Impacts of biochar and processed poultry manure,applied to a calcareous soil,on the growth of bean and maize

Direct use of poultry manure on agricultural lands may cause environmental concerns, so there is a need to establish the suitability of the application of biochar derived from poultry manure for calcareous soil chemical properties and plant growth. The purpose of this study was to evaluate the effects of processed poultry manure (0, 5, 10 and 20 g/kg) and its biochar (0, 2.5, 5, 10 and 20 g/kg) on soil chemical properties of a calcareous soil and growth of bean (Phaseolus vulgaris) and maize (Zea mays) plants. In the incubation experiment, both processed poultry manure (PPM) and biochar decreased pH and the concentration of plant‐available Fe of soil but increased plant‐available P, Zn, Cu and Mn concentrations. PPM and biochar increased the concentrations of exchangeable cations (K, Ca and Mg) in soil. PPM and biochar applications increased the growth of maize and bean plants. PPM and biochar resulted in increased concentrations of N, P, K, Ca, Fe, Zn, Cu and Mn in bean plants. In maize plants, PPM and biochar applications increased the N, P, K, Zn, Cu and Mn but decreased the Ca and Mg concentrations. Results of this study reveal that poultry manure biochar can be used effectively for agricultural purposes.     

土壤石油污染对植物苗期生长和土壤呼吸的影响

选取陕北延安地区原油和黄绵土，设计了完全混合和表面施油两种处理方式，通过盆栽试验，研究了不同浓度石油污染处理对植物生长和土壤呼吸的影响。结果表明，玉米和紫花苜蓿在完全混合的油污土壤上萌发良好，但生长受阻，而表面喷洒处理的石油污染严重影响紫花苜蓿的萌发和生长；土壤呼吸作用对石油污染十分敏感，完全混合处理土壤呼吸与石油污染比例成正相关关系，污染越重，土壤呼吸强度越大，所有污染处理1周后土壤呼吸强度出现抑制而迅速回落，并在波动中逐渐趋于稳定，但仍然显著高于对照组，表明黄土中存在对石油耐受的土著微生物群落。     

Remediation of oil polluted soils: 1. effect of organic and inorganic nutrient supplements on the performance of maize (Zea may L)

Percentage germination, plant height, leaf area, relative dry matter yield, plant nutrient concentration, soil chemical characteristics and source/sink relationship were assessed for maize (Zea mays L TZ-SR-Y) planted in a soil polluted with 3% (v/w) crude oil or 0% (untreated soil), after remediation of soil with different organic (Poultry manure, peptone water, sawdust and yeast extract) and inorganic (NPK, KNO₃, NH₄H₂PO₄ and (NH₄)₂SO₄) nutrient supplements applied 7 days after oil treatment. Germination of maize in oil polluted soil was not significantly affected by nutrient supplementation (P=0.05). Maize performance in terms of other studied parameters was highest in the oil polluted soil supplemented with poultry manure, and least in oil polluted soil supplemented with sawdust. Oil treatment correlated significantly with organic C, N, Na, Mg and ferrous in the soil (P=0.05) and with nutrient composition in maize plant tissues (P=0.05). For nutrient uptake, significant correlation was only established between soil N and plant N. Population of petroleum hydrocarbon tolerant microbes increased initially but decreased with time. There is every indication that nutrient supplementation of oil polluted soil especially with organic nutrient sources is beneficial for maize growth, because the C/N ratio is narrowed while the rate of biodegradation of oil and soil recovery is also enhanced. Poultry manure is recommended, however sawdust is not recommended since it tends to impose adverse effect by widening the C/N ratio in soil.     

土壤石油污染对植物种子萌发和幼苗生长的影响

为了研究土壤石油污染对植物种子萌发和幼苗生长的影响,选取中原油田地区的原油和潮土,通过盆栽试验研究了不同石油污染水平条件下的植物种子发芽率、株高和鲜重.结果表明,土壤中石油含量不同,对黑麦草(Lolium perenne L.)、高羊茅(Festuca arundinacea)、紫花苜蓿(Medicago sativa L.)、白三叶草(Trifolium repens L.)、红三叶草(Trifolium pratense)的各项生长指标影响不同,当土壤中的石油含量较高时,对植物的生长有抑制作用.向日葵(Helianthus annus L.)、棉花(Gossypium hirsutum L.)、高丹草(Sorghum sudangrass)、狗牙根(Cynodon dactylon)在试验设计石油污染水平范围内发芽率、株高及鲜重受影响较小,能生长在石油污染的土壤上,其中狗牙根,生存能力强,是试验中的最具有修复土壤石油污染研究潜力的植物.     

