Efficiency Of Agricultural Systems Research Articles

Streamlining Different Plant Breeding Methods to Enhance Water Use Efficiency in Agricultural Systems

The relevance of Water in human life and agro-ecosystems has been extensively illustrated for decades around the globe. Despite the reality that the earth is mostly surrounded by water, its utility has been limited to domestic consumption and agricultural purposes. Thus, tweaking water usage in agricultural systems has been a tricky problem in order to meet the requirements of the growing population and to obtain more crop yield per drop of water in agriculture. In this review, an attempt has been made to revisit the methods available to improve water use efficiency in agriculture.

Reduction of NH3 Emissions from Urea by Long-Term No-Tillage and Stover Mulching with Inhibitors: An Isotopic Field Study in Northeast China

Large nitrogen (N) losses during fertilization in agricultural production may result in energy wastage, soil and water contamination, and potentially influence crop development. Thus, with the help of a 15N-labeled tracer, we carried out a field monitoring analysis of NH3 emissions in a long-term (9-year) conservation tillage agroecosystem of Mollisols in northeast China, in order to determine whether a no-tillage regime and four levels of stover mulching (0%, 33%, 67%, and 100%), combined with urease and nitrification inhibitors, could improve fertilizer utilization efficiency in agricultural systems by reducing ammonia volatilization. Our results showed that in comparison with ridge tillage, no-tillage with stover mulching levels of 33%, 67%, and 100% significantly reduced NH3 emission rates and cumulative volatilization from 159.67 to 130.42 g N ha−1 and 15N-NH3 cumulative volatilization emission by 26% (on average). Furthermore, the application of urease and nitrification inhibitors significantly reduced 15N-NH3 volatilization levels from 1.19 to 0.98 g N ha−1. Our research results demonstrate that a long-term no-tillage regime and straw mulching can significantly reduce NH3 volatilization in fertilizers. Furthermore, when combined with the use of urease and nitrification inhibitors, these practices further enhance the reduction in NH3 volatilization. Although the volatilization of 15N-NH3 is minimally studied in Mollisols, these findings provide a solid foundation for improving fertilizer utilization efficiency, reducing crop production costs and mitigating subsequent environmental pollution.

Phosphate-Solubilizing Bacteria with Low-Solubility Fertilizer Improve Soil P Availability and Yield of Kikuyu Grass.

Inoculation with phosphate-solubilizing bacteria (PSB) and the application of phosphorus (P) sources can improve soil P availability, enhancing the sustainability and efficiency of agricultural systems. The implementation of this technology in perennial grasses, such as Kikuyu grass, for cattle feed in soils with high P retention, such as Andisols, has been little explored. The objective of this study was to evaluate the productive response of Kikuyu grass and soil P dynamics to BSF inoculation with different P sources. The experiment was conducted on a Kikuyu pasture, which was evaluated for 18 months (September 2020 to March 2022). Three P fertilizers with different solubility levels were applied: diammonium phosphate (DAP) (high-solubility), rock phosphate (RP), and compost (OM) (low-solubility). Moreover, the inoculation of a PSB consortium (Azospirillum brasilense D7, Rhizobium leguminosarum T88 and Herbaspirillum sp. AP21) was tested. Inoculation with PSB and fertilization with rock phosphate (RP) increased soil labile P and acid phosphomonoesterase activity. Increased grass yield and quality were related with higher soil inorganic P (Pi) availability. This study validated, under field conditions, the benefits of PSB inoculation for soil P availability and Kikuyu grass productivity.

Microdialysis fluxes of inorganic nitrogen differ from extractable nitrogen by minimising disturbance of mineral-associated sources

