Establishment of phosphate-solubilizing strains of Azotobacter chroococcum in the rhizosphere and their effect on wheat cultivars under green house conditions

A pot experiment was conducted in the green house to investigate the establishment of phosphate solubilizing strains of Azotobacter chroococcum, including soil isolates and their mutants, in the rhizosphere and their effect on growth parameters and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Five fertilizer treatments were performed: Control, 90 kg N ha^—1, 90 kg N + 60 kg P₂O₅ ha^—1, 120 kg N ha^—1 and 120 kg N + 60 kg P₂O₅ ha^—1. Phosphate solubilizing and phytohormone producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected by an enrichment method. In vitro phosphate solubilization and growth hormone production by mutant strains was increased compared with soil isolates. Seed inoculation of wheat varieties with P solubilizing and phytohormone producing A. chroococcum showed better response compared with controls. Mutant strains of A. chroococcum showed higher increase in grain (12.6%) and straw (11.4%) yield over control and their survival (12—14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M37 performed better in all three varieties in terms of increase in grain yield (14.0%) and root biomass (11.4%) over control.     

广西典型红壤旱地施用钙镁磷肥对玉米产量及其镉累积的影响

在广西典型类型红壤旱地布置玉米磷肥施用量的田间试验,研究不同钙镁磷肥施用量(磷肥Cd含量为0.0651 mg/kg)对玉米产量及地上部Cd累积的影响。结果表明,与不施磷肥处理(CK)相比,施磷肥可分别显著提高春、秋玉米籽粒产量8.2%—13.1%和13.7%—20.0%。高磷(600 kg P2O5/hm2)处理的春玉米秸秆产量比CK显著提高11.4%;施磷处理春、秋玉米秸秆Cd含量分别下降2.7%—45.8%和11.0%—43.6%;而籽粒Cd含量分别下降13.0%—40.6%和9.9%—31.5%,且秸秆和籽粒的Cd含量及累积量均随施磷量的增加而逐渐降低,其中以高磷处理最为显著。玉米秸秆及籽粒Cd累积量在高磷处理下(600 kg P2O5/hm2)分别比低磷处理(75—300 kg P2O5/hm2)降低13.6%—41.5%和8.8%—29.3%。相关分析表明,玉米Cd含量与土壤pH呈显著负相关,与土壤有效Cd含量呈显著正相关。施磷提高土壤pH,而降低土壤有效Cd含量。高量磷肥施用降低土壤Cd的有效性进而降低玉米对Cd的吸收累积。     

秸秆还田配施不同比例化肥对晚稻产量及土壤养分的影响

在不同秸秆还田方式对早稻的效应研究确定的最佳还田方式和还田量(粉碎还田3000 kg/hm2)基础上,以单施秸秆为对照,研究了秸秆还田配施不同比例化肥对晚稻产量、干物质积累与分配及土壤养分的影响。结果表明:(1)与对照相比,秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2增产效果最为显著,在水稻的每穗粒数、千粒重、结实率、充实度和产量等方面增加幅度最大,分别为9.32%、4.28%、13.70%、2.74%和26.38%。(2)各处理的干物质茎鞘比例随着生育进程不断降低,从孕穗期的66.68%—77.00%降低至成熟期的25.97%—34.79%,除SNPK1外,叶片比例从孕穗期的23.00%—33.32%降低至成熟期的7.41%—21.03%;秸秆还田配施不同比例化肥处理的茎鞘比例在孕穗期、抽穗期和成熟期高于对照,而叶片比例与茎鞘比例呈相反趋势。(3)与对照相比,秸秆还田配施不同比例化肥处理提高了土壤pH值、有机碳、全氮、碱解氮、全磷、有效磷、全钾、速效钾,降低了土壤C/N比。研究结果说明,秸秆还田配施不同比例化肥可以提高植株干物质积累速率、群体生物量,合理改善土壤养分,保证较高的水稻增产潜力,其中秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2效果最为显著。     

Influence of Rhizobial inoculation on yield of wheat (Triticum aestivum L.)

