Macronutrient accumulation in wheat crop (Triticum aestivum L.) with Azospirillum brasilense associated with nitrogen doses and sources

Abstract

New studies are needed to optimize the nitrogen (N) amount that can be applied to utilize the Azospirillum brasilense benefits. In addition, information regarding the interaction between the urease inhibitor and biological nitrogen fixation (BNF) and how they affect the macronutrients accumulation are also needed. We evaluate the effect of N sources and doses associated with A. brasilense regarding the macronutrients accumulation in straw and grains and wheat grain yield in tropical conditions. A randomized block experimental design was used with four replications in a 2?×?5?×?2 factorial arrangement as follows: two N sources (urea and urea with urease enzyme inhibitor NBPT; five N doses (0, 50, 100, 150, and 200?kg ha^?1) applied in topdressing; with and without A. brasilense inoculation. We found that an increase in N doses positively influenced the accumulation of macronutrients in straw and grains and the wheat grain yield. N sources have similar effects. Inoculation with A. brasilense increased accumulation of Mg and S in straw and P, Ca, and Mg in grains, regardless of the N dose. The inoculation with A. brasilense associated with 140?kg ha^?1 of N increased wheat grain yield. The inoculation can contribute in a more sustainable way to wheat nutrition and optimizing N fertilization.     

Soil microbial functional diversity response following nematocide and biocide amendments in a desert ecosystem

The aim of the current study was to gain a better understanding of the changes that occur in soil microbial community and in its functional diversity as a result of the use of nematocide and biocide inhibitors in natural ecosystems. Both inhibitors are known to have a great effect on the nematode community and total biota, playing an important role in soil food web and biota interactions. The experiment was set up in the Negev Desert using sixteen 1×1 m soil plots, to which two chemical inhibitors were applied: (a) a biocide, to eliminate the whole biotic community; and (b) a nematocide, to eliminate the nematode community in soil. In addition, water treatment was applied to the same soil plots, while untreated soil plots were used as control. Microbial functional diversity, together with abiotic parameters such as soil moisture and total organic carbon, was tested monthly in soil samples collected from the 0-10 and 10-20 cm soil layers. The results of the abiotic parameters showed similar patterns in the two soil layers regardless of the inhibitor treatments. An increase in soil water content followed rainfall patterns. Total organic carbon was low during the wet season and increased during the dry seasons. The Shannon-Weaver index value for microbial functional diversity was found to increase in spring after the wet season in both soil layers. In the upper soil layer, an increase was observed both in the inhibitor and water treatments. However, the increase in the water treatment lasted longer compared to the increase observed in the inhibitor-treated soil plots. In the 10-20 cm soil layer, a different pattern was observed: an increase in microbial functional diversity was observed in the inhibitor-treated soil plots, while an increase in the water-treated soil plots was seen at a later stage. Principal Component Analysis was also conducted, revealing different patterns between inhibitors and water treatments on both a temporal scale, when changes from a homogeneous to heterogeneous consumption pattern were observed, and in the nature of communities that proliferate in the soil. Differences were also observed in the microbial community between the upper 0-10 and the lower 10-20 cm soil layers, where an opposite pattern of substrate consumption was observed. This study emphasizes the important role the biotic component plays in the soil of an arid climate, studying the long-term effects of key species elimination on the microbial community in desert soil.     

Measurement of coupled nitrification-denitrification in paddy fields affected by Terrazole,a nitrification inhibitor

Coupled nitrification-denitrification and potential denitrification were measured as ¹⁵N₂O and ¹⁵N₂ evolution rates in ammonium sulphate-treated rice soils with or without Terrazole [5-ethoxy-3 (trichloromethyl) 1,2,3 Thiadizole] under laboratory and field conditions. The greatest coupled nitrification-denitrification activity was found after drying and rewetting the soil, with maximum values of 322 ng N cm^–2 h^–1 in the laboratory and 90.8 ng N cm^–2 h^–1 in the field. These ¹⁵N₂O + ¹⁵N₂ evolution rates were about 10 times lower than potential denitrification in these soils. These results and the observed decrease in ¹⁵N₂O + ¹⁵N₂ evolution rate in soils treated with Terrazole (60% under laboratory conditions and 52% under field conditions) indicate that denitrification was limited by coupled nitrification-denitrification activity. Oxygen and previous addition of ammonium sulphate appear to control the rate of ¹⁵N₂O + ¹⁵N₂ evolution in ammonium sulphate-fertilised soils.     