Measuring soil nitrogen (N) provides important information for ecosystem productivity and improving N use efficiency in agricultural systems. Conventional means of sampling N using soil extractions disturb soil structure and function, and likely distort accurate quantification. In situ microdialysis is a novel sampling method that generates differing N profiles compared to soil extractions. Here we test the hypothesis that differences observed between sampling methods are due to the minimal disturbance and sampling of a mobile N fraction when using microdialysis, with discernible patterns expected across soils with distinct clay and organic matter contents. In a short-term laboratory microcosm experiment with 21 sugarcane cropping soils, we compared salt (potassium chloride; KCl) or aqueous (H2O) extractants and microdialysis. KCl-extractable ammonium (NH4+) was highly correlated with the content of clay, total N and carbon, indicative of bound N being solubilised. In contrast, NH4+ contributed significantly less to microdialysis fluxes and was not correlated with the measured soil properties, which we attribute to minimal disturbance of bound N·H2O extracts sampled proportionally more NH4+ than microdialysis but were significantly correlated with fluxes. This suggests that while microdialysis and H2O extraction sample from a dissolved N pool, H2O extracts sample from an additional pool of loosely-bound NH4+. Nitrate (NO3−) measures were correlated between methods, but shared no relationship with the measured soil properties, indicating that NO3− sampling is less affected by the disturbance introduced by extractions. We conclude that sampling inorganic N is biased by the degree to which soil sampling methods disturb adsorbed N sources with implications for interpreting soil N measurements.

From Agricultural Wastes to Fermentation Nutrients: A Case Study of 2,3-Butanediol Production

The goal of this study was to improve resource use efficiency in agricultural systems and agro-based industries, reduce wastes that go to landfills and incinerators, and consequently, improve the economics of 2,3-butanediol (2,3-BD) production. This study evaluated the feasibility of 2,3-BD production by replacing the mineral nutrients, and buffers with anaerobic digestate (ADE), poultry-litter (PLBC)- and forage-sorghum (FSBC)-derived biochars. Fermentation media formulations with ADE and 5–20 g/L PLBC or FSBC were evaluated for 2,3-BD production using Paenibacillus polymyxa as a biocatalyst. An optimized medium containing nutrients and buffers served as control. While 2,3-BD production in the ADE cultures was 0.5-fold of the maximum generated in the control cultures, 2,3-BD produced in the PLBC and FSBC cultures were ~1.3-fold more than the control (33.6 g/L). Cost analysis showed that ADE and biochar can replace mineral nutrients and buffers in the medium with the potential to make bio-based 2,3-BD production profitably feasible.

Effect of nitrification inhibitor (DMPP) on nitrous oxide emissions from agricultural fields: Automated and manual measurements

Nitrogen fertilisation contributes significantly to the atmospheric increase of nitrous oxide (N2O). Application of nitrification inhibitors (NIs) is a promising strategy to mitigate N2O emissions and improve N-use efficiency in agricultural systems. This study investigated the effect of NI, 3,4-dimethylpyrazol phosphate (DMPP) on N2O mitigation from spring barley and spring oilseed rape. Manual and automatic chamber methodologies were used to capture spatial and temporal variability in N2O emissions. In a second experiment, we study the effect of N fertiliser levels without NI (0 %, 50 %, 100 %, 150 % and 200 % of recommended amount of N fertiliser), as well as 100 % of N with NI on N2O emissions in spring barley. The automated chamber measurements showed dynamics of N2O changes throughout the season, including positive and negative peaks that were unobservable with manual chambers due to low temporal resolution. Although not significant, application of NI tended to reduce N2O emissions. The reduction was on average 16 % in spring barley and 58 % in spring oilseed rape in manual chamber measurements. However, N2O reduction was 108 % in continuous automatic chamber measurements in spring barley. The N2O EFs for the growing season were very low (0.025 % to 0.148 %), with a greater reduction in EF in spring oilseed rape (76 %) than in spring barley (32 %) with NI application. A positive correlation (R = 80 %) was observed between N fertiliser levels and N2O emissions. Crop yield and crop N uptake were not significantly affected by the use of NI. This study highlighted that NI can reduce N2O emissions, but the reduction effects are plot, crop and microclimate specific. Long-term experiments with continuous plot-scale measurements are needed to capture and optimise N2O mitigation effect of NIs across wide variability in soils and microclimates in agroecosystems.

Efficiency of Combining Strains Ag87 (Bacillus megaterium) and Ag94 (Lysinibacillus sp.) as Phosphate Solubilizers and Growth Promoters in Maize.