Summary Soil + charcoal (1∶3) carrier based and liquid cultures of Rhizobia were used to inoculate wheat seed cv. HD2329. The plants received 100 kg N in two equal splits and 60 kg P₂O₅ and 40 kg K₂₀ ha⁻¹. Inoculation with rhizobia had little effect on grain yield of wheat. Significant increase in straw yield and N-uptake occurred due to inoculation. A comparison of results of a similar experiment conducted during 1983–84, showed that inoculation with the same strains of rhizobia and application 50 kg N ha⁻¹ as basal dressing, was more effective in increasing yield and N-uptake in wheat cv. HD2329. It appears reasonable to assume occurrence of nitrogen fixation by root nodule bacteria in rhizosphere of wheat.     

Soybean biofertilization in sandy soils of Egypt using15N tracer technique

The effect of inoculating soybean plants withBradyrhizobium japonicum andAzospirillum brasilense either solely or in mixture, and of using different N fertilizer levels was studied in pot experiments. The nodulation of soybean grown in a sandy soil was enhanced by the inoculation while the highest nodule numbers and fresh mass, recorded at a N-fertilizer dose of 20 kg N/hm², decreased when the fertilizer quantity increased to 40 kg N/hm². By contrast, the dry mass of above-ground parts and the N uptake was increased with increasing N fertilizer level. A similar effect was observed for inoculation as compared with the uninoculated variant. Although the nodulating and non-nodulating soybeans has nearly the same dry mass, the nodulating isoline accumulated more N than the non-nodulating. The percentage of nitrogen derived from air (%, Ndfa) and estimated by isotope dilution (ID) or N difference method (DM) dropped with increasing N level from 10 to 40 kg N/hm². Dual inoculation resulted in a high per cent of fixed N₂ (42.5%) at 10 kg N/hm². Correlation between the ID and DM methods was found to be dependent on inoculation treatments. The amount of nitrogen utilized by nodulating soybean (FUE %) was enhanced as a function of inoculation withB. japonicum.     

不同施肥对雷竹林径流及渗漏水中氮形态流失的影响

雷竹经营过程中化肥的大量施用,是产区水体污染的主要原因之一,养分管理技术可有效控制面源污染。为了探明减量施肥和有机肥施用对雷竹不同氮形态流失的影响,2012年在浙江省临安市雷竹产区设置了4种施肥处理:对照(CK);常规施肥(CF);减量无机(DI);减量有机无机(DOI),试验于5月18日、9月7日、11月9日分别施用肥料总量的40%,30%和30%,施肥后均进行浅翻,深度5 cm左右。通过建立径流场和土壤渗漏水收集装置,同时在试验田附近布置量雨筒,观察2012年不同氮形态浓度及流失负荷随降雨量的动态变化。研究结果表明:不同施肥处理径流水硝态氮、水溶性有机氮(WSON)以及颗粒态氮的浓度分别在3.82-6.82 mg/L、0.89-1.85 mg/L和0.89-1.83 mg/L,其占总氮的百分比分别为60.9%-68.2%、16.0%-18.1%和15.1%-21.6%。不同施肥处理渗漏水中硝态氮、铵态氮及WSON的浓度分别在26.2-92.5 mg/L、0.50-6.42 mg/L和6.57-12.6 mg/L,其占总氮的百分比分别为75.8%-82.9%、1.50%-6.36%和11.2%-20.6%。不同施肥处理径流水的氮总流失负荷,减量无机和减量有机无机相对于常规施肥来说减少了46.9%和23.1%;不同施肥处理的渗漏水的氮总流失负荷,减量无机和减量有机无机相对于常规施肥来说减少了19.1%和52.1%,可见减量施肥和减量有机无机减少氮流失的效果显著。     

