Plant Nutrient Demand Research Articles

Nonlinear responses of ericaceous and ectomycorrhizal Arctic shrubs across a long‐term experimental nutrient gradient

AbstractIn the Arctic tundra, warming is anticipated to stimulate nutrient release and potentially alleviate plant nutrient limitations. Typically simulated by fertilization experiments that saturate plant nutrient demand, future increases in soil fertility are thought to favor ectomycorrhizal (EcM) over ericaceous shrubs and have often been identified as a key driver of Arctic shrub expansion. However, the projected increases in fertility will likely vary in their alleviation of nutrient limitations. The resulting responses of shrubs and their mycorrhizae across the gradient of nutrient limitation may be nonlinear and could contradict the current predictions of tundra vegetation shifts. We compared the functional responses of two dominant shrubs, EcM dwarf birch (Betula nana) and ericaceous Labrador tea (Rhododendron tomentosum), across a long‐term nitrogen and phosphorus fertilization gradient experiment in Arctic Alaska. Using linear mixed‐effects modeling, we tested the responses of shrub cover, height, and root enzyme activities to soil fertility. We found that B. nana cover and height linearly increased with soil fertility. In contrast, R. tomentosum cover initially increased, but decreased after surpassing the intermediate levels of increased soil fertility. Its height did not change. Enzyme activity did not respond to soil fertility on EcM‐colonized B. nana roots, but sharply declined on R. tomentosum roots. Overall, the nonlinear responses of shrubs to our fertility gradient demonstrate the importance of experiments grounded in replicated regression design. Our results indicate that under moderate increases in soil fertility, Arctic shrub expansion may not only include deciduous EcM shrubs but also ericaceous shrubs. Regardless of shifts aboveground, changes in root enzyme activity belowground point to some EcM shrub species playing a more influential role in tundra soils; as EcM roots remained steady in their liberation of soil organic nutrients with heightened soil fertility, degradative root enzyme activity on the dominant ericaceous shrub dropped—in some instances with even the slightest increase in fertility.

Plant-soil synchrony in nutrient cycles: Learning from ecosystems to design sustainable agrosystems.

Redesigning agrosystems to include more ecological regulations can help feed a growing human population, preserve soils for future productivity, limit dependency on synthetic fertilizers, and reduce agriculture contribution to global changes such as eutrophication and warming. However, guidelines for redesigning cropping systems from natural systems to make them more sustainable remain limited. Synthetizing the knowledge on biogeochemical cycles in natural ecosystems, we outline four ecological systems that synchronize the supply of soluble nutrients by soil biota with the fluctuating nutrient demand of plants. This synchrony limits deficiencies and excesses of soluble nutrients, which usually penalize both production and regulating services of agrosystems such as nutrient retention and soil carbon storage. In the ecological systems outlined, synchrony emerges from plant-soil and plant-plant interactions, eco-physiological processes, soil physicochemical processes, and the dynamics of various nutrient reservoirs, including soil organic matter, soil minerals, atmosphere, and a common market. We discuss the relative importance of these ecological systems in regulating nutrient cycles depending on the pedoclimatic context and on the functional diversity of plants and microbes. We offer ideas about how these systems could be stimulated within agrosystems to improve their sustainability. A review of the latest advances in agronomy shows that some of the practices suggested to promote synchrony (e.g., reduced tillage, rotation with perennial plant cover, crop diversification) have already been tested and shown to be effective in reducing nutrient losses, fertilizer use, and N2 O emissions and/or improving biomass production and soil carbon storage. Our framework also highlights new management strategies and defines the conditions for the success of these nature-based practices allowing for site-specific modifications. This new synthetized knowledge should help practitioners to improve the long-term productivity of agrosystems while reducing the negative impact of agriculture on the environment and the climate.

