Effect of Foliar Sulfur and Nitrogen Fertilization on Wheat Storage Protein Composition and Dough Mixing Properties

Nitrogen (N) and sulfur (S) supplies have a strong influence on the quality and quantity of wheat storage proteins, which play an important role in the breadmaking process. Nitrogen derived from urea, S from micronized elemental sulfur, and a mixture of both (N+S) were applied at anthesis stage on wheat by foliar spray. To relate N and S incorporation in storage proteins to the quality of dough, their incorporation into each storage protein fraction was measured: monomers, low molecular weight glutenin subunits (LMW‐GS), and high molecular weight glutenin subunits (HMW‐GS). Then protein fraction quantities, molecular weight distribution (MWD), polymerization index (PI), and molecular dimensions of unextractable polymeric protein (UPP), as well as dough mixing properties were determined. Fertilizers N and S were differentially incorporated into each storage protein fraction, influencing protein synthesis. Moreover, after the N+S fertilization, the increase of the polymeric proteins induced an increase in molecular weight and compactness, as well as in dough strength and consistency. These results provide evidence that N and S fertilizers applied by foliar spray route at anthesis, simultaneously, play an important role in controlling the storage protein synthesis and the degree of polymerization, which in turn influence dough mixing properties.     

Link Between Mixing Requirements and Dough Strength

Industrial bakeries in Australia and New Zealand using the mechanical dough development (MDD) process have experienced undesirable increases in dough mixing requirements. This problem is an unwanted outcome of breeding programs that have endeavored to increase dough strength as a desirable characteristic. Research was undertaken to determine the nature of the link between dough strength and mixing requirements and its relevance to the MDD process across a wide range of wheat lines. Data from three similar trials of 20 wheat lines confirmed the existence of an apparently tight, positive correlation between mixing requirements and dough strength. Although a wide range in genotypes and environments was used, no significant outliers were found, despite the belief that the link between these quality attributes was breakable or at least flexible. This creates a dilemma, as it would be desirable to reduce work input (WI) for economic reasons but not at the expense of loaf quality, which could have a deleterious effect on product marketability. The resultant nexus between mixing requirements, as measured by MDD WI, and dough strength measured by extensigraph resistance to extension (Rmax), appeared to be influenced by the application of nitrogen fertilizer during cultivation, while the nexus between mixing requirements as measured by mixograph development time (MDT) and Rmax, was influenced by other factors associated with crop location. The nexus between farinograph development time (FDT) and Rmax was affected by both location and nitrogen fertilizer application. The rates of increase in WI, MDT, and FDT against Rmax appeared to differ between high molecular weight glutenin subunits (HMW-GS) 5+10 or 2+12 (the Glu-D1 alleles). The Glu-A1 and Glu-A3 loci also played a significant role, indicating that by manipulating them it may be possible to shift or manipulate the nexus between mixing requirements and dough strength. Alleles at these loci appeared to be additive in effect on WI, MDT, and FDT, as well as Rmax.     

Effects of Nitrogen and Sulfur Fertilizers on Gliadin Composition of Several Cultivars of Durum Wheat

Four fertilizer treatments were applied to 10 cultivars of durum wheat (Triticum turgidum var. durum L.) in three seasons of designed field trials. The fertilizer treatments were N0S0 ‐ neither N nor S applied; N1S0 ‐ only N applied; N1S1 ‐ both N and S applied; N0S1 ‐ only S applied. It was found, through densitometric SDS‐PAGE, that the relative proportion of different gliadin components was influenced by the distinct regimes, even though our region in the center of the Argentinean Pampa is not considered to be deficient in soil S‐availability. The effects observed were more marked in one particular season of the three studied, were principally associated with the treatment expected to produce the maximum degree of grain S‐deficiency (N1S0), and were consistent with the hypothesis that the relative content of S‐poor gliadins increases under conditions of S‐deficiency, as has been found in related crops. Multivariate reverse‐phase high‐performance liquid chromatography (RP‐HPLC) analysis of samples from the season most affected generally supported these observations, but refined them in identifying quantitative differences between all four fertilizer treatments for the cultivars studied. These findings imply that differences in industrial quality might also be expected between the fertilizer treatments. RP‐HPLC also identified numerous genetically controlled qualitative differences in the gliadins between the cultivars studied, adding to previous published work on these cultivars based on SDS‐PAGE. These observations confirmed that one particular cultivar of very low gluten strength showed a gliadin profile markedly distinct from the remaining cultivars studied.     

