Assessing post-anthesis nitrogen uptake, distribution and utilisation in grain protein synthesis in barley (Hordeum vulgare L.) using 15N fertiliser and 15N proteinogenic and non-proteinogenic amino acids

We investigated the effects of nitrogen (N) availability during the vegetative phase on (a) post‐anthesis N uptake and (b) its translocation into ears in barley plants grown in a greenhouse at two levels of N: low (50 mg N kg^?1 sand) and optimal N supply (150 mg N kg^?1 sand). Plants in the two N treatments were fertilised with the same amount of labelled ¹⁵N [50 mg ¹⁵N kg^?1 sand at 10% ¹⁵N_exc (N_excess, i.e. N_exc, is defined as the abundance of enriched stable isotope minus the natural abundance of the isotope) applied as ¹⁵NH₄¹⁵NO₃] 10 days after anthesis (daa). In a separate experiment, the uptake and transport into ears of proteinogenic and non‐proteinogenic amino acids were studied to determine whether a relationship exists between amino acid transport into ears and their proteinogenic nature. Plants were fed with either ¹⁵N‐α‐alanine, a proteinogenic amino acid, or ¹⁵N‐α‐aminoisobutyric acid, a non‐proteinogenic amino acid. Both these amino acids were labelled at 95.6% ¹⁵N_exc. Results showed that N accumulations in stems, leaves and especially in ears were correlated with their dry matter (dm) weights. The application of 150 mg N kg^?1 sand significantly increased plant dm weight and total N accumulation in plants. During their filling period, ears absorbed N from both external (growth substrate) and internal (stored N in plants) sources. Nitrogen concentration in ears was higher in optimal N‐fed plants than in low N‐fed plants until 10 daa, but from 21 to 35 daa, differences were not detected. Conversely, ¹⁵N_exc in ears, leaves and stems was higher in low N‐fed plants than in optimal N‐fed plants. Ears acted as strong sink organ for the post‐anthesis N taken up from the soil independently of pre‐anthesis N nutrition: on average, 87% of the N taken up from the soil after anthesis was translocated and accumulated in ears. Low N‐fed plants continued to take up N from the post‐anthesis N fertiliser during the later grain‐filling period. The increase of pre‐anthesis N supply rate led to a decrease in the contribution of nitrogen derived from post‐anthesis ¹⁵N‐labelled fertiliser (N_dff) to total N in all aboveground organs, especially in ears where 44% and 22% of total N originated from post‐anthesis N uptake in low N‐fed and optimal N‐fed plants, respectively. The experiment with labelled amino acids showed that there was greater transport of proteinogenic amino acid into the ear (50% of total ¹⁵N) than non‐proteinogenic amino acid (39%). However, this transport of the non‐proteinogenic amino acids into ear suggested that the transport of N compounds from source (leaves) to sink organs (ear) might not be intrinsically regulated by their ability to be incorporated into storage protein of ears.     

Immobilisation, remineralisation and residual effects in subsequent crops of dairy cattle slurry nitrogen compared to mineral fertiliser nitrogen

