Morphological and physiological studies on densely branched lateral roots triggered by localized phosphate in Sesbania cannabina

Densely branched lateral roots (DBLRs) in Sesbania cannabina are formed in response to patchily distributed phosphorus (P) in volcanic soils. Little attention has been paid to morphological and physiological responses of DBLRs. Here, we investigated the relation between plant growth and DBLR development, enzymatic activities involved in P acquisition, and the influence of arbuscular mycorrhizal fungi (AMF), which contribute to P uptake, to clarify the function of DBLRs. We investigated DBLR development induced by localized application of P fertilizer and we compared the activities of phosphoenolpyruvate carboxylase (PEPCase) and acid phosphatase (APase) between DBLRs and non‐DBLRs. Additionally, plants were grown with or without AMF to investigate the effect of AMF colonization on the numbers of DBLRs and plant P uptake, and we compared AMF colonization between DBLRs and non‐DBLR roots. Secondary to quaternary lateral DBLRs were produced after the primary lateral roots passed near P fertilizer. P_i content per DBLR increased as DBLRs developed, promoting higher shoot growth. Under P deficiency, PEPCase and APase activities increased in non‐DBLR, but were significantly lower in DBLRs in the same plants. AMF inoculation changed the root system architecture by significantly decreasing the number of DBLRs, and AMF colonization was lower in DBLRs than in non‐DBLRs. Our results indicate that DBLR formation is a P‐coacquisition strategy of S. cannabina grown in P‐deficient andosolic soil. Roots that form DBLR are clearly different from non‐DBLR roots in morphological and biochemical response and AMF symbiosis.     

Humus-Rich Compost Increases Lettuce Growth, Nutrient Uptake, Mycorrhizal Colonisation, and Soil Fertility

Sandy soils, typical of Australia's west, either have little or no habitat protection for microbes including arbuscular mycorrhizal (AM) fungi, which are essential for nutrient cycling. To minimize this problem, the application of organic matter, such as humus-rich composts, is necessary during vegetable crop production. This study aimed at determining the effects of humus-rich composts on either indigenous or inoculated AM fungal colonisation in roots, lettuce (Lactuca sativa L. var. Quechua) growth, and soil fertility improvement. Four different humus-rich composts with varying humus contents were applied at the same standard rate to lettuce grown under glasshouse conditions for 10 weeks after sowing and compared with two low-humus composts and non-amended soil (control). Humus-rich composts significantly increased lettuce shoot growth, root growth, and AM fungal colonisation in roots. Humus contents in the composts were also correlated with lettuce shoot and root growth. Soil dissolved organic carbon, microbial biomass carbon, and fertility were increased with the application of humus-rich composts. These humus-rich composts, especially the compost of higher humic acid with and without AM inoculation, might have a significant role in sustainable vegetable production, for example lettuce growth. Overall, the results indicate that supplementation with humus-rich compost is highly beneficial to enhance soil fertility and potentially maintain the sustainability of vegetable production.     

AMF和间作对作物产量和坡耕地土壤径流氮磷流失的影响

坡耕地氮、磷流失是导致河湖污染的主要因子。该文在坡耕地开展田间小区试验,定量研究了丛枝菌根真菌(AMF)与玉米大豆间作系统对径流氮、磷流失的协同削减贡献,可为滇池流域农业面源污染控制提供科学理论依据。结果表明,与单作玉米-抑菌处理相比,间作玉米-未抑菌处理显著提高了玉米的生物量;与单作-抑菌处理相比,玉米大豆间作-未抑菌处理均显著增加了植株茎叶、籽粒磷吸收量及茎叶、根系氮吸收量。与单作玉米-抑菌处理相比,间作玉米-未抑菌处理的土壤全磷、全氮的削减量分别为0.25、0.11 g/kg,径流总磷、总氮浓度的削减量分别为0.13、12.94 mg/L;与单作大豆-抑菌处理相比,间作大豆-未抑菌处理的土壤全磷、全氮的削减量分别为0.07、0.11g/kg,径流总磷、总氮浓度的削减量分别为0.27、24.80mg/L。与单作大豆-抑菌处理相比,玉米大豆间作-未抑菌处理的总磷、总氮流失量分别减少了0.51、19.93 kg/hm~2。经相关分析可知,径流颗粒态磷浓度与植株各部分磷吸收量均呈负相关,且与土壤全磷、速效磷含量也呈负相关性;径流各形态氮浓度与植株各部分氮吸收量、菌丝密度和球囊霉素均呈负相关。可见,丛枝菌根真菌协同玉米大豆间作模式能够通过促进植株对氮、磷养分的吸收而减少土壤氮、磷的残留,进而阻控了氮磷随径流迁移的损失。     