Mechanisms of Nutrient Uptake and Assimilation Processes in Some Plants: A Review

Nutrient demands of plants are fulfilled via nutrient uptake by the roots, even though minor quantities of certain nutrients might be assimilated via leaves. For the reason that the majority of nutrients are assimilated by roots, an understanding of root morphology and cell structure is crucial in knowing this basic plant process. Nutrient achievement by plants hinges on ion applications on superficial, root assimilation capacity, and plant requirement. Movement of ion in plant cells is classified into active and passive. Ion concentrations in the cytoplasm of plant cells are frequently and considerably observed to be greater than in soil solutions. Consequently, roots ought to be able to take up ions in contrast to broadly diverse concentration gradients. Currently, two major theories of ion transport across membranes are reported in literature: carrier theory where carrier agents accountable for transferring ions from one side of membrane to the other; encounter specific ions for which they have attraction, form carrier ion complexes; and move across membranes and connecting ATPase theory of ion transport; which is related with the plasmalemma and is activated by cations; the ion pump theory, which is a demanding proces, transporting via electrochemical gradient. Measurements of ion uptake could be achieved through tracer techniques. Long-distance transport of ions to shoots happens in the vascular system, with water being the transporting agent. New and stimulating developments in mineral uptake mechanism of plants have momentously added to our understanding of the function of nutrients uptake in plants. Most research comparative to physiology of nutrient uptake has been conducted under controlled environment by means of particular nutrient cultures in the growth medium.

Use of Digestate as an Alternative to Mineral Fertilizer: Effects on Soil Mineral Nitrogen and Winter Wheat Nitrogen Accumulation in Clay Loam

Knowledge of the mineralisation and nutrient release of organic fertilisers is essential to ensure plant nutrient demand and availability, to increase N use efficiency and to minimise environmental risks. In 2018–2020, two similar field experiments were carried out on clay loam Cambisol with winter wheat (Triticum aestivum L.) grown without N application and applying liquid anaerobic digestate (LD), pig slurry (PS) and ammonium nitrate (AN) fertilizer with and without additional fertilization (N120 and N120+50). The aim of the research was to compare the effect of organic and mineral fertilizers on the variation of soil mineral nitrogen forms in the 0–30, 30–60 cm soil layers and N accumulation in wheat yield. Fertilizers applied during the previous growing season increased the nitrate and ammonium nitrogen (N-NO3 and N-NH4) content after the resumption of winter wheat vegetation. The dry period in spring (2019) had a negative impact on winter wheat N uptake. In a year of normal moisture content (2020), PS and LD fertilizers and the fertilizer application of the previous year (2019) significantly increased the N-NO3 content in the topsoil, while all applied fertilizers increased it in the deeper soil layer (by a factor of between 3.6 and 12.3), compared to unfertilized soil.

Response of Pinus tabuliformis saplings to continuous autumn fertilization treatments in the mountains of Eastern Liaoning Province, China.

Autumn fertilization is an important cultivation and management measure used to provide nutrients at the hardening stage during the end of the growing season—bolstering nutrient reserves and promoting additional growth in the following spring. Previous studies mainly focused on short-term or one-time fertilization treatment of container seedlings, and few studies have observed the effects of autumn fertilization of large-area forests over multiple continuous years. The growth dynamics and nutrient changes during autumn in 324 Pinus tabuliformis saplings in the temperate zone of China (in the eastern Liaoning mountains) were studied under field conditions with different fertilizer treatments for three consecutive years. The second year of autumn fertilization promoted the growth of tree height and annual leaf length more significantly than that in the first year, the change in diameter at breast height (DBH) was significant. Tree height (TH) in spring increased at a faster rate than in autumn, while DBH stably increased throughout the year. The increase in TH, DBH, and annual leaf length (ALL) under all fertilization treatments was higher than that of the control group, and the decrease in annual branch length (ABL) was higher than that of the control group. High N significantly increased the concentration of new coniferous N (NLN), soil total N (STN), and soil alkali-hydrolyzable N (SAHN) in P. tabuliformis saplings. High P significantly increased the concentration of P in annual needles and soil total P (STP), and decreased the concentration of N in new needles. In addition, there is a certain correlation between the N and P concentration in the needles and soil, representing the competition and interactions between plant nutrient demand and soil nutrient supply. The most favorable fertilizer treatment consisted of high N and low P (urea 204 g, calcium superphosphate 104 g), which provide support for the formulation of a reasonable fertilization technology for P. tabuliformis in the mountains of Eastern Liaoning Province, China.