Effects of Nitrogen and Sulfur Fertilization on Commercial‐Scale Wheat Quality and Mixing Requirements

The effect on physical dough properties of nitrogen and sulfur fertilizer applied during cultivation was observed in two trials using the bread wheat (Triticum aestivum) cultivar Otane. Wheat flours from both trials were evaluated for physical dough properties under laboratory conditions and also under industrial conditions in the second trial. The laboratory and industrial optimum mechanical dough development (MDD) work input (WI) significantly increased when nitrogen (N) fertilizer was applied without sulfur fertilizer (S) during crop cultivation. With combined N and S fertilization, laboratory and industrial WI remained close to levels for grain grown without fertilizer. Reductions in extensigraph resistance to extension (Rmax) and increases in extensigraph extensibility (Ext) due to S fertilization also were observed. None of the observed changes in WI, Rmax, or Ext due to S fertilization significantly affected end‐product quality as measured by loaf volume, crumb grain, and bake score. The nexus between WI and Rmax was weakened by combined N and S fertilization in the first trial, but remained strong in the second trial. Both WI and Rmax increased as N fertilizer and flour nitrogen increased, but at different rates. This observation indicated that by applying N fertilizer to improve dough strength, a disproportionate and disadvantageous increase in WI also resulted, which could be tempered by S fertilization. In this regard, an optimum N:S fertilizer ratio of 3:1 was indicated, although this ratio would be dependent on the balance of available N and S in the soil. Flour N:S ratios <12.5 kept WI to levels desirable in an industrial MDD bakery. Correlations between laboratory WI, mixograph development time (except in the SN1 trial), and farinograph development time were significant. The 125‐g MDD mixers appeared to be more responsive when measuring mixing requirements than the mixograph and farinograph to variations in quality due to environmental and agronomic influences and correlated better with industrial performance.     

Effects of Cultivar and Temperature During Grain Filling on Wheat Protein Content,Composition, and Dough Mixing Properties

Three wheat cultivars, Bastian, Polkka, and Tjalve, were grown in growth chambers at 9, 12, 15, 18, and 21°C during grain filling in 1994, 1995, and 1996. The wheat samples were analyzed for protein content and sodium dodecyl sulfate (SDS) sedimentation volume. The mixing properties of sifted flours were determined by mixograph, and the flour protein composition was determined by size-exclusion fast protein liquid chromatography (SE-FPLC). The protein content, sedimentation volume, and mixogram parameters were affected by the temperature during grain filling. The protein content increased as the temperature increased. The sedimentation volumes and the mixograph data showed temperature effects that could not be explained by variation in protein content. The proportion of the polymeric flour proteins increased with increasing temperature. Positive correlations were found between the proportion of polymeric proteins and SDS sedimentation volume and, within each year, between the proportion of polymeric proteins and mixograph peak time. Negative correlations were found between the proportion of low molecular weight flour proteins (proportion of fraction IV) and sedimentation volume. The differences in these quality parameters among cultivars exceeded the effect of temperature during grain filling.     

灌浆期高温胁迫对不同品种小麦蛋白组分及面团揉混特性的影响

为研究灌浆期高温胁迫对不同品种小麦蛋白组分及面团揉混特性的影响,以济麦22(JM22)和新麦26(XM26)为材料,通过灌浆初期(S1)和灌浆中期(S2)在田间搭棚进行高温胁迫处理,以未进行高温胁迫的大田小麦作对照(CK),收获后对小麦淀粉黏滞谱、蛋白质组分含量和揉混参数等进行分析。结果表明,与各自CK相比,JM22的黏滞谱参数除回复值和糊化温度降低外,其余参数均升高,XM26的黏滞谱参数除峰值时间外均降低。S1和S2使JM22的峰值黏度、低谷黏度、崩解值、最终黏度、峰值时间分别较CK提高2.81%和18.63%、7.71%和19.51%、11.88%和21.15%、1.88%和12.22%、2.45%和4.08%,且S2均大于CK和S1,S1与CK差异不显著;S1和S2使XM26的峰值黏度、低谷黏度、最终黏度、回复值分别较CK降低12.95%和31.21%、1.81%和27.18%、2.50%和22.22%、3.57%和14.39%,其中,S2、S1与CK三者之间的峰值黏度均达显著水平。与CK相比,高温胁迫后JM22的蛋白质含量降低,而XM26升高。两品种各组分蛋白含量均发生改变,S...     