Increasing phosphorus (P) use efficiency in agricultural systems is urgent and essential to significantly reduce the global demand for this nutrient. Applying phosphate-solubilizing and plant growth-promoting bacteria in the rhizosphere represents a strategy worthy of attention. In this context, the present work aimed to select and validate bacterial strains capable of solubilizing phosphorous and promoting maize growth, aiming to develop a microbial inoculant to be used in Brazilian agriculture. Bacterial strains from the maize rhizosphere were evaluated based on their ability to solubilize phosphate and produce indole acetic acid. Based on these characteristics, 24 strains were selected to be further evaluated under laboratory, greenhouse, and field conditions. Among the selected strains, four (I04, I12, I13, and I17) showed a high potential to increase maize root growth and shoot P content. Strains I13 (Ag87) and I17 (Ag94) were identified by genomic sequencing as Bacillus megaterium and Lysinibacillus sp., respectively. These strains presented superior yield increments relative to the control treatment with 30% P. In addition, combining Ag87 and Ag94 resulted in even higher yield gains, indicating a synergistic effect that could be harnessed in a commercial inoculant for Brazilian agriculture.

Ammonia-oxidizing archaea are integral to nitrogen cycling in a highly fertile agricultural soil

Nitrification is a central process in the global nitrogen cycle, carried out by a complex network of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), complete ammonia-oxidizing (comammox) bacteria, and nitrite-oxidizing bacteria (NOB). Nitrification is responsible for significant nitrogen leaching and N2O emissions and thought to impede plant nitrogen use efficiency in agricultural systems. However, the actual contribution of each nitrifier group to net rates and N2O emissions remain poorly understood. We hypothesized that highly fertile agricultural soils with high organic matter mineralization rates could allow a detailed characterization of N cycling in these soils. Using a combination of molecular and activity measurements, we show that in a mixed AOA, AOB, and comammox community, AOA outnumbered low diversity assemblages of AOB and comammox 50- to 430-fold, and strongly dominated net nitrification activities with low N2O yields between 0.18 and 0.41 ng N2O–N per µg NOx–N in cropped, fallow, as well as native soil. Nitrification rates were not significantly different in plant-covered and fallow plots. Mass balance calculations indicated that plants relied heavily on nitrate, and not ammonium as primary nitrogen source in these soils. Together, these results imply AOA as integral part of the nitrogen cycle in a highly fertile agricultural soil.

A novel microcosm to identify inherently competitive microorganisms with the ability to mineralize phytate in solum

Fertilizer phosphorus (P) is a finite resource, necessitating the development of innovative solutions for P fertilizer efficiency in agricultural systems. Myo-inositol hexakisphosphate (phytate) constitutes the majority of identified organic P in many soil types and is poorly available to plants. Incorporating phytase-producing biofertilizers into soil presents a viable and environmentally acceptable way of utilizing P from phytate, while reducing the need for mineral P application. A deeper understanding of the microbial ecology in relation to degradation of phytate under natural soil conditions is however needed to obtain successful biofertilizer candidates able to compete in complex soil environments. Here we present the development of a microcosm for studying microbial communities able to colonize and utilize Ca-phytate hotspots in solum. Our results provide evidence that the recruited microbial population mineralizes Ca-phytate. Furthermore, quantification of bacterial genes associated with organic P cycling in alkaline soils indicated that the phosphatases PhoX and PhoD may play a larger role in phytate mineralization in soil than previously recognized. Amplicon sequencing and BioLog® catabolism studies show that hotspots containing Ca-phytate, recruited a different set of microorganisms when compared to those containing an addition of C source alone, with the genus Streptomyces specifically enriched. We propose that Streptomyces represents an hitherto unexplored resource as P biofertilizer with competitive advantage for utilizing CaPhy in an inherently competitive soil environment. We further conclude that the use of our newly designed microcosm presents an innovative approach for isolating soil microorganisms with the potential to degrade precipitated phytate in solum.

Response of tea yield, quality and soil bacterial characteristics to long-term nitrogen fertilization in an eleven-year field experiment