玉米、花生及其间作茬口与施磷对冬小麦光合特性及产量的影响机制

该试验在玉米单作茬口、玉米-花生间作茬口(间作茬口)、花生单作茬口共3种茬口,以及0 kg P_2O_5·hm~(-2)(P_0)和180 kg P_2O_5·hm~(-2)(P_1) 2个磷水平下,研究了间作茬口与施磷对冬小麦分蘖、叶面积指数(LAI)、干物质积累、光合特性及产量的影响机制,为玉米花生间作与小麦-玉米复种轮作提供理论依据。结果表明:(1)间作茬口较玉米茬口显著提高了冬小麦有效分蘖数、LAI、净光合速率和干物质积累量,并提高了冬小麦旗叶的SPAD值、CO_2饱和点、光饱和点及最大净光合速率(P_(nmax))、表观量子效率(AQY)、羧化效率(CE)、最大羧化速率(V_(cmax))、最大RUBP再生的电子传递速率(J_(max))和最大磷酸丙糖利用速率(V_(TPU)),且CE、V_(cmax)、V_(TPU)的增幅均达到显著水平(P0.05),有效改善了冬小麦产量构成,显著提高籽粒产量(P0.05)。(2)间作茬口较花生茬口提高了冬小麦乳熟期的P_(nmax)、AQY、CE,增加了穗粒数和粒重,提高了产量。(3)与不施磷相比,施磷180 kg P_2O_5·hm~(-2)显著促进间作茬口冬小麦生长,显著提高冬小麦旗叶的SPAD值、P_(nmax)、AQY、CE、V_(cmax)、J_(max)、V_(TPU)和籽粒产量(P0.05)。研究发现,间作茬口较玉米茬口能有效增强冬小麦旗叶表观量子效率和CO_2羧化能力,显著提高小麦花后光合能力,促进冬小麦生长,从而增加穗粒数、粒重和籽粒产量,且间作茬口结合施磷180 kg P_2O_5·hm~(-2)效果更好。     

Nitrogen fixation (15N dilution) with soybeans under Thai field conditions

Controlled environment and field studies were conducted to determine relationships between various measurements of N₂ fixation using soybeans and to use these measures to evaluate a number ofBradyrhizobium japonicum strains for effectiveness in N₂ fixation in Thai soils.¹⁵N dilution measurements of N₂ fixation showed levels of fixation ranging from 32 to 161 kg N ha⁻¹ depending on bacterial strain, host cultivar and location. Midseason measures of N₂ fixation were correlated with each other, but not related measures taken at maturity. Ranking ofB. japonicum strains based on performance under controlled conditions in N-free media were highly correlated with rankings based on soybean seed yields and N₂ fixation under field conditions. This study showed that inoculation of soybeans with effectiveB. japonicum strains can result in significant increases in yield and uptake of N through fixation. The most effective strains tested for use in Thai conditions were those isolated from Thai soils; however, effective strains from other locations were also of benefit.     

钾肥类型对菜心(菜薹)生长、细胞保护酶和内源激素的影响

为探讨钾肥类型对菜心(Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee)的作用效应,研究了不同钾肥类型和水平对菜心生长、细胞保护酶和内源激素的影响。结果表明,氯化钾或硫酸钾处理可提高菜心叶片的POD 和CAT 活性、IAA 和GA₃ 含量,降低MDA 含量,提高菜薹产量。随着钾水平的提高,叶片IAA 和GA₃ 含量、POD 和CAT 活性以及菜薹质量明显提高,MDA 含量降低。当施钾90 kg hm^-2 时,叶片的GA₃ 和IAA 含量显著下降,而POD 活性和菜薹产量没有显著变化。在相同水平下,氯化钾与硫酸钾对植株生长、菜薹产量、叶片GA₃ 含量的影响不显著。当施钾0~90 kg hm^-2 时,氯化钾处理的叶片POD 活性显著高于硫酸钾处理;而施钾135~180 kg hm^-2 时,氯化钾处理的叶片POD 活性则显著低于硫酸钾处理。除了90 kg hm^-2 氯化钾处理的CAT 活性和45 kg hm^-2 氯化钾处理的MDA 含量低于硫酸钾处理以及90 kg hm^-2 和180 kg hm^-2 氯化钾处理的IAA 含量高于硫酸钾处理的外,相同水平氯化钾和硫酸钾处理的CAT 活性、MDA 含量和IAA 含量没有显著差异。可见,钾肥类型对菜心的活性氧代谢系统及内源激素含量有一定的影响,但氯化钾与硫酸钾对菜心的施用效果相当,生产上可采用氯化钾代替硫酸钾以节约肥料成本,K₂O 施用量以90 kg hm^-2 为宜。     

Field evaluation of symbiotic nitrogen fixation by rhizobial strains using15N methodology

Summary Small differences in N₂ fixation by nodulated soybeans (Glycine max. (L.) Merr.), inoculated with various strains ofRhizobium japonicum, were assessed in field experiments using¹⁵N methodology, and compared with yields of plant dry matter and total N. Percentage of plant-N derived from atmospheric N₂ and from fertilizer, and values of %¹⁵N atom excess had lower coefficients of variation than did total N and dry matter yield. Nevertheless the precision of estimates of kg N/ha fixed were sufficient to differentiate only the extremes of the range of strains tested, and there were discrepancies between ranking of strains based on % N derived from fertilizer and on total N yield.     

