Phosphorus Supply Research Articles

Localized nutrient supply can facilitate root proliferation and increase nitrogen-use efficiency in compacted soil

Soil compaction constrains root growth and crop yield. Previous studies have shown that localized nutrient supply can significantly improve maize plant growth in field conditions at the early growth stage. However, this promoting effect has not been tested in the compacted soil. We describe 2-year field experimentation on a fluvo-aquic soil in the North China Plain to investigate the effect of localized vs. broadcast ammonium and phosphorus supply on maize under three soil compaction treatments (NC: non-compacted, C: compacted and SC: severely compacted) during 2012 and 2013. Results showed that compared with broadcast ammonium and phosphorus (BNP), localized ammonium and phosphorus supply (LNP) resulted in significantly higher PFPN in the NC (by 31–37%), C (by 43–44%) and SC (by 45%) treatments at harvest. When soil was compacted (C and SC), the enhancement of nitrogen (N) utilization in the LNP treatment was attributed to the increased root growth, including greater specific root length (a greater proportion of fine roots), lower root tissue density and deeper rooting at the seedling stage, especially in the compacted treatment (C). The enhanced root penetration capacity contributed to the increased N and water uptake from the deep soil layers. Our study highlighted the importance of nutrient management for mitigating negative impacts of soil compaction on crops, and will underpin new soil compaction management practices by considering optimal fertilization to strengthen the root-soil interactions.

Comparative study on the chemical composition of different bones/parts of bones in growing pigs differently supplied with inorganic phosphorus and phytase.

From the veterinarian point of view, the precise assessment of the phosphorus (P) supply of pigs is of great interest, especially in cases of clinical disorders like 'leg weakness' or lameness when bone mineralisation may be disturbed. Thus, the question arises which bone is most suitable for diagnostic purposes and is reflecting changes in dietary P supply most clearly. Thirty-six growing pigs (BHZP db.Viktoria x Piétrain, about eleven weeks old, mean bw: 28.3±3.44kg) were allotted to three groups differently supplied with P by receiving a diet either supplemented with inorganic P (iP) and phytase (500FTU/kg; controls/groupC), without iP but phytase added (500FTU/kg; group1) or containing only endogenous phytase (group2). The inclusion of iP resulted in total P contents in diets for groupC of 4.76 and 4.23g/kg as fed from 28 to 57 and >57kg body weight (bw), respectively. In diets for group1 and 2, the corresponding P contents were 3.08/2.72g/kg as fed (group1) and 3.08/2.88g/kg as fed (group2). On days 26, 47 and 82 of the dietary treatment, four pigs of each group were euthanised. Furthermore, four additional pigs were euthanised one day before starting the experiment. Standardised samples of the femur (distal part), tibia/fibula (proximal part) and os metatarsale III (MTIII, in toto) were taken during dissection and submitted to chemical analysis. At all time points, pigs of groupC had significantly higher ash contents in all types of bone samples compared to pigs from group1 and 2. Relative differences between means of groups (C=100%) were less for the ash content in MTIII (reduction by up to -9.1%) compared to the distal femur and the proximal tibia/fibula (reduction by up to -23.2 resp. -22.7%). Variation coefficient (irrespective of group and time point) was lower for ash content in MTIII (4.29%) compared to the distal femur and the proximal tibia/fibula (both: 11.8%). Under the conditions of this study, ash contents of the distal femur and the proximal tibia/fibula reflected the different P supply more pronounced indicating higher sensitivity compared to MTIII.

Phosphorus-Use Efficiency Modified by Complementary Effects of P Supply Intensity With Limited Root Growth Space.