Nitrogen (N) fertilization is an important field management practice in tea (Camellia sinensis L.) plantations. Although the supply of N fertilizer plays a vital role in the growth and quality of tea plants, the optimal N application rate and the effects of different N application regimens on tea yield and quality still remain unclear. In this study, we conducted an eleven-year field experiment to investigate the impact of N application on tea yield and quality, as well as soil bacterial characteristics. We found that N fertilization quadratically increased the yield and amino acid (AA) content of tea, but quadratically decreased total polyphenol (TP) content. Increasing N rates resulted in significant changes in soil community characteristics, including decreased diversity, weakened community function and lower community stability. Additionally, higher taxonomic levels and low-abundance taxa were affected most significantly by N fertilization. Based on PERMANOVA results, the variation of bacterial community composition can be largely explained (~50%) by the soil properties of pH, exchangeable magnesium (Exch-Mg), exchangeable potassium (Exch-K) and exchangeable hydrogen (Exch-H). Partial least squares regression (PLSR) and path modeling (PLS-PM) illustrated that N fertilization indirectly affected tea yield and quality mainly by causing changes in soil properties of Exch-Al and pH, respectively. Soil bacterial characteristics, on the other hand, contributed relatively little to the changes in tea yield and quality. Overall, excessive N application had an adverse effect on soil quality, despite mostly positive effects on tea growth and quality. N application rates of 119–285 kg N ha−1 yr−1 were the most optimal for high tea growth and quality. Understanding the response of above- and belowground plant characteristics to N application rates should help to guide field fertilization and achieve a higher N-use efficiency in agricultural systems.

Review on unmanned aerial vehicles, remote sensors, imagery processing, and their applications in agriculture

AbstractUnmanned aerial vehicles (UAV) and the sensors they can be equipped with are becoming more technologically advanced and common place within the agricultural industry. The output analyses from UAV captured data helps drive decisions for improving input efficiency in agricultural systems, which can result in maximum return on investment and reduced environmental impact. Advances in UAV technologies provides producers with options for assessment of crucial factors impacting crop yield and quality including crop water status and nutrient stress, competition from weeds, insects, and pathogens, and soil characteristics and precision field maps. Thus, integrating UAV technologies as a component of production agriculture enables producers to identify and locate problem areas in their fields in near real time and take corrective actions once these areas are verified. UAV technologies also offers researchers with a non‐destructive, objective manner for obtaining phenotypic measurements such as height assessment, biomass estimation, canopy reflectance, and abiotic and biotic stress tolerance, which can greatly expedite field data collection for advancing germplasm with desired agronomic traits. This review covers more than a hundred articles that were obtained from the existing literature and illustrates common UAV types, common sensor types, imagery processing options, and their practical application and pitfalls in the modern agricultural industry.

Resilience or how do we enable agricultural systems to ride the waves of unexpected change?

As the unfolding of the COVID-19 pandemic reminds us, change is not only of the planned kind, but often triggered by sudden and unexpected events. The impact of such an event on agricultural systems is unpredictable and can be far reaching. Thus, rather than focusing our research efforts only on increasing the productivity and efficiency of agricultural systems, we may also need to pay attention to what enables them to change and adapt. One approach is to give more attention to relations and processes in a system. This applies to relations within agricultural systems, and between the system and its context; but also to relations between scientific disciplines and between researchers and practitioners. Assessing the fixities and dynamics these relations promote, may enable us to contribute making agricultural systems better able to navigate change processes, may be even enable them to take advantage of openings created by unexpected events.

Water Distribution Uniformity in Driping System Under Growing Pressures

Increasing water use efficiency in agricultural systems is critical as it results in economic and environmental cost reductions, especially in localized irrigation, which depends on a number of factors, especially the flow rate of the emitters and proper uniformity of water distribution, both with respect to direct with the pressure of the emitters For this evaluation the use of coefficients of water uniformity, it is essential to indicate the best wetness management. The experiment was carried out in the Irrigation laboratory, in a test stand, using Christiansen uniformity coefficient - CUC, distribution uniformity coefficient - CUD and statistical uniformity coefficient - CUE. In the irrigation line, four pressures on the drip emitter (5, 10, 15 and 20 mca) were applied. The pressure variations obtained did not reduce the efficiency of the uniformity of water distribution by the drip system, falling into high efficiency ranges for all evaluated coefficients, representing adequate wetting rates.

