Intensive Fertilization Research Articles

Nitrogen dynamics in the Critical Zones of China

Nitrogen dynamics at ecosystem levels profoundly impact the Earth’s surface system due to their environmental and ecological significance. Exploring the sources and transformation of nitrogen in various Critical Zones is vital to understanding biogeochemical cycles and sustainable development. This study summarized nitrogen characteristics in soil profiles and nitrogen dynamics in diverse terrestrial ecosystems based on data from typical Critical Zones of China. The results indicated that nitrogen accumulates in the deep soils of cropland ecosystems due to intensive fertilizer applications, which potentially harms soil functions and water quality. Therefore, it is necessary and meaningful to take adequate measures to alleviate nitrogen accumulation in deep soils. Additionally, surplus nitrogen transported into groundwater and riverine systems from soil has emerged as an important issue for environmental management. There are serious nitrogen pollution issues in many river water and groundwater areas, which could be addressed by reducing the fast leaching and considerable nitrogen accumulation in the vadose zone. Systematic and long-term observational studies are needed to achieve the ultimate goal of ecological conservation and high-quality development. Therefore, future research should consider monitoring and evaluating ecosystems based on the long-term Critical Zone Observatories networks to advance appropriate environmental management strategies that adapt to nature’s rules and strengthen the ecosystem service function for sustainable development.

Microgreens Biometric and Fluorescence Response to Iron (Fe) Biofortification.

Microgreens are foods with high nutritional value, which can be further enhanced with biofortification. Crop biofortification involves increasing the accumulation of target nutrients in edible plant tissues through fertilization or other factors. The purpose of the present study was to evaluate the potential for biofortification of some vegetable microgreens through iron (Fe) enrichment. The effect of nutrient solution supplemented with iron chelate (1.5, 3.0 mg/L) on the plant's growth and mineral concentration of purple kohlrabi, radish, pea, and spinach microgreens was studied. Increasing the concentration of Fe in the medium increased the Fe content in the leaves of the species under study, except for radish. Significant interactions were observed between Fe and other microelements (Mn, Zn, and Cu) content in the shoots. With the increase in the intensity of supplementation with Fe, regardless of the species, the uptake of zinc and copper decreased. However, the species examined suggested that the response to Fe enrichment was species-specific. The application of Fe didn't influence plant height or fresh and dry weight. The chlorophyll content index (CCI) was different among species. With increasing fertilisation intensity, a reduction in CCI only in peas resulted. A higher dose of iron in the medium increased the fluorescence yield of spinach and pea microgreens. In conclusion, the tested species, especially spinach and pea, grown in soilless systems are good targets to produce high-quality Fe biofortified microgreens.

The influence of intensive fertilization on some indicators of groundwater quality in the area of the Western Plain of Romania

After the change of the communist regime and the takeover of agricultural areas by private permits, they, in the context of the presence on the market of a limited range of chemical fertilizers at low prices, began their irrational application, in order to obtain large yields. Although most farmers currently apply fertilizer resources on a scientific basis, the effect of previous practices is still felt, affecting groundwater quality. This paper aims to assess the impact of chemical fertilizers on water quality indicators in a former rural area, now peri urban in the Banat Plain. 10 water sampling points were established (wells and boreholes), and the sampling was done over a period of 6 months (from November 2020 till June 2021). The parameters determined and the range of values were: pH: 6,65 ÷ 7,90; NO3- (mg·l-1): 1,23 ÷ 158,15; NO2- (mg·l-1): 0 ÷ 10,76; NH4+ (mg·l-1): 0 ÷ 5,12, EC (μS/cm): 420 ÷ 1918; PO43- (mg·l-1): 0,0107 ÷ 1,518; Cl- (mg·l-1): 9,35 ÷ 174; SO42- (mg·l-1): 18,79 ÷229,18. The interdependencies between these parameters were also studied.