Sugar beet and barley yields in relation to inoculation with N2-fixing and phosphate solubilizing bacteria

Recently, there has been a resurgence of interest in bioorganic fertilizers as part of sustainable agricultural practices to alleviate drawbacks of intensive farming practices. N₂-fixing and P-solubilizing bacteria are important in plant nutrition increasing N and P uptake by the plants, and playing a significant role as plant growth-promoting rhizobacteria in the biofertilization of crops. A study was conducted in order to investigate the effects of two N₂-fixing (OSU-140 and OSU-142) and a strain of P-solubilizing bacteria (M-13) in single, dual and three strains combinations on sugar beet and barley yields under field conditions in 2001 and 2002. The treatments included: (1) Control (no inoculation and fertilizer), (2) Bacillus OSU-140, (3) Bacillus OSU-142, (4) Bacillus M-13, (5) OSU-140 + OSU-142, (6) OSU-140 + M-13, (7) OSU-142 + M-13, (8) OSU-140 + OSU-142 + M-13, (9) N, (10) NP. N and NP plots were fertilized with 120 kg N ha^–1 and 120 kg N ha^–1 + 90 kg P ha^- for sugar beet and 80 kg N ha^–1 and 80 kg N ha^–1 + 60 kg P ha^–1 for barley. The experiments were conducted in a randomized block design with five replicates. All inoculations and fertilizer applications significantly increased leaf, root and sugar yield of sugar beet and grain and biomass yields of barley over the control. Single inoculations with N₂-fixing bacteria increased sugar beet root and barley yields by 5.6–11.0% depending on the species while P-solubilizing bacteria alone gave yield increases by 5.5–7.5% compared to control. Dual inoculation and mixture of three bacteria gave increases by 7.7–12.7% over control as compared with 20.7–25.9% yield increases by NP application. Mixture of all three strains, dual inoculation of N₂-fixing OSU-142 and P-solubilizing M-13, and/or dual inoculation N₂-fixing bacteria significantly increased root and sugar yields of sugar beet, compared with single inoculations with OSU-140 or M-13. Dual inoculation of N₂-fixing Bacillus OSU-140 and OSU-142, and/or mixed inoculations with three bacteria significantly increased grain yield of barley compared with single inoculations of OSU-142 and M-13. In contrast with other combinations, dual inoculation of N₂-fixing OSU-140 and P-solubilizing M-13 did not always significantly increase leaf, root and sugar yield of sugar beet, grain and biomass yield of barley compared to single applications both with N₂-fixing bacteria. The beneficial effects of the bacteria on plant growth varied significantly depending on environmental conditions, bacterial strains, and plant and soil conditions.     

Association between N2-fixing bacteria and pearl millet plants: Responses,mechanisms and persistence

Responses to inoculation with N₂-fixing bacteria were studied in relation to genotypic differences in pearl millet, effect of nitrogen levels, and FYM additions in India. In some experiments, inoculation increased mean grain yield up to 33% over the uninoculated control, whereas in the remaining 11 experiments there was no significant increase. Increased grain yields, >10% over the uninoculated controls were observed in 46% of the experiments withAzospirillum lipoferum (18.7% average increase) and withAzotobacter chroococcum (13.6% average increase). Yield increases were nil or reduced in three experiments withAzos. lipoferum and four experiments withAztb. chroococcum. In two experiments continued inoculation for two or three years resulted in increased grain, plant biomass yield, and N uptake. Interactions of bacterial cultures with cultivars or years were not observed. The counts of the inoculated strains increased two to three-fold when inoculation was continued for three years. Repeated inoculations increased the mean cumulative N uptake from season 1 to season 3 by 19 kg ha^–1. Repeated inoculations withAztb. chroococcum andAzos. lipoferum increased mean grain yield of a succeeding crop by 14.4% and 9.8%, respectively, over the uninoculated control. Inoculation increased the efficiency of N-assimilation by pearl millet. Marginal increase in nitrogenase activity, associated with the inoculated plants was observed during later stages of plant growth. Increased leaf nitrate reductase activity (NRA) was observed after inoculation with these bacteria. The responses to inoculation are mainly attributable to increased plant N assimilation which could be the effect of growth promoting substances secreated by the bacteria; and thus the contribution from BNF may be small.CRISAT, journal article 732.     