Biochemical effects of banding limit the benefits of nitrification inhibition and controlled-release technology in the fertosphere of high N-input systems

Enhanced efficiency fertilisers (EEFs) may have an important role in improving nitrogen (N) use efficiency in agricultural systems. The performance of EEFs when applied by broadcasting and incorporation is well documented; however, little information is available for sub-surface banded N-fertiliser. This study aimed to determine the effectiveness of EEFs within the fertosphere in several soils. This was determined by: (i) establishing the key chemical effects and N-transformation activity within a urea band, and (ii) contrasting these findings with nitrification inhibitor (NI)-coated urea and a controlled-release polymer-coated urea (PCU). A 112-day incubation experiment was conducted with the EEFs band-applied in three contrasting soils with a history of sugarcane production. In standard urea and NI-urea treated soils, the pH within the fertosphere significantly increased to a maximum of ~pH 9.2–9.3. Alkaline conditions and high ammonium concentrations promoted elevated aqueous ammonia concentrations, resulting in complete nitrification inhibition. The PCU granules released ~40% of total urea content within 14 days, followed by subsequent release at significantly lower rates. The initial rapid urea release was attributed to damaged polymer coats, while close proximity of neighbouring granules within the band may have contributed to the subsequent slower release phase through reduced concentration gradients and restricted diffusion from granules. Variation between soils suggests that soil properties such as clay content and pH buffer capacity may influence urea hydrolysis, but not nitrification. These results suggest that both NI and controlled-release technology may not have the expected impacts on N transformations and availability when applied in a concentrated band.

Combining cleaner production and life cycle assessment for reducing the environmental impacts of irrigated carrot production in Brazilian semi-arid region

Agriculture is the activity that contributes most to the emission of greenhouse gases, water quality degradation, soil loss and nutrient runoff worldwide. These harmful environmental impacts are issues in irrigated agriculture in the Brazilian semi-arid region. The rational use of natural resources and the efficiency of agricultural systems can reduce the environmental impacts and are essential for a more sustainable agriculture. However, a limited amount of data concerning the environmental impacts of horticultural practices is available. To date, no evaluation of a carrot crop life cycle in Brazil could be found in the literature. The purpose of this paper is to present a methodological approach combining Life Cycle Assessment (LCA) and Cleaner Production (CP) principles in the environmental and economic evaluation of irrigated carrot farming. Life Cycle Impact Assessment was carried using the International Reference Life Cycle Data System (ILCD, 2011) method, including data uncertainty. We evaluated the base scenario based on management practices widely adopted in the studied area, and the recommended scenario based on adoption of CP selected opportunities using agronomic recommendations for the carrot production system. By these means, the environmental impacts can be reduced between 15 and 70% in the evaluated categories from the base to the recommended scenario. Most environmental impacts were related to fertilizer production and field emissions. The global warming effect related to the emission of 0.12 kg CO2 eq/kg product from the base scenario can be reduced to 0.07 kg CO2 eq/kg product in the recommended scenario. This represents a lower value than most global warming rates for carrots found in literature. The costs of inputs were reduced by 49% from in the recommended scenario. Most costs of inputs were related to fertilizers and seed purchasing. The combined use of the two methods proved feasible as LCA identifies the main hotspots of the analyzed system, while CP support practices that reduce costs and the use of inputs such as water, energy, fertilizers, seeds and pesticides. CP provided a higher level of compliance with the technical requirements for the studied system and proved to be more economically and environmentally efficient than ‘end of pipe’ practices. The complementary use of CP and LCA provided better support for a more sustainable irrigated carrot production in the semiarid region of Brazil.

RGB and Spectral Root Imaging for Plant Phenotyping and Physiological Research: Experimental Setup and Imaging Protocols.

Better understanding of plant root dynamics is essential to improve resource use efficiency of agricultural systems and increase the resistance of crop cultivars against environmental stresses. An experimental protocol is presented for RGB and hyperspectral imaging of root systems. The approach uses rhizoboxes where plants grow in natural soil over a longer time to observe fully developed root systems. Experimental settings are exemplified for assessing rhizobox plants under water stress and studying the role of roots. An RGB imaging setup is described for cheap and quick quantification of root development over time. Hyperspectral imaging improves root segmentation from the soil background compared to RGB color based thresholding. The particular strength of hyperspectral imaging is the acquisition of chemometric information on the root-soil system for functional understanding. This is demonstrated with high resolution water content mapping. Spectral imaging however is more complex in image acquisition, processing and analysis compared to the RGB approach. A combination of both methods can optimize a comprehensive assessment of the root system. Application examples integrating root and aboveground traits are given for the context of plant phenotyping and plant physiological research. Further improvement of root imaging can be obtained by optimizing RGB image quality with better illumination using different light sources and by extension of image analysis methods to infer on root zone properties from spectral data.