Phosphorus uptake and rhizosphere properties of intercropped and monocropped maize, faba bean, and white lupin in acidic soil

Little information is available on phosphorus (P) uptake and rhizosphere processes in maize (Zea mays L.), faba bean (Vicia faba L.), and white lupin (Lupinus albus L.) when intercropped or grown alone in acidic soil. We studied P uptake and soil pH, carboxylate concentration, and microbial community structure in the rhizosphere of maize, faba bean, and white lupin in an acidic soil with 0–250 mg P (kg⁻¹ soil) as KH₂PO₄ (KP) or FePO₄ (FeP) with species grown alone or intercropped. All plant species increased the pH compared to unplanted control, particularly faba bean. High KP supply (>100 mg P kg⁻¹) significantly increased carboxylate concentration in the rhizosphere of maize. The carboxylate composition of the rhizosphere soil of maize and white lupin was significantly affected by P form (KP or FeP), whereas, this was not the case for faba bean. In maize, the carboxylate composition of the rhizosphere soil differed significantly between intercropping and monocropping. Yield and P uptake were similar in monocropping and intercropping. Monocropped faba bean had a greater concentration of phospholipid fatty acids in the rhizosphere than that in intercropping. Intercropping changed the microbial community structure in faba bean but not in the other corps. The results show that P supply and P form, as well as intercropping can affect carboxylate concentration and microbial community composition in the rhizosphere, but that the effect is plant species-specific. In contrast to previous studies in alkaline soils, intercropping of maize with legumes did not result in increased maize growth suggesting that the legumes did not increase P availability to maize in this acidic soil.     

露天煤矿排土场覆土厚度对土壤水分入渗及植物水分利用的影响

表土回覆是露天煤矿排土场生态修复的关键步骤，覆土厚度直接影响植物生长和复垦成本，为研究露天煤矿排土场不同覆土厚度对土壤水分入渗及植物水分利用的影响，采用室内土柱模拟试验，设置10,20,30,40,50 cm共5个覆土厚度，分别进行垂直入渗试验和室内盆栽试验(玉米),并结合氢氧同位素稳定示踪技术，研究不同覆土厚度土壤入渗和玉米水分利用特征，筛选研究区排土场最佳覆土厚度。结果表明：覆土厚度为10～30 cm(27.05～33.02 mm/min)的初始入渗速率显著高于40～50 cm(21.59～24.89 mm/min)的初始入渗速率(p<0.05),稳定入渗速率随覆土厚度的增加而增大，当覆土厚度高于40 cm后，随着覆土厚度的增加稳定入渗速率维持在3 mm/min左右。矸石层入渗过程受覆土层的影响较大，覆土厚度高于40 cm后，矸石层入渗速率基本稳定在土层连接面的入渗速率上。不同覆土厚度下玉米木质部水氢氧同位素值与土壤水氢氧同位素随土层变化曲线交点主要集中在覆土层，因此，玉米生长水分主要来源于覆土层。覆土厚度越大，2条线交点增多、交点分布范围增大，玉米对土壤水分的利用范围越大，...     

Effects of compost type and storage conditions on climbing bean on Technosols of Tantalum mining sites in Western Rwanda