Growth Environment Influences Grain Protein Composition and Dough Functional Properties in Three Australian Wheat Cultivars

The objectives of this study were to assess how functional properties of proteins in whole meal wheat (Triticum aestivum L.) flour vary across different growth environments. Grain from three commercial Australian Hard milling wheat cultivars was analyzed from four growth locations in 2008 and from two of the corresponding cultivars and locations in 2009. The protein content of the grain, soluble and insoluble extractable protein fractions, swelling index of glutenin (SIG), glutenin‐to‐gliadin ratio (Glu:Gli), percent unextractable polymeric protein (%UPP), and dough properties including force at maximum resistance (Rmax) and extensibility were measured. Based on analysis of variance of aggregated data for the cultivars, growth locations, and seasons, growth environment factors made significant contributions to variability in the total grain protein, Glu:Gli ratio, %UPP, SIG, Rmax, and extensibility of the wheat flour. Variability of protein content of the soluble and insoluble extractable protein fractions was mostly owing to genotype.     

Effects of Nitrogen Fertilizer on Protein Quantity and Gluten Strength Parameters in Durum Wheat (Triticum turgidum L. var. durum) Cultivars of Variable Gluten Strength

Field studies were conducted over three years at two locations in Saskatchewan, Canada, to determine the effect of nitrogen fertilizer on protein quantity and protein strength in 10 cultivars of durum wheat (Triticum turgidum L. var. durum) representing a range of gluten strength. Increasing nitrogen fertilizer resulted in increased protein content in all cultivars across environments. Cultivars were clearly differentiated on the basis of gluten strength using a gluten index (GI), SDS sedimentation (SDSS), alveograph indices of overpressure (P) and deformation energy (W), mixograph energy to peak (ETP), and mixograph bandwidth energy (BWE) at all fertilizer levels. Variable cultivar response to nitrogen fertilizer was observed only for protein content, GI, and alveograph W. The nature of the cultivar‐by‐fertilizer interaction for GI suggested that the conventional strength cultivars would benefit more from nitrogen fertilizer than the extra‐strong types, which showed no change or slight decreases in GI with nitrogen fertilizer despite an increase in total gluten. SDSS increased with nitrogen fertilizer, following similar trends as protein. Gluten strength rankings of the cultivars by SDSS were maintained with increased fertilizer. Fertilizer had little effect on alveograph P, mixograph ETP, and mixograph BWE. Overall, GI values were more stable across increasing levels of nitrogen fertilizer and resultant increased protein content compared with SDSS, mixograph development time, and alveograph W and L, suggesting it is a good test for estimating intrinsic gluten strength for cultivars with a wide range of protein content.     

Response of Wheat Cultivars to Nitrogen and Sulfur for Crop Yield,Nitrogen Use Efficiency,and Protein Quality in the Semiarid Region

ABSTRACT

The effects of nitrogen (N at 0, 100 and 180 kg N ha-1) and sulfur (S at 0, 20, 40 and 60 kg S ha-1) on crop yield, nutrient uptake, nitrogen use efficiency (NUE), and amino acid composition of two bread wheat cultivars, ‘Shehan’ and ‘Enkoy,’ grown in Andisols and Cambisols in randomized blocks with three replications were evaluated. Both cultivars responded significantly (P < 0.05) to N and S applications and S application with N improved the NUE by 28%. The yield increase for the two cultivars by N and S application ranged between 0.8 to 2.4 Mg ha^?1. The N concentration increased significantly from N0 to N2 in both cultivars. Sulfur fertilization increased the concentration of cysteine and methionine by 27% and 14%, respectively, as compared to N alone. The grain yield, NUE, N, and S uptake, and the S-amino acid concentration of ‘Enkoy’ were significantly higher than ‘Shehan’ cultivar.     