Differential responses of soil nirS- and nirK-type denitrifying microbial communities to long-term application of biogas slurry in a paddy soil

Biogas slurry (BS) has been widely used as an organic fertilizer in rice paddy fields in China, with potential impacts on the diversity and activity of many biogeochemically important microbial communities. Among these communities, denitrifiers play a significant role in nitrogen (N) transformation and loss in such ecosystems. Here, we examined the abundance, diversity, and community composition of nirS- and nirK-type denitrifiers in paddy soils after long-term application of BS with different N contents using quantitative PCR and high-throughput sequencing. The experiment included four treatments: 1) mineral fertilizer with 270 kg N ha−1; 2) BS with 270 kg N ha−1; 3) BS with 405 kg N ha−1; and 4) BS with 540 kg N ha−1. Our results showed that BS application increased the soil nitrite reductase (NIR) activity by 5.9–27.5 % compared to mineral fertilizer application. Higher nirS gene abundance was observed in BS fertilized soils with increasing N content and was significantly correlated with NIR activity, but nirK gene abundance did not change with different fertilization intensities. Biogas slurry as a substitute for mineral fertilizer significantly decreased the alpha-diversity of only nirS-type denitrifiers at low application rate, but such negative effect was offset by increasing BS fertilization intensity. The community compositions of both nirS- and nirK-type denitrifiers shifted following changes in fertilizer type or intensity, and were significantly influenced by soil organic carbon (SOC), available phosphorus (AP), zinc (for both groups), and copper (for only nirK-type denitrifiers). The structural equation model indicated that the differences in soil NIR activity were mainly explained by SOC, AP, Zn, and the nirS-type denitrifier communities. Sulfurifustis, Thiobaclillus, Microvirgula and Duganella appeared to be the main genera governing NIR activity in the studied paddy fields. In conclusion, increasing BS application intensity can greatly alter the abundance and structure of the nirS-type denitrifying communities, and to a lesser extent, those of the nirK-type denitrifiers in paddy soils.

Regional Differences and Key Influencing Factors of Fertilizer Integrated Efficiency in China

Overuse and low efficiency of chemical fertilizers have caused severe non-point source pollution in China. The investigation of regional difference and the key influencing factors of fertilization intensities (FI) and efficiency can provide references for decision-makers to establish efficient policies for fertilizer use. Using simple models of fertilizer allocation efficiency (FAE) and fertilizer integrated efficiency (FIE), it was found that the east of China excessively used fertilizers, and both the middle and west showed both excessive and insufficient fertilizer use. The average values of the FIE in the east, middle and west of China were 0.69, 0.68 and 0.64, respectively, all of which were at low efficiency. The inter-provincial differences of FIE throughout the country ranged from 0.47 in Shannxi to 0.94 in Shanghai. The population aging rate (PAR), effective irrigation rate (EIR), natural disasters affected rate (DAR) and disaster damaged rate (DDR) are considered the key factors influencing the FIE, based on the new concept of cumulative weight (CW). PAR and EIR are the positive factors, while DAR and DDR are negative. The average FIE is now 0.67 in China, which implies that the increase of chemical fertilizer use efficiency or the reduction of chemical fertilizer amount has a potential of approximate 33%, with the current grain yield and other inputs unchanged. The increase of fertilizer use efficiency should be conducted under local conditions. Optimized intensification of grain production should be given more attention in the east, and implementing disaster prevention and reduction technologies and water-saving irrigation technologies are the preference in the middle and west of China.

Analysis on the changes of fertilization intensity and efficiency in China's grain production from 1980 to 2019.

