Contribution of green manure legumes to nitrogen dynamics in traditional winter wheat cropping system in the Loess Plateau of China

Excessive application of N fertilizer in pursuit of higher yields is common due to poor soil fertility and low crop productivity. However, this practice causes serious soil depletion and N loss in the traditional wheat cropping system in the Loess Plateau of China. Growing summer legumes as the green manure (GM) crop is a viable solution because of its unique ability to fix atmospheric N₂. Actually, little is known about the contribution of GM N to grain and N utilization in the subsequent crop. Therefore, we conducted a four-year field experiment with four winter wheat-based rotations (summer fallow-wheat, Huai bean–wheat, soybean–wheat, and mung bean–wheat) and four nitrogen fertilizer rates applied to wheat (0, 108, 135, and 162 kg N/ha) to investigate the fate of GM nitrogen via decomposition, utilization by wheat, and contribution to grain production and nitrogen economy through GM legumes. Here we showed that GM legumes accumulated 53–76 kg N/ha per year. After decomposing for approximately one year, more than 32 kg N/ha was released from GM legumes. The amount of nitrogen released via GM decomposition that was subsequently utilized by wheat was 7–27 kg N/ha. Incorporation of GM legumes effectively replaced 13–48% (average 31%) of the applied mineral nitrogen fertilizer. Additionally, the GM approach during the fallow period reduced the risk of nitrate-N leaching to depths of 0–100 cm and 100–200 cm by 4.8 and 19.6 kg N/ha, respectively. The soil nitrogen pool was effectively improved by incorporation of GM legumes at the times of wheat sowing. Cultivation of leguminous GM during summer is a better option than bare fallow to maintain the soil nitrogen pool, and decrease the rates required for N fertilization not only in the Loess Plateau of China but also in other similar dryland regions worldwide.     

Zn distribution and bioavailability in whole grain and grain fractions of winter wheat as affected by applications of soil N and foliar Zn combined with N or P

A two-year field experiment was conducted to investigate the effects of foliar Zn combined with N or P on Zn concentration and bioavailability in wheat grain and its milling fractions under different soil N levels. At maturity, grains were harvested and fractionated into flour and bran for nutrient analysis. Both high soil N supply and foliar Zn-enriched fertilizer applications greatly increased Zn concentration and bioavailability in both whole grain and grain fractions. Compared with foliar Zn alone, foliar Zn combined with N increased Zn concentration and bioavailability, whereas foliar Zn combined with P decreased Zn concentration and bioavailability. However, foliar Zn combined with P slightly increased the protein concentration compared to foliar Zn alone. Protein concentration significantly increased, whereas phytate concentration decreased, in whole grain and flour, both in soil N and foliar Zn-enriched N treatments. Therefore, foliar Zn plus N (with appropriate soil N management) may be a promising strategy for addressing dietary Zn micronutrient deficiencies, especially in countries where flour is a significant component of the daily diet.     

三种荒漠植物叶绿素荧光参数日变化特征

利用Photosynq MultiseQ多功能植物测量仪测定塔克拉玛干沙漠腹地3种主要防护林植物头状沙拐枣、多枝柽柳和梭梭的叶绿素荧光参数日变化,探讨其与环境因子的关系,以揭示3种植物对极端环境的适应策略,为沙漠公路防护林的管护提供理论依据。结果表明：1）3种土壤都呈碱性;0~30 cm土层中的电导率（EC）远高于30 cm以下的土层。1 m内梭梭土层中的含水量高于多枝柽柳高于头状沙拐枣。2）3种植物的光合有效辐射（PAR）、叶片温度和线性电子传递（LEF）及植物周围的大气温度日变化均先升后降,且都在14：00达到最高;而大气湿度、实际光化学效率Y_（II）日变化均呈‘V’型。3）PAR基本上与3种植物的LEF、非光化学淬灭系数（NPQ）、调节性能量耗散量子产量Y_（NPQ）、非调节性能量耗散量子产量Y_（NO）呈显著正相关,与实际光化学效率Y_（II）呈显著负相关;3种植物的Y_（II）与Y_（NPQ）、Y_（NO） 均呈极显著负相关。3种植物的LEF、Y_（II）、Y_（NPQ）的日均值差异不显著,但梭梭与多枝柽柳的NPQ和Y_（NO）日均值差异显著。4）在3种植物的叶绿素荧光参数中,梭梭和头状沙拐枣的LEF、NPQ和Y_（II）要高于多枝柽柳;而多枝柽柳的Y_（NO）要显著高于头状沙拐枣和梭梭。因此,高温和高光均对3种植物造成了不同程度的影响,通过主成分分析表明,3种植物的抗逆性强弱顺序分别为梭梭>头状沙拐枣>多枝柽柳。     