Seasonality drives microbiome composition and nitrogen cycling in soil below biocrusts

Biological soil crusts (biocrusts) recently discovered in agroecosystems have the potential to enrich soil moisture and nitrogen (N) concentrations and structure the subsurface microbiome. In citrus agroecosystems, year-round N availability is vital for production, with vegetative flushes in the spring and fall and fruit development in the fall and winter. Due to the N demand and natural formation of biocrusts in citrus orchards, we investigated the influence of biocrusts on soil moisture content, N cycling, and microbiome composition in the upper root zone of a sandy soil citrus orchard (Florida, USA). Soils sampled from below biocrusts (1–5 cm) were collected at eight sampling dates over a one-year period in the orchard from biocrust-covered and proximate bare areas. Samples were analyzed for moisture content, soluble and microbial N pools, and potential ammonia oxidation. Bacterial and fungal communities were characterized using the 16S rRNA gene and ITS region sequences, respectively, at five sampling dates from September 2019 through March 2020. Biocrust presence and sampling date significantly impacted soil moisture and soluble and microbial N pools (p < 0.05). Soil moisture and inorganic N were enriched below biocrusts compared to below bare soil controls during the dry season from fruit set through harvest. Microbial biomass N and potential ammonia oxidation activity were also higher in September and November during fruit set. During fruit set and maturation, there was a corresponding greater abundance of copiotrophic bacteria and fungi capable of heterotrophic nitrification in soil below biocrusts. Overall, these results indicate soil under biocrusts had increased moisture, N concentrations, and relative abundances of microbiota with functional potential for cycling N. These results support a potential role for biocrust influence on crop N availability and soil health during periods of plant nutrient demand.

Nutrient uptake behavior of peanut under optimum fertilization management in China

AbstractBalanced fertilization is one of the most critical management factors for attaining high yields. Assessing pod yield and plant nutrient demand can provide theoretical guidance for fertilization management of high yielding peanut (Arachis hypogaea L.). Following this rationale, a large dataset was collected from field experiments (n = 313) across the main peanut planting regions of China for a period spanning from 2000 to 2019 to evaluate nutrient uptake behavior of peanut under current optimum fertilization management. Across the entire dataset, the results showed that average peanut pod yield and harvest index (HI) were 4.5 Mg ha−1 and .54, respectively. The average peanut nitrogen (N), phosphorus (P), and potassium (K) requirements were of 48, 7.1, and 21 kg Mg−1 pod yield, respectively. Across five ranges of pod yields (&lt;3, 3–4, 4–5, 5–6, and &gt;6 Mg ha−1), both nutrient uptake and HI increased with increasing pod yield. The N and K requirements (kg Mg−1) decreased with increasing pod yield, respectively, mainly due to reductions in pod N and K concentrations. The P requirement increased with yield, attributed to an increase in straw P concentration as P luxury uptake occurs under high pod yield.

Reduced N‐Limitation and Increased In‐Stream Productivity of Autotrophic Biofilms 5 and 15 Years After Severe Wildfire

AbstractThe ecosystem services provided by forests are under threat as wildfire frequency and severity increase throughout the western US. Severe wildfire can change physical environments and biogeochemical processes in watersheds with lasting effects on watershed nutrient cycling. For example, nitrate‐nitrogen (NO3‐N) export often increases following wildfire and can remain elevated for decades in severely burned watersheds. In this study, we investigated the effects of wildfire on stream biotic processing and watershed nutrient balance following two wildfires that burned along the Colorado Front Range. We evaluated stream water chemistry, nutrient limitation, benthic biomass, and stream metabolism along stream reaches within three burned and three unburned watersheds from July 26 to August 16, 2017. Although the two high‐severity wildfires occurred 5 and 15 years prior to the study, the streams draining burned watersheds still had 23‐times higher NO3‐N concentrations than unburned watersheds, a trend that is consistent across seasons and throughout the 15‐year post‐fire record. Autotrophic nitrogen (N) limitation was reduced in the nitrate‐rich burned streams. Consequently, autotrophic biomass and primary productivity were 2.5 and 20‐times greater, respectively, in burned relative to unburned streams. Together, these data suggest that N supply from burned uplands exceeded the increase in stream N demand and was the primary cause of chronic, elevated NO3‐N export from these severely burned watersheds. Accordingly, aquatic ecosystems within or downstream of burned watersheds may be susceptible to eutrophication and harmful algal blooms until vegetation recovery and plant nutrient demand reduce N supply to streams.

