Reduce Fertilizer Use Research Articles

Plant Growth-Promoting Soil Bacteria: Nitrogen Fixation, Phosphate Solubilization, Siderophore Production, and Other Biological Activities.

This review covers the literature data on plant growth-promoting bacteria in soil, which can fix atmospheric nitrogen, solubilize phosphates, produce and secrete siderophores, and may exhibit several different behaviors simultaneously. We discuss perspectives for creating bacterial consortia and introducing them into the soil to increase crop productivity in agrosystems. The application of rhizosphere bacteria-which are capable of fixing nitrogen, solubilizing organic and inorganic phosphates, and secreting siderophores, as well as their consortia-has been demonstrated to meet the objectives of sustainable agriculture, such as increasing soil fertility and crop yields. The combining of plant growth-promoting bacteria with mineral fertilizers is a crucial trend that allows for a reduction in fertilizer use and is beneficial for crop production.

Long-term control of non-point source pollution by adjusting human environmental behavior in watershed-a new perspective.

The control of non-point source pollution is a major scientific and technological problem faced by mankind. We proposed a new approach to eliminate non-point source pollution, focusing on adjusting human environmental behavior. The implementation procedures are as follows: (1) Investigate the intention of pollution discharge behavior through interviews and questionnaires. (2) Carry out targeted intervention within the framework of social psychology to transform it into an environmentally friendly mode. (3) Calculate the amounts of pollutants produced and discharged before and after the intervention, and then evaluate the effect of the intervention on reducing pollution. (4) Based on successful interventions, a scheme can be developed to curb non-point source pollution. Aiming to reduce fertilizer use, a case study was conducted in Hetao Irrigation District, one of the three major Irrigation districts in China. The results showed that the interventions indirectly affected intention through attitude, subjective norm, and perceived behavioral control. The structural equation model explained 76.0% of the total variance of farmers' intention to reduce fertilizer application (SMC = 0.760), indicating effective intervention. Subsequently, a program to curb non-point source pollution was developed. This study can provide a key scientific and applied reference for the long-term control of non-point source pollution in watershed.

Percentage of Flower and Fruit Fall, and Red Chili Production in Ultisol Applied Biostimulants and Inorganic Fertilizers

Ultisol has main problem of low nutrient availability causing a high percentage of flowers and fruit fall and reducing red chili production. This study aimed to find out effectiveness of biostimulants in reducing percentage of flower and fruit fall, use of inorganic fertilizer doses, and their role in increasing production red pepper in Ultisol. The method used experimental and randomized block design with 9 treatments. The treatment used application of flush biostimulants and without watering into soil with various doses inorganic fertilizers. The fertilizer doses were 100%, 75%, and 50% based on fertilization recommendations. The study results showed that application of biostimulants combined with inorganic fertilizers of various doses had a significant effect on fruit weight/plant and red pepper production, but had an insignificant effect on the percentage of flowers and fruits, as well as number of fruits/plant. Application of biostimulants and various doses of inorganic fertilizers tended to increase fall of flowers, number of fruits/plant, and the percentage of fruit fall. Biostimulants combined with inorganic fertilizers were able to reduce fertilizer use as much as 50%. Production of red pepper with application of biostimulants and 50% of inorganic fertilizers reached 5.36 tons/ha. The results of the economic feasibility analysis of red chili peppers were 1.69 R/C and 0.69 B/C ratio, meaning that the cultivation of red chili with application of biostimulants was profitable and worthy of development. So, application of biostimulants is able to reduce fertilizers by 50% and increase production of red peppers.

Hydro-bio-geo-socio-chemical interactions and the sustainability of residential landscapes.

Residential landscapes are essential to the sustainability of large areas of the United States. However, spatial and temporal variation across multiple domains complicates developing policies to balance these systems' environmental, economic, and equity dimensions. We conducted multidisciplinary studies in the Baltimore, MD, USA, metropolitan area to identify locations (hotspots) or times (hot moments) with a disproportionate influence on nitrogen export, a widespread environmental concern. Results showed high variation in the inherent vulnerability/sensitivity of individual parcels to cause environmental damage and in the knowledge and practices of individual managers. To the extent that hotspots are the result of management choices by homeowners, there are straightforward approaches to improve outcomes, e.g. fertilizer restrictions and incentives to reduce fertilizer use. If, however, hotspots arise from the configuration and inherent characteristics of parcels and neighborhoods, efforts to improve outcomes may involve more intensive and complex interventions, such as conversion to alternative ecosystem types.