Genotypic variation for phosphorus uptake dinitrogen fixation in cowpea on low‐phosphorus soils of southern Cameroon

In cowpea, efficient N₂‐fixing genotypes are being selected to promote sustainable cropping systems in southern Cameroon (SC). However, N₂ fixation and growth of these genotypes are largely hampered by low levels of soil plant‐available P. To evaluate the genotypic variation in N₂ fixation and P uptake among cowpea (Vigna unguiculata L.) genotypes, field experiments were conducted over two years on two acid soils low in available P. The experiments were laid out in a split‐block design with four replications on typic (TK) and rhodic (RK) Kandiudult soils with seven cowpea genotypes. Phosphorus (P) fertilizers were applied on the main plots with 0 kg P, 30 kg P ha^–1 as triple superphosphate (TSP) and 90 kg P ha^–1 as Togo phosphate rock (PR). Nodule dry matter (DM), shoot DM, grain yield, and P uptake of cowpea significantly varied with site, P application, and genotype (p < 0.05). The N₂ fixation of the cowpea genotypes ranged from 29 to 51 kg N ha^–1 on both TK and RK soils and was significantly increased with P application. Significant genotypic variations in N₂ fixation were observed with superior ability of the genotypes IT89KD‐391 and IT90K‐59 to fix N₂. The harvest index (HI) did not significantly differ between soils and P application levels (p > 0.05). Four genotypes were selected to investigate root mechanisms responsible for efficient P acquisition in pot experiments. The results suggest that a better root infection by arbuscular mycorrhizal fungi (AMF) in genotype IT90K‐59 and root morphological and physiological characteristics in IT89KD‐391 were the most important factors for increasing P uptake.     

Effects of nitrogen feeding for extraradical mycelium of Rhizophagus irregularis maize symbiosis incorporated with phosphorus availability

In terrestrial ecosystems, plants are frequently in symbiosis with arbuscular mycorrhizal fungi (AMF) with mineral nutrients and photosynthesis carbon exchanges in between. This research sought to identify the effects of phosphorus (P) levels on the nitrogen (N) uptake via extraradical mycelium (ERM) and the mycorrhizal growth response (MGR) of maize plants within the AMF symbiosis. Pots were separated into root compartments and hyphae compartments (HCs) with two layers of a 30‐μm mesh membrane and an air gap in between, where only hyphae could pass through, to avoid both N diffusion and root growth effects. Maize plants were inoculated with Rhizophagus irregularis with different N fertilization in HCs under two different P fertilization levels. Our results indicated that a strong increase in MGR with low‐P fertilization. The same tendency was not observed with high‐P fertilization, although both had a large increase in P concentration as a potential source of growth in shoot tissue of mycorrhizal plants. Substantial effects (10.5% more N) were observed in the case of high‐P availability for the host plants from ERM fed with N, whereas under low‐P conditions ERM may prioritize P uptake rather than N uptake. The AM fungi increase the uptake of N and P, which are most limiting in the soil with fewer forces from soil resources. In addition, there was still more P accumulated than N due to the high N for ERM with high‐P supply. Low N in HCs corresponded with a lower colonization rate in roots but with high hyphae density in HCs; this result suggest that N and P availability might change the ratio of extraradical to intraradical hyphae length.     