Protein Allelic Composition,Dough Rheology,and Baking Characteristics of Flour Mill Streams from Wheat Cultivars with Known and Varied Baking Qualities

Flour mill streams obtained by milling grain of 10 bread wheat cultivars grown in the Skopje region of Macedonia were analyzed for rheological and breadmaking quality characteristics and for composition of gliadins and HMW‐GS. The objective of this study was to examine the relationships between the composition of gluten proteins and breadmaking quality, as well as to determine the importance of gluten proteins for technological quality of flour mill streams. The grain was milled in an experimental mill according to a standardized milling procedure, with three break and three reduction passages. The addition of two vibratory finishers in the milling scheme enabled better separation of bran. A small‐scale baking method for evaluation of the breadmaking properties was developed, and electrophoretic methods including acid‐PAGE and SDS‐PAGE were used to determine the composition of the gluten proteins. There were significant differences in the degree of dough softening of individual and total flour fractions of the flour mill streams for cultivars with different alleles from six loci, for farinograph water absorption from seven loci, and for bread loaf volume and crumb quality score from six loci. The Glu‐1 quality scores for the wheat cultivars investigated were 3–9 and proved to be a useful indicator of breadmaking quality. The novel feature of the investigation related to the breadmaking potential of the flour mill streams compared with straight‐run flours.     

Effects of Wheat Cultivar and Nitrogen Application on Storage Protein Composition and Breadmaking Quality

Influences of cultivar and nitrogen application on protein concentration and composition, and amount and size‐distribution of different protein components, were investigated in 10 spring wheat cultivars (Triticum aestivum L.) with widely varying gluten strength, grown under four nitrogen fertilizer conditions. The results showed that cultivar differences in gluten strength were determined by storage protein composition, differences in total amount of HMW glutenin subunits, the glutenin‐to‐gliadin ratio, and the relationship between SDS‐soluble and SDS‐insoluble protein polymers. Negative correlations were found between protein parameters related to gluten strength and bread volume. No cultivar stability for gluten strength in relation to differences in nitrogen application was found. Thus, the gluten strength was influenced by the nitrogen application in all the investigated cultivars. Increased nitrogen supply correlated significantly to an increase in all protein components containing gliadins and glutenins, but not to those containing albumins and globulins. The increase in protein components containing gliadins and glutenins correlated significantly with an increase in protein concentration and bread volume.     

Effects of Mixing Conditions and Wheat Flour Dough Composition on Lipid Hydrolysis and Oxidation Levels in the Presence of Exogenous Lipase

The lipid profiles of wheat flour doughs containing exogenous lipase were studied under different mixing conditions using a microscale mixer. An experimental design comparing the effects of dough water content (52–68%), the speed of mixing (50–100 rpm), and the mixer temperature (18–32°C) showed that the hydrolysis levels were positively influenced by temperature and speed of mixing and negatively influenced by water content. The positive effect of temperature was enhanced both by highspeed mixing and low water content. The lipid oxidation levels were positively influenced by the speed of mixing and negatively influenced by the water content. The positive effect of temperature on the oxidation levels was less important. A series of experiments conducted with different types of industrial and semi-industrial mixers with equal concentrations of lipase added to the dough showed large differences among the rates of lipid hydrolysis and oxidation. However, the mixing conditions proposed by bakers to obtain doughs with similar handling properties led to similar dough lipid profiles. Sodium chloride did not change the lipid profile when added to dough. Conversely, calcium chloride promoted a large increase of lipid hydrolysis and oxidation due to its activation of lipase activity. Addition of yeast increased the lipid hydrolysis and slightly decreased lipid oxidation.     