Life Cycle Assessment of Total Fatty Acid (TFA) Production from Microalgae Nannochloropsis oceanica at Different Sites and Under Different Sustainability Scenarios

The environmental sustainability of the microalgae Nannochloropsis oceanica cultivation for total fatty acid (TFA) production was analyzed using life cycle assessment (LCA). Pilot data provided by the plant operator from cultivation in Italy using Green Wall Panel (GWP®) photobioreactors were upscaled to a 20-ha production process, and an LCA was conducted and assessed for the Italian regions of Tuscany and Sicily. Two additional scenarios were modelled to analyze the influence of more sustainable framework conditions, respectively nutrient recycling and renewable energy supply. The results show that environmental impacts per functional unit are around 15% less at the site with optimal growth conditions. Between 60 and 80% of the impacts are due to the energy demand during plant operation, infrastructure, and nutrient demand. Nutrient recycling and the gain of an energy credit from the separated biocrude with the hydrothermal liquefaction (HTL) process reduce the environmental impacts in all six International Reference Life Cycle Data System (ILCD) impact categories by an average of 11% compared to a scenario without nutrient recycling. The additional consideration of a renewable energy supply allows for an average reduction of 36% and together with the nutrient recycling of an average of 45% for the global warming potential (GWP) and most of the other impact categories.

Smart fertilizers: What should we mean and where should we go?

The current agricultural system faces several challenges, the most important being the ability to feed the increasing world population and mitigate climate change. In this context, the improvement of fertilizers’ agronomic efficiency while reducing their cost and environmental impact is one of the biggest tasks. Available literature shows that many efforts have been made to develop innovative fertilizers defined as ‘smart fertilizers’, for which, different interpretations and definitions have been used. This paper aims to define, classify, and describe the new frontier of the so-called smart fertilizers with a particular focus on field-scale studies on herbaceous species. Most of the analysed papers associate the ‘smart’ concept to the controlled and/or slow release of nutrients, using both terms as synonymous. Some others broadened the concept, including the controlled release of nutrients to reduce the environmental impact. Based on our critical analysis of the available literature, we conclude that a fertilizer can be considered ‘smart’ when applied to the soil, it allows control over the rate, timing, and duration of nutrients release. Our new definition is: ‘Smart fertilizer is any single or composed (sub)nanomaterial, multi-component, and/or bioformulation containing one or more nutrients that, through physical, chemical, and/or biological processes, can adapt the timing of nutrient release to the plant nutrient demand, enhancing the agronomic yields and reducing the environmental impact at sustainable costs when compared to conventional fertilizers’. Highlights - A smart fertilizer allows to control the rate, timing and duration of nutrients release. - Nanofertilizers are powder or liquid formulations which involve the synthesis, design and use of materials at the nanoscale level. - Composite fertilizers are formulations containing nutrients mixed or coated with one or more materials that exploit synergy among materials. - Bioformulations are fertilizers containing active or dormant microorganisms capable to trigger physiological growth responses in plants. - Limited information is available for smart fertilizers on herbaceous crops in open field conditions.