Relieving serious non-point source pollution of nitrogen (N), phosphorus (P), and potassium (K) is an urgent task in China. It is necessary to explore the changing characteristics of chemical fertilization intensity (FI) and efficiency to provide references. A new method of 'relative productivity proportion weight', which was simpler than data envelope analysis, was proposed to construct models of fertilizer allocation efficiency (FAE) and chemical fertilizer integrated efficiency (FIE) by considering NPK multi-inputs and the grain output scale, respectively. During 1980-2014, the FIs of NPK chemical fertilizers in China showed a significant growing trend. After reaching the highest value of 339 kg ha-1 in 2014, FIs were reduced to 303 kg ha-1 in 2019, higher than the 225 kg ha-1 maximum safe usage internationally recognized. Meanwhile, the pattern of change of FAE was one of 'decreasing to increasing', with values of 1 in 1980, 0.66 in 2003, and 0.80 in 2019. FIE basically showed an increasing trend, which could be divided into three stages: the first stage of low efficiency during 1980-2009, the second stage of medium efficiency after 2010, and the third stage of high efficiency after 2018. From 1980 until 2019, a reduction of FAE from 1 to 0.80 with an average of 0.75 was observed in China. FIE was found between 0.65 and 0.85 and had the potential of upgrading by 15-35%. Therefore, China needs to improve the fertilizer use efficiency in order to strive for negative growth of chemical fertilizer intensity and ecological agriculture construction. © 2022 Society of Chemical Industry.

Drivers of soil respiration across a management intensity gradient in temperate grasslands under drought

Soil respiration is an important pathway of soil organic carbon losses in temperate grasslands; however, it is rarely studied across broad management intensity gradients in a landscape. Using the soda-lime method, we measured in-situ soil CO2 efflux with single measurements of long exposure time (i.e. 3 day long) in 150 grasslands in three German regions in early summer 2018 and 2019. The grasslands ranged from unfertilized and grazed grasslands to intensively fertilized and frequently harvested ones. To assess effects of grazing and fertilization intensities and plant diversity on soil CO2 efflux, we used Structural Equation Modeling to account for direct effects and indirect effects through soil and plant organic matter quantity and quality. Soil CO2 efflux was suppressed by limited water availability caused by naturally occurring droughts in both study years. Under the prevailing environmental conditions, grazing intensity, plant biomass and plant C:N ratio were not related to soil CO2 efflux. In contrast, fertilization intensity was positively associated with soil CO2 efflux (standardized coefficient of net effect: + 0.04 in 2018 and + 0.03 in 2019). This was because fertilization led to lower plant species richness and, thus, to lower C:N ratios in soils, which were associated with higher soil CO2 efflux (plant species richness net effect: −0.09 in 2018 and −0.18 in 2019; soil C:N ratio direct effect: −0.23 in 2018 and −0.33 in 2019). Intensively managed grasslands have higher soil respiration than extensively managed, plant species-rich grasslands even under the extreme conditions of natural droughts.

Potential effects of soil chemical and biological properties on wood volume in Eucalyptus urophylla × Eucalyptus grandis hybrid plantations and their responses to different intensity applications of inorganic fertilizer.

Long-term and high-intensity application of inorganic fertilizer leads to a strong variation of soil characteristics. The changes in soil chemical and biological properties can significantly affect the yield of Eucalyptus plantation. However, the mechanism of soil chemical properties affecting wood volume mediated by biological factors is not clear. The purpose of this study was to identify which soil properties were affected by different fertilization intensities and to disentangle the dominant factors affecting Eucalyptus volume. After clear felling evergreen broad-leaved forest, a Eucalyptus plantation was established that was coppiced every 5 years and fertilized every year. Within this plantation, areas with different treatments were established. These treatments were a 5-year growth period (low); two times 5-year growth period (medium); and three times 5-year growth period (high). In each treatment area and in a nearby evergreen broad-leaved forest (EBLF Control), five sample plots per treatment were set up. Various biological and chemistry analyses (18 in total) were related to determining the most important path and index for optimizing Eucalyptus plantation. The analysis of variance of enzyme activity and microbial biomass showed that the soil biological characteristics decreased over 10 years of plantation, and the enzyme activity was close to the state of EBLF control in medium, while the microbial biomass failed to return to its original state during continuous planting. Redundancy analysis results show that there was a strong correlation in chemical indicators and biological characteristics. Partial least square structural equation model showed that total phosphorus, nitrate nitrogen, urease, catalase, and microbial biomass nitrogen and phosphorus were the most influential soil biochemical factors, and the indirect effect of chemical properties on volume was achieved by microorganisms through enzyme activity. Continuous planting and large-scale application of inorganic fertilizer would lead to a decrease in plantation yield and fertilizer utilization efficiency and would affect the microbial biomass and enzyme activity by destroying the stability of soil chemical properties.