Space availability and the maintenance of adequate phosphorus (P) supply in the root zone are essential for achieving high yield and P-use efficiency in maize production by manipulating the root morphology and arbuscular mycorrhizal (AM) fungi colonization. A major trade-off exists between root growth and AM colonization that is influenced by soil P supply intensity and space availability. However, how soil P manipulates the root morphological characteristics and AM colonization to compensate for the limitation of root-growth space induced by high-planting density is not clear. Therefore, pot experiments were conducted to investigate interactions between the root growth and AM fungi by optimizing soil P supply to compensate for limited root growth space induced by high-planting density. Similar shoot biomass and P uptake values were obtained in P200 (200 mg P kg−1 soil) under D = 40 (i.e., diameter of the pot is 40 cm) and P400 under D = 30, and similar values were obtained for root length, tap root length, root angle, lateral root density, and AM colonization. However, the improvement in P supply in the root zone, shoot biomass, and P uptake in P400 under D = 20 were lower than in P200 under D = 30, and there were no significant differences in the root parameters between P200 and P400 under D = 20; similarly, the root growth and AM colonization exhibited similar trends. These results suggest that optimizing P supply in the root zone to regulate the interaction between root morphological traits and AM colonization can compensate for limited root-growth space. Although P supply in the root zone increased after the root-growth space was compressed, it could not meet the P demand of maize; thus, to achieve the most efficient use of P under intensive high-density maize production, it is necessary to optimally coordinate root growth space and P supply in the root zone.

Effects of Phosphorus Supply on the Leaf Photosynthesis, and Biomass and Phosphorus Accumulation and Partitioning of Canola (Brassica napus L.) in Saline Environment

Salt stress is a major negative factor affecting the sustainable development of agriculture. Phosphorus (P) deficiency often occurs in saline soil, and their interaction inhibits plant growth and seed yield for canola (Brassica napus L.). P supply is considered an effective way to alleviate the damage of salt stress. However, the knowledge of how P supply can promote plant growth in saline environment was limited. A field experiment was conducted to explore the effects of P rate on accumulation, and partitioning, of biomass and P, leaf photosynthesis traits, and yield performance in saline soil in the coastal area of Yancheng City, Jiangsu Province, China, during the 2018–2019 and 2019–2020 growing seasons. P supply increased biomass and P accumulation in all organs, and root had the most increments among different organs. At flowering stage, P supply increased the biomass and P partitioning in root and leaf, but it decreased the partitioning in stem. At maturity stage, P supply facilitated the biomass and P partitioning in seed, but it decreased the partitioning in stem and shell, and it increased the reproductive-vegetative ratio, suggesting that P supply can improve the nutrients transporting from vegetative organs to reproductive organs. Besides, P supply improved the leaf area index and photosynthetic rate at the flowering stage. As a result, the seed yield and oil yield were increased. In conclusion, P supply can improve the canola plant growth and seed yield in a saline environment. P fertilizer at the rate of 120 kg P2O5 ha−1 was recommended in this saline soil.

Critical review on arsenic: Its occurrence, contamination and remediation from water and soil

With the increasing pollution in today’s world, importance is being given to solve a problem and do it in a sustainable, eco-friendly manner. Arsenic is a class-1 carcinogen and also causes many other side effects to humans, plants and animals. The utilization of arsenic as wood preservatives, pesticides, or its historical overuse by some military units for rice killing operations has led to the increase in the toxic effects of arsenic like its carcinogenicity, decreased immune response etc. Although conventional methods like coagulation, lime softening, adsorption, membrane technology are effective, they have their disadvantages like additional waste generation, causing increased pollution and are expensive. The better alternative is phytoremediation. Appropriate plants like Brassica juncea, Hydrilla verticilata, Pteris vittata L., Vallisneria natans, can be chosen based on the method of the remediation like phytoextraction, phytostabilization and phytofiltration or phytovoltalization. This review provides the list of a few plants which can be likely chosen for the purpose of both water and soil remediation. Advancements are occurring in bioremediation studies with the development of transgenic plants like transgenic tobacco, transgenic Arabidopsis thaliana for better phytoremediation. Understanding the mechanism employed by the plant for its uptake/detoxification can aid in the enhancement of the process of remediation with the external supply of phosphorus. Along with this, the proper and safe disposal of plants is crucial for the remediation process. In addition, awareness of this solution to the general public is to be made for its effectiveness.