Greenhouse gas emissions along the value chain in palm oil producing systems: A case study of Cameroon

The agricultural sector is the second most emitting sector globally, contributing about 18% of total global greenhouse gas (GHG) emissions. Multipurpose high in-demand commodities like palm oil contribute significantly to these emissions. The Roundtable on Sustainable Palm Oil (RSPO) with an objective to make the palm oil sector sustainable, developed a new tool to quantify carbon emissions from palm oil mills. The PalmGHG tool has been used in Southeast Asia to measure carbon emissions from palm oil production and for palm oil certification. However, no studies have used the tool to evaluate GHG emissions from palm oil mills in sub-Saharan Africa, which contributes about 24% of global palm oil production and is home to one of the last remaining primary forests in the world. In this study, we quantify GHG emissions along the crude palm oil (CPO) life cycle in a growing palm oil producing region in Cameroon. We use the RSPO PalmGHG accounting tool, to identify sources of CO2 emissions and quantify them in tons of CO2 equivalent. Six mills across the South West and Center regions of Cameroon were sampled. We found that the sources of carbon emissions from our sampled mills in decreasing order of magnitude are land conversion (78%), palm oil mill effluent (21%), fertilizer use (0.9%), mill fuel combustion (0.1%) and grid electricity utilization (0.04%). The average GHG emissions per ton of crude palm oil produced were exceptionally high at 22.3 tCO2e compared to other palm oil producing regions in the world such as Indonesia with only 1.6 tCO2e/ton of CPO. In addition, we found that planting oil palm on previously logged land instead of primary forest conversion could prevent field emissions by up to about 89% and by up to about 69% for replanting old oil palm stands. Intensification measures like improving palm oil mill extraction rates and improving yields would drastically reduce emissions per ton of crude palm oil produced. Although land conversion associated with deforestation remains the major source of palm oil GHG emissions, farm and mill practices such as reduction in fertilizer use, biogas capture and use of clean energy could help reduce emissions in the long run.

A global meta-analysis on surface and drip fertigation for annual crops under different fertilization levels

So far, many studies have examined the effects of surface (FF) and drip (DF) fertigation compared to surface (FC) and drip (DC) irrigation along with fertilization at different levels of fertilizer on crop yield indices, nutrient use efficiency (NUE), and irrigation water productivity (WP); however, each of them have been conducted under different conditions. Because of the scattered results and the lack of a general conclusion from the published results, conducting a meta-analysis as a structured method for arriving at an overall conclusion regarding the effects of different fertigation methods on different indices is essential. This study was conducted to examine the effects of surface and drip fertigation methods and different fertilizer application levels on crop yield, NUE, and WP. To this end, eight global databases of publications (e.g., Scopus and Web of Science) were reviewed. A total of 5494 studies were extracted, of which 32 studies met the entry criteria for the meta-analysis. To assess the effects of fertigation, each study was used to extract the effect sizes for each index. A total of 119 effect sizes were obtained for crop yield, 85 for NUE, and 84 for WP. The meta-analysis results showed that surface and drip fertigation methods increased the average yield by 20%. NUE and WP on an average increased by 26% and 51%, respectively. Based on the reported results, the optimal fertilizer application level is 75% of the recommended dose, which can reduce fertilizer use by 25% without significantly reducing the yield. In general, fertigation can be recommended as an effective operation for improving the proposed indices examined in both surface and drip fertigation methods.