Little is known about the effects of compost application to reclaim artisanal mining sites for agriculture in Central Africa. A field experiment was therefore conducted to examine the effects of locally available organic household waste composted under traditional (pit under leaf shade) versus improved management (pit under double plastic sheeting) and mixed with either Tithonia diversifolia biomass or Minjingu Phosphate Rock (13–15% P) on climbing bean sown on degraded Technosols (former Tantalum mining sites) and un‐mined control soils (Cambisols). Both soil types were derived from pegmatite. After 6 months of composting, nutrient concentrations in traditional compost were 0.27–0.32% N, 0.06–0.08% P, and 0.20–0.22% K. Comparative values in amended compost were 1.02–1.65% N, 0.10–0.31% P, and 0.41–1.13% K. In farmyard+solid waste, composted under traditional system, dry matter was 65.4%, pH 6.7, and C : N ratio 13.0, as opposed to 81.5% DM, a pH of 8.6, and a C : N ratio of 8.6 in farmyard+solid waste+Minjingu phosphate under improved compost, and 68.3% dry matter, a pH of 8.4, and a C : N ratio of 7.4 for Tithonia +farmyard+solid waste under improved conditions. Compared to bean (Phaseolus vulgaris L.) grain yields of 0.28 (mined soil) and 0.11 (unmined soil) without amendments, the application (on a dry matter basis) of 5 t compost ha⁻¹ led to yields of 3.54 t DM ha⁻¹ for improved compost Tithonia +farmyard+solid waste on mined soil versus 2.26 t DM ha⁻¹ (P < 5%) for the same treatment at the un‐mined sites. The yield obtained for farmyard+solid waste+Minjingu phosphate composted under improved conditions averaged 3.06 t DM ha⁻¹ at mined sites compared with 2.85 t DM ha⁻¹ at un‐mined sites (P > 5%). All amendments were more effective in enhancing bean yields on Technosols with significant positive effects with improved compost than on Cambisols.     

Long-Term Spreading of Olive Mill Wastewater on Olive Orchard: Effects on Olive Production,Oil Quality,and Soil Properties

In Italy, the law no 574 of 1996 permits and regulates the disposal of olive mill wastewater (OMW), the liquid by-product obtained in oil mill when olive fruits are processed to extract virgin olive oil, by its controlled spreading on cultivated soil. With the aim to verify the long-term effects of the practice on olive production, oil quality, and physical–chemical and microbiological characteristics of soil, different amounts of OMW were spread in February, for 9 years consecutively, on soil cultivated with olive trees. The results obtained confirmed that the controlled spreading of OMW is not harmful for the plant production. On the contrary, OMW spread on olive grove is useful for the fertility of soil and the growth of microflora for the important supply of nitrogen (N), phosphorus (P), potassium (K), and, above all, of organic matter. The evaluated biological properties indicated that OMW spreading stimulates the growth of soil fungal and fungus-like communities and aerobic N₂ fix micro-organisms. With regard to the oil quality, the data indicate that no significant differences were ascertained on the analyzed parameters.     

Double mulching improves soil properties and productivity of maize-based cropping system in eastern Indian Himalayas

A field experiment was conducted for two consecutive years at North Eastern Indian Himalayan region to assess the effect of soil moisture conservation measures on soil and water productivity of different rainfed maize (Zea mays L.) - based cropping sequences. Results revealed that double mulching with in-situ maize stover mulch (MSM) + fresh biomass of white hoary pea (WHP-Tephrosia candida) and MSM + fresh biomass of ragweed (RW- Ambrosia artemisiifolia) improved soil moisture content (SMC) and leaf relative water content of crops during dry season. The soil organic carbon (SOC) content and stocks under MSM + WHP and MSM + RW mulches were significantly higher than that under no mulch at 0–15 cm depth. The soil microbial biomass carbon and dehydrogenase activity were maximum under MSM + WHP/RW. The highest system productivity was obtained from maize-French bean (Pole type-PT) sequence under MSM + RW followed by MSM + WHP. The water productivity was the highest under MSM + WHP. While SOC content was the highest under maize-French bean (PT), the maximum plant available nitrogen and phosphorus were obtained under maize-black gram sequence.Thus, double mulching technology involving MSM and RW (available in plenty) is a viable option for improving soil, crop and water productivity under rainfed hill ecosystems of eastern Indian Himalayas.     