RGB and Spectral Root Imaging for Plant Phenotyping and Physiological Research: Experimental Setup and Imaging Protocols

Better understanding of plant root dynamics is essential to improve resource use efficiency of agricultural systems and increase the resistance of crop cultivars against environmental stresses. An experimental protocol is presented for RGB and hyperspectral imaging of root systems. The approach uses rhizoboxes where plants grow in natural soil over a longer time to observe fully developed root systems. Experimental settings are exemplified for assessing rhizobox plants under water stress and studying the role of roots. An RGB imaging setup is described for cheap and quick quantification of root development over time. Hyperspectral imaging improves root segmentation from the soil background compared to RGB color based thresholding. The particular strength of hyperspectral imaging is the acquisition of chemometric information on the root-soil system for functional understanding. This is demonstrated with high resolution water content mapping. Spectral imaging however is more complex in image acquisition, processing and analysis compared to the RGB approach. A combination of both methods can optimize a comprehensive assessment of the root system. Application examples integrating root and aboveground traits are given for the context of plant phenotyping and plant physiological research. Further improvement of root imaging can be obtained by optimizing RGB image quality with better illumination using different light sources and by extension of image analysis methods to infer on root zone properties from spectral data.

Improving phosphorus use efficiency: a complex trait with emerging opportunities.

Phosphorus (P) is one of the essential nutrients for plants, and is indispensable for plant growth and development. P deficiency severely limits crop yield, and regular fertilizer applications are required to obtain high yields and to prevent soil degradation. To access P from the soil, plants have evolved high- and low-affinity Pi transporters and the ability to induce root architectural changes to forage P. Also, adjustments of numerous cellular processes are triggered by the P starvation response, a tightly regulated process in plants. With the increasing demand for food as a result of a growing population, the demand for P fertilizer is steadily increasing. Given the high costs of fertilizers and in light of the fact that phosphate rock, the source of P fertilizer, is a finite natural resource, there is a need to enhance P fertilizer use efficiency in agricultural systems and to develop plants with enhanced Pi uptake and internal P-use efficiency (PUE). In this review we will provide an overview of continuing relevant research and highlight different approaches towards developing crops with enhanced PUE. In this context, we will summarize our current understanding of root responses to low phosphorus conditions and will emphasize the importance of combining PUE with tolerance of other stresses, such as aluminum toxicity. Of the many genes associated with Pi deficiency, this review will focus on those that hold promise or are already at an advanced stage of testing (OsPSTOL1, AVP1, PHO1 and OsPHT1;6). Finally, an update is provided on the progress made exploring alternative technologies, such as phosphite fertilizer.