Reduced fertilizer use – increased risk? Qualitative and quantitative analysis of economic risks and risk perceptions of German vegetable growers

Reduced fertilizer use – increased risk? Qualitative and quantitative analysis of economic risks and risk perceptions of German vegetable growers

Achieving Sustainable Earth Futures in the Anthropocene by Including Local Communities in Critical Zone Science

AbstractCritical Zone Science (CZS) explores the deep evolution of landscapes from the base of the groundwater or the saprolite‐rock interface to the top of vegetation, the zone that supports all terrestrial life. Here we propose a framework for CZS to evolve further as a discipline, building on 1st generation CZOs in natural systems and 2nd generation CZOs in human‐modified systems, to incorporate human behaviour for more holistic understanding in a 3rd generation of CZOs. This concept was tested in the China‐UK CZO programme (2016–2020) that established four CZOs across China on different lithologies. Beyond conventional CZO insights into soil resources, biogeochemical cycling and hydrology across scales, surveys of farmers and local government officials led to insights into human‐environment interactions and key pressures affecting the socio‐economic livelihoods of local farmers. These learnings combined with the CZS data identified knowledge exchange (KE) opportunities to unravel diverse factors within the Land‐Water‐Food Nexus, that could directly improve local livelihoods and environmental conditions, such as reduction in fertilizer use, contributing toward Sustainable Development Goals (SDGs) and environmental policies. Through two‐way local KE, the local cultural context and socio‐economic considerations were more readily apparent alongside the environmental rationale for policy and local action to improve the sustainability of farming practices. Seeking solutions to understand and remediate CZ degradation caused by human‐decision making requires the co‐design of CZS that foregrounds human behavior and the opinions of those living in human modified CZOs. We show how a new transdisciplinary CZO approach for sustainable Earth futures can improve alignment of research with the practical needs of communities in stressed environments and their governments, supporting social‐ecological and planetary health research agendas and improving capacity to achieve SDGs.

Extreme weather and agricultural management decisions among smallholder farmers in rural Thailand and Vietnam

AbstractIn this article, we explore whether and to what extent smallholder farmers in Northeastern Thailand and Central Vietnam adjust their farm‐level management strategies in response to droughts. We hereby consider adjustments in flexible adaptive strategies including water management, fertilizer and pesticide application, labor, and machine use in response to a contemporaneous drought, and adjustments in crop diversification and investments in response to a previous year drought. To that end, we combine longitudinal household data from the two regions from 2007 to 2017 with monthly high‐resolution rainfall and temperature data to characterize droughts at the subdistrict level. We find that Thai farmers scale down input costs in terms of fertilizer and hired labor and outsource tasks to service providers with equipment such as a combine, especially when exposed to extreme droughts. Their diversification and investment response seems, however, muted. While Vietnamese farmers are also reducing fertilizer use, they are expanding both the number of hired laborers and rented machinery services. They are also diversifying their cropping portfolio and investing in agricultural equipment.

Screening Digitaria eriantha cv. Suvernola Endophytic Bacteria for Maize Growth Promotion.

The search for sustainable agriculture has increased interest in using endophytic bacteria to reduce fertilizer use and increase stress resilience. Stress-adapted plants are a potential source of these bacteria. Some species of these plants have not yet been evaluated for this, such as pangolão grass, from which we considered endophytic bacteria as potential plant growth promoters. Bacteria from the root, colm, leaves, and rhizospheric soil were isolated, and 132 strains were evaluated for their in vitro biological nitrogen fixation, IAA and siderophores production, and phosphate solubilization. Each mechanism was also assessed under low N availability, water stress, and low-solubility Fe and P sources in maize greenhouse experiments. All strains synthesized IAA; 63 grew on N-free media, 114 synthesized siderophores, and 46 solubilized P, while 19 presented all four mechanisms. Overall, these strains had better performance than commercial inoculant in all experiments. Still, in vitro responses were not good predictors of in vivo effects, which indicates that the former should not be used for strain selection, since this could lead to not testing strains with good plant growth promotion potential. Their heterologous growth promotion in maize reinforces the potential of stress-adapted plant species as potential sources of strains for inoculants.