Analysis of agricultural greenhouse gas emissions using the STIRPAT model: a case study of Bangladesh.

The agriculture sector is one of the leading emitters of greenhouse gases in Bangladesh, owing to increasing mechanization, changing population patterns and increasing cultivation of irrigation intensive crops like rice. The objective of this research is to analyze how population trends, energy use and land use practices impact the emissions of three greenhouse gases from the agriculture sector in Bangladesh. The gases studied are carbon dioxide, methane and nitrous oxide. The Stochastic Impacts by Regression on Population, Affluence, and Technology (STIRPAT) model and ridge regression are used to analyze the drivers of emissions covering the period from 1990 to 2014. Explanatory factors of emissions are the total and rural population, affluence, urbanization, fertilizer intensity and quantity, carbon and energy intensity, irrigation, rice cultivation, cultivated land and crop yield. The findings reveal that the country’s total population has a negative effect, and the rural population has a negative, nonlinear impact on the emissions of methane. Affluence affects emissions of all the gases. The energy intensity and carbon intensity of agriculture increase carbon dioxide emissions. The cultivated land area, rice cultivation quantity and crop yield increase methane emissions, while irrigated land area decreases it. Rural population, total population and urbanization have a positive linear effect on carbon dioxide and nitrous oxide emissions. Fertilizer quantity and intensity increase nitrous oxide emissions. The findings imply that increasing agricultural mechanization should be based on clean energy, and land management should be regulated to enable the country to meet its Nationally Determined Contribution (NDC) targets as well as the targets of Sustainable Development Goal (SDG) 7 of increasing the share of clean energy.Graphic abstract

Моніторинг забур’яненості посівів сої у короткоротаційній сівозміні

Goal. To monitor the species and quantity composition of weeds in soy sowings of short crop rotation. Methods. Field, laboratory, calculation, and comparison. Results. The research was carried out in 2016–2021 in a stationary 2-factor field experiment on typical chornozem in a short crop rotation (spring barley — sunflower — soy — winter wheat), which includes 3 tillage systems (shelf, shallow disk, and no-till technology), and 3 fertilizer systems (without fertilizers, resource-saving minimized, intensive). The given data indicated that in the agrocenosis of soy, the main type of weediness was mixed, and consisted of small-year monocotyledonous-dicotyledonous, and accompanying rhizomes. It was established that late spring species had the largest share (45–55%). The share of early spring weeds was 18–26%, winter and winter weeds — 7.0–24%, and perennial species — 8–18% of the total amount. The lowest number of weeds in soy crops was fixed for shelf tillage. Conclusions. In the conditions of the zone of unstable moisture of the Left Bank Forest Steppe in short crop rotation with the long-term use of various systems of main tillage on typical shallow low-humus chornozem, for growing soy, it was established that the system of main tillage, which was based on shelf tillage, had significant advantages in terms of reducing weediness of soy sowings over the shelf-less cultivation system with disc tools and no-till technology. It was found that under an intensive fertilizer system, Amaranthus retroflexus L. and Echinochloa crusgalli (L.) Roem. et Schult. develop more intensively. Stellaria media (L.) Vill. and Polygonum scabrum Moench. spread in the background without the use of fertilizers, while under the resource-saving minimized fertilizer system, their number decreases due to the increase in the competitiveness of the culture. The use of shelf cultivation leads to the spread of dicotyledonous weed species in soy agrocenosis. The number of young monocotyledonous and dicotyledonous weed species increases during tillage.