Phosphorus supply level is more important than wheat variety in safe utilization of cadmium-contaminated calcareous soil

Screening and cultivating crop varieties with low Cd accumulation is an effective way to safely utilize the Cd slightly contaminated soil. The characteristics and mechanism of Cd uptake by 13 wheat varieties in two calcareous soils with similar Cd contamination level but different P supply level were studied. The grain Cd concentration of almost all varieties in low-P soil was significantly higher than that in high-P soil and exceeded the maximum level of 0.2 mg kg−1 recommended by the Codex Alimentarius Commission. The pH value of low-P soil was significantly lower than that of high-P soil by 0.27 units, while leaf [Mn] (proxy for rhizosphere carboxylates) and the activities of soil alkaline phosphatase and phytase were significantly higher than those of high-P soil by 35%, 55%, and 286%, respectively. The exchangeable Cd concentration in low-P soil was 2.93 times higher than that in high-P soil, while the Cd concentration of oxides and organic species was significantly lower than that in high-P soil by 21% and 64%, respectively, collectively increasing soluble Cd concentration in low-P soil by 38%. In low-P calcareous soil, P mobilization induced the change of root-zone microenvironment, resulting in the mobilization of Cd.

Mycorrhizal symbiosis and phosphorus supply determine interactions among plants with contrasting nutrient‐acquisition strategies

Abstract Highly diverse plant communities growing on nutrient‐impoverished soils are test beds for theories on species coexistence. Here, neighbouring mycorrhizal and non‐mycorrhizal plants compete for limited phosphorus. The impact of below‐ground interactions on community dynamics is underexplored. We used an experimental approach to investigate effects of inoculation with arbuscular mycorrhizal (AM) fungi and a phosphorus supply gradient on competitive and facilitative interactions among mixed assemblages of woody plants in microcosms. The plant species, one cluster root‐forming (CR) species and four AM species, are native to jarrah forest that grows on nutrient‐impoverished soils in south‐western Australia. We measured plant growth in microcosms, with and without inoculation with the AM fungus Rhizophagus irregularis, and across a gradient of P supply: 0, 9, 27 and 243 mg P per kg of soil. Our data show evidence of plant–plant facilitation at low P supply and competition at high P supply. Growth of the CR species, Hakea undulata, was highest in microcosms with 0P and without AM inoculation. One AM species, Bossiaea aquifolium, also performed better at lower P levels, possibly benefitting from P mobilised by H. undulata. The other three AM species, one strongly obligates, performed better at higher P levels. Data for Acacia celastrifolia suggested it was facultatively mycotropic, and because there was no correlation between AM colonisation and the relative inoculum effect, we suggest positive effects of AM inoculation at 9P might be due to benefits other than P acquisition, such as pathogen defence. Benefit of AM inoculation diminished for three of four mycorrhizal species at the highest P level as we had predicted. The fourth species, Eucalyptus marginata (jarrah), had higher growth in microcosms that were not inoculated with AM, perhaps because the species benefits more from ectomycorrhizas. Synthesis. Our experimental data suggest spatial heterogeneity of soil P, coupled with a diversity of nutrient‐acquisition strategies, and plasticity among plant–plant and plant–AM fungi interactions, contributes to plant species coexistence in the nutrient‐impoverished jarrah forest. Our research highlights the importance of below‐ground mechanisms for understanding factors determining community structure including a potential role of AM fungi in plant pathogen defence.

X-ray Spectroscopic Quantification of Phosphorus Transformation in Saharan Dust during Trans-Atlantic Dust Transport.

Saharan dust is an important phosphorus (P) supply to remote and oligotrophic parts of the oceans and American lowland tropical rainforests. Phosphorus speciation in aeolian dust ultimately controls the release and bioavailability of P after dust deposition, but the speciation in Saharan dust and its change during the trans-Atlantic transport remains unclear. Using P K-edge X-ray absorption near edge structure (XANES) spectroscopy, we showed that with increasing dust traveling distance from the Sahara Desert to Cape Verde and to Puerto Rico, about 570 and 4000 km, respectively, the proportion of Ca-bound P (Ca-P), including both apatite and non-apatite forms, decreased from 68-73% to 50-71% and to 21-37%. The changes were accompanied by increased iron/aluminum-bound P proportion from 14-25% to 23-46% and to 44-73%, correspondingly. Laboratory simulation experiments suggest that the changes in P speciation can be ascribed to increasing degrees of particle sorting and atmospheric acidification during dust transport. The presence of relatively soluble non-apatite Ca-P in the Cape Verde dust but not in the Puerto Rico dust is consistent with the higher P water solubility of the former than the latter. Our findings provide insights into the controls of atmospheric processes on P speciation, solubility, and stability in Saharan dust.