氮肥底追比例及施硫对小麦氮素吸收利用的调控

为明确氮肥底追比例与施硫间的互作效应,采用盆栽方式,以京冬8号和济麦20为供试材料,设置氮肥底追比例为3∶7(N_1)、5∶5(N_2)和7∶3(N_3)3个处理水平,每个底追比例下设置2个硫肥施用量:0kg·hm~(-2)(S0)和45kg·hm~(-2)(S_1),运用15N示踪技术研究开花期、成熟期营养器官及籽粒中氮素积累、分配以及对不同来源氮素利用的情况,同时对花后营养器官贮藏氮素的转运、对籽粒的贡献率及氮素利用效率进行分析比较。结果表明,2个小麦品种植株中积累氮素主要来自肥料氮,京冬8号成熟期来自肥料氮的积累量达60%~70%,而济麦20则达70%~80%。氮肥底追比例及硫肥互作对2个品种氮素吸收、转运和分配的影响存在差异,其中京冬8号成熟期籽粒氮素积累量、营养器官贮藏氮素花后的转运量、转运率、对籽粒的贡献率、籽粒产量以及氮肥的利用效率均在N_1S_0时较高;济麦20营养器官贮藏氮素花后的转运量、转运率、对籽粒的贡献率在N1S0时较高,而在N3S1时,成熟期籽粒氮素积累量、籽粒产量、氮肥的利用效率均较高。综上所述,本试验栽培环境下,氮肥底追比例为N1时能够提高花前贮藏氮素的转运量、转运率、对籽粒的贡献率、籽粒蛋白质含量及氮素收获指数;氮肥底追比例为N3时有利于提高籽粒产量、氮肥生产效率。综合考虑籽粒产量、氮肥生产效率、氮肥利用效率和氮素收获指数,京冬8号最优肥料组合为N_1S_0,济麦20最优肥料组合为N_3S_1。本研究结果为冬小麦大田生产中合理的肥料运筹提供了理论参考。     

有机肥替代部分化学氮肥对春小麦产量与氮肥利用率的影响

用田间试验的方法,研究不同比例有机肥替代化学氮肥对土壤养分及小麦(籽粒、秸秆、颖壳)养分吸收、产量和氮肥利用率的影响,寻求有机肥替代化学氮肥的合理范围,以期在提高肥料利用率、增加小麦产量的同时减少土壤过量施用化肥的负面作用。田间试验设不施肥(CK)、有机肥替代100%化学氮肥(N0)、有机肥替代50%化学氮肥(N0.5)、有机肥替代25%化学氮肥(N0.75)及100%化学氮肥(N1)5个处理;其中,100%化学氮肥处理为当地化学氮肥常规用量。结果显示:小麦收获期N0.75处理土壤有机碳含量最高;N0和N0.5处理土壤有机碳含量较CK处理下降,而N0.75处理和N1处理土壤有机碳含量较CK处理增加,但处理之间差异不显著。有机肥替代化学氮肥处理可影响小麦籽粒、秸秆(叶和茎秆)、颖壳中N、P2O5、K2O养分含量,小麦生物量和籽粒产量随施用化学氮肥比例的增加而增加。相关分析结果显示,施用氮化肥比例与小麦籽粒氮素含量之间呈极显著正相关关系(P <0.01);小麦秸秆和颖壳中N含量均以N0.5处理较高,P2O5含量处理之间差异不显著,K2O含量以N1和N0.5处理最高、且处理间差异显著。...     

Effect of Nitrogen Fertilization on Quantity of Flour Protein Components,Dough Properties,and Breadmaking Quality of Wheat

Three winter wheat varieties with differing breadmaking quality were grown at two locations in two years at 0 or 3 × 60 kg of nitrogen application. The effect of nitrogen on amount of different components of gluten proteins was determined by reverse-phase HPLC. A high amount of nitrogen led generally to a significant increase of total protein content. However, this increase was obvious only for the gluten proteins; albumins and globulins remained nearly unaffected. The effect of increased protein content on gliadin to glutenin (gli-glu) ratio was inconsistent. While increased protein content increased the gli-glu ratio in the variety Capo, the opposite was true for the variety Renan. Gli-glu ratio of the variety Lindos showed no discernible tendency. As total protein content increased, the ratio of low molecular weight (LMW) to high molecular weight (HMW) glutenins decreased consistently, i.e., in all varieties, in both years and locations. Change of LMW to HMW ratio showed a significant negative correlation to sedimentation value and bread volume. There was no consistent change in the ratio between x- and y-type HMW subunits due to fertilization, as could be shown by densitometric measurements on SDS-PAGE gels. This ratio appeared to be dependent on the genotype and has decreased with decreasing quality. The amount of x-type subunits correlated closely with sedimentation value and bread volume. These results suggest that ratio of HMW glutenins, especially x-type subunits, to total protein content could be the best early detectable parameter with high predictive value for breadmaking quality.     