Decay Kinetics of Enzymes as Influenced by Manuring Under Varying Hydrothermal Regimes in a Wheat–Maize Cropping System of Subtropical Cambisols in India

This study highlighted the impact of different organic manuring on the decay kinetics and temperature sensitivity (Q10) of three enzymes viz. dehydrogenase (DHA), fluorescein diacetate hydrolase (FDA) and β-glucosidase (GLU) under varying hydrothermal regimes in the subtropical Cambisols in India. We hypothesised that along with organics, water content and temperature will also affect enzyme activities. Soil samples were collected from five treatments, viz., control, 100% nitrogen-phosphorus-potassium (NPK), vermicompost, compost and farmyard manure (FYM)–treated plots in an on-going maize-wheat field experiment, and were incubated at 25 and 35 °C temperatures and 0.033 and 0.1 MPa soil water contents. Activities of all enzymes were found higher in organic-treated plots than NPK-treated plots throughout the incubation period due to higher substrates and energy supply. At constant water content, the increased temperature significantly increased the decay rates of all the enzymes owing to dissolution and diffusion of carbon substrates towards active sites of enzymes. However, at a specified temperature, water stress decreased the decay rates in vermicompost- and compost-treated soils but increased in FYM-treated soils, indicating a significant influence of soil amendments on the decay kinetics due to specific microbial adaptation mechanisms and substrate biochemistry of FYM. The Q10 values of DHA and FDA increased by ~ 59 and 46%, respectively but that of GLU decreased by ~ 44% with declining water content due to their capacity to degrade diverse substrates in the soils. FYM application could be beneficial for nutrient mineralisation under adverse conditions to support plant nutrient demand.

Comparative Study on Soil Microbial Biomass in Tarai and Hill Sal (Shorearobusta Gaertn.) Forests of Tropical Region in Eastern Nepal

A comparative study was conducted to investigate the effect of altitudinal variation and seasonality on soil microbial biomass carbon (MB-C), nitrogen (MB-N), and phosphorus (MB-P) between Tarai Sal forest (TSF) and Hill Sal forest (HSF) of the tropical region in eastern Nepal. Soil microbial biomass was estimated by chloroform fumigation - extraction method in summer, rainy and winter seasons in the upper (0-15 cm) soil depth in both forests. Pre-conditioned soil samples were saturated with purified liquid chloroform, represented fumigated sample. Another set of soil samples without using chloroform, represented unfumigated samples and soil biomass was estimated from these samples. MB-C, MB-N, and MB-P were higher by 66%, 31%, and 9%, respectively, in HSF than TSF. Distinct seasonality was observed in soil microbial biomass. It was maximum in summer and minimum in rainy season in both the forest stands. The value decreased from summer to rainy season by 46 to 67% in HSF and by 32 to 80% in TSF. Higher soil microbial biomass in the summer season may be due to its accumulation in soil when the plant growth and nutrient demand are minimal. Analysis of variance suggested that MB-C, MB-N, and MB-P were significantly different for both sites and seasons (P &lt; 0.001). Soil organic carbon, TN, and TP were positively correlated with MB-C, MB-N, and MB-P in both the forests. In conclusion, the higher value of soil microbial biomass in HSF may be due to the higher concentration of soil organic matter and decreasing turnover rate of microbial biomass due to higher altitude. On the other hand, the lower value of microbial biomass at TSF may indicate its fast turnover rate due to lowland tropics to enhance the nutrient cycling process.

Water and Fertilizer Use Efficiency in Subirrigated Containerized Tomato

Greenhouse cultivation is highly efficient in the use of water and fertilizers. However, due to intensive production, the greenhouse industry applies ample amounts of water and fertilizers. An alternative to minimize water and nutrient loss is zero-leaching systems, such as closed-loop subirrigation. The objective of the present study was to compare the water and fertilizer use efficiency in containerized tomato plants grown in a subirrigation system and a drip irrigation system. Subirrigated plants exhibited lower biomass than drip-irrigated plants. However, the amount of nutrient solution required to restore evapotranspirated water was lower in subirrigation. The yield was marginally decreased in subirrigated plants compared to drip-irrigated plants. The amount of nutrient solution required to produce 1 kg of fresh tomatoes was 22 L in subirrigation, whereas in drip irrigation, plants demanded 41 L. The total nitrogen applied through the nutrient solution was 75% lower in subirrigation than in drip irrigation, while the phosphorus, potassium, calcium and magnesium applied was 66%, 59%, 70% and 74% lower, respectively. We concluded that the subirrigation system proved to be more water- and nutrient-efficient than the drip irrigation system due to the zero leaching of the nutrient solution, the lower number of irrigation events required and the lower nutrient demand of plants.