Development of microbial community during primary succession in areas degraded by mining activities

Together with plants, soil microbial communities play an essential role in the development of stable ecosystems on degraded lands, such as postmining spoil heaps. Our study addressed concurrent development of the vegetation and soil fungal and bacterial communities in the course of primary succession in a brown coal mine spoil deposit area in the Czech Republic across a chronosequence spanning 54 years. During succession, the plant communities changed from sparse plants over grassland and shrubland into a forest, becoming substantially more diverse with time. Microbial biomass increased until the 21st year of ecosystem development and later decreased. Although there was a close association between fungi and vegetation, with fungi mirroring the differences in plant community assemblages, the development of the bacterial community was different. The early succession community in the barren nonvegetated soil largely differed from that in the older sites, especially in its high abundance of autotrophic and free‐living N₂‐fixing bacteria. Later in succession, bacterial community changes were minor and reflected the chemical parameters of the soil, including pH, which also showed a minor change with time. Our results show that complex forest ecosystems developed over 54 years on the originally barren soil of the temperate zone and indicate an important role of bacteria in the initial stage of soil development. Although the arrival of vegetation affects substantially fungal as well as bacterial communities, it is mainly fungi that respond to the ongoing development of vegetation.     

Short-term effects of olive mill waste water (OMW) on chemical and biochemical properties of a semiarid Mediterranean soil

Olive mill waste water (OMW), a by-product of the olive mill industry, is produced in large amounts in Mediterranean countries. Olive mill waste water contains a high organic load, substantial amounts of plant nutrients but also several compounds with recognized toxicity towards living organisms. Moreover, OMW may represent a low cost source of water. Thus, the use of OMW for soil fertigation is a valuable option for its disposal, provided that its impact on soil chemical and biochemical properties is established. Investigations were performed on the short-term influence of OMW on several chemical and biochemical properties of a soil from a continental semi-arid Mediterranean region (Morocco). The soil was amended with 0, 18 and 36 ml 100 g⁻¹ soil of OMW (corresponding to a field rate of 0, 40 and 80 m³ ha⁻¹, respectively) and changes in various functionally related properties such as microbial biomass, basal respiration, extractable C and N, and soil hydrolases and oxido-reductases activities were measured over time. The variations of the main physical and chemical properties as well as the residual phytotoxicity of OMW amended and non-amended soils as assessed by tomato seed germination tests were also monitored. Temporary and permanent changes in several chemical and biochemical soil properties occurred following OMW application, thus being these properties varied in sensitivity to the applied disturbance. A sudden increase of total organic C, extractable N and C, available P and extractable Mn and Fe contents were measured. Simultaneously, a rapid increase of soil respiration, dehydrogenase and urease activities and microbial biomass (at 14 day incubation) of OMW amended soils occurred. In contrast, the activities of phosphatase, β-glucosidase, nitrate reductase and diphenol oxidase decreased markedly. The soil became highly phytotoxic after OMW addition (large decline of soil germination capability), mainly at 80 m³ ha⁻¹ OMW. After 42 days' incubation, however, a complete recovery of the soil germination capability and a residual phytotoxicity of about 30% were observed with 40 and 80 m³ ha⁻¹ OMW, respectively. These findings indicate that the impact of OMW on soil properties was the result of opposite effects, depending on the relative amounts of beneficial and toxic organic and inorganic compounds present. The toxic compounds contained in OMW most likely counteracted the beneficial effect of organic substrates provided, which promoted the growth and activity of indigenous microorganisms.     

两株PGPR对豇豆苗期生长及土著细菌群落的影响

以扬豇40为材料,研究了植物根际促生菌Pseudomonas chlororaphis RA6和Bacillus pumilus WP8对豇豆种子出苗及幼苗生长的作用,评价浸种及拌土处理的差异,揭示一段时间内,两株植物根际促生菌（PGPR）在土壤中的行为特征及其对土著细菌群落结构的影响。结果表明：PGPR对豇豆的促生作用因接种方式、接种量的不同而不同。WP8、RA6浸种处理的出苗率分别比对照提高14.29%和9.52%（P〈0.05）;15 d时的株高分别比对照提高14.39%和10.40%（P〈0.05）;茎叶干物重分别比对照增加19.69%和17.71%（P〈0.05）。WP8、RA6低剂量拌土处理（104cfu·g-1soil,以下简作＂低拌处理＂）各指标与对照相比,均无显著差异（P〉0.05）。WP8、RA6中剂量拌土处理（106cfu·g-1soil,以下简作＂中拌处理＂）出苗率和株高均比对照提高,但未达显著差异（P〉0.05）;茎叶干物重分别比对照增加12.71%和18.59%（P〈0.05）。WP8、RA6高剂量拌土处理（108cfu·g-1soil,以下简作＂高拌处理＂）出苗率分别比对照提高9.52%和14.29%（P〈0.05）;15 d时的株高分别比对照提高6.37%和7.64%（P〈0.05）;茎叶干物重分别比对照增加27.37%和20.43%（P〈0.05）。DGGE指纹图谱分析结果显示：各处理在15 d和45 d时,除WP8浸种处理外,其余土壤微生物群落多样性和对照均已发生明显变化,随时间推延,RA6菌株在土壤中优势地位更趋明显,表现在45 d时仍可明显检测到;WP8在土壤中存活时间不长,但拌土处理改变了土著细菌的群落结构。推测WP8的促生作用很可能与土著微生物群落的变化有关。     

