动物饲料国际贸易、养殖密度与环境氮磷平衡的关系

粮食和饲料的国际贸易促进了许多国家农业生产系统的专业化和集约化。专业化动物养殖越来越多地依赖进口大豆和玉米,虽然提高了动物生产力,但也促使作物和动物生产系统在空间上的分离。本文综述了几十年来全球范围内大豆和玉米的贸易变化,并将其与养殖密度和整个食品系统中营养平衡的变化联系起来。这一变化与不同的营养管理条例的差异和动物饲养密度的空间变化有关。深入解析这些变化有助于理解动物饲料国际贸易、养殖密度与氮磷平衡之间的复杂关系。     

Screening and identification of soybean varieties with high phosphorus efficiency at seedling stage

In order to simplify the workload and find a reliable method for screening soybeans with different phosphorus(P)efficiencies,47 soybean varieties were screened from 90 varieties according to yield under normal phosphorus,and 10 indicators including root phenotype,phosphorus utilization efficiency at the seedling stage and yield were measured.Through single-index cluster analysis,the performance value and relative value of the abovementioned indexes under low-phosphorus conditions were analyzed,and then,the combined indexes were analyzed by principal components method.The membership function method and the cluster analysis method was used to calculate and analyze the comprehensive score value.Three indexes of root P utilization efficiency(X₁),relative value of root P utilization efficiency(X₂),and root volume(X₃)under low P at the seedling stage were selected as the most consistent with the yield screening results under low P condition,and the mathematical model of the comprehensive score value was obtained:D=1.218X₁t 0.320X₂t 0.007X₃-0.664(P=0.000,R²=1.000).The comprehensive score can screen and identify the P efficiency of soybeans with fewer indexes in the early growth stages,which provides a more rapid and reliable mathematical model for screening and identifying a larger number of germplasm resources for P efficiency.     

氮磷钾配比对长优2号产量和经济性状的影响

采用“3414”方案设计试验,研究氮磷钾不同配比施肥对长优2号产量及经济性状的影响,结果表明,氮、磷、钾对长优2号都有一定的增产效应,其中以氮的增产效应最为显著,磷与钾次之。初步得出本次试验最佳施肥量为“N”16.23㎏/667㎡、“P2O5”8.46㎏/667㎡、“K2O”16.06㎏/667㎡,NPK比接近“1：0.5：1”水平。     

pH值和碳氮比对微生物燃料电池脱氮除磷效果的影响

【目的】探究pH值和碳氮比对微生物燃料电池脱氮除磷的影响,找出适宜pH值的和碳氮比。【方法】采用单室微生物燃料电池装置,设置不同的阳极液的pH值(W1=5、W2=6、W3=7、W4=8、W5=9);选取pH值=7,设置不同的碳氮比(N1=1∶1、N2=2∶1、N3=4∶1、N4=8∶1、N5=16∶1),共10个处理,测量2个反应周期内输出电压值、COD、氨态氮、硝态氮、总氮和总磷的变化。【结果】在其他条件相同的情况下,只改变阳极液的pH值,输出电压随pH值增大先增大后减小;pH值为8时产电性能最佳,最大电压为204.74 mV;COD、氨态氮、硝态氮、总氮随pH值增大呈先降低后增大的趋势,在pH值为8时,其去除效率最高,分别为74%、38%、93%和58%;在pH值为9时,总磷的去除效率最优为24%。只改变碳氮比时,当碳氮比为4时电压最大,为158.33 mV;COD、氨态氮、硝态氮、总磷的去除率随碳氮比增大先增大后减小,当碳氮比为4时,COD的降解率最大为65%;当碳氮比为2时,氨态氮的降解效率最好为35%;当碳氮比为8时,硝态氮和总磷的去除效率最高,分别为96%和16%;总氮的去除效率随碳氮比的增大而提高,当碳氮比为16时,总氮的去除效率最高,为59%。【结论】碳氮比为4∶1、pH值为8时可以取得较好的脱氮除磷效果。     

AM真菌改善植物磷营养吸收和转运机制的研究进展

旨在深入了解丛枝菌根(Arbuscular mycorrhizae,AM)真菌在植物吸收和转运磷元素方面的机制。本研究归纳了近年来关于AM真菌能够促使植物改善磷营养（如磷酸盐转运蛋白、磷酸酶基因等）相关的最新研究成果,着重分析了AM真菌的菌根吸收途径,总结了国内外关于AM真菌对水溶性无机磷、难溶性无机磷和有机磷等3种土壤磷存在形态下的利用机制。最后指出该领域仍存在的一些问题以及未来的研究侧重点。     

黄河三角洲潮间带盐地碱蓬湿地土壤磷含量和储量的季节动态变化特征

以黄河三角洲潮间带盐地碱蓬湿地为研究对象,通过在春季、夏季和秋季分别采集0～10 cm和10～20 cm土层的土壤样品,分析了盐地碱蓬湿地土壤磷素的时空动态变化特征。研究结果表明:盐地碱蓬湿地土壤总磷(TP)、有效磷(AP)和AP/TP比值的变化趋势相似,且具有高度的时间异质性,都呈现秋季低、夏季和次年春季高的"V"形分布特征;湿地土壤TP水平较高,已超过生态毒性的最低阈值(600 mg·kg~(-1)),但该区土壤AP/TP比值低于磷的生物利用度的阈值(2%);湿地土壤TP储量随夏季、秋季、次年春季呈依次减少的变化趋势,AP储量也呈现秋季低、夏春季高的"V"形分布特征;湿地土壤TP、AP含量和储量在两个土层之间不存在显著性差异(P0.05)。湿地土壤TP和土壤含水量(P0.05)、Al和Mg(P0.01)均存在显著正相关关系,和土壤盐度呈显著负相关关系(P0.05);AP和土壤含水量及容重显著正相关(P0.05);土壤磷素与土壤有机质、土壤pH的相关性均未达到显著性水平(P0.05)。总体上,黄河三角洲盐地碱蓬湿地土壤磷的垂直变异性不大,但具有明显的季节变异性,其含量与土壤铝镁化合物以及土壤盐度和含水量具有显著的相关性。     