不同外源碳对AM真菌吸收氮源合成精氨酸的影响

本文意在探究外源碳对丛枝菌根（arbuscular mycorrhiza, AM）真菌吸收氮源合成精氨酸(Arg)的影响。采用三室隔离盆栽培养系统,以高粱（Sorghum bicolor L. Moench）为宿主植物,接种AM真菌Glomus intraradices,在菌丝室施加4 mmol/L的NH4NO3,同时在根室施加不同形式的碳源,测定分析不同外源碳条件下根外菌丝体（ERM）、菌根和植物茎叶中的Arg含量和总氮含量。结果表明ERM和菌根中的Arg含量远远高于茎叶中;虽然不同形式外源碳提高了AM真菌的ERM干重和菌根侵染率,但是葡萄糖降低了ERM、菌根和茎叶中的Arg含量,蔗糖和甘油对Arg含量没有显著的影响,只有外源Arg和谷氨酰胺（Gln）使ERM中的Arg含量显著增加;不同外源碳对菌根和茎叶的总氮含量没有显著影响。由上述结果分析可知在根室施加外源碳对AM真菌的氮代谢和宿主植物氮素营养水平没有显著影响,Arg合成所需的碳可能大多来自宿主植物供给的碳水化合物;但是施加外源碳能够促进AM真菌的生长繁殖。     

The effect of plant mycotrophy and soil disturbance on soil microbial activity

In cropping systems, the choices adopted for the tillage system used and plants cultivated can strongly influence the soil microbial population and its functional profile. Arbuscular mycorrhizal fungi are an important component of soil microbiome and their mutualistic symbiosis with the majority of higher plants grant the latter a wide range of benefits. The extraradical mycelium developed by these fungi expands the volume of soil influenced and harbours a diversity of microbes establishing a distinct environment of complementary interactions. We assessed how growing plants with different levels of mycotrophy modifies the biological activity profile in the soil under Mn toxicity and whether this is modified by soil disturbance. Following mycotrophic plants, soil contained a more active microbiome than after the non-mycotrophic plants, as expressed by higher values of soil basal respiration or dehydrogenase activity. Additionally, the count of phosphorus solubilizes and activity of phosphatase were greater after mycotrophic plants. Even among mycotrophic plants, different profiles of biological activity can be distinguished after growing a legume or grass. ERM disruption by soil disturbance decreased most of the parameters studied and for phosphatase activity and P solubilizers in a more significant way. These results indicate that even under Mn toxicity, the microbiome associated with AMF symbiosis following mycotrophic plants growth presented a higher biological activity and had a differential biological response towards the stress imposed by soil disturbance, when compared with the microbiome associated with non-mycotrophic roots.     

Effects of early mycorrhization and colonized root length on low‐soil‐phosphorus resistance of West African pearl millet

Phosphorus (P) deficiency at early seedling stages is a critical determinant for survival and final yield of pearl millet in multi‐stress Sahelian environments. Longer roots and colonization with arbuscular mycorrhizal fungi (AMF) enhance P uptake and crop performance of millet. Assessing the genotypic variation of early mycorrhization and its effect on plant growth is necessary to better understand mechanisms of resistance to low soil P and to use them in breeding strategies for low P. Therefore, in this study, eight pearl millet varieties contrasting in low‐P resistance were grown in pots under low P (no additional P supply) and high P (+ 0.4 g P pot^?1) conditions, and harvested 2, 4, 6, and 8 weeks after sowing (WAS). Root length was calculated 2 WAS by scanning of dissected roots and evaluation with WinRhizo software. AM infection (%) and P uptake (shoot P concentration multiplied per shoot dry matter) were measured at each harvest. Across harvests under low P (3.3 mg Bray P kg^?1), resistant genotypes had greater total root length infected with AMF (837 m), higher percentage of AMF colonization (11.6%), and increased P uptake (69.4 mg P plant^?1) than sensitive genotypes (177 m, 7.1% colonization and 46.4 mg P plant^?1, respectively). Two WAS, resistant genotypes were infected almost twice as much as sensitive ones (4.1% and 2.1%) and the individual resistant genotypes differed in the percentage of AMF infection. AMF colonization was positively related to final dry matter production in pots, which corresponded to field performance. Early mycorrhization enhanced P uptake in pearl millet grown under P‐deficient conditions, with the genotypic variation for this parameter allowing selection for better performance under field conditions.     

