸提温度浸提时间,最佳提取工艺为:浸提温度60℃、乙醇体积分数65%、浸提时间31 min,在此条件下多酚得率为2.19%,多糖得率为8.14%;多酚提取物对DPPH·具有较强清除能力,其半抑制质量浓度为0.20 mg/mL,多糖提取物对DPPH·和·OH均具有较强的清除能力,其半抑制质量浓度分别为1.45、2.38 mg/mL;高效液相色谱法初步检测表明,菜籽蛋白加工废液中含有香豆酸、丁香酸、对香豆酸、芥子酸和苯甲酸。研究结果为菜籽蛋白加工废液的再利用提供参考。     

Silage yield and quality of row intercropped maize and soybean in a crop rotation following winter wheat

Maize (Zea mays L.) intercropped with soybean (Glycine max L.) may be a viable option to improve the quality of the silage. In this study, maize and soybean intercropped in different numbers of rows and their monocropping equivalents were tested to determine the best intercropping system in a crop rotation following winter wheat. The treatments were monoculture maize (M), monoculture soybean (S), 75% maize + 25% soybean (3M:1S), 50% maize + 50% soybean (2M:2S) and 25% maize + 75% soybean (1M:3S). The experiment was laid out in a randomized complete block design with three replications in 2011 and 2012 in Antalya, Turkey. Highest fresh forage yields were obtained from maize (53.3 t ha^?1) and 3M:1S (62.8 t ha^?1) treatments in 2011 and 2012, respectively. Maize treatment had highest dry matter yield (21.1 and 22.0 t ha^?1) in both years. Quality analysis of silage revealed that 3M:1S was superior to maize treatment in terms of dry matter (25.23%), crude protein (7.31%), crude fiber (18.27%), neutral detergent fiber (42.56%), acid detergent fiber (25.81%), lactic acid (4.71%) and acetic acid (4.05%). In conclusion, 3M:1S row intercropped production system was a better alternative for silage to monoculture maize in a crop rotation following winter wheat.     

Rapid method for quantitative analysis of the aroma impact compound, 2-acetyl-1-pyrroline, in fragrant rice using automated headspace gas chromatography

A rapid method employing static headspace gas chromatography (HS-GC) has been developed and validated for quantitative analysis of the impact aroma compound, 2-acetyl-1-pyrroline (2AP), in grains of fragrant rice. This developed method excludes wet extraction, and the rice headspace volatiles are brought directly and automatically to GC analysis. The conditions of the static HS autosampler were optimized to achieve high recovery and sensitivity. The most effective amount of rice sample used was 1 g, which provided 51% recovery and a linear multiple headspace extraction (MHE) plot of the peak area of 2AP. The sensitivity of the method was enhanced by utilizing a megabore fused silica capillary column in conjunction with a nitrogen-phosphorus detector (NPD). Method validations performed for both static HS-GC-FID and HS-GC-NPD demonstrated linear calibration ranges of 20-10 000 (r(2) = 0.9997) and 5-8000 (r(2) = 0.9998) ng of 2AP/g of rice sample, respectively. The limits of detection for both systems were 20 and 5 ng of 2AP, and the limits of quantitation were 0.30 and 0.01 g of brown rice sample, respectively. Reproducibility calculated as intraday and interday coefficients of variation were 3.25% RSD (n = 15) and 3.92% RSD (n = 35), respectively, for SHS-GC-FID and 1.87% RSD (n = 15) and 2.85% RSD (n = 35), respectively, for SHS-GC-NPD. The method was found to be effective when applied to the evaluation of aroma quality, based on 2AP concentrations, of some fragrant rice samples.     

基施缓释肥等氮替代化肥对径流氮素流失和青贮玉米生长的影响

[目的]探究配施两种释放方式不同的缓释氮肥对滇中地区坡耕地径流氮素流失及青贮玉米生长的影响,为滇中坡耕地水土保持提供理论依据和支持。[方法]通过研究自然降雨条件下的径流槽模拟试验,在等氮条件下设置普通尿素(CK),40%添加了硝化抑制剂的速溶诺泰克^?21+60%普通尿素(处理I)和40%包膜缓释氮肥聚谷氨酸增效3代+60%普通尿素(处理Ⅱ)3个处理。[结果]生育期内各处理氮素流失呈先上升后下降的趋势,其中CK流失量最高,处理I和处理Ⅱ较CK有显著减少,总氮流失量分别下降了29.95%和16.77%,硝态氮分别减少了14.55%和6.53%,铵态氮分别减少了16.08%,8.24%。尿素配施缓释氮肥能够有效提高土壤全氮和铵态氮含量,减少硝态氮含量。处理I,Ⅱ较CK相比土壤全氮含量增加了3.25%和0.87%,铵态氮含量分别显著增加了30.57%,25.70%;较CK相比,处理I、处理Ⅱ硝态氮含量分别减少了22.49%和16.61%。[结论]3个处理间青贮玉米的产量无显著性差异,但配施缓释肥可以在保证土壤肥力和满足青贮玉米正常生长需求的同时减少坡耕地径流养分流失,其中...     