Evaluation of Methane Emission Reduction Potential of Water Management and Chinese Milk Vetch Planting in Hunan Paddy Rice Fields

In order to explore the methane reduction potential with two scenarios of water management and Chinese Milk Vetch return, we calculated the methane emissions of Hunan Province rice fields in 2019 using the SECTOR tool based on Excel and released by the International Rice Research Institute. Thus, we preliminarily established an agricultural carbon emissions monitoring, reporting, and verification (MRV) system. The results showed that: (1) There was significant spatial variation in methane emissions in Hunan rice fields, with higher emissions in both the south and north and lower emissions in the east and west. Late rice was the main contributor to methane emissions, and the cities of Changde, Hengyang, Yueyang, and Shaoyang were high-emission areas due to differences in rice planting types and areas. Compared with flooding (1275.75 Gg), optimized water management measures (mid-drainage and AWD irrigation) reduced methane emissions by 29~45% (905.79 and 701.66 Gg, respectively). (2) Under the same nitrogen input conditions, compared with a solely straw return (375.24 Gg), combining green manure with straw return could partially reduce methane emissions from Hunan super hybrid rice (327.63 Gg). Compared with the control fertilizers (404.28 Gg), the reduction rates of winter-planted Chinese Milk Vetch, the return of rice straw, and the incorporation of both Chinese Milk Vetch and straw were 7.19%, 13.01%, and 18.96%, respectively. Based on scientific accounting tools, a preliminary MRV system for rice field carbon emissions was established. Under the national demand for reducing fertilizer use and increasing efficiency, equal nitrogen organic amendments could effectively contribute to the development of green, low-carbon, and high-quality agriculture.

Ökoszisztéma-szolgáltatások javítása terménydiverzifikációval a Kiskunsági-homokháton – különös tekintettel a szélerózió elkerülésére

The destructive environmental impacts of large-scale agriculture are further aggravated by drier climate in the Danube-Tisza sand region, where soil fertility is low, water retention is very limited and groundwater levels are steadily dropping. The prevention of wind erosion is a central task in raising the level of ecosystem services. Among other related services the enrichment of the blown-sand soil with organic matter (enhancing carbon sequestration), the improvement of soil structure and water retention capacity and achieving higher soil biodiversity are major objectives. The international Diverfarming project (2017–2022) within the EU Horizon 2020 Program focussed on the impacts of crop diversification and low-input practices. In the experiments intercropping with different annual crops was investigated and its influences on some provisioning and regulating ecosystem services were evaluated in an asparagus field in Jakabszállás. Although the findings point out the decisive role of soil moisture conditions, the positive impacts of diversification are also remarkable. The local farmer agrees that crop diversification improves soil quality, but he denies that it would directly influence farm competitiveness, which is primarily dependent on the costs of fertilization, plant protection and labour. Further analyses are needed to prove the benefits of diversification through enriching soil microbial life and the possible reduction of fertilizer use while water demand is kept at a low level and the same crop quality is ensured.

Influence of Climate Change on Carbon Emissions during Grain Production and Its Mechanism

Abnormal climatic changes and related disasters are increasing in prevalence, with many negative impacts on ecosystems and agricultural production. The area of land in China is vast, including diverse terrain and climate types, and a substantial area is used to grow food crops. Therefore, climate change is having a huge impact on China’s grain production. Currently, the relationship between climate change and carbon emissions during grain production and the underlying mechanism have not been fully clarified. Therefore, this study used an ordinary least squares regression (OLS) model and the system generalized method of moments (SYS-GMM) to examine the influence of climatic change and carbon emissions during grain production, and we constructed mediation effect models to explore the mechanism of influence between them by utilizing panel data in China from 2000 to 2020. In addition, we also examined the adjustment effect of green technology progress and farmland scale. The study found that China’s carbon emissions during grain production increased from 2000 to 2015 and then presented a decreasing trend after 2015. We found that the annual average temperature has a prominent positive effect on carbon emissions during grain production, while the annual average rainfall has a negative effect. Among them, temperature changes mainly lead to the increase in carbon emissions during grain production through the increase in “fertilizer use” and “multiple cropping index”, but the mechanism of rainfall changes’ impact on carbon emissions during grain production is still unclear. In addition, green technology progress and farmland scale play adjustment roles in the impact of climate change on carbon emissions during grain production, and they could significantly suppress carbon emissions. On the basis of the conclusions in this paper, we propose that strengthening climate change adaptation is an important prerequisite for reducing carbon emissions during grain production. Furthermore, China should continue to reduce fertilizer use, facilitate the application of agriculture green technology, and expand the scale of farmland to achieve agricultural carbon emission reduction.