不同降雨强度下旱地农田氮磷流失规律

为阐明旱地农田径流氮磷流失规律，以种植空心菜的旱地为研究对象，采用人工模拟降雨方式，设计10、15、25 mm·h^-1三个降雨强度，研究不同雨强下旱地氮磷流失特征和径流拦截效果。结果表明：在相同降雨量条件下，旱地径流量随降雨强度的增大而增加，10、15、25 mm·h^-1雨强下产生的径流总量分别为197.07、381.92、649.45 m³·hm^-2，对应的径流系数分别为0.20、0.38、0.65。总氮（TN）浓度变化随产流时长呈现出先上升后下降的趋势，峰值明显，氮的流失形态以硝酸盐氮（NO₃^--N）为主；TN流失量随着降雨强度的增大而增加，10、15、25 mm·h^-1雨强下分别为0.67、2.48、9.74 kg·hm^-2。总磷（TP）流失浓度随降雨强度的增大而降低，流失过程相对平缓，磷的流失形态以颗粒态磷（PP）为主；10、15、25 mm·h^-1雨强下TP流失量分别为0.061、0.050、0.030 kg·hm^-2。通过田间沟渠水位的管控，可有效减少TN的径流排放，不同雨强下减少比例分别为100.00%、63.56%、33.98%。研究表明，氮的拦截是控制旱地面源污染的重点，在拦截能力有限的情况下，选择污染负荷较高的时段可有效提高面源污染拦截效果。     

Comparison of EDTA and ammonium Bicarbonate-DTPA for the extraction of phosphorus in calcareous soils from Kerman,Iran

Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate sodium ethylene diamine tetra acetic acid (Na₂-EDTA) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) to determinate the relationships between extractable P and its uptake by crop in calcareous soils. Na₂-EDTA and AB-DTPA was compared by the amounts of extracted P by analyzing soil samples collected from agricultural production areas. There were significant correlations between Na₂-EDTA and AB-DTPA for soil test P based on soils collected from the agricultural field. Soil test P by both extractants was significantly correlated with plant P concentration. Na₂-EDTA was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.     

Crop use and profile distribution of phosphorus in soils that developed on mafic rocks in southern Portugal

The phytoavailability of soil phosphorus (P) depends on the different forms in which it occurs and how these forms change after the application of P fertiliser to the soil. Forms of P in the A, B and C horizons of eleven pedons that developed on mafic rocks were characterised by a fractionation method before and after fertilisation with single superphosphate, and a micropot experiment was conducted to assess the short-term use of P fertiliser by rye (Secale cereale L.). The main sources of P to the crop were (i) phosphate adsorbed on mineral surfaces and pedogenic Fe, Al or Ca phosphates in the A horizon and (ii) Ca-phosphates in B and C horizons. In the C horizons, poor in Fe/Al phases and clay, the precipitated Ca-P showed low solubility, resulting in a reduction in shoot biomass. The apparent P recovery by rye was similar in the A (36%) and B (29%) but decreased in the C (15%) horizons. The partial factor productivity (g g^?1) decreased from the A (58) to B (11) and C (5) horizons. P phytoavailability decreased with increasing profile depth because the transformation of P fertiliser to poorly soluble Ca-P forms increased with depth.     

农田汇水河道水生植物原位净化工程处理效果分析

为了研究水生植物原位净化工程处理效果,于2017年5—11月,在江苏省泗洪县四河乡的农田汇水河道,利用水葫芦和绿狐尾藻构建组合生态浮床,沿着水流方向设置4个水质采样点,每月监测水体基本理化指标,主要包括水温(T)、酸碱度(pH)、溶解氧(DO)、总氮(TN)、总磷(TP)、化学需氧量(COD_(Cr))、悬浮物(SS),分析河段水质沿程变化;在试验开始时、每次采收时监测单位面积植物生物量,干物质含量与氮磷含量,计算植物氮磷富集量。结果显示:植物种养后,沿程各采样点数据对比,水体pH值逐渐趋于中性;各采样时间数据对比,水体DO浓度呈升高趋势。在植物旺盛生长期(7—10月),组合生态浮床对河段水体TN、TP、COD和SS的沿程总消减率分别为50.41%～78.00%、44.62%～73.33%、46.15%～57.82%和33.33%～52.38%,其中最高值出现在8月。按照有效试验周期180 d(5—10月)计算,水葫芦的氮、磷去除量分别约为0.76 g·m~(-2)·d~(-1)和0.09 g·m~(-2)·d~(-1);绿狐尾藻的氮、磷去除量分别约为1.17 g·m~(-2)·d~(-1)和0.08 g·m~(-2)·d~(-1)。除了植物自身的吸收作用,根系微生物降解作用在污染物净化过程中也发挥了重要作用。在农田汇水河道原位净化工程中,水葫芦与绿狐尾藻组合生态浮床大幅消减水体氮磷浓度,有效降解有机物及拦截颗粒物,对于缓解下游水域富营养化问题具有积极的意义。