The role of N form supply for PGPM‐host plant interactions in maize

The form of nitrogen (N) supply has a significant impact on rhizosphere chemistry and root growth responses of higher plants. The respective effects are also employed as management options to improve nutrient acquisition and to minimize nutrient losses in cropping systems. However, surprisingly little is known concerning the interactions with rhizosphere biota. In this study, we investigated the effects of selected bacterial and fungal inoculants with proven plant growth‐promoting and phosphate (P)‐solubilizing potential (plant growth‐promoting microorganisms, PGPM) in maize with nitrate or stabilized ammonium supply, on soils with limited P availability and sparingly soluble rock phosphate (Rock‐P) applied as P fertilizer. The combination of the bacterial inoculants Pseudomonas sp. DSMZ 13134 (Proradix) and Bacillus amyloliquefaciens FZB42 with ammonium sulphate fertilization, stabilized with the nitrification inhibitor 3,4‐dimethylpyrazole‐phosphate (DMPP), resulted in a superior shoot biomass production (79–111%) and shoot P accumulation (109–235%) as compared with nitrate supply. This effect could be partially attributed to (1) ammonium‐induced rhizosphere acidification via increased root extrusion of protons, (2) promotion of root hair elongation, and (3) increased shoot concentrations of hormonal growth regulators (indole‐3‐acetic acid, zeatin, gibberellic acid). The effects, induced by the microbial inoculants were mainly related to increased root length development (43–44%), associated with a 60% increase in auxin production potential. No inoculant effects were detected on root hair elongation or on chemical modifications of the rhizosphere involved in P solubilisation, such as rhizosphere acidification, release of carboxylates or secretory phosphohydrolases. However, the ammonium‐induced stimulation of root hair elongation increased preferential sites for root colonization by the selected inoculants, which may explain the increase in rhizosphere abundance of PGPMs, exemplarily recorded for the fungal inoculant Trichoderma harzianum OMG16 (210%). The presented data suggest a network of positive interactions between stabilized ammonium fertilization and plant growth‐promoting functions of various bacterial and fungal PGPM inoculants. This offers perspectives to increase the efficiency and the reproducibility of PGPM‐assisted fertilization strategies.     

Coffee‐husk biochar application increased AMF root colonization,P accumulation,N2 fixation,and yield of soybean grown in a tropical Nitisol,southwest Ethiopia

Low soil fertility and soil acidity are among the major bottlenecks that limit agricultural productivity in the humid tropics. Soil management systems that enhance soil fertility and biological cycling of nutrients are crucial to sustain soil productivity. This study was, therefore, conducted to determine the effects of coffee‐husk biochar (0, 2.7, 5.4, and 16.2 g biochar kg^?1 soil), rhizobium inoculation (with and without), and P fertilizer application (0 and 9 mg P kg^?1 soil) on arbuscular mycorrhyzal fungi (AMF) root colonization, yield, P accumulation, and N₂ fixation of soybean [Glycine max (L.) Merrill cv. Clark 63‐K] grown in a tropical Nitisol in Ethiopia. ANOVA showed that integrated application of biochar and P fertilizer significantly improved soil chemical properties, P accumulation, and seed yield. Compared to the seed yield of the control (without inoculation, P, and biochar), inoculation, together with 9 and 16.2 g biochar kg^?1 soil gave more than two‐fold increment of seed yield and the highest total P accumulation (4.5 g plant^?1). However, the highest AMF root colonization (80%) was obtained at 16.2 g biochar kg^?1 soil without P and declined with application of 9 mg P kg^?1 soil. The highest total N content (4.2 g plant^?1) and N₂ fixed (4.6 g plant^?1) were obtained with inoculation, 9 mg P kg^?1, and 16.2 g biochar kg^?1 soil. However, the highest %N derived from the atmosphere (%Ndfa) (> 98%) did not significantly change between 5.4 and 16.2 g kg^?1 soil biochar treatments at each level of inoculation and P addition. The improved soil chemical properties, seed yield, P accumulation and N₂ fixation through combined use of biochar and P fertilizer suggest the importance of integrated use of biochar with P fertilizer to ensure that soybean crops are adequately supplied with P for nodulation and N₂‐fixation in tropical acid soils for sustainable soybean production in the long term.     

Trace and major element contents,microbial communities,and enzymatic activities of urban soils of Marrakech city along an anthropization gradient

Journal of Soils and Sediments - Due to their close proximity with the population, urban soils are extensively affected by human activities that release considerable technogenic inputs resulting in...     