Reintroduction of a native Glomus to a tropical Ultisol promoted grain yield in maize after fallow and restored the density of arbuscular mycorrhizal fungal spores

Maize (Zea mays L.) is an important crop in central Thailand where fallow is widely practiced and farmers are interested in crop rotation and beneficial soil biota. A pot experiment using a Typic Paleustult (topsoil + subsoil) from the National Corn and Sorghum Research Centre, Nakhonratchasima Province, Thailand was undertaken over three successive crops to evaluate effects of agronomic practices on populations of arbuscular mycorrhizal (AM) fungi and to determine whether reintroduction of a local Glomus was beneficial to maintain maize yield. The three crops and their treatments were: (1) preceding crop: maize grown in all pots; (2) subexperiment 1: agronomic practices [maize, fallow ± soil disturbance, fallow with solarization, non–AM host (cabbage)]; and (3) subexperiment 2: maize ± Glomus sp. 3 at three rates of P fertilization (0, 33, 92 kg P ha^–1). The AM‐fungal community was established under the preceding crop. In subexperiment 1, the three fallow treatments decreased (30%–40%) the total AM spore number in the topsoil whereas there was no change under maize or cabbage. Glomus, the dominant genus, showed sensitivity to fallow. In subexperiment 2, inoculation with Glomus sp. 3 enhanced total AM spore number and root colonization when applied following the three fallow treatments. Furthermore, inoculation promoted grain yield; at nil P following fallow ± soil disturbance, at 33 kg P ha^–1 following fallow without soil disturbance, and following solarization. Two treatments, maize following maize and maize following cabbage, did not respond to inoculation with Glomus sp. 3. Overall, the results suggest that reintroduction of Glomus sp. 3, a local AM fungus in this soil, may overcome negative effects of fallow and promote effectiveness of P fertilizer. Further work is needed to evaluate the benefits of other indigenous AM species that persist under modern fertilization practices.     

Control of Fusarium Wilt of Cucumber Seedlings by Inoculation with an Arbuscular Mycorrhical Fungus

A glasshouse pot experiment was conducted to investigate the impact of inoculation of cucumber at the germination stage with Glomus etunicatum BEG168 on plant yield and incidence of Fusarium oxysporum f.sp. cucumerinum inoculated 28 days after the start of the experiment. Inoculation with the AM fungus decreased both disease incidence and disease index. Mycorrhizal inoculation also increased P concentrations in the cucumber seedlings. The mycorrhizal seedlings had higher concentrations of proline and polyphenol oxidase activity but lower malondialdehyde than non-mycorrhizal seedlings, indicating that AM inoculation may have protected membrane permeability and reduced the extent of the damage caused by F. oxysporum. The results indicate that the mycorrhizal fungus may influence plant secondary metabolites and increase resistance to wilt disease in cucumber seedlings and may therefore have some potential as a biological control agent.     

菌根技术对磷石膏农用的强化效应

磷石膏资源农业利用的可行性已成为磷复肥生产实现可持续发展的关键,而菌根技术的引入可能是磷石膏在低硫缺磷土壤上农用的有效新途径。该文以小葱（Allium schoenoprasum L.）为供试植物进行模拟试验,研究添加不同量（0、20、40 g/kg）磷石膏（phosphogypsum,PG）和接种不同丛枝菌根真菌（arbuscular mycorrhizal fungi,AMF）（Glomus mosseae、Glomus aggregatum、Diversispora spurcum）对其生长及磷、硫、砷吸收的影响。结果表明：小葱植株生物量、磷、硫、砷含量及磷砷吸收比均随磷石膏添加水平的提高而有增加趋势。与未接种相比较,在添加了磷石膏的基础上接种上述AMF均能不同程度改善小葱生长并促进其磷素养分的吸收,而添加40 g/kg 磷石膏（PG40）处理接种Glomus mosseae（GM）和Diversispora spurcum（DS）的宿主植株砷含量显著较低,其中以PG40-GM组合处理的小葱生长量、磷、硫吸收量及磷砷吸收比最大,在缺磷低硫土壤上促生效果最好。PG20添加水平时接种上述任意AMF后的小葱砷含量明显降低（且在食品砷限量标准范围内）;而PG40添加水平时只有接种DS的小葱砷含量基本在限量标准之内,且抗砷效果较好。     