Mineral nutrients needs of cucumber and its yield in protected winter cultivation, with HPS and LED supplementary lighting

The objective of the study was to evaluate yield, mineral nutrients uptake and nutrient demands of cucumber plants in winter cultivation with HPS and LED supplementary lighting. The experiment was carried out in the three variants: 1) HPS - top light only; 2) HPS + LED - top light + 2 lines of LED inter-row light; 3) LED + LED - top LED + 2-line LED inter-row light. In these variants the same PAR intensity level, of about 320 μmol m−2 s−1 (PPFD), was provided. Midi-cucumber parthenocarpic cultivar ‘Svyatogor’ F1, of high shade tolerance and 18–22 cm fruit lenght, was grown for 17 weeks during winter, in mineral-rock slabs. The plants were trained on a single stem up a string, according to the ‘high wire system’ method. Number and weight of every-day harvested fruit were determined. On the basis of monitoring, content of macro- and micro-elements in drip and drain solutions that was undertaken during every two-week period and constant monitoring of total daily drip irrigation quantity with nutrient solution per one plant, as well as total daily drain of the nutrient solution, the daily uptake of nutrient solutions and nutrients per one plant was calculated. The nutrient status of the plants was determined by leaf samples analysis performed for the younger, upper 3rd–5th leaves, as well as for the older, 10th–12th, lower leaves. Cucumber plants were characterized by stable yield and showed high fruit yield of very good quality. The highest yield was found for the plants grown with supplementary lighting with LED + LED. Leaves from the plants grown with the standard HPS top lighting showed faster senescence than the leaves of the plants grown with inter-row lighting. This is evidenced by a higher concentration of Ca, Mg, S, Mn and B ions, together with a lower concentration of K ions, in 10th–12th leaves in the plants grown with the standard HPS top lighting, compared with the plants grown with the HPS + LED lighting, as well as with the LED + LED lighting. The plants grown with the inter-row lighting showed a higher nutritional demands than the plants grown with the standard HPS top lighting. Parallelly used LED top lighting resulted in a higher and more stable yield, compared to standard HPS lighting conditions.

Long-term effects of controlled-release potassium chloride on soil available potassium, nutrient absorption and yield of maize plants

Controlled-release potassium chloride (CRK) has been shown to improve potassium (K) use efficiency (KUE) and crop yields. However, its widespread use has limited by its high manufacturing costs. To help address this problem and to find the best techniques for using CRK, we mixed it with traditional potassium chloride (KCl) in 1:1 ratios in a five-year field test to find the resulting KUE, bleeding sap, yields, and economic returns of maize (Zea mays L.). There were six treatments subjected to varying K fertilization: full-dose, traditional KCl; full-dose, CRK; reduced-dose, CRK; full-dose, mixed CRK and traditional KCl; reduced-dose, mixed CRK and traditional KCl; and the control, which had no added K fertilizer. Applying high dose, mixed CRK and traditional KCl and high dose, CRK to maize significantly increased grain yields 14.0% and 7.2%, respectively, compared with the traditional KCl treatment during 2014–2018. When the K was provided at the low rate (reduced by one-third), the low dose, mixed CRK and traditional KCl and low dose, CRK treatments led to the same yields as the traditional KCl treatment. However, crude starch contents of the mixed CRK and traditional KCl and CRK treatments each were significantly increased compared with the traditional KCl treatment in 2018. Mean KUE increased 30.5%–56.5% for mixed CRK and traditional KCl treatments, compared with traditional KCl during 2016–2018. Mean net profits from the high dose, mixed CRK and traditional KCl treatment significantly increased 18.9%, when K was provided by the lower rate of mixed CRK and traditional KCl led to the same net profit, compared with traditional KCl treatment from the 2016–2018 years. During the milky maturity stage of maize plants, bleeding sap in the high dose, mixed CRK and traditional KCl treatment were 47.5% and 23.4% lower than from the traditional KCl and high dose, CRK treatments, respectively. Meanwhile, the high dose, mixed CRK and traditional KCl and high dose, CRK treatments significantly increased soil available K levels compared with the traditional KCl treatment, hence, meeting the nutrient demands of maize plants during their later growth stages. The exchangeable Ca2+ levels within the soil near the surface was also maximized by the long-term application of mixed CRK and traditional KCl treatments. Hence, applying mixed CRK and traditional KCl fertilizers were recommended for maintaining continued nutrient absorption soil fertility, sustainable increases in crops yields and for maximizing net profits.