反刍动物脲酶抑制剂的研究进展

尿素作为非蛋白氮饲料直接饲喂动物 ,在瘤胃中分解速度快于微生物利用速度 ,这不仅降低尿素利用效率 ,而且容易造成氨中毒。脲酶抑制剂可以降低尿素的分解速度 ,提高尿素利用效率。文章就目前国内外各种瘤胃脲酶抑制剂对动物瘤胃尿素分解速度、氨浓度、营养物质利用及对动物生产性能的影响进行了综述。     

土壤粘粒吸附脲酶特征的研究

研究了 8种土壤粘粒对脲酶的吸附情况 ,结果显示 ,土壤粘粒对脲酶吸附 12 0 min可达平衡。土壤粘粒对脲酶的吸附等温线为 L型 ,可用双表面 L angm uir方程较好描述。初步认为土壤粘粒对脲酶吸附为化学吸附和物理吸附 ,且以化学吸附为主     

土壤肥力对其脲酶与汞镉关系的影响

对受汞镉污染的不同肥力土壤脲酶活性的测定结果表明 ,汞镉不同程度地抑制土壤脲酶活性 ,其中Hg +Cd的抑制幅度最大。随重金属浓度增加 ,酶活性降低 ,其强度Hg Cd。通过计算得到脲酶生态剂量ED50Hg Cd ,揭示出脲酶对Hg的敏感性远大于Cd。获得 土娄土脲酶ED50 值 :Hg 0 .5 0 8～ 2 .2 4 8mg/kg ,Cd35 0 .0～4 81.0 9mg/kg ,建议将其作为土壤汞镉污染的参考指标。相关分析显示 ,在肥力水平差异较大的土壤上 ,脲酶活性仍可表征土壤受汞镉污染的程度。在复合污染条件下 ,脲酶活性不仅受到单因素影响 ,而且存在汞、镉间弱的拮抗作用 ,但仍以单独效应为主。高肥土壤由于有机质等对脲酶的保护容量较大 ,对重金属的缓冲作用明显 ,导致汞镉对脲酶的生态毒性较弱 ,而低肥土壤则相反     

5%氟铃脲乳油在棉田生态系统中的安全使用评价

利用HPLC建立了棉田生态系统中氟铃脲的残留行为、消解动态,及其对棉田土壤中脲酶和过氧化氢酶的影响,为其环境和生态安全提供重要的科学依据。结果表明:(1)土壤和棉籽样品中的氟铃脲残留物用甲醇提取,而棉叶样品中的氟铃脲用二氯甲烷提取,土壤样品和棉叶样品均过弗罗里硅土柱用乙酸乙酯淋洗。棉籽样品过弗罗里硅土柱采用乙酸乙酯和丙酮混合淋洗液,浓缩后用高效液相色谱仪(带UVD)进行检测;当添加浓度为0.022、0.050、0.504mg·kg-1时,添加回收率为80.05%～105.16%,变异系数为1.17%～7.98%,最小检出量为2.36×10-9g。(2)氟铃脲在棉叶和土壤中的半衰期分别为长沙4.19和7.73d,天津9.76和7.99d,符合一级动力学方程;氟铃脲在使用剂量下,有效成分在棉籽中的残留量为LOD,保证了棉籽使用的安全性。(3)氟铃脲对各浓度处理的土壤脲酶活性均产生了一定的影响,施药初期,各浓度处理的土壤脲酶活性均被抑制,且浓度越高,抑制作用越明显。之后0.504mg·kg-1处理的土壤脲酶活性逐渐恢复到和对照相一致,5.040mg·kg-1处理的土壤脲酶活性则从第6d起一直处于被激活状态,而10.080mg·kg-1处理的土壤脲酶活性则在整个培养期间一直处于被抑制状态。(4)从施药后第1d到第14d,低浓度(0.504和5.040mg·kg-1)氟铃脲处理的土壤多酚氧化酶的活性被激活,之后逐渐恢复到和对照一致。而高浓度处理(10.080mg·kg-1)的土壤多酚氧化酶活性,从施药后第1d到第14d一直处于被抑制状态,从第14d开始一直到培养结束均处于被激活的状态。(5)氟铃脲0.504和5.040mg·kg-1处理均不会对土壤脲酶和多酚氧化酶造成不利影响,根据试验氟铃脲在长沙和天津两地的土壤原始附着量分别为0.541和0.653mg·kg-1,按氟铃脲的使用剂量施药,对土壤生态系统影响很小。     