Association of Glutenin Subunit Composition and Dough Rheological Characteristics with Cookie Baking Properties of Soft Wheat Cultivars

The effect of flour type and dough rheology on cookie development during baking was investigated using seven different soft winter wheat cultivars. Electrophoresis was used to determine the hydrolyzing effects of a commercial protease enzyme on gluten protein and to evaluate the relationships between protein composition and baking characteristics. The SDS‐PAGE technique differentiated flour cultivars based on the glutenin subunits pattern. Electrophoresis result showed that the protease degraded the glutenin subunits of flour gluten. Extensional viscosities of cookie dough at all three crosshead speeds were able to discriminate flour cultivar and correlated strongly and negatively to baking performance (P < 0.0001). The cookie doughs exhibited extensional strain hardening behavior and those values significantly correlated to baking characteristics. Of all rheological measurements calculated, dough consistency index exhibited the strongest correlation coefficient with baking parameters. The degradation effects of the protease enzyme resulted in more pronounced improvements on baking characteristics compared with dough rheological properties. Stepwise multiple regression showed that the dough consistency index, the presence or absence of the fourth (44 kDa) subunit in LMW‐GS and the fifth subunit (71 kDa) subunit in HMW‐GS were predominant parameters in predicting cookie baking properties.     

氮硫互作对冬小麦旗叶衰老、产量和氮素利用效率的影响

试验采用裂裂区设计,小麦品种(烟农19和汶农6号)为主区,施氮(N)量为裂区,设0(N0)、120(N120)、240(N240)kg hm-2三个施N水平,施硫(S)量为裂裂区,设0(S0)、20(S20)、40(S40)、60(S60)kg hm-2四个施S水平。结果表明,汶农6号开花后旗叶超氧化物歧化酶(SOD)活性、旗叶净光合速率、产量和氮素利用效率均高于烟农19。在一定施氮水平下适量施硫显著提高烟农19和汶农6号小麦开花后旗叶SOD活性和可溶性蛋白质含量,提高旗叶净光合速率和开花后干物质积累量,增加植株地上部氮素积累量和籽粒产量;当施氮水平为120 kg hm-2施硫量超过40 kg hm-2和施氮240 kg hm-2施硫量超过20 kg hm-2时,汶农6号植株地上部氮素积累量仍继续增加,但旗叶抗氧化能力和光合同化能力均无明显提高,籽粒产量不再增加,烟农19号旗叶SOD活性、可溶性蛋白质含量和光合速率均降低,植株地上部氮素积累量和籽粒产量均减少。在同一施氮水平下,两小麦品种氮素利用效率总体表现为随施硫量增加而降低的趋势。在土壤有效硫为38.9~42.1 mg kg-1的条件下,适量施用氮肥和硫肥有利于延缓小麦花后旗叶衰老,提高光合同化能力,增加籽粒产量,但不同品种小麦对氮肥和硫肥施用量的响应不同,氮素利用效率较高的品种在较高的氮硫供给水平下仍有较好的光合同化和产量表现,而氮素利用效率相对低的品种对高氮高硫的适应性较差,后期易早衰,影响产量和氮素利用效率。     