ЕФЕКТИВНІСТЬ ДОБРИВА ПЛАНТАФОЛ У ПОСІВАХ СОЇ ЗА НЕСТАЧІ ЕЛЕМЕНТІВ ЖИВЛЕННЯ В ЧОРНОЗЕМІ ТИПОВОМУ

The agrochemical composition of chernozems typical of the agrobiological laboratory of Ternopil Volodymyr Hnatiuk National Pedagogical University has been studied and the economic expediency of using complex mineral fertilizer Plantafol 10.54.10 during cultivation of soybeans, to eliminate the shortage of some elements of mineral nutrition and increase crop productivity was analyzed. 
 It was found that chernozems is characterized by a close to neutral exchange (pH 5.6) and hydrolytic (2.16 mg-eq. / 100 g) reaction, an increased amount of absorbed bases (19.0 mg-eq. / 100 g) and increased rate of saturation of bases (89.8 %), which is typical of agricultural lands with high carbonate content. Сhernozem soil has a low amount of easily hydrolyzed Nitrogen (102.0 mg / kg), an average supply of humus (2.63 %) and mobile Phosphorus (71.0 mg / kg) and a very high level of metabolic Potassium (189.0 mg / kg).
 Based on the specified agrochemical composition of the soil, taking into account the peculiarities of mineral nutrition of soybean plants, the importance for the formation of generative organs of Phosphorus and its ability to highly effective symbiotic nitrogen fixation in the study area, it is suggested to eliminate possible shortages of soil nutrients, in the first of Phosphorus, foliar fertilization with Plantafol 10.54.10.
 Complex mineral fertilizer Plantafol 10.54.10 contains Nitrogen – 10 %, Phosphorus – 54 %, Potassium – 10 %, as well as trace elements in chelated form EDTA – Boron 0.02 %, Iron – 0, 07 %, Manganese – 0.03 %, Zinc – 0.01 %, Copper – 0.005 %.
 It was found that double foliar fertilization with Plantafol 10.54.10 fertilizer at a dose of 3 kg / ha increases the yield of soybean grain cultivar Annushka, which is grown on chernozems typical of agrobiolaboratory, by 0.34 t / ha or 15.5 %. Yield growth was mainly due to a 16.8 % higher biological yield of aboveground mass and an increase in the number of beans on plants – by 15.3 %, seed weight – 16.0 %, total number of seeds – 11.4 %, as well as less pronounced increase in the height of attachment of the lower beans, the density and height of plants in the crop and the weight of 1000 seeds. The length of the fruits and their glazing did not change as affected by fertilizer.
 The obtained data allow to offer foliar fertilization with complex fertilizer Plantafol 10.54.10, as one of the elements of the system of soybean fertilization on chernozems with close to neutral reaction, increased amount of absorbed bases, low amount of easily hydrolyzed Nitrogen, average supply of humus and mobile Potassium and a very high level of exchangeable Potassium, which reduces the negative impact of deficiencies in the root nutrition of plants, increases crop productivity and provides additional income of 4078 UAH / ha.

Phosphate Fertilization as a Modulator of Enzymatic Browning in Minimally Processed Cassava.

This study proposes to relate the increase in phosphorus (P) supply in the soil, via phosphate fertilization, to oxidative damage and protection, phenylpropanoid metabolism, and enzymatic browning in minimally processed cassava. The roots were grown with 0, 60, and 120 kg ha-1 P2O5. The roots were harvested, and the yield and P content in the root, stem, and leaves were quantified. The roots were minimally processed and stored for 12 days at 5 °C. The higher supply of P in the soil increased the P content of roots and stems but not the agro-industrial yields. Roots grown at 120 kg ha-1 P2O5 showed higher detection of hydrogen peroxide, which was accompanied by increased phenolic compounds, soluble quinones, and antioxidant capacity and increased activities of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase, and peroxidase. The present study thus demonstrates the role of phosphorus application, induction of the synthesis of phenolic compounds, and quality of fresh-cut cassava.