Designing Iowa Agricultural Landscapes to Improve Environmental Co-Benefits of Bioenergy Production

Cellulosic bioenergy feedstocks are needed to improve carbon (C) management while provisioning biomass for bioproducts and biofuel. The transition to increased cellulosic biomass production can be guided by land management plans designed to improve economic, environmental, and ecological performance. We constructed a sustainability model to compare landscape designs for biofuel production from corn (Zea mays L.) stover and switchgrass (Panicum virgatum L.) in central Iowa, USA. We used the model to compare environmental and socioeconomic outcomes associated with four landscape management strategies, with and without cellulosic biomass markets. We evaluated (1) a fuelshed area containing over 1.2 million ha (3 million acres) of corn and soybean (Glycine max (L.) Merr.) within 80 km (50 miles) of a commercial-scale cellulosic biorefinery in Nevada, Iowa, and (2) the South Fork watershed containing over 72,000 ha (178,000 acres) of these row crops within eight north central Iowa HUC-12 (hydrologic unit code) watersheds. At both landscape scales, we found that it is possible to achieve multiple environmental and socioeconomic benefits concomitantly with cellulosic biomass production by strategically collecting corn stover and converting the 10% of the lowest-profitability row crop land to perennial switchgrass. Potential benefits from landscape design include increased biodiversity, soil and water quality improvements, increased soil carbon sequestration for climate change mitigation, and reduced fertilizer use and cost. Our model results showed that increasing benefits can accrue when complementary conservation practices (e.g., reduced tillage, use of a rye cover crop) are combined and integrated throughout a fuelshed or watershed area. We conclude that ecologically based landscape designs offer valuable insights about costs and benefits of land management alternatives, with relevance for achieving stakeholder goals.

Biochar-extracted liquor stimulates nitrogen related gene expression on improving nitrogen utilization in rice seedling.

Biochar has been shown to be an effective soil amendment for promoting plant growth and improving nitrogen (N) utilization. However, the physiological and molecular mechanisms behind such stimulation remain unclear. In this study, we investigated whether biochar-extracted liquor including 21 organic molecules enhance the nitrogen use efficiency (NUE) of rice plants using two N forms (NH4 +-N and NO3 --N). A hydroponic experiment was conducted, and biochar-extracted liquor (between 1 and 3% by weight) was applied to rice seedlings. The results showed that biochar-extracted liquor significantly improved phenotypic and physiological traits of rice seedlings. Biochar-extracted liquor dramatically upregulated the expression of rice N metabolism-related genes such as OsAMT1.1, OsGS1.1, and OsGS2. Rice seedlings preferentially absorbed NH4 +-N than NO3 --N (p < 0.05), and the uptake of NH4 +-N by rice seedlings was significantly increased by 33.60% under the treatment of biochar-extracted liquor. The results from molecular docking showed that OsAMT1.1protein can theoretically interact with 2-Acetyl-5-methylfuran, trans-2,4-Dimethylthiane, S, S-dioxide, 2,2-Diethylacetamide, and 1,2-Dimethylaziridine in the biochar-extracted liquor. These four organic compounds have similar biological function as the OsAMT1.1 protein ligand in driving NH4 +-N uptakes by rice plants. This study highlights the importance of biochar-extracted liquor in promoting plant growth and NUE. The use of low doses of biochar-extracted liquor could be an important way to reduce N input in order to achieve the purpose of reducing fertilizer use and increasing efficiency in agricultural production.

Utilizing waste compost to improve the atmospheric CO2 capturing in the rice-wheat cropping system and energy-cum‑carbon credit auditing for a circular economy