Soil property differences among high‐ and average‐yielding soya bean areas in Arkansas,USA

Soya bean [Glycine max (L.) Merr] yields >6719 kg/ha (100 bu/ac) have only recently and infrequently been achieved. Quantifying soil property differences between high‐ and average‐yielding areas can help to further identify non‐plant‐related properties contributing to soya bean yield potential. The objective of this study was to evaluate the effects of region and soil depth on soil property differences between high‐ and average‐yielding areas. In each of the seven regions of the ‘Grow for the Green’ yield contest in Arkansas, prior to or just after harvest in 2014 and 2015, soil samples were collected from the top 20 cm of one contest high‐yield (HY ) area that was in close proximity to an average‐yield (AY ) area. Across all regions and both years, soya bean yields differed (P  <  0.05) between yield areas, averaging 4701 and 5498 kg/ha in AY and HY areas, respectively. Averaged across soil depth and years, numerous soil properties differed (P  <  0.05) between HY and AY areas within at least one of seven regions. Total soil C content was at least 20.2% greater in the HY than in the AY area in three of seven regions. Extractable soil P content was, on average, 19.4 kg/ha greater in HY than in AY areas in three of the seven regions. Results from this study have the potential to help producers better understand soil properties that contribute to or hinder achieving ultra‐high (>6719 kg/ha) soya bean yields.     

Influence of landuse on soil erosion risk in the Cuyaguateje watershed (Cuba)

Landuse changes may dramatically enhance erosion risk. Besides deforestation, also arable landuse may have an important influence on soil loss. We investigated the erosion risk in a 151 km² subwatershed of the Cuyaguateje watershed (Cuba) using the RUSLE model. It was found that the valleys used for agriculture have the highest erosion risk, with actual erosion surpassing soil loss tolerance. Over the period 1985–2000, about 14 km² of forest has been converted into arable land. As a result, the area with a very high erosion risk increased with 12%. On arable land it was found that the crop management factor C of a “tobacco/maize” rotation was 0.478, compared to 0.245 for a rotation of various crops (sweet potato, beans, maize, cassava and fallow). When maize in the “tobacco/maize” rotation was intercropped with a leguminous crop (hyacinth bean) the C factor decreased to a value of 0.369. Also contouring may halve soil loss on moderate slopes (< 10%) when high ridges are applied, which is in Cuba generally the case for maize, cassava and sweet potato.     

Maize grain production,plant nutrient concentration and soil chemical properties in response to different residue levels from two previous crops

ABSTRACT

The incorporation of previous crop residues in agricultural management benefits soil fertility, crop production, and environment. However, there is no enough information about maximum residue application level without negative effect over next crop yield. To evaluate maize (Zea mays L.) yield under short-time conservation management with incorporation and/or importation of different residue levels, a biannual rotation experiment was conducted in ash volcanic soil in south-central Chile. The experiment consisted of two previous crops, canola (Brassica napus L.) and bean (Phaseolus vulgaris L.), and four levels of residue incorporation (0%, 50%, 100%, and 200% of generated residue; from 0 to 21.4?Mg?ha^?1 for canola and from 0 to 19.0?Mg?ha^?1 for bean). Previous crop species and residue level affected some nutrients concentrations in grain and plant and some soil chemical properties, without effect in maize yield, which averaged 16.6?Mg?ha^?1. Bean residue increased Ca and reduced S in maize plant, increasing soil P, Ca, Mg and K (P?<?0.05). Maize grain Ca content was positively and proportionally affected by canola residue level and negatively and proportionally affected by bean residue level. All canola residue levels increased soil pH and Mg, but the highest level reduced soil S; soil P concentration increased proportionally with bean residue level. The highest bean residue level increased soil S. Different crop and levels of residue did not affect maize yield but did some plant nutrient concentration, and also affected some soil chemical properties.     