喀斯特不同植被恢复阶段土壤AMF组成及多样性研究

选择贵州花江、织金、花溪3个典型喀斯特地段的不同恢复阶段(乔木、灌木和草本)土壤丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)为研究对象,基于AMF孢子的形态鉴定,计算AMF孢子密度、分离频度、物种丰度、重要值、物种均匀度指数及Shannon-Wiener多样性指数,研究喀斯特不同恢复阶段土壤AMF物种组成及多样性。结果表明:3个采样地段共分离AMF菌种4目8科10属68种,其中球囊霉属(Glomus)数量最大达35种,其次是无梗囊霉属(Acaulospora)为17种,巨孢囊霉属(Gigspora)、类球囊霉属(Paraglomus)及原囊霉属(Archaeospora)各1种;不同采样地段各植被恢复阶段的优势种不同,所有样地中层状球囊霉Glomus lamellosum具有最大的相对丰度、分离频度和重要值;AMF种分类水平上,花江样地不同恢复阶段AMF丰度表现为乔木灌木草本,织金样地为灌木草本乔木,花溪样地为灌木乔木草本;不同植被恢复阶段土壤AMF均匀度指数和香农多样性指数在花江和织金多表现为乔木灌木草本,花溪样地Shannon-Wineer指数则是灌木显著高于乔木和灌木阶段。研究表明,喀斯特土壤中因异质生境条件的差异AMF菌种组成和物种多样性具有较大的差异。     

外源磷与AMF对间作玉米种植红壤无机磷形态的影响

通过三室隔网分室盆栽模拟试验,研究了分室不同磷(P)源[无机磷(磷酸二氢钾)和有机磷(大豆卵磷脂),P添加量均为50 mg·kg-1]添加和根室接种不同丛枝菌根真菌(AMF)[Glomus mosseae(GM)、Glomus etunicatum(GE)]对间作玉米种植红壤无机磷形态的影响。结果表明:无论接种与否,间作处理使根室土壤有效磷含量显著降低,说明间作能够促进玉米植株对土壤有效磷的吸收,且有效磷的耗竭从根际土壤开始。除OP50-单作玉米处理的Org-P外,接种AMF均一定程度增加了各形态无机磷含量。此外,根室土壤有效磷的主要组分为Ca2-P、Al-P和Org-P,其中Org-P与土壤有效磷有着极显著的负相关关系。     

接种丛枝菌根真菌对小麦根内氮转运蛋白基因表达的影响

通过盆栽试验,研究了在低氮(不施氮)和高氮(施氮0.2 g·kg~(-1))水平下接种不同种类丛枝菌根(AM)真菌[Funneliformis mosseae(BGC-NM03D)、Claroideoglomus etunicatum(BGC-NM01B)和Rhizophagus intraradices(BJ09)]对小麦生长、氮吸收及根内4个硝态氮转运蛋白(NRT)基因、1个辅助蛋白(NAR)基因和2个铵态氮转运蛋白(AMT)基因表达的影响。结果表明,3种AM真菌均能够侵染小麦根系,以R.intraradices菌根的侵染率最高;接种R.intraradices或C.etunicatum能够显著提高小麦的生物量或地上部氮吸收量;无论是高氮还是低氮处理,接种AM真菌后均显著下调了小麦根内NRT、NAR和AMT基因的表达水平,且不同AM真菌调控小麦根内氮转运蛋白基因表达的能力具有明显差异。     

Arbuscular mycorrhizal fungi in degraded typical steppe of inner Mongolia

Arbuscular mycorrhizal (AM) fungi may have some potential use in the restoration of degraded grassland through beneficial effects on plant growth and soil quality. A field investigation was conducted in three grassland sites of typical steppe in Inner Mongolia. The three plant communities, one of which was undegraded, one moderately degraded and the third severely degraded, were studied by collecting soil samples and samples of four plant species that occurred in all three sites. The percentage of root length colonized by AM fungi was estimated and the species composition and diversity of AM fungus spores recovered from the soil were determined using spore morphological characteristics. Although differences between the sites may have been due partly to other factors, it is likely that the degree of degradation was an important factor. No decline was found in the AM colonization of the roots of the indicator plant species in the moderately or severely degraded plant communities, and two plant species showed higher colonization status in the two degraded areas. Glomus geosporum and Scutellospora calospora were the dominant AM fungi in the undegraded steppe, while G. geosporum and Glomus aggregatum dominated the two degraded sites which also had low spore densities, species richness and diversity indices. However, different AM species showed different distributions among the three plant communities and the results indicate that both biotic and abiotic factors were important in determining the AMF communities, with biotic factors possibly the more important. Copyright © 2008 John Wiley & Sons, Ltd.     