复合菌剂对青贮玉米营养成分及其饲喂滩羊效果的研究

筛选复配适合宁夏地区的青贮微生物菌剂,可解决在青贮自然发酵过程中,青贮玉米营养损失多且易发霉等问题。本研究对从宁夏中部干旱区自然发酵的青贮玉米饲料中分离鉴定的1株乳酸菌(Lactobacillus acidophilus)和1株酵母菌(Saccharomyces cerevisiae)进行性能测定,复配后形成复合菌剂并进行45 d的大型窖贮青贮发酵试验,设置不添加菌剂和添加商业菌剂的青贮饲料为对照组。营养成分测定结果显示,与不加菌剂和添加商业菌剂的对照组相比,经复合菌剂处理后饲料中性洗涤纤维和酸性洗涤纤维显著下降(P0.05),干物质和粗脂肪含量显著增加(P0.05),粗蛋白含量变化不显著。为期75 d的滩羊肥育饲喂和5 d的消化代谢试验表明,对照组与试验组滩羊的日均采食量差异显著(P0.05),平均日增重、末重、料重比差异不显著。试验组滩羊对青贮玉米饲料中粗蛋白、粗脂肪表观消化率显著提高(P0.05),中性洗涤纤维表观消化率提高,对酸性洗涤纤维的表观消化率影响不显著。结果表明,复合菌剂显著改善了青贮玉米饲料的品质,复合菌剂发酵的饲料玉米对滩羊生长有良好的促进作用。     

玉米秸秆与废弃白菜的混合青贮品质及产沼气能力分析

为实现干玉米秸秆(dried maize straw,DMS)的长时间保质贮存,利用青贮原理将DMS与废弃白菜(cabbage waste,CW)连续混贮90 d,设置DMS单贮组和6个不同质量比例(DMS:CW=29:19、27:21、25:23、23:25、21:27和19:29)混贮组,间隔30 d分析其贮存品质,筛选适宜贮存条件,并考察秸秆贮存前后的微观结构变化和产沼气潜力。结果表明,与单贮组相比,6个混贮组的p H值均显著下降(P0.05),乳酸含量显著升高(P0.05),混贮品质优于单贮。6个混贮组贮存30 d时的p H值均为最低,乳酸含量最高,感官评价均为优级,30 d后p H值有所上升,乳酸含量急剧下降,60d时的木质素含量显著降低(P0.05),综纤维素含量显著升高(P0.05)。随着CW比例增加,混贮组p H值逐渐减小,乳酸含量逐渐增加,MEⅤ组(DMS:CW=21:27)p H值最低,乳酸含量最高,能使DMS连续贮存60 d不变质。扫描电镜结果显示,青贮发酵使干秸秆原先致密复杂的木质纤维结构开始瓦解,青贮秸秆表面有很多裂缝和孔洞,与微生物或酶的可接触面积增加。沼气发酵试验表明,MEⅤ组混贮秸秆的累积产气量略高于未贮存干秸秆,且累积甲烷产量提高了61.67%,是未贮存干秸秆的1.6倍。Modified Gompertz模型显示混贮秸秆的甲烷生成速率增加,产甲烷能力提高。总之,当DMS∶CW质量比为21∶27(含水率为73%)时DMS能连续保质贮存2月,且贮存后秸秆的甲烷产量明显提升。     