Limited soil carbon storage under long‐term organic fertilization in solar greenhouses

AbstractEnvironmental conditions, fertilization systems and cultivation practices in greenhouses differ from those in arable soil. Despite being a widespread intensive management practice, large uncertainties exist on the effects of long‐term fertilization on soil organic carbon (SOC) in greenhouse cultivation. The objective of this study was to explore the effects of 11‐year‐long fertilization on carbon (C) stocks in soil aggregates (>2 mm; 2–0.25 mm; 0.25–0.053 mm; <0.053 mm) and SOC fractions (free light fraction (free LF), intra‐aggregate particulate organic carbon (iPOC), mineral‐associated organic carbon (mAOC)) at 0–20 cm and 20–40 cm depth in a solar greenhouse. Five treatments were examined: control (no fertilizer), chicken manure (M), chicken manure plus straw (M + S), chicken manure plus lime (M + Ca), chicken manure plus straw and lime (M + S + Ca). Over the 11 years of continuous intensive organic fertilization, SOC contents of all fertilization treatments first increased sharply and then stabilized after 5 years. The M + S + Ca treatment increased the proportion of aggregate masses, SOC concentrations as well as SOC stocks of soil aggregates >2 mm, 2–0.25 mm, but straw or lime application alone had no significant effects. The M + S + Ca treatment increased the SOC stock of free LF, fine iPOC, coarse iPOC and mAOC by 97%, 38%, 22% and 25% compared with the M treatment, respectively. Straw treatment alone only significantly increased the soil labile C stock (free LF, iPOC). At 0–40 cm depth, the regression between the C stock and the C input had the steepest slope in bulk soil (slope = 0.223, R2 = 0.87**). After 11 years, about 15% of the C inputs were sequestered in the soils. As the mAOC remained largely unaffected, the increase in SOC seems only short‐lived and reaches a new equilibrium within a few years when C inputs are balanced out by mineralization. Consequently, the intensive fertilization and management practices in greenhouse cultivation allowing obtaining high tomato yields results in an overall negative C balance.

Different Fertility Approaches in Organic Hemp (Cannabis sativa L.) Production Alter Floral Biomass Yield but Not CBD:THC Ratio

Industrial hemp is once again legal in the United States but agronomic practices are not well characterized, especially for organic production systems. Many producers are concerned that while increased fertility may increase biomass yield it will also disproportionally increase that rate of total tetrahydrocannabinol (THC) accumulation, making their crop more likely to be noncompliant at harvest. We measured the effect of four organic fertility treatments: (1) no fertility (NA); (2) manure-based compost (CM); (3) an industry-standard organic fertilizer blend (ST); and (4) an intensive fertility treatment designed for cannabis production (BQ), on biomass yield and cannabinoid accumulation over multiple timepoints and two years. We found that higher fertility (ST and BQ) led to increased biomass but did not influence the ratio of cannabidiol (CBD) to THC over time. We also found the ST treatment yielded the most consistently across years, whereas CM and BQ were less predictable and more costly, respectively. Our results show that fertility recommendations can be made to increase biomass yield without increasing the chance of noncompliance. Additional research addressing specific fertility requirements in organic cropping systems for hemp will be needed to meet consumer demand while remaining profitable and sustainable for growers.

Potential to Reduce Chemical Fertilizer Application in Tea Plantations at Various Spatial Scales.

Tea is the main commercial crop grown in China, and excessive application of chemical fertilizers in tea plantations is common. However, the potential to reduce chemical fertilizer use in tea plantations is unclear. In this study, Zhejiang Province was selected as the research object to systematically analyze the potential for tea plantation chemical-fertilizer reduction at different spatial scales. The geographic information system-based analytic hierarchy process method and Soil and Water Assessment Tool model were used to determine the chemical fertilizer reduction potential at the province scale and watershed scale, respectively. At the field scale, two consecutive years of field experiments were conducted on a tea plantation. Province-level analysis showed that 51.7% of the area had an average total fertilization intensity greater than 350 kg/hm2 and a high reduction potential. Watershed analysis revealed that chemical fertilizer reduction had better potential in reducing total nitrogen and total phosphorus inputs to runoff in the short term, whereas 50% organic fertilizer substitution was the best strategy to achieve long-term effects. The field experiments further proved that organic fertilizer substitution balanced tea growth and environmental protection. This study provides a useful method to investigate strategies to reduce chemical fertilizer use in tea-growing areas.