施氮对小麦产量和氮素径流损失及氮肥投入阈值的研究

为明确巢湖流域小麦季氮肥投入阈值,在连续3年田间试验条件下,研究了(2012—2014年)不同氮肥水平下(N0、N1、N2、N3、N4、N5分别为0,157.5,210.0,262.5,310.0,420.0kg/hm~2)小麦产量、植株氮素积累量、氮肥利用率、土壤无机氮残留量(0—20cm)及氮素径流流失;同时,利用回归方程模型对其间的相关关系进行拟合。结果表明:(1)与不施氮肥相比,施用氮肥可不同程度提高小麦产量,其中以N3处理增加的比例最大,为64.8%。利用二次函数分析,当施用氮肥超过290.9kg/hm~2时,小麦产量下降。(2)植株氮素累积量和氮肥利用率随施氮量的增加均呈先上升后下降的趋势,当实际施氮量为296.6kg/hm~2时,小麦地上部植株氮素积累量最高;当施氮量为158.5kg/hm~2时,氮肥利用率最高。(3)随着施氮量的增加,土壤中无机氮的残留量(0—20cm)和氮素的径流损失逐渐升高,但是在310.0kg/hm~2之前累积量无显著变化,当施氮量达到420.0kg/hm~2时,土壤中无机氮的残留量及氮素的径流流失变化明显,累积量平均达67.0kg/hm~2,流失量平均达8.3kg/hm~2。因此,施氮量过高时,会增加土壤无机氮残留及氮素径流损失的风险,对环境造成污染。结合巢湖地区土壤肥力条件,综合考虑试验施肥处理、施氮量对小麦产量、植株氮素积累量、氮肥利用率、土壤无机氮残留量(0—20cm)及氮素径流流失因素,提出适宜巢湖地区的氮肥投入阈值为157.5~262.5kg/hm~2。     

有机肥替代化肥氮素对麦田土壤碳氮迁移特征的影响

利用小麦田间试验,设置控释尿素(CRU)、有机肥(OF)替代30%,50%,70%控释尿素氮量处理,并以普通尿素(Urea)为对照,研究等氮条件下有机肥替代不同比例化肥氮素对土壤碳氮迁移特征及小麦产量的影响。结果表明:有机肥处理小麦总生物量较Urea显著增加13.83%～17.57%,籽粒产量增加1.6%～10.5%,随有机肥替代化肥氮素比例增加,籽粒增产效应降低,70%OF与Urea无显著差异,但显著低于CRU处理。CRU、30%OF和50%OF处理氮素农学效率较Urea显著提高90.2%～124.4%,70%OF与Urea相比差异不显著。有机肥比例增加,土壤总碳含量呈上升趋势,且高于CRU和Urea;全氮含量大致呈下降趋势,整个生育期先增加后降低,30%OF自灌浆期至成熟期含量高于其他施氮处理。随土层深度增加,硝态氮和铵态氮含量减少,有机肥比例增加,各层土壤硝态氮减少,铵态氮增加(尤以返青期最为显著);整个生育期土壤无机氮呈下降趋势,但与Urea相比,有机肥处理的硝态氮主要集中在0—40 cm土层,且0—100 cm土壤铵态氮含量高于Urea和CRU(苗期除外)。因此,用30%～50%有机肥替代化肥氮素,配合控释尿素施用,可显著增加土壤总碳和铵态氮含量,减少60—100 cm土壤硝态氮淋溶,提高小麦氮素利用率和籽粒产量。     

Environmental Influences on Flour Composition,Dough Rheology,and Baking Quality of Spring Wheat

The highly variable environmental conditions across the Pacific Northwest (PNW) influence the milling and baking quality of wheat grain produced in this region. This study was conducted to compare the flour composition, dough rheology, and baking quality of soft and hard spring wheat grain produced in diverse environments. Thirteen soft and five hard spring wheat cultivars were grown at Lind, WA (semiarid) and Fairfield, WA (high precipitation) for three years. Grain was evaluated for flour composition, rheology, and experimental baked product quality. Flour composition, rheological properties, and baking qualities were primarily influenced by the environment. Protein contents, microSDS values, and water absorption levels were significantly (P < 0.0001) higher for all cultivars grown at Lind compared with those from Fairfield. Cookie diameters were larger (P < 0.0001) for soft flours from Fairfield, whereas loaf volumes were higher (P < 0.0001) for hard wheat flours from Lind. Results indicate that producing soft or hard wheat outside of its optimal climatic zone reduces experimental baked product quality.