The study aimed to manage industrial wastes and create a module for using compost from waste for crops cultivation to conserve energy, reduce fertilizer use and Greenhouse gas (GHG) emissions, and improve the atmospheric CO2 capturing in agriculture for a green economy. In the main-plot, the experiment's results using NS3 found 50.1 and 41.8 % more grain yield and total carbon dioxide (CO2) sequestration in the wheat-rice cropping sequence, respectively, compared to the NS0. Moreover, the treatment CW + TV in the sub-plot observed 24.0 and 20.3 % higher grain yield and total CO2 sequestration than B + PS. Based on interaction, the NS3× CW + TV resulted in a maximum total CO2 sequestration and C credit of 47.5 Mg ha−1 and US$ 1899 ha−1, respectively. Further, it was 27.9 % lower in carbon footprints (CFs) than NS1 × B + PS. Regarding another parameter, the treatment NS3 observed a 42.4 % more total energy output in the main-plot than that of NS0. Further, in the sub-plot, the treatment CW + TV produced 21.3 % more total energy output than B + PS. Energy use efficiency (EUE) and net energy return in the interaction of NS3× CW + TV were 20.5 and 138.8 % greater than the NS0 × B + PS, respectively. In the main-plot, the treatment NS3 obtained a maximum of 585.0 MJ US$−1 and US$ 0.24 MJ−1 for energy intensity in economic terms (EIET) and eco-efficiency index in terms of energy (EEIe), respectively. While in the sub-plot, the CW + TV was observed at a maximum of 571.52 MJ US$−1 and US$ 0.23 MJ−1 EIET and EEIe, respectively. The correlation and regression study showed a perfect positive correlation between grain yield and total C output. Moreover, a high positive correlation (0.75 to 1) was found with all other energy parameters for grain energy use efficiency (GEUE). The variability in the wheat-rice cropping sequence's energy profitability (EPr) was 53.7 % for human energy profitability (HEP). Based on principal component analysis (PCA), the eigenvalues of the first two principal components (PCs) had been greater than two, explaining 78.4 and 13.7 % of the variability. The experiment hypothesis was to develop a reliable technology for safely using industrial waste compost, minimizing energy consumption and CO2 emissions by reducing chemical fertilizer input in agriculture soils.

Atmospheric Reactive Nitrogen Deposition from 2010 to 2021 in Lake Taihu and the Effects on Phytoplankton

The effects of nitrogen deposition reduction on nutrient loading in freshwaters have been widely studied, especially in remote regions. However, understanding of the ecological effects is still rather limited. Herein, we re-estimated nitrogen deposition, both of wet and dry deposition, in Lake Taihu with monthly monitoring data from 2010 to 2021. Our results showed that the atmospheric deposition of reactive nitrogen (namely NH4+ and NO3-) in Lake Taihu was 4.94-11.49 kton/yr, which equaled 13.9%-27.3% of the riverine loading. Dry deposition of NH4+ and NO3- contributed 53.1% of the bulk deposition in Lake Taihu. Ammonium was the main component of both wet and dry deposition, which may have been due to the strong agriculture-related activities around Lake Taihu. Nitrogen deposition explained 24.9% of the variation in phytoplankton community succession from 2010 to 2021 and was the highest among all the environmental factors. Atmospheric deposition offset the effects of external nitrogen reduction during the early years and delayed the emergence of nitrogen-fixing cyanobacterial dominance in Lake Taihu. Our results implied that a decrease in nitrogen deposition due to a reduction in fertilizer use, especially a decrease in NH4+ deposition, could limit diatoms and promote non-nitrogen-fixing cyanobacterial dominance, followed by nitrogen-fixing taxa. This result was also applied to other shallow eutrophic lakes around the middle and lower reaches of the Yangtze River, where significant reduction of fertilizer use recorded during the last decades.

Fertirrigation with nanofiltration retentate from thermomechanical pulp mill effluents

The objective of the present study was to evaluate the potential for using the retentate from nanofiltration (NF) treatment of thermomechanical pulp (TMP) effluent for fertirrigation. Nanofiltration retentates from tertiary effluent treatment from a Brazilian TMP pulp mill were used. Electrical conductivity (EC) and the concentration of both metals (Mn2+, Mg2+, Fe2+, Ca2+, Na+, K+, Cu2+) and chlorides in the NF retentate were evaluated. The sodium (SAR) and potassium (PAR) adsorption ratios were calculated. The risks of increasing the salinity, effects on the infiltration rate, toxicity and excess nutrients were evaluated according to the American and European standards, and application according to crop and soil were analyzed according to the Brazilian standard. The NF retentate is classified as irrigation water Class I for the risks of reduced water infiltration into the soil, availability of nutrients and the concentration of copper and iron, Class II for the risks of toxicity, pH and concentration of manganese and Class III for the risks of salinity and concentrations of TS, TSS and turbidity, according to American and European standards. The salinity content and the physicochemical characteristics classify the effluent NF retentate, according to the Brazilian standard, as fresh water and Class III for irrigation. The NF retentate from thermomechanical pulp mill effluents, according to both the American and the European standards, cannot be used for fertirrigation, as it is classified as Class III. However, the Brazilian standard allows its use for the irrigation of any tree species, cereals and forages and as a source of nutrients to reduce fertilizer use. The retentate can be applied to highly salt-tolerant plant crops such as Eucalyptus globulus, Eucalyptus camaldulensis and sugarcane, and may be used in soil with a basic pH and high permeability.