Effect of Long-Term Agricultural Management on the Soil Microbiota Influenced by the Time of Soil Sampling

Application of agrochemicals and mechanization enabled increasing agricultural productivity yet caused various environmental and soil health-related problems. Agricultural practices affect soil microorganisms, which are the key players of many ecosystem processes. However, less is known about whether this effect differs between time points. Therefore, soil was sampled in winter (without crop) and in summer (in the presence of maize) from a long-term field experiment (LTE) in Bernburg (Germany) managed either under cultivator tillage (CT) or moldboard plow (MP) in combination with either intensive nitrogen (N)-fertilization and pesticides (Int) or extensive reduced N-fertilization without fungicides (Ext), respectively. High-throughput sequencing of 16S rRNA gene and fungal ITS2 amplicons showed that changes in the microbial community composition were correlated to differences in soil chemical properties caused by tillage practice. Microbial communities of soils sampled in winter differed only depending on the tillage practice while, in summer, also a strong effect of the fertilization intensity was observed. A small proportion of microbial taxa was shared between soils from the two sampling times, suggesting the existence of a stable core microbiota at the LTE. In general, taxa associated with organic matter decomposition (such as Actinobacteria, Bacteroidetes, Rhizopus, and Exophiala) had a higher relative abundance under CT. Among the taxa with significant changes in relative abundances due to different long-term agricultural practices were putative pathogenic (e.g., Gibellulopsis and Gibberella) and beneficial microbial genera (e.g., Chitinophagaceae, Ferruginibacter, and Minimedusa). In summary, this study suggests that the effects of long-term agricultural management practices on the soil microbiota are influenced by the soil sampling time, and this needs to be kept in mind in future studies for the interpretation of field data.

Родючість чорнозему опідзоленого за різних систем удобрення в агроценозі Центрального Лісостепу

Goal. To substantiate scientifically and theoretically as well as develop a comparative basic model of physicochemical state of the soil stratum for the conditions of reproduction of fertility of podzolic chornozem at long-term use of organic and intensive fertilizer system in growing grain crops in short-term grain-row crop rotation for the conditions of Central Forest-Steppe. Methods. Field — to establish and conduct field stationary experiment to study the impact of fertilizer systems on the change of physicochemical properties of podzolic chornozem and determine the productivity of crop rotation; laboratory — to establish quantitative and qualitative characteristics of physicochemical and humus states of chornozem; comparative and statistical — to model the relationship between the parameters of physicochemical and humus states and determine the productivity of agrocenosis. Results. It is established that the functional relationship between humus content, actual, hydrolytic acidity, and the sum of absorbed bases in the one-meter thickness of podzolic chornozem in an organic fertilizer system is closer than in an intensive one: the coefficient of determination between humus content and physicochemical indices is 56–72%, at intensive fertilizer system — 48–55%, which is provided by strengthening the processes of degradation of the one-meter thickness of chornozem and is manifested in the increase of the boiling line of CaCO3, which is at a depth of 55–60 cm from the soil surface against 65–70 cm at intensive fertilizer system. Conclusions. The high values of the number of absorbed bases according to the upper typical values are due to the presence of carbonates in the lower part of the one-meter thickness, the amount of which increases at the use of the organic fertilizer system: there is an intensification of the degradation process. The boiling line of CaCO3 is located at a depth of 55–60 cm from the soil surface against 65–70 cm at the use of an intensive fertilizer system. On average, in 2016–2019, the highest productivity in terms of grain, feed, feed-protein units and digestible protein in the organic system was in winter wheat: 5.51 t/ha, 7.05 t/ha, 6.52 t/ha and 0,92 t/ha, respectively, or 90–92% of the output at the use of the intensive fertilizer system. The coefficient of variation of grain yield under the organic fertilizer system was lower, except for the barley yield, compared to the intensive fertilizer system: 7.95% vs. 10.5%.