Effects of Different Stand Types on Soil Chemical Properties in Rainy Zone of West China

In order to explore different forest types effects on soil chemical properties, four stand types, namely pure Cunninghamia lanceolata forest, pure Cryptomeria fortunei forest, pure Liriodendron chinense forest and Cryptomeria fortune × Phoebe zhennan mixed forest, were selected as the research objects, and the difference of soil chemical properties and the organic contents of different forest types were analyzed by variance analysis. The results showed that there were significant differences in soil pH, available potassium, total phosphorus, total potassium and total nitrogen among different forest types, but there were no significant differences in available phosphorus, alkali-hydrolyzable nitrogen, and soil organic matter. The soil pH value of the four forest stands was between 4.02 and 5.33, which was acidic, and increased with the increase of soil depth. The contents of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable and available phosphorus in different forests types all decreased with the increase of the soil depth. The 0~10cm total phosphorus content of soil in four different forest stands was higher than that of 10~20 cm. The soil total potassium content of pure C. lanceolata forest, pure C. fortunei forest and pure L. chinense forest all fluctuated up and down with the increase of the soil depth, while the content of C. fortune × P. zhennan mixed forest increased gradually. The contents of soil alkali-hydrolyzable nitrogen and available phosphorus in soil of four forest stands all decreased with the increase of soil depth. The soil available potassium content of pure C. lanceolata forest and pure C. fortunei forest increased first and then decreased, while that of pure L. chinense forest and C. fortune × P. zhennan mixed forest increased gradually. The average phosphorus supply intensity of the four stands at the soil layer of 0~10cm, 10~20cm, 20~40cm and 40~60cm was 2.64%, 2.71%, 2.57% and 2.61%, respectively. Soil K supply intensity of pure L. chinense forest and C. fortunei × P. zhennan mixed forest increased with the increase of soil layer, while that of pure C. fortunei forest first increased and then decreased.

Evaluating the relevance of species sorting and physiological plasticity of phytoplankton communities grown in a multifactor environment

Abstract The two important mechanisms influencing the response of phytoplankton communities to alterations of abiotic factors in their environment are difficult to distinguish: species sorting resulting from a change in interspecific competitive pressure, and phenotypic plasticity (here explicitly physiological plasticity i.e. species‐specific physiological adjustment). A shift in species composition as well as physiological adjustments in species can lead to changes in fatty acid composition that determine the food quality for zooplankton consumers. We used phytoplankton communities consisting of five species and exposed them to two different light intensities, two light conditions (constant and variable), and two levels of phosphorus supply. Changes in fatty acid and species composition were analyzed. We compared community pairs differing in one factor by calculating the Bray‐Curtis similarity index for the composition of both variables. Comparing the Bray‐Curtis similarity index of the species composition with the index of the fatty acid composition was used to estimate the effects of species sorting and physiological plasticity. Changes in nutrient supply influenced fatty acid responses based on species sorting and physiological plasticity the most. On one hand, the relevance of physiological plasticity was highest at cultivation in different nutrient supplies but the same light environment. Conversely with low nutrients species sorting appeared to dominate the response to changes in light, while at high nutrients physiological plasticity appeared to influence the response. Overall, under low phosphorus supply the communities showed a lower total fatty acid content per carbon and had increased proportions of saturated and monounsaturated fatty acids. Instead, communities in low light produced more of eicosapentaenoic acid. Our results suggest that the relevance of species sorting and physiological plasticity in shaping the community response highly depends on the environmental factors that influence the system. Nutrient supply had the largest effect, while light had more limited conditional effects. However, all of these factors are important in shaping the food quality of the phytoplankton community for higher trophic levels.

Response of Normal and Low-Phytate Genotypes of Pea (Pisum sativum L.) on Phosphorus Foliar Fertilization.