内蒙古东部中晚熟区青贮玉米产量和品质与气象因素的关系

为研究青贮玉米(Zea mays L.)产量和品质与气象因素的关系,于2018—2019年在通辽市农业科学研究院试验基地,以北农青贮368、东科301、京科青贮516及京科968为材料,设置D1(4月24日)、D2(5月1日)、D3(5月8日)和D4(5月15日)4个播期,比较不同播期条件下青贮玉米产量和品质的变化,分析青贮玉米产量和品质形成与气象因素的关系。结果表明,随着播期的推迟,各品种青贮玉米生育期缩短,株高和茎粗均呈增加趋势,绿叶数变化不大,D2播期的穗位较高。各品种在D2播期的平均生物产量最高(35.2～40.2 t·hm^-2)。随着播期推迟,中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)含量呈增加趋势,粗蛋白含量变化不明显,D2播期淀粉含量较高。生育期日照时数(R²=0.381,P=0.031)和吐丝后日照时数(R²=0.507,P=0.003)与干物质产量呈负相关,生育期降雨量(R²=0.591,P<0.001)和吐丝后降雨量(R²=0.367,P=0.03...     

Simultaneous detection of residues of 25 β₂-agonists and 23 β-blockers in animal foods by high-performance liquid chromatography coupled with linear ion trap mass spectrometry

A sensitive method has been developed for the simultaneous determination of residues of 25 β?-agonists and 23 β-blockers in animal foods by high-performance liquid chromatography coupled with linear ion trap mass spectrometry (HPLC-LIT-MS). This method is based on a new procedure of hydrolysis and extraction by 5% trichloracetic acid, and then cleaned up by mixed strong cation exchange (MCX) cartridges coupled with a novelty cleanup step by methanol. Methanol and 0.1% formic acid were used as mobile phases for gradient elution, while a Supelco Ascentis Express Rp-Amide column was used for LC separation. ESI positive ion scan mode was used with consecutive reaction monitoring (CRM, MS3). Nine β?-agonists labeled by the deuterium isotope were used as internal standards for quantification. The linear ranges of 48 analytes were from 5 to 200 μg/L; the coefficient of correlation was not less than 0.995. Blank pork muscle, blank liver, and blank kidney were selected as representative matrix for spiked standard recovery test. The recoveries of each compound were in the range of 46.6-118.9%, and the relative standard deviations were in the range of 1.9-28.2%. Decision limits (CCα, α = 0.01) of 48 analytes in muscles, liver, and kidney samples ranged from 0.05 to 0.49 μg/kg, and the detection capability (CCβ, β = 0.05) ranged from 0.13 to 1.64 μg/kg. This method was successfully applied to 110 real animal origin food samples including meat, liver, and kidney of pig and chicken samples.     

Optimization of extraction conditions for active components in Hypericum perforatum using response surface methodology

Optimal conditions for extraction of Hypericum perforatum were determined using response surface methodology. A 3 x 4 x 4 full factorial design representing three extraction temperatures, four extraction times, and four solvent concentrations was executed. The overall extraction efficiency was defined by comparing either the total extractable material weight or the individual component peak area to the peak area of luteolin as internal standard. Of the tested variables, the extraction temperature most significantly affected extraction efficiency. Higher temperatures gave better extraction efficiencies, but high temperature also caused decomposition of hypericin. Within the test range, responses for most variables had local maxima. Optimum ranges of time and concentration for individual variables were overlaid. Considering all variables, optimum ranges for extraction time and extraction solvent concentration (percent ethanol in acetone) were 5.0-6.7 h and 44-74% at 23 degrees C, 5.4-6.9 h and 45-72% at 40 degrees C, and 5.3-5.9 h and 44-69% ethanol in acetone at 55 degrees C, respectively.     

Dissolution of rock phosphate in silage leachate

Abstract

Following a favourable crop response to rock phosphate (RP) in a long term fertility trial in DeKalb, IL, an experiment was designed to dissolve RP in silage leachate on the premise that silage has a pH of 4.0 to 4.2 and that once drained of its leachate, it can be used for animal feed. Two types of RP, Brown Sugar RP and Ruhm's RP, having 30% P₂O₅ were dissolved in pure organic acids similar to those present in silage leachates. The amount of dissolved phosphorus (P) from RP in organic acids increased with organic acid:RP ratio. The highest amount of P dissolution was found with butyric acid. Thus, butyric acid with Brown Sugar RP, 2519, 1500, and 710 μg P/g RP were dissolved at 800, 400, and 200 acid:RP ratio, respectively; with Ruhm's RP the values were 3900, 1988, and 835, μg P/g RP, respectively. After dissolution of the two types of RP in the acids, there was an increase in solution pH of 1 to 2 units. Of the three types of silage leachates used, grass silage leachate had the highest acidity and calcium (Ca) concentration followed by high moisture and low moisture corn silage leachates, respectively. Soluble P concentration was five times higher in high moisture corn and grass leachates than in low moisture corn silage leachate. There was a decrease in acidity, Ca, and P content with the number of successive leachings. In low moisture corn silage leachate, 13.9 and 3.05 mg P/g Brown Sugar RP and 14.4 and 3.05 mg P/g Ruhm's RP were solubilized in the 1st and 2nd leaching, respectively. The study shows that corn low moisture silage leachate can dissolve RP efficiently and that it is a good, promising, and environmentally safe method for RP dissolution.     