Differentiated response of plant and microbial C: N: P stoichiometries to phosphorus application in phosphorus-limited paddy soil

Phosphorus (P) application is an indispensable practice in agricultural crop production. However, the effect of P on crop and microbial biomass stoichiometries as well as its role in soil nutrient dynamics, remain poorly understood, thereby limiting our ability to predict the ecological consequences of agricultural practices. Herein, we conducted a P application experiment in a subtropical P-limited paddy soil to examine the effect of P addition on soil nutrient availability as well as on rice and the microbial C:N:P stoichiometries. The results showed that soil dissolved organic carbon (DOC) and available P content were simultaneously affected by P application and rice growth stage. Further, addition of P served to increase rice C and N content while decreasing the C: P and N: P stoichiometric ratios, indicating that P input contributed to rice growth and N absorption. Marked increases in soil microbial biomass carbon (MBC) and phosphorus (MBP) were also observed in soil treated with P. Moreover, the microbial C:N:P stoichiometry increased with rice growth stage, suggesting that changes in microbial and plant nutrient demand throughout the rice plant growth cycle causes competition between microorganisms and plants for N and P. Pearson's correlation and redundancy analyses revealed that available nutrients of soil were intercorrelated and regulated the patterns of rice and microbial C:N:P stoichiometries. In conclusions, P enrichment altered soil nutrient composition, microbial nutrient mining strategies, and rice C:N:P stoichiometry, thereby contributing to rice growth and improving crop yield.

Characteristics of Yield and Harvest Index, and Evaluation of Balanced Nutrient Uptake of Soybean in Northeast China

The balance between fertilizer application and plant nutrient demand is essential for ensuring agricultural production because it is effective to prevent nutrient deficiency and excess, especially for soybean. This study used data from 29 sites of field experiments carried out in the soybean planting area of Liaoning province, China in 2011 to 2013. We (i) study the characteristics of yield, nutrient concentration, and harvest index to (ii) valuate the balanced nutrient uptake at different potential yield levels for soybean. The grain yield ranged from 804 to 4484 kg/ha, and average N, P, and K concentrations in grains were 45.7, 5.0, and 10.1 g/kg, respectively, while those in straw were 14.1, 1.8, and 6.7 g/kg, respectively. Average harvest index values of N, P, and K were 0.69, 0.65, and 0.52 kg/kg, respectively, while approximately 69% N and 65% P of the plant were stored in soybean grain, and 48% K was stored in straw. The two boundary lines of the QUEFTS (quantitative evaluation of the fertility of tropical soils) model were aN = 10.5, dN = 20.6, aP = 65.6, dP = 289.6, aK = 30.4, and dK = 162.7 as model parameters. The QUEFTS model estimated the balanced nutrient uptake with yield targets increased following a linear–parabolic–plateau curve. A continual linear increase in grain yield with 65.5 kg N, 7.0 kg P, and 13.9 kg K was required to produce 1000 kg grain, until the yield target reached approximately 60–70% of the potential yield, and the corresponding ratio of N, P, and K was 9.35:1:1.8. Results could be used to estimate balanced nutrient uptake to prevent excessive fertilizer being applied and reduce environment risk for ensuring sustainable agricultural development.