Phosphorus (P) is an important nutrient in plant nutrition. Its absorption by plants from the soil is influenced by many factors. Therefore, a foliar application of this nutrient could be utilized for the optimal nutrition state of plants. The premise of the study is that foliar application of phosphorus will increase the yield of normal-phytate (npa) cultivars (CDC Bronco a Cutlass) and low-phytate (lpa) lines (1-2347-144, 1-150-81) grown in soils with low phosphorus supply and affect seed quality depending on the ability of the pea to produce phytate. A graded application of phosphorus (H₃PO₄) in four doses: without P (P0), 27.3 mg P (P1), 54.5 mg P (P2), and 81.8 mg P/pot (P3) realized at the development stages of the 6th true leaf led to a significant increase of chlorophyll contents, and fluorescence parameters of chlorophyll expressing the CO2 assimilation velocity. The P fertilization increased the yield of seeds significantly, except the highest dose of phosphorus (P3) at which the yield of the npa cultivars was reduced. The line 1-2347-144 was the most sensible to the P application when the dose P3 increased the seed production by 42.1%. Only the lpa line 1-150-81 showed a decreased tendency in the phytate content at the stepped application of the P nutrition. Foliar application of phosphorus significantly increased ash material in seed, but did not tend to affect the protein and mineral content of seeds. Only the zinc content in seeds was significantly reduced by foliar application of P in npa and lpa pea genotypes. It is concluded from the present study that foliar phosphorus application could be an effective way to enhance the pea growth in P-deficient condition with a direct effect on seed yield and quality.

Influence of Interactions between Nitrogen, Phosphorus Supply and Epichloёbromicola on Growth of Wild Barley (Hordeum brevisubulatum).

Epichloë endophytes are biotrophic fungi that establish mutualistic symbiotic relationship with grasses and affect performance of the host under different environments. Wild barley (Hordeum brevisubulatum) is an important forage grass and often infected by Epichloë bromicola, thus showing tolerances to stresses. Since the plant growth correlates with both microbial infection and nutrient stoichiometry, this study was performed to investigate whether the function of Epichloë bromicola endophyte to improve host growth depend upon the nitrogen (N), phosphorus (P) fertilization. Epichloë-infected (E+) and Epichloë-free (E−) wild barley plants were subjected to nine types of mixed N (0.2 mM, 3 mM, 15 mM) and P (0.01 mM, 0.1 mM, 1.5 mM) levels treatments for 90 d to collect plant samples and determine multiple related indexes. We found that E. bromicola and N, P additions positively affected seed germination. Further, E. bromicola significantly enhanced chlorophyll content and root metabolic activity under N-deficiency, and meanwhile, might alter allocation of photosynthate under different conditions. The contents of N, P and stoichiometry of C:N:P of E+ plants were significantly higher than that of E− under nutrient deficiency, but contrary results were observed under adequate nutrients. Therefore, we propose that the growth-promoting ability of E. bromicola is closely correlated with N and P additional levels. Under low N, P additions, positive roles of endophyte are significant as opposed to negative roles under high N, P additions.

Sanitized human urine (Oga) as a fertilizer auto-innovation from women farmers in Niger

Poor soil chemical fertility and climate change restrict pearl millet grain yield in Niger Republic. Apart from the seedball technology, which targets majorly early phosphorus supply to the plants, the recommended practices of mineral fertilization and seed treatments (coating and priming) are barely affordable to the local farmers in particular. In the case of female farmers, who usually have chemically infertile farmlands often located far away from their homestead, low pearl millet grain yield can be exacerbated. In quest for a cheap, affordable, and effective solution, we hypothesized that the application of sanitized human urine (Oga), in combination with organic manure (OM) or solely, increases pearl millet panicle yield in women’s fields and on different local soils. In on-farm large-N trials (N = 681) with women farmers in two regions of Niger (Maradi, Tillabery), pearl millet panicle yields were compared between the control (farmer practice), and a combination of Oga and OM in the first and second year, and Oga alone in the third year. Our results showed an average panicle yield increase of about +30%, representing +200 to +300 kg ha−1. Major factors determining the yield effect are season, village, and local soil type. This study shows for the first time that Oga innovation can be used to increase pearl millet panicle yield particularly in the low fertile soils of women’s farmlands in Niger. Oga innovation is affordable, locally available, and does not pose a risk to resource-poor female farmers of Niger.