Design properties for molded,corn-based DDGS-filled phenolic resin

With the rapid growth in the ethanol fuel industry in recent years, considerable research is being devoted to maximizing the use of processing coproducts, such as distillers dried grains with solubles (DDGS), typically for livestock diets. Because these residues contain high fiber levels, they may be amendable to incorporation into polymers as well, which is an option that could garner greater economic returns. Thus, the goal of this study was to demonstrate the viability of using corn-based DDGS as a biofiller with phenolic resin, in order to produce a novel biomaterial. DDGS was blended with phenolic resin at four levels (0%, 25%, 50%, and 75%, by weight), and then compression molded at 13.8, 34.5, or 48.3 MPa (1.0, 2.5, or 3.5 tons/in.²) and 157, 174, or 191 °C (315, 345, or 375 F). Molded specimens were then tested for a variety of mechanical and physical properties. Pressure and temperature each had little effect on the resulting properties. DDGS, on the other hand, greatly influenced all of the properties. Tensile yield strengths ranged from 14.5 MPa (2102 psi) to 4.3 MPa (621 psi), while the Young's modulus ranged from 2296 MPa (333,000 psi) to 841 MPa (122,000 psi) as the DDGS content increased. For all time periods studied, water absorption increased as DDGS level increased. Moreover, as DDGS content increased to a maximum of 75%, biodegradability increased from 0% to 38% while the surface hardness decreased 25%. These results were similar to those from other studies that have investigated biofillers. Follow-up studies should aim to optimize the strength of the DDGS-blended resins through the use of coupling agents or other additives.     

NITROGEN USE AND MANAGEMENT IN ORCHARDS AND VEGETABLE FIELDS IN CHINA: CHALLENGES AND SOLUTIONS

● Excessive application of N fertilizers in orchards and vegetable fields (OVFs) in China is particularly common. ● Long-term excessive application of N fertilizers has made OVFs hotspots for N surplus and loss in China. ● Nitrate accumulation in the soil profile is the main fate of N fertilizers in OVF systems. ● Reducing the N surplus is the most effective way to reduce N loss and increase NUE. China is the largest producer and consumer of fruits and vegetables in the world. Although the annual planting areas of orchards and vegetable fields (OVF) account for 20% of total croplands, they consume more than 30% of the mineral nitrogen fertilizers in China and have become hotspots of reactive N emissions. Excess N fertilization has not only reduced the N use efficiency (NUE) and quality of grown fruits and vegetables but has also led to soil acidification, biodiversity loss and climate change. Studies using ¹⁵N labeling analysis showed that the recovery rate of N fertilizer in OVFs was only 16.6%, and a high proportion of fertilizer N resided in soils (48.3%) or was lost to the environment (35.1%). Nitrate accumulation in the soil of OVFs is the main fate of N fertilizer in northern China, which threatens groundwater quality, while leaching and denitrification are the important N fates of N fertilizer in southern China. Therefore, taking different measures to reduce N loss and increase NUE based on the main pathways of N loss in the various regions is urgent, including rational N fertilization, substituting mineral N fertilizers with organic fertilizers, fertigation, and adding mineral N fertilizers with urease inhibitors and nitrification inhibitors.     