不同施氮措施对旱作玉米地土壤酶活性及CO2排放量的影响

对施用速效氮肥(尿素)和缓释氮肥的旱作夏玉米地土壤酶活性及CO2排放量进行分析。结果表明,与不施肥处理比较,不同氮肥种类和施用量均可显著提高土壤脲酶、蔗糖酶、过氧化氢酶活性和CO2的排放量。在整个生育期,尿素与缓释氮肥处理土壤酶活性和土壤CO2排放量表现出相同变化趋势,尿素和缓释氮肥处理土壤CO2平均排放量分别为459.12 mg·m-·2h-1和427.11 mg·m-·2h-1,两者达到显著差异水平(P<0.5)。相关分析表明,土壤脲酶、蔗糖酶和过氧化氢酶活性与土壤CO2排放量呈显著或极显著正相关,相关系数分别为0.79、0.64和0.80。说明相同施氮量缓释氮肥较尿素能有效提高土壤酶活性并降低土壤碳排放量。     

陕西关中小麦-玉米轮作区协调作物产量和环境效应的农田适宜氮肥用量

为了确定陕西关中小麦-玉米轮作区兼顾作物产量和环境效应的农田适宜氮肥用量,通过玉米-小麦-玉米连续3季田间试验研究了作物产量、氮肥利用效率、氮肥表观损失和土壤氮素平衡等对施氮量的响应。结果表明,随着氮肥用量的增加,不同年份作物产量和3季作物累计产量均表现为先增加后降低的趋势,而累计氮肥农学效率、氮肥表观利用率、氮肥吸收效率和氮肥偏生产力均表现为显著的降低趋势。土壤氮素平衡结果表明,随着施氮量的增加,低量施氮时(小麦施N150 kg/hm2,玉米施N180 kg/hm2),氮肥残留显著增加,表观损失和损失率变化不明显,而高量施氮时(小麦施N150 kg/hm2,玉米施N180 kg/hm2),氮肥残留变化不明显,表观损失和损失率却显著增加。回归和相关分析显示,矿质氮在土壤较深层次(100—200cm土层)大量累积是氮肥表观损失的重要途径之一。小麦施N 150 kg/hm2、玉米施N 180 kg/hm2时,作物即可获得相对较高的产量和氮肥利用率,且能保持作物收获前后土壤无机氮库的基本稳定,同时也可将氮肥表观损失降至较低水平。     

Physiological changes in soybean (Glycine max) Wuyin9 in response to N and P nutrition

Phosphorus deficiency is a very common problem in the acid soil of central China. Previous research has shown that starter N and N topdressing at the flowering stage (Rl) increased soybean (Glycine max) yield and N₂ fixation (Gan et al, 1997, 2000). However, there is little information available concerning soybean response to P‐fertiliser in soybean production in central China (Gan, 1999). A field experiment was conducted to investigate the response to P (0 kg P ha^?1, 22 kg P ha^?1, 44 kg P ha^?1 before sowing) and N fertiliser application (N1: 0 kg N ha^?1, N2: 25 kg N ha^?1 before sowing, N3: N2 + 50 kg N ha^?1 at the V2 stage and N4: N2 + 50 kg N ha^?1 at the R1 stage) on growth, yield and N₂ fixation of soybean. Both N and P fertiliser increased growth and seed yield of soybean (P < 0.01). Application of basal P fertiliser at 22 kg P ha^?1 or 44 kg P ha^?1 increased total N accumulation by 11% and 10% (P < 0.01) and seed yield by 12% and 13% (P < 0.01), respectively, compared to the zero P treatment. Although application of starter N at 25 kg N ha^?1 had no positive effect on seed yield at any P level (P > 0.05), an application of a topdressing of 50 kg N ha^?1 at the V2 or R1 stage increased total N accumulation by 11% and 14% (P < 0.01) and seed yield by 16% and 21% (P < 0.01), respectively, compared to the zero N treatment. Soybean plants were grown on sterilised Perlite in the greenhouse experiment to study the physiological response to different concentrations of phosphate (P1: 0 mM; P2: 0.05 mM; P3: 0.5 mM; P4:1.0 mN) and nitrate (N1: 0 mM with inoculation, N2: 20 mM with inoculation). The result confirmed that N and P nutrients both had positive effects on growth, nodulation and yield (P < 0.01). The relative importance of growth parameters that contributed to the larger biomass with N and P fertilisation was in decreasing order: (i) total leaf area, (ii) individual leaf area, (iii) shoot/root ratio, (iv) leaf area ratio and (v) specific leaf area. The yield increase at N and P supply was mainly associated with more seeds and a larger pod number per plant, which confirmed the result from the field experiment.     