Intensive management of phosphorus fertilization in Camellia oleifera Abel. to minimize phosphorus losses to the environment

Camellia (Camellia oleifera Abel.) plantation often needs fertilizer application to ensure fruit yield, and camellia fruit yield might be affected by soil phosphorus supply and microbial community and function. However, a large fraction of applied phosphorus is lost through leaching and runoff, which may cause eutrophication risks in waterbodies. Intensive management of phosphorus fertilization based on the comprehensive balance among fruit yield, soil nutrient and microbial property is required to quantify appropriate phosphorus fertilization rate. In this study, a camellia plantation located in southern China was selected, and four different fertilization treatments were established: control without P fertilizer (P0); 114.5 kg phosphorus pentoxide ha−1 applied as sodium dihydrogen phosphate (P1); 229.0 kg phosphorus pentoxide ha−1 (P2) and 343.5 kg phosphorus pentoxide ha−1 (P3). The fruit yields of P1, P2 and P3 treatments were approximately 1.5, 2.0 and 2.0 times of that measured from the P0 treatment, respectively. Bacterial community richness estimators and diversity indices in the P2 treatment were significantly higher than those in the P3 treatment. Relative abundances of Bacteroidetes, Planctomycetes, Verrucomicrobia and Eremiobacterota were significantly affected by the phosphorus fertilization. The gram-negative bacterial relative abundance was significantly lower in the P3 treatment than in the other treatments. Relative to the P2 treatment, the P3 treatment had significant decreases in soil pH, bacterial community diversity and gram-negative bacterial relative abundance, which might offset the stimulation of higher phosphorus supply for fruit yield. Based on the comprehensive balance among fruit yield, fertilization input cost, soil environment impact and microbial property, 229.0 kg phosphorus pentoxide ha-1 fertilization is appropriate for this camellia plantation. Future phosphorus fertilization in the camellia plantation should consider the comprehensive balance among yields, soils and microbial properties.

Association Between Subcatchment Land Cover and Ecological Stoichiometry Along a Human Modified Stream Network

The intersection between land cover and topography at the subcatchment scale can generate spatial heterogeneity in carbon (C), nitrogen (N), and phosphorus (P) supplies and alter ecological stoichiometry within river networks. Recognition of spatial patterns in the balance of energy and elements at the stream network scale is needed to increase our comprehension of the importance that watershed physiography has on stream functionality. Here we assessed the influence of topographically weighted land cover on the ecological stoichiometry of stream water, periphyton, and benthic macroinvertebrates among 18 stream segments within the Beaver River watershed (Ontario, Canada). Natural and anthropogenic land cover classes were topographically weighted within each subcatchment by increasing the weight of land cover located in hydrologically connected areas of the landscape (i.e., proximity to stream network, flow distance to sampling location, and flow accumulation). Univariate regression models were used to evaluate the influence of topographically weighted land cover and land use on the C, N, and P content and ratios of stream water, periphyton, and benthic macroinvertebrate consumers while accounting for spatial autocorrelation within the river network. We found that topographically weighted developed land was largely associated with the balance and concentrations of nutrients in stream water and primary consumer nutrient ratios, whereas topographically weighted agriculture inversely correlated with natural and wetland cover was associated with periphyton stoichiometry in addition to that of stream water and primary consumers. Spatial patterns in primary consumer elemental composition coincided with that of stream water and periphyton indicating a potential intermediary effect of land use on resource quality. Our results suggest that heterogeneity in the spatial arrangement of land cover within river networks can influence the ecological stoichiometry of stream water, periphyton, and benthic macroinvertebrates at the subcatchment scale.

Root morphology and rhizosheath acid phosphatase activity in legume and graminoid species respond differently to low phosphorus supply

Given the worldwide effort to improve crop phosphorus (P) efficiency, it is important to understand the adaptive strategies of crops with different root types and properties under limited P availability. The present study examined root morphological and physiological responses of two graminoids (wheat and maize), and three legumes (soybean, white lupin and narrow-leafed lupin) to low P supply under two difference growth conditions. Two experiments using non-destructive root observation systems (Expt.1, semi-hydroponic system; Expt.2, rhizoboxes) were conducted under low P (Expt.1: 2 μM; Expt.2: 9 mg kg−1 soil) and optimal P (Expt.1: 200 μM; Expt. 2: 60 mg kg−1 soil). Plants were assessed 40 days after transplanting (Expt. 1) and 35 days after sowing (Expt. 2). Results showed that low P stress generally suppressed plant shoot and root growths of all crops and significantly increased root-shoot ratio in graminoid plants in both experiments. Root length vertical distribution in each 10 cm layer was relatively lower in low P than in optimal P treatments with the majority roots distributed in 10–40 cm layers in both experiments. Under low P, all plants accumulated significantly less P in plant tissues. Maize, soybean and white lupin plants had larger dry weights and P contents than wheat and narrow-leaf lupin under respective P treatment under both experiments except high P content in wheat cv Zhongyu 6 under optimal P in Expt. 2. Low P stress significantly increased plant P-use efficiency in both experiments with more profound increase in maize and white lupin in Expt. 1. Low P stress stimulated cluster roots formation in white lupin. Both lupin species had significantly higher rhizosheath acid phosphatase activity than other crops under low P supply. In conclusion, five crop species differed in their adaptive strategies to low P availability. Graminoid species had strong response by modifying their root morphology while legumes especially lupin species used the limited P more efficiently through enhancing rhizosheath acid phosphatase activity to cope with soil P deficit.