Setting conservation priorities for crop wild relatives in the Fertile Crescent

The aim of this paper is to contribute directly to the systematic, long-term conservation of crop wild relatives (CWR) in the Fertile Crescent by setting conservation priorities to secure and improve CWR conservation in situ and ex situ as a means of underpinning global food security. We established the first priority list of CWR within the Fertile Crescent following several criteria comprising production value (m × p), projected production value (m × p), production area (ha), projected production area (ha), native status, energy supply (kcal/capita/day), protein supply (g/capita/day), fat supply (g/capita/day), occurrence status, gene pool, taxon group, and threat status. An inventory of 220 priority CWR was established for the Fertile Crescent region. We followed twelve prioritisation approaches and assessed 21,080 species. About 4% of the total species (835 species) were identified as CWR that have socio-economic value for the region. These 835 CWR species were prioritised to create the CWR priority list which consisted of 220 species (1% of the total species assessed). The majority of the CWR priority list (185 species) were related to cereal, vegetable, and industrial crops and 35 of them are related to fruits and trees. The CWR priority list includes crop wild relatives of the genera Aegilops (20 species), Lactuca (11 species), Avena (11 species), Carthamus (11 species), Allium (9 species), Thinopyrum (10 species), and Triticum (3 species). We present the first inventory of 220 priority CWR for the Fertile Crescent. The inventory helps to improve in situ and ex situ conservation and the genetic diversity of CWR. Both the inventory and the methodology applied in prioritisation can be used in setting national, regional, and global conservation strategies. The recommendations will help the Fertile Crescent meet its targets in conserving CWR diversity as well as making sure that CWR genetic resources are preserved to prevent and tackle global food insecurity.     

Nitrogen Fertilizer and Its Residual Effect on Cotton Yield and Biomass Accumulation

[Objective] The optimum nitrogen rate of 300 kg·hm^－2 is well documented for cotton in the Yangtze River Valley, China. It can be reduced to 225 kg·hm^－2 without reducing yield in late sowing under high planting density. The aim of this study was to determine the possibility of further reducing the nitrogen application rate at the first flower stage, its residual effects and influence on cotton yield formation rule. [Method] A pot experiment was conducted with five nitrogen levels (120, 150, 180, 210 and 240 kg·hm^－2) in 2014, but only 180 kg·hm^－2(for studying nitrogen residual effect) in 2015, to study the cotton growth process, yield and its components and biomass accumulation. [Result] Nitrogen levels significantly affected the yield and biomass accumulation, but not the growth process and nitrogen residual effect. Maximum seed cotton yield (30.5 g·plant^－1), boll weight (3.8 g) and biomass accumulation, especially in the reproductive and vegetative organs, was recorded in the 180 kg·hm^－2 nitrogen treatment. In the rapid accumulation period, the proportion of biomass accumulation in the reproductive organs was the highest. [Conclusion] In a soil with medium fertility level, the application of 180 kg·hm^－2 nitrogen was optimal, because the strength of biomass accumulation in reproductive organs increased during the rapid accumulation period.     

Aging effects of organic and inorganic fertilizers on phosphorus fractionation in a calcareous sandy loam soil

In most arid and semiarid soils, naturally occurring phosphorus(P) is a major yield-limiting plant nutrient. In this study, to investigate the effects of organic(OP) and inorganic P(IP) sources on P fractionation, a calcareous sandy loam alkaline soil was fertilized with OP and IP fertilizers at low(80 mg P kg~(-1) soil) and high(160 mg P kg~(-1) soil) application rates. Three combinations of OP and IP(i.e., 75% OP + 25% IP, 50% OP + 50% IP, and 25% OP + 75% IP) were applied at low and high application rates,respectively, followed by soil aging for 21 d. Soil samples were collected after 1, 2, 3, 7, and 21 d and subjected to sequential extraction to analyze soluble and exchangeable, Fe-and Al-bound, Ca-bound, and residual P fractions. The soluble and exchangeable P fraction significantly increased up to 24.3%, whereas the Ca-bound fraction decreased up to 40.7% in the soils receiving 75% OP + 25% IP and 50% OP + 50% IP, respectively, compared with the control(receiving no P fertilizer). However, the transformation of P fractions was influenced by aging time. Addition of P sources caused instant changes in different P fractions, which then tended to decline with aging time. Change in soil p H was the limiting factor in controlling P availability. At high application rate, the OP source significantly increased soil P availability compared with the IP source with soil aging. Depending on P fractionation, a proper combination of OP and IP fertilizers, as long-term slow and instant P-releasing sources for plant uptake, respectively, may be a sustainable strategy to meet crop P requirements in the arid and semiarid soils.     