About 50–60% of dairy cattle slurry nitrogen is ammonium N. Part of the ammonium N in cattle slurry is immobilised due to microbial decomposition of organic matter in the slurry after application to soil. The immobilisation and the remineralisation influence the fertiliser value of slurry N and the amount of organic N that is retained in soil. The immobilisation and the remineralisation of 15 N-labelled dairy cattle slurry NH₄-N were studied through three growing seasons after spring application under temperate conditions. Effects of slurry distribution (mixing, layer incorporation, injection, surface-banding) and extra litter straw in the slurry on the plant utilisation of labelled NH₄-N from slurry were studied and compared to the utilisation of ¹⁵N-labelled mineral fertiliser. The initial immobilisation of slurry N was influenced by the slurry distribution in soil. More N was immobilised when the slurry was mixed with soil. Surface-banding of slurry resulted in significant volatilisation losses and less residual ¹⁵N in soil. Much more N was immobilised after slurry incorporation than after mineral fertiliser application. After 2.5 years the recovery of labelled N in soil (0–25 cm) was 46% for slurry mixed with soil, 42% for injected slurry, 22% for surface-banded slurry and 24% for mineral fertiliser N. The total N uptake in a ryegrass cover crop was 5–10 kg N/ha higher in the autumn after spring-application of cattle slurry (100–120 kg NH₄-N/ha) compared to the mineral fertiliser N reference, but the immobilised slurry N (labelled N) only contributed little to the extra N uptake in the autumn. Even in the second autumn after slurry application there was an extra N uptake in the cover crop (0–10 kg N/ha). The residual effect of the cattle slurry on spring barley N uptake was insignificant in the year after slurry application (equivalent to 3% of total slurry N). Eighteen months after application, 13% of the residual ¹⁵N in soil was found in microbial biomass whether it derived from slurry or mineral fertiliser, but the remineralisation rate (% crop removal of residual ¹⁵N) was higher for fertiliser- than for slurry-derived N, except after surface-banding. Extra litter straw in the slurry had a negligible influence on the residual N effects in the year after application. It is concluded that a significant part of the organic N retained in soil after cattle slurry application is derived from immobilised ammonium N, but already a few months after application immobilised N is stabilised and only slowly released. The immobilised N has negligible influence on the residual N effect of cattle slurry in the first years after slurry application, and mainly contributes to the long-term accumulation of organic N in soil together with part of the organic slurry N. Under humid temperate conditions the residual N effects of the manure can only be optimally utilised when soil is also covered by plants in the autumn, because a significant part of the residual N is released in the autumn, and there is a higher risk of N leaching losses on soils that receive cattle slurry regularly compared to soils receiving only mineral N fertilisers.     

Nitrous oxide emissions following application of residues and fertiliser under zero and conventional tillage

Emissions of N₂O were measured following combined applications of inorganic N fertiliser and crop residues to a silt loam soil in S.E. England, UK. Effects of cultivation technique and residue application on N₂O emissions were examined over 2 years. N₂O emissions were increased in the presence of residues and were further increased where NH₄NO₃ fertiliser (200 kg N ha^–1) was applied. Large fluxes of N₂O were measured from the zero till treatments after residue and fertiliser application, with 2.5 kg N₂O-N ha^–1 measured over the first 23 days after application of fertiliser in combination with rye (Secale cereale) residues under zero tillage. CO₂ emissions were larger in the zero till than in the conventional till treatments. A significant tillage/residue interaction was found. Highest emissions were measured from the conventionally tilled bean (Vicia faba) (1.0 kg N₂O-N ha^–1 emitted over 65 days) and zero tilled rye (3.5 kg N₂O-N ha^–1 over 65 days) treatments. This was attributed to rapid release of N following incorporation of bean residues in the conventionally tilled treatments, and availability of readily degradable C from the rye in the presence of anaerobic conditions under the mulch in the zero tilled treatments. Measurement of ¹⁵N-N₂O emission following application of ¹⁵N-labelled fertiliser to microplots indicated that surface mulching of residues in zero till treatments resulted in a greater proportion of fertiliser N being lost as N₂O than with incorporation of residues. Combined applications of ¹⁵N fertiliser and bean residues resulted in higher or lower emissions, depending on cultivation technique, when compared with the sum of N₂O from single applications. Such interactions have important implications for mitigation of N₂O from agricultural soils.     

Effect of the combination of bio-organic fertiliser with Bacillus amyloliquefaciens NJN-6 on the control of banana Fusarium wilt disease,crop production and banana rhizosphere culturable microflora

Soil amended with organic amendments has been suggested to be a strategy for managing the Fusarium wilt disease which severely hindered the banana production. The effects of four fertilisation regimes, including chemical fertiliser, manure composts and bio-organic fertiliser (BIO) containing Bacillus amyloliquefaciens NJN-6 for 2-year continuous application on the banana Fusarium wilt disease incidence, crop yield and rhizosphere culturable microbial community were investigated. To explore the soil microflora, plate counting method, in vitro screening method for antagonism, eco-physiological index and culture-dependent denaturing gradient gel electrophoresis method (CD DGGE) were used. The highest banana yield, culturable bacteria, actinobacteria and Bacillus populations, culturable bacteria to fungi (B/F) value, antagonistic Bacillus ratio and lowest Fusarium wilt disease incidence were observed in the BIO treatment. Based on CD DGGE results, the BIO application significantly altered the soil bacteria structure and showed highest richness and diversity. The phylogenetic analysis of the selected bands showed that the most abundant phyla were Proteobacteria and Bacteroidetes and BIO application enriched the genera Comamonas, Chitinophaga, the species Bacillus flexus and uncultured Bacillus. All the results showed that 2-year continuous application of BIO containing B. amyloliquefaciens NJN-6 more effectively controlled Fusarium wilt disease and improved fruit yields under field conditions and modulated banana rhizosphere microflora.     