氮磷肥配施对苦荞根系生理生态及产量的影响

以苦荞品种‘迪庆’为材料,在盆栽试验条件下,研究了氮(纯氮用量分别为0g/kg、0.1g/kg、0.2g/kg)、磷(P2O5用量分别为0.1g/kg和0.2g/kg)配施对苦荞根系生长、生理指标及其产量的影响,旨在为黄土高原苦荞高产优质栽培提供理论依据。结果表明:(1)在相同施磷量条件下,苦荞幼苗的株高、茎粗、茎叶干重、主根长、根表面积、根系体积、根系直径、根系干重以及壮苗指数等均随施氮量的增加而呈先升后降的趋势,但根冠比随施氮量的增加而呈先降后升的趋势;叶片叶绿素含量以及根系活力、酸性磷酸酶(Apase)活性、可溶性蛋白含量和植株氮积累量随施氮量的增加呈抛物线变化趋势,根系硝酸还原酶(NR)活性和植株氮含量随施氮量的增加而增加;而根系可溶性糖含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、丙二醛(MDA)含量和游离脯氨酸含量等指标均随施氮量的增加而呈先降后升的趋势,0.1g/kg施氮处理各指标均显著低于其他处理;成熟期单株粒重、百粒重随施氮量的增加呈先升后降的趋势,0.1g/kg施氮处理各指标均显著高于其他处理。(2)在相同施氮量条件下,随着施磷量的增加,苦荞根系酸性磷酸酶(Apase)活性、SOD活性、POD活性、MDA含量、可溶性糖含量、可溶性蛋白以及游离脯氨酸含量等指标均降低,其余各指标则呈增加趋势。(3)无论施磷量条件如何,0.1g/kg的施氮处理下苦荞产量最高,与其他施氮处理相比,在低磷和高磷处理下的增产幅度分别为7.04%~37.40%和14.73%~68.26%;在施氮量一定的情况下,高磷处理比低磷处理增产15.96%~42.00%。(4)在该试验条件下,适当的氮磷肥配施表现出了明显的正加和效应,但过量施肥也有可能导致增产幅度下降,中氮高磷(施纯N量0.1g/kg,施P2O5量0.2g/kg)配施效果最优。     

不同施氮量对桑园红壤耕层酶活性的影响

在广西红壤典型气候区研究施用氮肥对桑园土壤过氧化氢酶、脲酶、酸性磷酸酶和转化酶酶活性的影响,为广西红壤区桑园合理施氮和耕地保育提供科学依据。试验设置3个施氮量水平(N1:120.75 kg N/hm2,N2:172.5 kg N/hm2,N3:207 kg N/hm2),在冬季测定不同氮肥处理下耕层土壤酶活性,并与桑叶产量进行相关分析。结果表明,土壤脲酶和转化酶活性均随着施氮量的增加而增加,过氧化氢酶和酸性磷酸酶活性在中等施氮量(N2处理)下较大。土壤转化酶和脲酶活性呈显著的正相关关系、转化酶和磷酸酶活性呈显著的正相关关系,土壤脲酶、磷酸酶、转化酶活性与桑叶产量呈极显著相关。合理施用氮肥能提高桑园土壤转化酶、磷酸酶、脲酶活性,土壤脲酶和蔗糖酶活性可作为评价桑园土壤肥力质量的指标之一。     