Identifying Lettuce Accessions for Efficient Use of Phosphorus in Hydroponics

Lettuce (Lactuca sativa L.) is the most common leafy vegetable produced hydroponically in the United States. Although hydroponic systems are advantageous due to lower pest and disease pressure, and reduced water and nutrient requirements, the increasing prices of fertilizers, including phosphorus (P), still influences the profitability of hydroponic production of lettuce. Characterizing lettuce germplasm capable of producing high yield using less P inputs may help reduce fertilizer use, production costs, and P loads in wastewater. In this study, 12 lettuce accessions were grown in four experiments in a nutrient film technique system. In the first two experiments, the treatments consisted of two P concentrations (3.1 and 31 mg·L−1). Lettuce cultivated with 3.1 mg·L−1 of P had variable shoot and root biomass, root–shoot ratio, P uptake efficiency, and P utilization efficiency, indicating the existence of genetic variation. Five accessions (‘Little Gem’, 60183, ‘Valmaine’, BG19-0539, and ‘Green Lightning’) were considered efficient to P because produced similar shoot biomass with the low and high P treatments. In the third and fourth experiments, the treatments consisted of two P sources (monosodium phosphate (NaH2PO4) and tricalcium phosphate [TCP; Ca3(PO4)2]. Initially, extra 5 mM of calcium (Ca) was added to the TCP solution to reduce the TCP solubility and, hence, P bioavailability to plants. All accessions produced similar shoot and root weight with both treatments, indicating that the TCP treatment did not cause low-P stress to the plants. After, the extra Ca concentration added to TCP was increased to 10 mM, resulting in low-P stress and a significant reduction in shoot weight of all accessions. Despite the severe P stress, ‘Little Gem’ and 60183 were among the accessions with the least shoot weight reduction in the TCP treatment. Variability was observed in root biomass root–shoot ratio among accessions under the TCP treatment, suggesting that lettuce accessions responded differently to P stress conditions. The genetic variation for P use efficiency (PUE) and PUE-related traits in lettuce grown hydroponically suggests the feasibility of breeding new lettuce cultivars from elite lettuce germplasm adapted to low P availability in hydroponics.

Unraveling seasonal and interannual nutrient variability shows exceptionally high human impact in eutrophic coastal waters

AbstractNutrient import into eutrophic estuarine‐coastal zones is modulated by river discharge and anthropogenic activities (agriculture, industry, sewage, etc.). Comparing anthropogenic vs. hydrological influences on nutrient loading is important for ecosystem managers but has been a long‐standing challenge. As an attempt to fill this gap, a retrospective study was conducted using multiyear (2012–2022) data in one of the most eutrophic coastal seas in China, the Jiangsu coastal waters. Of the two main pollutants on the Jiangsu coast, dissolved inorganic nitrogen (DIN) is extremely overloaded relative to phosphate (PO4). Their spatial distribution shows clear terrestrial sources as concentrations decrease offshore. Although in each survey DIN and PO4 are enriched in low‐salinity waters, their spatially averaged concentrations are out of phase with river discharge on the seasonal and interannual scales. A box model was applied to decompose contributions of river discharge and nutrient import by anthropogenic activities. Results show that the human impacts on the interannual nutrient variability exceed those of hydrological factors on the Jiangsu coast. Anthropogenic nutrient loading decreases during 2012–2020, paralleled with the reduced fertilizer use and other nonpoint sources. Sporadic nutrient fluxes from point sources are likely responsible for the aseasonal nutrient‐rich patches. Our study demonstrates that water quality in the Jiangsu coastal waters is highly affected by anthropogenic activities. Findings in this study have broad implications for local monitoring strategies and restoration efforts and provide insight into assessing human stress from field data in global eutrophic ecosystems.