西北地区赤霞珠葡萄根际土壤中AM真菌的多样性

对西北地区5个酿酒葡萄赤霞珠（Vitis vinifera L. cv. Cabernet Sauvignon）葡萄园根际土壤060 cm土层的AM真菌空间分布进行了研究。结果表明,葡萄根系可形成丛枝菌根,且侵染率较高,最高达79%; 在西北地区的5个样地中共分离出AM真菌4属22种,其中球囊霉属（Glomus）15种,无梗囊霉属（Acaulospora）4种,盾巨孢囊霉属（Scutellospora）2种,巨孢囊霉属（Gigaspora）1种。5个样地孢子密度大小顺序为: 陕西泾阳（JY）＞山西永济（YJ）＞陕西杨凌（YL）＞宁夏银川（YC）＞甘肃莫高（MG）。各样地葡萄根际土壤中AM真菌种的丰富度不同,陕西泾阳地区最高; 分布于葡萄根际的AM真菌按种类多少排序的属依次是: 球囊霉属无梗囊霉属盾巨孢囊霉属巨孢囊霉属,球囊霉属占据的比例保持着绝对优势; 根内球囊霉、摩西球囊霉、地表球囊霉在不同样地中均为优势菌株,副冠球囊霉,集球囊霉,细凹无梗囊霉是多数样地中的稀有种类。研究表明,葡萄与AM真菌具有良好的共生关系,二者协同进化产生了具有生态环境特异性的菌根真菌多样性; 葡萄根际存在较为丰富的丛枝菌根真菌资源,可供进一步开发利用。     

Cultivation of flax in spoil‐bank clay: Mycorrhizal inoculation vs. high organic amendments

A greenhouse experiment was focused on the application of arbuscular mycorrhizal fungi (AMF) in effective crop production during reclamation of coal‐mine spoil banks. The aim of the study was to find out whether mycorrhizal inoculation improves growth of flax (Linum usitatissimum L.) and whether it can compensate for high doses of expensive organic amendment. Flax was planted in original spoil‐bank gray Miocene clay amended with organic matter used for spoil‐bank reclamation (mixture of composted urban waste and lignocellulose papermill waste). This amendment was applied in four descending doses equivalent to the application of 500, 200, 100, and 0 t ha^–1. The plants received either a mixed inoculum of three AMF species (Glomus mosseae, G. claroideum, and G. intraradices) or were left uninoculated. Growth of flax was significantly increased by mycorrhizal inoculation in pure clay (by 60%) as well as in clay with all amendment doses (by 119% on average). Also, the addition of organic matter increased plant growth but, interestingly, the biomass production was comparable regardless the dose of amendment. Our results suggest that similar yields are attainable with only one fifth of the usual fertilization dose, which can significantly decrease costs related to the reclamation of spoil banks. If mycorrhizal inoculation is applied together with the optimized fertilization, growth of flax planted in spoil‐bank clay can be further improved.     