Plant carbon partitioning below ground in the presence of different neighboring species

Knowledge about carbon allocation below ground is necessary to understand soil ecosystem functioning and the global C cycle. It is common knowledge that different plant species coexist in natural and agricultural systems. By using a modified ¹³C pulse-chase approach, which enabled us to label individual plants in either mono- or mixed cultures, we investigated the effect of coexistence of different neighboring species on plant carbon partitioning. Maize and faba bean were used as our test plants and isotope pulse labeling was performed twice at 26 and 54 d after emergence. The results showed that a higher proportion of photoassimilates was distributed below ground in maize than in faba bean, resulting in a greater ratio of root to shoot biomass for maize plants during the experiment. The carbon distribution to roots was slightly higher in mixed cultures at 26 d than the counterpart monocultures. The distribution of the plant-assimilated ¹³C to soil dissolved organic carbon was also greater in mixed cultures at 26 d relative to the monocultures. The most significant effect of the mixed culturing was a dramatic increase of ¹³C incorporation into the soil microbial biomass. These results indicated that the plant carbon allocation below ground was altered in the presence of a different neighboring species. The increase of plant diversity probably enhances the soil microbial activity and hence the turnover of the plant-derived carbon in soil.     

Ecological Performance of the Restored South East New Territories (SENT) Landfill in Hong Kong (2000–2012)

South East New Territories (SENT) landfill (Phase I) was saturated with wastes and capped with a cover system to prevent rainfall infiltration and gas emission and to support plant growth. Subsequently, a revegetation program was conducted in 1997. Line transects were used for monitoring (i) the restored area (AT), (ii) the area adjacent to AT (BT) and (iii) the area outside AT, which served as control (CT). Flora and fauna diversities, plant performance (chlorophyll florescent and stomatal resistance of Acacia confusa) and soil properties were monitored during 2000–2012. There were 28, 24 and 23 plant species, and 61, 39 and 61 animal species found at AT, BT and CT during the past 13 years, respectively. The total number of plants recorded at AT fluctuated considerably, and was more stable at BT, especially CT. The results of similarity analyses showed that the plant community at AT were significantly different (P < 0·01) from those at BT and CT, whereas no difference was noted among fauna communities at different sites. Soil properties, including pH, bulk density, moisture content, total organic content, organic matter, total Fe and total Zn were significantly different (P < 0·05) among sites. The decreasing trend of soil pH in all sites indicated that regional soil acidification may have occurred. Soil moisture content and stomatal resistance of A. confusa were negatively correlated, which showed that AT was more subjected to drought than BT and CT. Plants in restored area were more sensitive to the changes in environmental conditions compared with those of control site. Copyright © 2015 John Wiley & Sons, Ltd.     

Plant monocultures produce more antagonistic soil Streptomyces communities than high-diversity plant communities

Plant–soil feedbacks are important to productivity and plant community dynamics in both natural and managed ecosystems. Among soil bacteria, the Streptomyces possess particularly strong antagonistic activities and inhibit diverse plant pathogens, offering a clear pathway to involvement in plant–soil feedbacks. We hypothesized that feedback effects and the ability of individual host plant species to foster antagonistic Streptomyces populations may be modified by the richness of the surrounding plant community. To test this, we collected soil associated with four different plant species (two C4 grasses: Andropogon gerardii, Schizachyrium scoparium; and two legumes: Lespedeza capitata, Lupinus perennis), grown in communities that spanned a gradient of plant species richness (1, 4, 8, 16, or 32 species). For each of these soils, we characterized the potential of soil Streptomyces to antagonize plant pathogens, using an in vitro plate assay with indicator strains to reveal inhibition. We cultivated each plant species in each conditioned soil to assess feedback effects on subsequent plant growth performance. Surrounding plant richness modified the impacts of particular plant species on Streptomyces antagonistic activity; A. gerardii supported a higher proportion of antagonistic Streptomyces when grown in monoculture than when grown in 32-spp plant communities, and L. capitata supported more strongly antagonistic Streptomyces when grown in 4- or 32-spp plant communities than in 8-spp plant communities. Similarly, the feedback effects of particular plant species sometimes varied with surrounding plant richness; aboveground biomass production varied with plant species richness for A. gerardii in L. perennis-trained soil, for L. capitata in A. gerardii-trained soil, and for L. perennis in L. capitata-trained soil. Streptomyces antagonist density increased with overall Streptomyces density under low but not under high plant richness, suggesting that plant diversity modifies selection for antagonistic phenotypes among soil Streptomyces. This work highlights the complexity of feedback dynamics among plant species, and of plant–microbiome interactions in soil.     