Kajian Peranan Biopori Dan Intensitas Pemupukan Terhadap Kuantitas Dan Kualitas Produksi Pepaya Calina

Calina papaya is very popular with the public because of its rough, thick flesh texture, very sweet taste, oval-shaped fruit with medium size. The demand for calina papaya which tends to increase must be accompanied by high and continuous productivity through fertilization, for that it is necessary to do research on the intensity of fertilization and its efficiency with the application of biopori. The purpose of this study was to examine the role of biopore and fertilization intensity on the quantity and quality of calina papaya production. The study was carried out in the generative phase in the rice fields of Kemuning Sari Kidul village (50 m asl), Jenggawah District, Jember Regency using a randomized block design (RBD) with a 3 x 3 factorial pattern and repeated three times. The factors studied were the number of biopori (B) per tree consisting of B1 = 4 biopori per tree; B2= 3 biopori per tree; B3 = 2 biopori per tree and fertilization intensity (I) consists of I1 = fertilization 1 time per month; I2= fertilization 2 times per month; I3 = fertilization 3 times per month. The results showed that the intensity of fertilization 3 times per month significantly resulted in the highest fruit weight and sugar content. The fruit weights in the 2nd and 3rd measurements were 1.83 kg and 1.72 kg, respectively, the subsequent measurements were not significantly different, ranging from 1.1 to 1.3 kg, the intensity of fertilization 3 times per month also resulted in higher sugar content, namely 14 -15% brix. The combination of 4 biopore holes and fertilization intensity 3 times per month (B1I3) resulted in higher fruit weight at the 6th measurement, namely 1.33 kg. The intensity of fertilization and the use of biopori on the parameters of productive internodes and abnormal fruit did not show a significant difference.

Intensive agriculture, nitrogen legacies, and water quality: intersections and implications

More than a century of land-use changes and intensive agriculture across the Mississippi River Basin (MRB) has led to a degradation of soil and water resources. Nitrogen (N) leaching from the excess application of fertilizers has been implicated in algal blooms and the development of large, coastal ‘dead zones’. It is, however, increasingly recognized that water quality today is a function not only of the current-year inputs but also of legacy N within the watershed—legacy that has accumulated in soil and groundwater over decades of high-input agricultural practices. Although attempts have been made to quantify the extent to which soil organic nitrogen (SON) is being sequestered in agricultural soils with intensive fertilization, improved residue management, and the adoption of conservation tillage practices, the controls on accumulation dynamics as well as linkages between legacy N accumulation and water quality remain unclear. Here, we have used the process-based model CENTURY to quantify accumulation and depletion trajectories for soil N across a range of climate and soil types characteristic of the MRB. The model was calibrated against crop yield data and soil N accumulation data from a long-term field site. Model runs highlighted that under current management scenarios, N accumulation is greatest in regions with the highest crop yield, and this can be attributed to the higher residue rates with greater yields. We thus find that humans, through management practices, have homogenized spatial patterns of SON across the landscape by increasing SON magnitudes in warmer and drier regions. Results also suggest a regime shift in the relationship between soil organic N and N mineralization fluxes, such that N fluxes are greater now than in the 1930s, despite similar soil organic N magnitudes, mainly due to higher proportions of labile, unprotected soil organic matter. This regime shift leads to elevated N leaching to tiles and groundwater in landscapes under intensive agriculture.

Soil pH: a key edaphic factor regulating distribution and functions of bacterial community along vertical soil profiles in red soil of pomelo orchard