黄淮地区涝渍胁迫影响夏玉米生长及产量

在黄淮平原,夏玉米常因降水过多遭受涝渍害而减产,确定其能忍受的涝渍胁迫天数,可为该区减轻涝渍引起的夏玉米产量损失和农业生产防灾减灾管理提供依据。该研究在田间条件下以玉米品种浚单20为试验材料,分别于玉米拔节期和抽雄期设置持续淹水(3和5 d)和渍水(5、7和10 d)处理,旨在研究黄淮地区夏玉米拔节期和抽雄期持续涝渍胁迫对其生长及产量的影响。结果表明:玉米拔节期连续淹水3 d或拔节期、抽雄期连续渍水5 d夏玉米产量开始降低,产量损失率随涝渍时间延长而增加:拔节期淹水3 d、抽雄期淹水5 d,其产量损失率分别为28.4%和42.8%;拔节期或抽雄期渍水5 d的产量损失分别为13.8%和5.5%(2011年)和3.0%和3.4%(2012年);拔节期淹水5 d产量损失是淹水3 d的3.1倍;拔节期或抽雄期渍水10 d产量损失分别为渍水5 d的1.3和3.0倍(2011年)、2.4和3.2倍(2012年)。淹水天数相同时,拔节期淹水产量损失率大于抽雄期淹水。所有淹水处理都会降低每平方米有效株数,而抽雄期淹水5 d还影响秃尖比,拔节期淹水5 d影响所有测定指标如收获指数、果穗性状等。不同于淹水处理,所有渍水处理都不影响每平方米有效株数,但影响果穗长和秃尖比、收获指数(抽雄期渍水5 d除外)。涝渍胁迫的后续影响与胁迫生育期、及涝渍天数有关,如抽雄期淹水3~5 d和抽雄期渍水5 d只影响乳熟期地上部分干质量累积,而抽雄期渍水7 d会影响所有生育期干质量累积。拔节期淹水5 d和渍水10 d使玉米后期(吐丝后25~35 d)灌浆速度降低59.6%和28.9%。因此在玉米实际生产中出现连续强降水天气时,建议尽快采取排涝降渍措施减少以避免玉米拔节期连续淹水3 d或抽雄期连续渍水5 d,从而降低涝渍胁迫对玉米生长及产量的影响。     

配施硫基肥对夏玉米镉铅累积的阻控效应

该文以府河流域污灌区农田为研究对象,通过田间小区试验研究了5种施肥措施对土壤重金属镉(Cd)、铅(Pb)有效性以及夏玉米(Zea mays L.)对Cd、Pb富集和转运能力的影响。结果表明:与农民常规施肥(CK)相比,尿素、磷酸二铵和氯化钾配施(N-P-K)以及腐殖酸复合肥、尿素和磷酸二铵配施(HA-N-P)的表层土壤Cd、Pb有效性以及夏玉米对Cd、Pb的富集和迁移能力差异均不显著(P0.05)。然而,腐殖酸复合肥、硫酸铵和磷酸二铵配施(HA-S-P)以及硫酸铵、磷酸二铵和硫酸钾配施(S-P-K)2种施肥措施的表层土壤有效Cd含量分别比CK降低了10.60%和6.36%,表层土壤有效Pb含量分别比CK降低了11.49%和6.00%。此外,HA-S-P处理和S-P-K处理夏玉米Pb转运系数分别比CK降低了50.33%和77.10%,且夏玉米籽粒Pb含量分别比CK降低了59.75%和80.43%(P0.05),但各处理间夏玉米对Cd的转运和富集能力差异并不显著,这说明施用硫基肥可有效抑制夏玉米对Pb的富集和转运,但并未影响其对Cd的富集和转运。综上所述,该污灌区轻度Cd、Pb复合污染农田土壤种植夏玉米建议硫酸铵、磷酸二铵和硫酸钾配施,或者腐殖酸复合肥、硫酸铵和磷酸二铵配施。