不同施肥措施臭氧浓度升高对不同水稻品种光合特性的影响

近地层臭氧(O₃)已严重威胁到作物生产,而施肥可以调节土壤的养分平衡,进而促进作物生长。以两个水稻品种(徽两优898和南粳9108)为研究对象,利用开顶式气室,设置2个O₃浓度处理(NF:环境大气为对照;NF40:环境大气+40 nmol/mol O₃),每个O₃处理下嵌套设置3个肥料处理(Ino:施无机肥处理,270 kg N hm^-2 a^-1;Red:减施无机肥30%处理,189 kg N hm^-2 a^-1;Com:有机无机肥配施处理,Red+有机肥鸡粪5000 kg hm^-2 a^-1),通过测定不同生育期水稻光合参数,探究不同肥料处理下O₃对水稻不同生育阶段光合生理的影响。结果表明,NF40对水稻营养生长阶段的饱和光合速率(A_sat)没有显著影响,而显著地降低了水稻灌浆期的A_sat。基于两个水稻品种的A_sat和相对叶绿素含量(SPAD)相对减少量与O₃累积剂量关系的斜率,发现杂交稻徽两优898(A_sat和SPAD的斜率:-1.55和-0.98)比常规稻南粳9108(A_sat和SPAD的斜率:-0.92和0.06)对O₃更敏感。此外,基于不同O₃处理下水稻的气孔导度(g_s)和胞间二氧化碳浓度(C_i),可以看出O₃造成南粳9108光合速率降低的主要是非气孔因素,而徽两优898光合的降低是由气孔因素和非气孔因素共同限制。与Ino处理相比,Red处理主要通过降低叶片SPAD进而显著地抑制两种水稻品种的A_sat,但Ino处理和Com处理间A_sat没有显著差异,说明有机无机肥配施能部分缓解减施无机肥造成水稻光合的降低。O₃和肥料处理对两个水稻的所有光合参数都没有显著的交互影响,表明短期有机无机肥配施并不能有效缓解O₃对作物造成的负面影响。在O₃污染背景下,研究结果可以为通过合理的农田氮肥管理措施减缓O₃造成的作物减产提供理论依据。     

Effect of inoculation ofAzospirillum lipoferum on nitrogen fixation in rhizosphere soil,their association with root,yield and nitrogen uptake by mustard (Brassica juncea)

Summary A microplot field experiment was conducted in the presence or absence of P and N application to evaluate the influence of the seed inoculation of mustard (cv. Baruna T₅₉) withAzospirillum lipoferum on N₂-fixation in rhizosphere, association of the bacteria with the roots and grain yield and N uptake. Inoculation significantly increased the N content in rhizosphere soil particularly at early stage (40 days) of plant growth, which was accompanied by the increased association of the bacteria (A. lipoferum) in rhizosphere soil, root surface washing and surface-sterilized macerated root. A significant increase in grain yield and N uptake was also observed due to inoculation. Application of P particularly at the 20 kg. ha^–1 level further enhanced the beneficial effect ofAzospirillum lipoferum inoculation, while N addition markedly reduced such an effect.     

秸秆还田与氮肥施用对稻田温室气体排放的影响

秸秆还田与氮肥施用是农田生态系统中碳氮元素的两大主要补给途径,其在调控稻田甲烷(CH₄)和氧化亚氮(N₂O)排放以及水稻产量方面具有重要作用。以往的研究主要关注秸秆还田或氮肥施用单因素对稻田温室气体排放的影响,而双因素互作对甲烷和氧化亚氮排放的影响尚未明确。同时,在秸秆还田条件下如何进行合理的氮肥施用鲜有深入研究。本研究基于3个氮肥处理(0、180、360 kg N/hm²)和3个秸秆还田处理(0、2.25、3.75 t/hm²)进行多年水稻田间定位试验,研究结果表明:CH₄季节累积排放随秸秆还田量增加而增加,与施氮量无显著正相关关系;N₂O季节累积排放随施氮量增加而增加,与秸秆还田量无显著正相关关系;秸秆还田对于产量的影响具有不确定性,两年均在秸秆不还田+不施氮处理(S0N0)出现最低产量,2021与2022年最低产量分别为5740.64和4903.75 kg/hm²。2021与2022年最高产量分别在秸秆不还田+高氮(S0N2)和高量秸秆还田+高氮(S2N2)出现,分别为10938.48和10384.83 kg/hm²。同时,本研究发现在低量秸秆还田条件下,在碳足迹(CF, Carbon Footprint)方面,施氮量为251 kg N/hm²时碳足迹达到最低点,为1.01 kg C/kg;而在生态经济净收益(NEEB, Net Ecosystem Economic Benefits)方面,施氮量为294 kg N/hm²时生态经济净收益达到最高点,为11778.15 元/hm²。为协同生态经济净收益与碳排放,在低量秸秆还田(S1)下,配合251-294 kg N/hm²的施氮量为最优施肥方案。研究结果为指导稻田温室气体减排、实现稻田碳中和以及农田管理提供了理论支撑,为实现水稻的高产稳产与低碳生产科学依据。