Mixed infection, risk projection, and misdirection: Interactions among pathogens alter links between host resources and disease.

A growing body of literature links resources of hosts to their risk of infectious disease. Yet most hosts encounter multiple pathogens, and projections of disease risk based on resource availability could be fundamentally wrong if they do not account for interactions among pathogens within hosts. Here, we measured infection risk of grass hosts (Avena sativa) exposed to three naturally co‐occurring viruses either singly or jointly (barley and cereal yellow dwarf viruses [B/CYDVs]: CYDV‐RPV, BYDV‐PAV, and BYDV‐SGV) along experimental gradients of nitrogen and phosphorus supply. We asked whether disease risk (i.e., infection prevalence) differed in single versus co‐inoculations, and whether these differences varied with rates and ratios of nitrogen and phosphorus supply. In single inoculations, the viruses did not respond strongly to nitrogen or phosphorus. However, in co‐inoculations, we detected illustrative cases of 1) resource‐dependent antagonism (lower prevalence of RPV with increasing N; possibly due to competition), 2) resource‐dependent facilitation (higher prevalence of SGV with decreasing N:P; possibly due to immunosuppression), and 3) weak or no interactions within hosts (for PAV). Together, these within‐host interactions created emergent patterns for co‐inoculated hosts, with both infection prevalence and viral richness increasing with the combination of low nitrogen and high phosphorus supply. We demonstrate that knowledge of multiple pathogens is essential for predicting disease risk from host resources and that projections of risk that fail to acknowledge resource‐dependent interactions within hosts could be qualitatively wrong. Expansions of theory from community ecology theory may help anticipate such relationships by linking host resources to diverse pathogen communities.

The Phosphate Inhibition Paradigm: Host and Fungal Genotypes Determine Arbuscular Mycorrhizal Fungal Colonization and Responsiveness to Inoculation in Cassava With Increasing Phosphorus Supply.

A vast majority of terrestrial plants are dependent on arbuscular mycorrhizal fungi (AMF) for their nutrient acquisition. AMF act as an extension of the root system helping phosphate uptake. In agriculture, harnessing the symbiosis can potentially increase plant growth. Application of the AMF Rhizophagus irregularis has been demonstrated to increase the yields of various crops. However, there is a paradigm that AMF colonization of roots, as well as the plant benefits afforded by inoculation with AMF, decreases with increasing phosphorus (P) supply in the soil. The paradigm suggests that when fertilized with sufficient P, inoculation of crops would not be beneficial. However, the majority of experiments demonstrating the paradigm were conducted in sterile conditions without a background AMF or soil microbial community. Interestingly, intraspecific variation in R. irregularis can greatly alter the yield of cassava even at a full application of the recommended P dose. Cassava is a globally important crop, feeding 800 million people worldwide, and a crop that is highly dependent on AMF for P uptake. In this study, field trials were conducted at three locations in Kenya and Tanzania using different AMF and cassava varieties under different P fertilization levels to test if the paradigm occurs in tropical field conditions. We found that AMF colonization and inoculation responsiveness of cassava does not always decrease with an increased P supply as expected by the paradigm. The obtained results demonstrate that maximizing the inoculation responsiveness of cassava is not necessarily only in conditions of low P availability, but that this is dependent on cassava and fungal genotypes. Thus, the modeling of plant symbiosis with AMF under different P levels in nature should be considered with caution.