设施大棚间作玉米对丛枝菌根网络形成及辣椒疫病防治的影响

丛枝菌根（Arbuscular mycorrhizal,AM）真菌对辣椒疫病等土传病害具有生防潜力,但由于难以纯培养而未能实现规模化生产应用,如能调动土著AM真菌的抑病功能则对实际生产具有重要指导意义。依托重庆石柱辣椒科技园,研究设施大棚中间作玉米对土著AM真菌生长及辣椒疫病防治的影响。结果表明,与辣椒单作相比,间作玉米处理辣椒根系AM真菌侵染率、根际AM真菌数量与土壤磷酸酶活性以及小区作物养分总吸收量均显著提高,辣椒疫病发病率与病情指数、单株辣椒的磷吸收量及果实生物量均显著下降,其中种植密度更高的等垄宽间作处理两种作物根系AM真菌侵染率、小区玉米产量及作物养分总吸收量均显著高于等行距间作处理,辣椒疫病发病率与之正好相反。设施环境下间作玉米或能通过促进AM真菌生长及其对辣椒根系的侵染来增强其对辣椒疫病的防治功效,其中等垄宽间作处理具有更好的经济效益。     

添加矿物质对猪粪好氧堆肥中有机物降解的影响

为了探讨添加矿物材料对猪粪堆肥过程中有机物动态变化的影响,通过好氧堆肥的方式向猪粪和玉米秸秆粉混合物料中添加干质量分数为2.5%的粉煤灰、膨润土和风化煤等矿物质,用化学分析和红外光谱技术相结合的方法,对90 d好氧高温堆肥过程中有机质的动态变化特征进行了研究。结果表明:添加粉煤灰、风化煤或膨润土对猪粪堆肥的堆体温度变化均无明显影响,堆体温度能迅速升至近70℃,并维持在55℃以上超过7 d,达到高温堆肥的温度要求;随着堆肥时间的延长,各处理中总有机碳(TOC)和水溶性有机碳(WSC)含量均呈现出逐渐降低最后趋于相对稳定的趋势,但添加粉煤灰、风化煤和膨润土处理,能促进有机质的降解,促进能力依次为粉煤灰、膨润土、风化煤;添加粉煤灰、风化煤和膨润土等矿物质有利于猪粪堆肥的腐殖化过程进行,堆肥过程的雪里蕻种子萌发指数(GI)与WSC显著负相关、GI与胡敏酸的百分比(PHA)和腐殖酸聚合度(DP)显著正相关;红外光谱数据显示,在好氧堆肥过程中,含有—OH、—CH3和—CH2基团的化合物相对减少,而含有—CO、C—O—C、—COO基团和含芳香环类物质的含量逐渐增加,堆肥有机质降解可持续至60 d以后;添加粉煤灰、风化煤和膨润土会影响堆肥初期GI增加,但经过90 d好氧堆肥后,雪里蕻种子的GI均能大于0.5,所有堆肥处理均基本达到腐熟水平。     

石灰和有机质对不同性质镉污染土壤中镉有效性的影响

通过土培试验研究了添加不同改良剂(鸡粪、泥炭和石灰)对我国不同性质土壤(云南赤红壤、江西红壤、吉林黑土和内蒙栗钙土)镉污染的改良差异。结果表明,不同改良剂0～60 d内对四种镉污染土壤的改良效果均较为显著。鸡粪对云南赤红壤、江西红壤、吉林黑土和内蒙栗钙土镉污染的固定率分别为37.0%、52.7%、29.3%和49.6%,显示鸡粪对这四种不同性质镉污染土壤的改良效果是江西红壤≈内蒙栗钙土云南赤红壤吉林黑土;泥炭对云南赤红壤、江西红壤、吉林黑土和内蒙栗钙土镉污染的固定率分别为33.1%、51.7%、30.5%和51.2%,显示泥炭对这四种不同性质镉污染土壤的改良效果是江西红壤≈内蒙栗钙土吉林黑土≈云南赤红壤;石灰对云南赤红壤、江西红壤、吉林黑土和内蒙栗钙土镉污染的固定率分别为60.7%、55.5%、40.7%、41.7%,显示石灰对这四种不同性质镉污染土壤的改良效果是云南赤红壤江西红壤吉林黑土≈内蒙栗钙土。综上可知,在对镉污染的酸性土壤改良上,石灰好于有机质,而对镉污染的中性和碱性土壤改良上,有机质则好于石灰。     