生物有机肥对盐碱地水稻叶片的影响转录组分析

改良修复盐碱地对保障粮食安全和守护耕地红线具有重要意义,种植水稻配施生物有机肥是修复改良盐碱地的一项有效措施。基于生物有机肥肥料效应,测定水稻灌浆期农艺性状,开展叶片转录组测序,通过基因本体(GO)和京都基因与基因组百科全书(KEGG)数据库分析差异基因的生物学功能和代谢通路,以期揭示生物有机肥对盐碱地水稻的潜在促生机制。试验共设置4个处理,生物有机肥+化肥(T1)、生物有机肥灭活+化肥(T2)、化肥(T3)和空白对照(T4),结果表明,施用生物有机肥能够显著提高水稻叶面积和叶绿素、植株分蘖数和干物质量(P<0.05);T2vsT1、T3vsT1、T4vsT1、T4vsT3差异基因数量分别为6593、4796、6976和1866条,生物有机肥配施化肥引起差异基因表达数量最高,其次为灭活生物有机肥,单施化肥最小;GO分析显示,生物有机肥主要影响水稻叶片肽和酰胺的生物合成与代谢、翻译过程、细胞器及细胞器膜等,化肥对水稻叶片生物学过程影响的差异基因无显著富集(P>0.05);KEGG分析表明,施用生物有机肥差异显著基因主要富集在核糖体和能量代谢相关途径,核糖体相关基因差异表达较多...     

噬菌体鸡尾酒联合生物有机肥防控番茄青枯病的效果研究

【背景】前期研究表明,可专性侵染青枯菌的噬菌体鸡尾酒(组合)可有效减少番茄青枯病的发生。生物有机肥虽然可降低青枯病发病率,但受田间环境影响,防控效果常不稳定。【目的】为了提高生物有机肥的防控效果,靶向抑制番茄青枯病,探究噬菌体鸡尾酒联合含有解淀粉芽孢杆菌的生物有机肥防控番茄青枯病的田间效果,以及该防控方法对番茄根际细菌群落结构的影响。【方法】将经解淀粉芽孢杆菌T-5二次发酵获得的生物有机肥(Bio-Organic Fertilizer,BOF)在春季作为基肥施入番茄大棚,开花期在番茄根部浇灌噬菌体鸡尾酒悬液,统计青枯病的发生情况和番茄根际青枯菌的数量,根据高通量测序结果分析番茄根际细菌群落的结构变化。【结果】与常规施肥相比,生物有机肥配合噬菌体鸡尾酒(BOF+P)可显著降低番茄青枯病的发病率,显著改变根际细菌群落的β多样性,提高拟杆菌门(Bacteroidetes)的相对丰度,并降低芽单胞菌门(Gemmatimonadetes)的相对丰度。【结论】噬菌体鸡尾酒可显著提升生物有机肥防控番茄青枯病的效果,具有良好的应用潜力。     

The use of nitrogen fertiliser in agriculture. Where do we go practically and ecolotically?

Nitrogen fertilisers were produced in 72 countries in 1982, total world capacity being 99 mt of N, having been 50 mt in 1970. Consumption was 31.8 mt in 1970, rising to 60.3 mt in 1980 (Av. annual growth rate 7%). Forecasts suggest N use of 90 mt in 1990 rising to between 111–134 mt by the year 2000.The large amount of N added to only some 11% of the earth's land surface as fertilisers, coupled with concurrent increases in biological N fixation, mainly by grain legumes, is bound to result in increases in the total N content of soils, waters, crop residues and municipal wastes. The need to use N to produce sufficient food and fibre for the 7 billion humans must be set against the need to maintain a good and safe environment. Nitrate levels are increasing in both surface and ground water supplies. The amount of ammonia and oxides of nitrogen in the atmosphere produced by volatilisation and denitrification from soils and animal excreta is also rising. Such increases may have detrimental environmental effects to human health and to the ecology of downstream or polluted non-agricultural ecosystems though the severity and extent of these effects requires verification. As yet, there is little hard evidence of direct damage to human health due to high levels of nitrate in diet or of NH₃ and NO_x in the atmosphere, but effects on natural and forest ecosystems in some areas are proven.With this background, strategies are examined which should help to increase the efficiency with which N is utilised by crops and animals and so decrease losses of nitrogen from farmland.These include the selection of optimum N fertiliser practices based on knowledge of plant requirements, soil N supply, and the use of carefully chosen times, methods and forms of N fertiliser application. Other technological approaches such as use of slow release fertilisers, chemicals that inhibit certain biological transfers of N in soils and amendments added to N fertilisers, to soils or to animal excreta to alter their chemical properties could be developed. Greater use of legumes and enhanced levels of N₂-fixation may also help to lessen the need for N fertiliser.To achieve further improvement in the ways of using N in agriculture, more precise knowledge is needed of the dynamics of nitrogen turnover in soils, of translocation and assimilation in plants, and of interactive flows between soil, plants and animals, and the atmosphere. Only with full understanding of the many biological processes that affect N in ecosystems obtained by multidisciplinary research will it be possible to determine the guidelines for environmentally kind, socially acceptable and economically sound management of nitrogen utilisation in agriculture.     