不同林龄橡胶(Hevea brasiliensis)林土壤微生物群落和磷组分的变化

PDF HTML阅读 XML下载 导出引用 引用提醒 不同林龄橡胶(Hevea brasiliensis)林土壤微生物群落和磷组分的变化 DOI: 10.5846/stxb201705020803 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（31640014）；中央级公益性科研院所基本科研业务费专项（17CXTD-04，2015hzs1J012）；海南省自然科学基金（317235） Effects of rubber (Hevea brasiliensis) plantations on soil phosphorus fractions and microbial community composition Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:橡胶林是我国热带地区重要的经济林，而土壤磷是热带地区植物生长的重要限制因子之一，理解土壤磷转化机理对于生态系统的磷管理和可持续发展具有重要意义。因此，以热带地区海南儋州不同林龄（4、15、31a）橡胶人工林为研究对象，采用Hedley连续浸提法研究了土壤磷组分，磷脂脂肪酸法（Phospholipid fatty acids，PLFAs）分析了土壤微生物群落。结果表明，在橡胶林内各磷组分的相对含量大小顺序为：闭蓄态磷 > 中等活性态磷 > 活性态磷 > 团聚体内磷 > 钙磷。随着林龄的增加，橡胶林土壤中的磷组分发生显著变化。4、15、31a橡胶林的闭蓄态磷分别占总提取磷的52.61%、47.17%和34.91%，而活性态磷分别占总提取磷的6.67%、11.32%、13.68%。土壤总微生物、细菌、革兰氏阴性菌（G-）、革兰氏阳性菌（G+）的PLFAs含量均表现为15a > 4a > 31a，而31a橡胶林放线菌、真菌（F）和丛枝菌根真菌（AMF）的PLFAs含量均低于4a和15a。冗余分析（RDA）显示，全氮、有机碳、pH、F、AMF、G-、G+是引起不同林龄橡胶林土壤磷组分变化的重要贡献因子。研究表明，在橡胶林发育过程中，土壤理化性质和微生物群落发生了明显的变化，进而影响到土壤磷的转化过程。 Abstract:Phosphorus (P) is recognized as one of the most limiting nutrients for primary production in tropical forests because much of the soil P stocks are geochemically bound to iron and aluminum oxides in forms that are largely unavailable for plant uptake. The availability of P to microorganisms and plants can be assessed by evaluating different soil P fractions, and soil P occurs in both organic and inorganic forms, which differ in behavior, mobility, and bioavailability (i.e., labile P, moderately labile P, non-labile P). Labile and non-labile P fractions can serve as sources or sinks of available P, and non-labile P can be released into soil solutions as available P through desorption when the content of available P decreases in the soil. Therefore, it is critical to understand the transformation between different soil P fractions when developing best practices for fertilizer management that aim to enhance the P use efficiency of agricultural systems. Soil microorganisms are important mediators of P mineralization and immobilization, owing to their ability to reduce P availability by immobilizing P in their biomass, which subsequently increases stocks of microbial P in the soil. In addition, lower available P content was observed in tropical soil, accompanied by higher soil phosphatase activity. Furthermore, arbuscular mycorrhizal fungi (AMF) can take up P from pools that are normally considered unavailable to plants. However, the relationship between the dynamics of soil P forms, soil properties, and soil microbial communities has yet to be established in rubber plantation at different ages. Therefore, we compared the soil P fractions (i.e., labile P, moderately labile P, sonicate P, Ca-P, and occluded P) and soil microbial community composition of 4-, 15-, and 31-year-old rubber plantations on Hainan Island, Southern China. The aims of this study were (1) to determine whether the soil P stock and fractions would change with increasing plantation age; (2) to test whether the composition of soil microbial communities would change with plantation age; and (3) to quantify the relationships between P fraction, microbial community, and other soil attributes. The results could be used to develop recommended P fertilizer management practices for sustainable rubber plantations. We found that occluded P was the largest phosphorus fraction, followed by moderately labile P, labile P, sonicate P, and Ca-P in all plantations. The levels of bacteria and both gram-positive and gram-negative bacterial Phospholipid fatty acids (PLFAs) were highest in the 15-year-old plantation, whereas the levels of actinomycetes, arbuscular mycorrhizal fungi (16:1ω5c), and fungal PLFAs were lowest in the 31-year-old plantation. The level of soil acid phosphatase activity did not change with increasing plantation age, and redundancy analysis indicated that both biotic and abiotic factors were important contributors to variation in soil P fractions. Accordingly, the present study demonstrates that the age of rubber plantations significantly affects the soil physicochemical properties and microbial communities of rubber plantations and, consequently, soil P availability and cycling. 参考文献 相似文献 引证文献

Phosphate depletion modulates auxin transport in Triticum aestivum leading to altered root branching.

Understanding the mechanisms by which nutritional signals impact upon root system architecture is a key facet in the drive for greater nutrient application efficiency in agricultural systems. Cereal plants reduce their rate of lateral root emergence under inorganic phosphate (Pi) shortage; this study uses molecular and pharmacological techniques to dissect this Pi response in Triticum aestivum. Plants were grown in coarse sand washed in high- or low-Pi nutrient solution before being assessed for their root branching density and expression of AUX/IAA and PIN genes. Seedlings were also grown on media containing [(14)C]indole acetic acid to measure basipetal auxin transport. Seedlings grown in low-Pi environments displayed less capacity to transport auxin basipetally from the seminal root apex, a reduction in root expression of PIN auxin transporter genes, and perturbed expression of a range of AUX/IAA auxin response genes. Given the known importance of basipetally transported auxin in stimulating lateral root initiation, it is proposed here that, in T. aestivum, Pi availability directly influences lateral root production through modulation of PIN expression. Understanding such processes is important in the drive for greater efficiency in crop use of Pi fertilizers in agricultural settings.