Co-amelioration of red soil acidity and fertility with pig manure rather than liming

Lime (calcium oxide), animal manure and crop straw soil treatments have been shown to ameliorate soil acidity, yet their effectiveness at concurrently enhancing soil fertility status and improving crop yields is less well understood. In this study, an acidic nutrient deficient red soil (Ferralic Cambisol) received these treatments at various dosage rates (% of DW soil) in pot experiments with maize plants. Lime was applied at four dosage rates (0.05%, 0.10%, 0.15% and 0.20%), pig manure at three rates (0.50%, 1.00% and 1.50%), maize straw or milk vetch at two rates (0.50% and 1.00%) and combinations of lime (0.10% or 0.15%) with maize straw (0.50%) and/or pig manure (0.50%). Soils treated with and without chemical fertilizers were also included as controls. Measurements of soil pH, exchangeable acidity, plant available nutrients and maize shoot biomass were recorded. Maize shoot biomass increased by 4.7–7.6 times under pig manure treatments, 1.1–1.6 times under milk vetch, 0.4–1.5 times under lime and 1.1–6.2 times under combination treatments, compared with the control. Soil pH increased by 0.5–0.9 units under lime, by 0.2–0.4 units under pig manure and by 0.7 pH units under the combination treatment relative to the control. Variance partitioning analysis showed that on an individual basis, soil acidity amelioration (pH, exchangeable H⁺ and Al³⁺) or nutrient input (C, N, P, K, Ca, Mg, Zn) explained only 4.3% and 5.6% of improved maize growth, respectively. Whereas, their interaction explained 85.9% of the variation. We also report that the over-application of pig manure could lead to P saturation and negative impacts on aquatic systems in the wider environment. Therefore, we recommend a combination of lime, pig manure and straw provides an optimal solution for addressing soil acidity and limiting P saturation in acid soils.     

Enhancement of arbuscular mycorrhizal fungus (Glomus versiforme) on the growth and Cd uptake by Cd-hyperaccumulator Solanum nigrum

Arbuscular mycorrhizal fungus (AMF) can enhance plant growth and resistance to toxicity produced by heavy metals (HMs), affect the bioavailability of HMs in soil and the uptake of HMs by plants, and thus has been emerged as the most prominent symbiotic fungus for contribution to phytoremediation. A greenhouse pot experiment was conducted to assess the effect of Glomus versiforme BGC GD01C (Gv) on the growth and Cd accumulation of Cd-hyperaccumulator Solanum nigrum in different Cd-added soils (0, 25, 50, 100 mg Cd kg⁻¹ soil). Mycorrhizal colonization rates were generally high (from 71% to 82%) in Gv-inoculated treatments at all Cd levels. Gv colonization enhanced soil acid phosphatase activity, and hence elevated P acquisition and growth of S. nigrum at all Cd levels. Moreover, the presence of Gv significantly increased DTPA-extractable (phytoavailable) Cd concentrations in 25 and 50 mg Cd kg⁻¹ soils, but did not affect phytoavailable Cd in 100 mg Cd kg⁻¹ soil. Similarly, inoculation with Gv significantly increased Cd concentrations of S. nigrum in 25 and 50 mg Cd kg⁻¹ soils, but decreased Cd concentrations of the plants in 100 mg Cd kg⁻¹ soil. Overall, inoculation with Gv greatly improved the total Cd uptakes in all plant tissues at all Cd levels. The present results indicated that S. nigrum associated with Gv effectively improved the Cd uptake by plant and would be a new strategy in microbe-assisted phytoremediation for Cd-contaminated soils.