水分和铅胁迫对槐树幼苗渗透调节物质的影响

【目的】比较西北干旱、半干旱地区常见造林树种刺槐(Robinia pseudoacacia)和紫穗槐(Amorphafruticosa)对重金属铅的耐受性,为干旱半干旱地区重金属铅污染土壤的修复提供依据。【方法】采用盆栽试验,对1年生刺槐和紫穗槐幼苗进行水分胁迫(土壤相对含水率分别为100%,80%,60%,40%)和铅胁迫(土壤铅含量分别为0,300,500,1 000,2 000,3 000mg/kg)处理,分析在水分和铅单一及交互胁迫条件下,2种植物叶片有机渗透调节物质含量的变化。【结果】刺槐和紫穗槐叶片脯氨酸、可溶性糖、可溶性蛋白含量随水分和铅胁迫程度的加剧而呈现复杂的变化规律。单一水分胁迫下,刺槐叶片脯氨酸含量的变化幅度高于单一铅胁迫,当土壤铅含量相同时,土壤相对含水率为40%的处理脯氨酸含量显著高于其他水分胁迫处理;在铅或水分单一胁迫及二者的交互胁迫中,当土壤铅含量相同时(土壤铅含量为3 000mg/kg处理除外),各水分胁迫处理的刺槐叶片可溶性糖含量差异不显著(P>0.05)。在单一水分或铅胁迫条件下,刺槐、紫穗槐叶片可溶性蛋白含量均未随胁迫程度的加剧而降低。【结论】水分和铅交互胁迫条件下,脯氨酸对提高刺槐和紫穗槐抗旱性的贡献大于抗铅性;刺槐积累脯氨酸提高自身抗逆性的能力强于紫穗槐,而紫穗槐合成可溶性蛋白和可溶性糖提高自身抗逆性的能力强于刺槐。     

运用“碳足迹”的方法评估小麦秸秆及其生物质炭添加对农田生态系统净碳汇的影响

为分析添加秸秆、生物质炭后小麦生产过程中碳足迹的动态、分布以及构成,研究了不同处理在小麦生长期的CO2、N_2O、CH4排放情况,以及不同处理的单位面积碳足迹构成与碳足迹总量,试验设置5个处理:对照(CK)、常规施肥(N)、施肥并添加4 t·hm-2秸秆(NS)、施肥并添加4 t·hm-2生物质炭(NBClow)、施肥并添加8 t·hm-2生物质炭(NBChigh)。结果表明,小麦生产中碳足迹的构成主要为农田生态系统净初级生产力(NPP)和氮肥生产过程中的能源消耗,与常规施肥相比:添加4 t·hm-2秸秆、4 t·hm-2生物质炭与8 t·hm-2生物质炭处理,小麦产量分别增加了30.9%、66.3%和36.6%;添加4 t·hm-2秸秆使土壤CO2的季节排放总量增加了68.7%,生态系统N_2O的季节排放总量降低了33.9%,添加4 t·hm-2和8 t·hm-2生物质炭生态系统N_2O的季节排放总量降低了23.8%和58.6%,但是土壤CO2的季节排放总量没有显著性的差异;添加4 t·hm-2秸秆使小麦生产过程中的碳足迹升高了26.0%,添加4 t·hm-2和8 t·hm-2生物质炭碳足迹分别降低了198.0%和112.9%。生物质炭的添加降低了小麦生产过程中的碳足迹。