反刍动物瘤胃脲酶抑制剂的作用及应用

反刍动物能够利用饲料中的非蛋白氮 (NPN )作为氮源 ,尿素是反刍动物重要的 NPN。在瘤胃脲酶的作用下 ,进入瘤胃的尿素快速分解 ,氨释放速度是瘤胃微生物利用速度的 4倍。瘤胃脲酶抑制剂的应用 ,减缓了尿素在瘤胃内的分解。土壤脲酶抑制剂种类很多 ,但能够用做反刍动物瘤胃脲酶抑制剂的并不多 ,文章总结了几种研究较多的瘤胃脲酶抑制剂的作用及其应用。     

紫色土脲酶活性与土壤营养的研究

对中性紫色土脲酶活性与土壤营养因子的相关性研究表明,紫色土脲酶活性(Y)与土壤中的全氮(X_1)、速效氮(X_4)、全钾(X_3)、速效钾(X_6)含量相关。即Y=-0.2976 0.2353X_1 0.1153×10~(-1)X_3 0.2133×10~(-2)X_4-0.2068×10~(-2)X_6。土壤全氮是影响脲酶活性的最主要因子。速效氮对酶活性的正效应,是由全氮对酶活性的作用表现。全钾的直接作用为正,速效钾为负,二者通过氮对酶活性的间接作用也为负,与钾相关的决定系数均较小,因而对脲酶的影响程度小于氮。     

樟科植物提取物对断奶仔猪粪尿氮排放的影响

为研究樟科植物提取作为脲酶抑制剂对仔猪粪尿氮排泄的影响,选取杜长大三元杂交30日龄断奶仔猪480头,按胎次、体重相近和公母基本一致分成5个处理组,分别饲喂添加不同剂量樟科植物提取物的日粮,即空白对照组Ⅰ、150 mg·kg-1组Ⅱ、300 mg·kg-1组Ⅲ、450 mg·kg-1组Ⅳ、600 mg·kg-1组Ⅴ,每个处理设3个重复,每个重复32头猪.结果表明:第Ⅳ、Ⅲ组与第Ⅰ组相比,料肉比分别降低5.67%(P＜0.01)和4.64%(P＜0.01);第Ⅳ、Ⅴ组与第Ⅰ组相比,粪样中微生物的脲酶活性显著降低(P＜0.05);第Ⅴ、Ⅳ组的尿素分解减少,总氮保持率提高,48 h后与第Ⅰ组差异均达到极显著水平(P＜0.01).樟科植物提取物的添加使血清中总蛋白含量提高、尿素氮含量降低.试验结果表明樟科植物提取物添加在断奶仔猪日粮中能够促进仔猪生长,抑制粪中脲酶活性,减少粪尿氮排泄,最佳使用剂量为450 mg·kg-1饲料(Ⅳ组).