A technique for studying rhizosphere processes in tree crops: soil phosphorus depletion around camellia (Camellia japonica L.) roots

Rhizosphere studies on tree crops have been hampered by the lack of a satisfactory method of sampling soils at various distances in the rhizosphere. A modified root study container (RSC) technique developed for annual crops, grasses and legumes was used to study the mechanisms by which camellia plants (Camellia japonica L.) utilise soil P in the glasshouse and field. Plants belonging to the Camellia family (e.g. tea) have the ability to utilise P from relatively unavailable native P sources and for this reason camellia plants were selected for this study.In the glasshouse trial, the RSCs were filled with a Recent soil, treated with P fertilisers; North Carolina phosphate rock (NCPR), diammonium phosphate (DAP), mono calcium phosphate (MCP) and single superphosphate (SSP) at 200 g P g^-1 soil. A planar mat of roots was physically separated by a 24 m polyester mesh and the soil on the other side of this mesh was cut into thin slices parallel to the rhizoplane and analysed for pH, and different forms of P (organic, P_o and inorganic, P_i) to understand P depletion at different distances from camellia roots. In the field trial this technique was modified and used to study the rhizosphere processes in mature camellia trees fertilised with only SSP and NCPR.In both field and glasshouse trials, all P fertilisers increased all the bulk soil P fractions except NaOH-P_o over unfertilised soil with the greatest increases being in the H₂SO₄-P_i fraction in the NCPR treatment and NaOH-P_i in the SSP treatment. Resin-P, NaOH-P_i and H₂SO₄-P_i were significantly lower in the rhizosphere soil compared to the bulk soil whereas NaOH-P_o was higher in the rhizosphere soil than in the bulk soil. Plant and microbial P uptake were thought to be the major causes for the low resin-P rather than P fixation by Fe and Al because the NaOH-P_i fraction which is a measure of Fe-P and Al-P, also decreased in the rhizosphere soil. The rhizo-deposition of NaOH-P_o suggests that labile inorganic P was immobilized by rhizosphere microbes which were believed to have multiplied as a result of carbon exudates from the roots. A marked reduction in pH (about 0.2–0.4 in the glasshouse and 0.2 in the field trial) was observed near the rhizoplane compared to that in the bulk soil in all treatments. The pH near the rhizoplane as well as in the bulk soil was highest for NCPR treated soil. The increase in pH in the NCPR treatment over the control was consistent with the number of protons consumed during the dissolution of NCPR. In both trials, the dissolution of NCPR in the rhizosphere was higher than in the bulk soil due to lower pH and plant uptake of solution P in the rhizosphere. The RSC technique proved to be a viable aid to study the rhizosphere processes in tree crops.     

Effect of leaf age and nitrogen fertilisation on sporulation of crown rust (Puccinia coronata var. lolii) on perennial ryegrass (Lolium perenne L.)

Individual leaves of perennial ryegrass cv. Aberystwyth S23 of two leaf ages and at two levels of nitrogen fertilisation were point inoculated with Puccinia coronata f.sp. coronata in a growth chamber. In general, there was no significant difference in the lifespan of inoculated versus control leaves. However, the higher rate of nitrogen extended leaf lifespan more markedly in rusted than in control leaves. Uredospore production varied according to leaf age: colonies on juvenile leaves produced three times as many spores as those on mature leaves.