Population structure and frequency differences of CYP51 mutations in <Emphasis Type="Italic">Zymoseptoria tritici</Emphasis> populations in the Nordic and Baltic regions

Septoria tritici blotch caused by the fungus Zymoseptoria tritici (formerly Mycosphaerella graminicola) is one of the most yield-reducing diseases worldwide. Effective disease management involves the use of resistant cultivars and application of fungicides. In this study, the population structure and genetic diversity of 183 Z. tritici isolates from Denmark, Sweden, Finland and the Baltic countries were analysed by molecular markers. In population structure analysis, isolates from Denmark and Sweden were grouped together, whereas isolates from the Baltics and Finland were grouped together. Analysis of genetic diversity and ?-values confirmed the division of Nordic and Baltic regions. Danish isolates sampled from different regions and different varieties were not genetically different. However, significant genetic differences were detected between isolates sampled from different years in Denmark and for isolates sampled from specific cultivars in different years. Additionally, the frequency of several known point mutations in the gene cyp51, conferring decreased sensitivity to DMI fungicides, was investigated. Several of the examined mutations were detected at a lower frequency in Baltic isolates compared to Danish and Swedish isolates. Analysis of the Danish population revealed a significant increase in specific mutations over the years. Lastly, some mutations were significantly more frequent in isolates derived from certain varieties. By using different resistance sources in breeding programmes and application of a wide range of fungicides, a sustainable and efficient disease management can be obtained.     

Potential of rooftop rainwater harvesting to meet outdoor water demand in arid regions

The feasibility of rooftop rainwater harvesting(RRWH) as an alternative source of water to meet the outdoor water demand in nine states of the U.S. was evaluated using a system dynamics model developed in Systems Thinking, Experimental Learning Laboratory with Animation. The state of Arizona was selected to evaluate the effects of the selected model parameters on the efficacy of RRWH since among the nine states the arid region of Arizona showed the least potential of meeting the outdoor water demand with rain harvested water. The analyses were conducted on a monthly basis across a 10-year projected period from 2015 to 2024. The results showed that RRWH as a potential source of water was highly sensitive to certain model parameters such as the outdoor water demand, the use of desert landscaping, and the percentage of existing houses with RRWH. A significant difference(as high as 37.5%) in rainwater potential was observed between the projected wet and dry climate conditions in Arizona. The analysis of the dynamics of the storage tanks suggested that a 1.0–2.0 m~3 rainwater barrel, on an average, can store approximately 80% of the monthly rainwater generated from the rooftops in Arizona, even across the high seasonal variation. This interactive model can be used as a quick estimator of the amount of water that could be generated, stored, and utilized through RRWH systems in the U.S. under different climate conditions. The findings of such comprehensive analyses may help regional policymakers, especially in arid regions, to develop a sustainable water management infrastructure.     

Cross-bred Cattle Protected against Hyalomma anatolicum anatolicum by Larval Antigens Purified by Immunoaffinity Chromatography

Antigens from larvae of Hyalomma anatolicum anatolicum were extracted and purified by immunoaffinity chromatography using immunoglobulin ligands from cross-bred animals immunized with soluble larval antigen. Affinity-purified antigen (Aff-TLE) and a total larval extract (TLE) were used to immunize cross-bred (Bos indicus×Bos taurus) cattle. The group immunized with Aff-TLE rejected 71.6% of larvae and 77.3% of nymphs. However, the rejection percentages were lower in the TLE-immunized group. No significant changes in the feeding period, moulting percentages or moulting period of engorged larvae and nymphs were recorded. There was, however, a significant decrease in the number of resultant nymphs p<0.01) and adults (p<0.01) in the ticks fed on the Aff-TLE-immunized group. The Aff-TLE antigen was 93.3% purified. SDS-PAGE analysis identified a 39 kDa protein, reported for the first time, as the antigen responsible for the induction of resistance in the host.     

Evaluation of Trichoderma harzianum for controlling root rot caused by Phytophthora capsici in pepper plants

The ability of Trichoderma harzianum to control the rotting of pepper ( Capsicum annuum ) plant roots caused by Phytophthora capsici was studied. Interactions between the fungi were assessed in vitro on three culture media (V8c, Czapek and 2% water agar) and in vivo in plants grown in a substrate inoculated with P. capsici and T. harzianum . Studies on mutual antagonism in vitro showed that P. capsici was inhibited by T. harzianum ; however, the intensity of inhibition differed according to the medium used, being greatest on Czapek. Analysis of the fungal populations in the plant growth substrate showed that T. harzianum consistently reduced that of P. capsici over time. This reduction in the pathogen population was associated with a reduction in root rot of between 24 and 76%, although plant growth (dry weight) was still reduced by 21.2–24.7%, compared with the uninoculated control. In the absence of T. harzianum with the same pathogen inoculum levels, the reduction in dry weight was 59.8–68.6%, suggesting that T. harzianum reduced the damage.