丛枝菌根真菌群落对白三叶草植株生物量磷吸收和土壤磷酸单酯酶活性的影响

丛枝菌根真菌（AMF）在土壤与植物的磷素循环中发挥着关键的作用。采用盆栽实验研究了丛枝菌根真菌群落对白三叶草植株生物量、磷吸收和土壤磷酸单酯酶活性的影响。结果表明,接种不同AMF群落均能显著地促进白三叶草植株的生长及其对磷素的吸收,提高根际土壤磷酸单酯酶的活性。Mnp处理中,白三叶草生物量最大,白三叶草总生物量、茎叶生物量和根系生物量分别比对照处理（-M）提高64.48%、61.48%和84.91%。不同菌根处理中,Mck处理显著地提高白三叶草磷吸收和土壤磷酸单酯酶活性,白三叶草磷吸收总量和茎叶磷吸收量分别比对照（-M）提高107.18%和91.91%,土壤碱性磷酸单酯酶和酸性磷酸单酯酶活性相对对照（-M）分别提高54.33%和138.43%。碱性磷酸单酯酶活性与AMF群落中的Acaullospora属孢子数呈显著的正相关关系,而酸性磷酸单酯酶活性则主要受Paraglomus属孢子数的影响。说明接种AMF群落可显著地影响土壤的磷酸单酯酶活性,从而影响白三叶草的生长及其对磷素的吸收。     

Mycorrhizal,nutritional and virgin olive oil parameters affected by groundcovers

Management of olive groves faces the challenge of reconciling yield, soil degradation and virgin olive oil (VOO) quality. We evaluated the effect of replacing tillage management by vegetal groundcovers (GC) on the relationships between mycorrhizal symbiosis, olive nutritional status, and VOO quality under field rainfed conditions. The experiment was set up in 2014 in an existing Cornicabra olive orchard with a Haplic Gypsisol soil under a Mediterranean semiarid climate. Four treatments were replicated four times and consisted of: (1) annual cover of bitter vetch, (2) permanent Brachypodium distachyon, (3) spontaneous vegetation cover (mainly Brassicaceae species), and (4) tilled soil. The use of bitter vetch GC increased the olive root colonization by 50% compared with the tillage treatment. The effect of tillage on VOO differed from that of GC use. Tillage treatment decreased maturity index and its VOO had lower polyphenol content and less luminosity than that from the GC treatments. Olive root colonization, together with changes in nutrients such as Cu, B and other elements resulting from GC use, seems to play an important role in explaining the variability of VOO quality parameters. Although tillage may lead to higher yield by controlling competition for water and nutrients, the introduction of GC in olive groves led to higher polyphenol contents, enhancing VOO quality and, at the same time, protecting soil from erosion.     

Growth Behavior,Nutrient Harvest Index,and Soil Fertility in Okra-Pea Cropping System as Influenced by AM Fungi,Applied Phosphorus,and Irrigation Regimes in Himalayan Acidic Alfisol

The impact of arbuscular mycorrhizal fungi (AMF), inorganic phosphorus (P), and irrigation regimes was studied in an okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system in an acidic Alfisol. Experimentation was carried out at Palampur, India, in a randomized bock design (RBD), replicated three times with fourteen treatments comprising AM fungi (Glomus mosseae), inorganic phosphorus (50, 75, and 100% soil-test-based recommended P dose), irrigation regimes (at 40 and 80% available water capacity), generalized recommended NPK and irrigations (GRD), and farmers’ practice. Effects of AM fungi on plant height, leaf area index (LAI), and dry-matter accumulation (DMA) were nominal at early crop growth stage, i.e., 50 DAS (days after sowing). However, at 100 DAS, AMF imbedded treatments led to higher plant height (4%), LAI (3%), and DMA (6%) in okra, whereas in pea the magnitude of increase in these parameters following AMF inoculation was 6, 5, and 8%, respectively, over non-AMF counterparts. AMF + 75% soil-test-based P dose at either of these irrigation regimes gave statistically similar yields in both okra and pea as that obtained under 100% soil-test-based P dose at either of two irrigation regimes, thus indicating an economy of about 25% in soil-test-based P dose. Regarding nutrient harvest index in okra and pea, statistically similar values were registered with most nutrients under both AMF inoculated and non-AMF counterparts. In the case of okra, P harvest index was registered less by 3% with AMF inoculation; however, its magnitude increased by 3% in pea following AMF inoculation compared to non-AMF counterparts at similar levels of P and irrigation. At completion of two cycles of okra-pea system, AMF imbedded treatments did not alter available soil nutrient status significantly in comparison to non-AMF counterparts. Overall, current study suggests that practice of AMF inoculation has great potential in enhancing growth parameters for better productivity, fertilizer-P economy, and nutrient harvest efficiency in okra-pea production system in Himalayan acidic Alfisol.