BackgroundSoil microbes exist throughout the soil profile and those inhabiting topsoil (0–20 cm) are believed to play a key role in nutrients cycling. However, the majority of the soil microbiology studies have exclusively focused on the distribution of soil microbial communities in the topsoil, and it remains poorly understood through the subsurface soil profile (i.e., 20–40 and 40–60 cm). Here, we examined how the bacterial community composition and functional diversity changes under intensive fertilization across vertical soil profiles [(0–20 cm (RS1), 20–40 cm (RS2), and 40–60 cm (RS3)] in the red soil of pomelo orchard, Pinghe County, Fujian, China.ResultsBacterial community composition was determined by 16S rRNA gene sequencing and interlinked with edaphic factors, including soil pH, available phosphorous (AP), available nitrogen (AN), and available potassium (AK) to investigate the key edaphic factors that shape the soil bacterial community along with different soil profiles. The most dominant bacterial taxa were Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, Crenarchaeota, and Bacteriodetes. Bacterial richness and diversity was highest in RS1 and declined with increasing soil depth. The distinct distribution patterns of the bacterial community were found across the different soil profiles. Besides, soil pH exhibited a strong influence (pH ˃AP ˃AN) on the bacterial communities under all soil depths. The relative abundance of Proteobacteria, Actinobacteria, Crenarchaeota, and Firmicutes was negatively correlated with soil pH, while Acidobacteria, Chloroflexi, Bacteriodetes, Planctomycetes, and Gemmatimonadetes were positively correlated with soil pH. Co-occurrence network analysis revealed that network topological features were weakened with increasing soil depth, indicating a more stable bacterial community in the RS1. Bacterial functions were estimated using FAPROTAX and the relative abundance of functional bacterial community related to metabolic processes, including C-cycle, N-cycle, and energy production was significantly higher in RS1 compared to RS2 and RS3, and soil pH had a significant effect on these functional microbes.ConclusionsThis study provided the valuable findings regarding the structure and functions of bacterial communities in red soil of pomelo orchards, and highlighted the importance of soil depth and pH in shaping the soil bacterial population, their spatial distribution and ecological functioning. These results suggest the alleviation of soil acidification by adopting integrated management practices to preserve the soil microbial communities for better ecological functioning.

Contaminated Groundwater by Nitrate in Sidoarum Village, Godean District, Sleman Regency, Special Region of Yogyakarta

Sidoarum Village, Godean District, Sleman Regency, Special Region of Yogyakarta become one of the developing areas for getting influenced by Yogyakarta City center which is only 8 kilometers away. Population growth has occurred from 2010 to 2019 which has led to land use changes from agricultural areas to residential areas. Land use change, population growth, incorrect space using, excessive use of fertilizers, agricultural activities, and industrial waste disposal affects the groundwater quality resources, especially nitrate (NO3) compound. This research was aimed to determine the distribution of groundwater quality based on nitrate parameters and to analyze the relationship between land use changing and nitrate concentrations in groundwater. This mixed-method research used to survey and mapping methods to collect the data. The analysis was conducted by laboratory tests and spatial analysis method using Arc GIS software. The sampling of groundwater was carried out by purposive sampling method based on differences in land use. The results indicated that most of the groundwater in Sidoarum Village has been contaminated by nitrate due to activity in agricultural areas like intense fertilizer application and farming in household-scale in densely populated areas, especially with the bad sanitation system. The distribution of nitrate contaminated groundwater was correlated to the types of land use. The monitoring of land use change is needed especially from the agricultural areas to residential areas due to excessive population growth.

Mineral Fertilization and Maize Cultivation as Factors Which Determine the Content of Trace Elements in Soil

This study has been carried out in order to determine the effect of increasingly intensive fertilization with potassium, applied in combination with nitrogen, on the content of trace elements in soil after the harvest of maize (Zea mays L.). The soil content of trace elements depended on the fertilization with potassium and nitrogen. Potassium fertilization had a stronger effect on the content of trace elements in the pots fertilized with the lower nitrogen dose (130 mg N kg−1 of soil). The increasing doses of potassium led to a higher soil content of zinc (Zn), and especially of nickel (Ni). The impact of potassium fertilization on the content of the remaining trace elements in the soil was less unambiguous, and depended on the dose of potassium and nitrogen fertilization. Nitrogen fertilization resulted in a higher soil content of manganese (Mn), chromium (Cr), nickel (Ni) and cadmium (Cd), as well as a decreased soil content of lead (Pb). It needs to be underlined that changes in the soil content of Ni, Cd, and Pb, effected by nitrogen fertilization, were larger than in the cases of the other trace elements. The influence of potassium and nitrogen fertilization did not result in exceeding the current threshold amounts of trace elements set for agriculturally used soil. An increase in the contents of some trace elements in soil is beneficial from an agricultural point of view. Some of these elements are necessary for the correct growth and development of arable plants.