Effect of elevated carbon dioxide on growth, nutrient partitioning, and uptake of major nutrients by soybean under varied nitrogen application levels

AbstractRising carbon dioxide (CO2) concentration causes fertilization effects resulting in enhanced crop biomass and yields and thus likely enhances nutrient demand of plants. Hence, this field study was carried out to investigate the effects of elevated CO2 and N on biomass yield, nutrient partitioning, and uptake of major nutrients by soybean (Glycine max L.) using open‐top chambers (OTCs) of 4 m × 4 m size. Soybean was grown in OTCs under two CO2 [ambient and elevated (535 ± 36.9 mg L−1)] and four N levels during July to October 2016. The four N levels were N0, N50, N100, and N150 referring to 0, 50, 100, and 150% recommended dose of N. Both CO2 and N significantly affected biomass and grain yield, though the interaction was non‐significant. CO2 enrichment produced 30–65% higher biomass and 26–59% higher grain yield under various N levels. As compared to the optimum N application (N100), the CO2‐mediated increment in biomass yield decreased with either lower or higher N application, with the response being lowest at N150. As compared to ambient concentration, elevated CO2 resulted in significant reduction of seed P concentration at all N application levels but at N150, an opposite trend was observed. The decrease in seed P was maximum at N0 and N50 (7–9%) and by 3% at N100, whereas there was a gain of 7.5% at N150. The seed N and K concentrations were not affected either by CO2 or N application. Total N, P, and K uptake at harvest were significantly affected by CO2 and N, but not by CO2 × N interaction. Elevated CO2 resulted higher uptake of N by 18–61%, P by 23–62%, and K by 22–62% under various N treatments.

Assessing Nitrogen Limitation in Inoculated Soybean in Southern Brazil

Core Ideas Soybean yield did not respond to low starter fertilizer N rates in soils with high organic matter content. Nitrogen limitation tended to be greater in low compared with medium‐high yield levels. Nitrogen limitation is potentially related to lower contribution of N coming from biological nitrogen fixation (BNF) and mineralization. Overcoming potential N limitation in soybean [Glycine max (L.) Merr.] is a critical factor for sustaining plant nutrient demand and improving productivity. Following this rationale, a set of studies were executed in southern Brazil with the goals of quantifying yield response to early season fertilizer N rates (up to 40 kg ha−1), “starter N fertilization,” and to understand if soybean seed yields are limited by N (testing a non‐limiting N scenario) when grown in soils with medium to high organic matter content. The main key outcomes of this research were: (i) starter N fertilization did not increase yields compared with non‐fertilized soybean, potentially highlighting the absence of an early season N limitation; and (ii) N limitation was observed when soybean yields were compared with non‐limiting N scenario and it tended to be greater in low compared with medium‐high yield levels, potentially connected with co‐limitations on both N sources (N2 fixation and mineralization) to satisfy soybean N demand. Producing soybean in a sustainable manner implies focus on production practices to conserve and, potentially, to increase soil organic matter on a long‐term basis. Furthermore, it requires enhancing the biological N2 fixation process for satisfying the large plant N demand for achieving high soybean yields. Future research should be focused on understanding factors governing biological N2 fixation and N mineralization processes in soybean grown in soils with medium‐high organic matter content.

Global changes alter plant multi-element stoichiometric coupling.

Plant stoichiometric coupling among all elements is fundamental to maintaining growth-related ecosystem functions. However, our understanding of nutrient balance in response toglobal changes remains greatly limited to plant carbon : nitrogen : phosphorus (C : N : P) coupling. Here we evaluated nine element stoichiometric variations with one meta-analysis of 112 global change experiments conducted across global terrestrial ecosystems and one synthesis over 1900 species observations along natural environment gradients across China. We found that experimentally increased soil N and P respectively enhanced plant N:potassium (K), N:calcium (Ca) and N:magnesium (Mg), and P:K, P:Ca and P:Mg, and natural increases in soil N and P resulted in qualitatively similar responses. The ratios of N and P to base cations decreased both under experimental warming and with naturally increasing temperature. With decreasing precipitation, these ratios increased in experiments but decreased under natural environments. Based on these results, we propose a new stoichiometric framework in which all plant element contents and their coupling are not only affected by soil nutrient availability, but also by plant nutrient demand to maintain diverse functions under climate change. This study offers new insights into understanding plant stoichiometric variations across a full set of mineral elements under global changes.