Nutrient Amendments Research Articles

Diatom nutrient requirements change with lake nutrient limitation and enrichment in New Zealand dune lakes

ABSTRACT Nutrients are important determinants of diatom growth in lakes, and diatoms are considered reliable indicators of changing lake nutrient concentrations and eutrophication. However, diatom ecologies are not static, nor are they linked to single environmental variables, leading to imprecise diatom nutrient inferences. Anthropogenic nutrient enrichment is the principal issue facing New Zealand’s lakes. Thus, knowledge of diatom responses to nutrients in New Zealand lakes will be important for understanding contemporary and past changes in nutrient availability. Using a nutrient amendment experiment and diatom communities from dune lakes, here we show that the response of specific diatom species is not universal among lakes and is partly determined by lake nutrient concentrations and limitation status. The response of focal diatom species to nutrient additions differed from previously reported nutrient requirements, and did not align with published, assigned trophic statuses. This study highlights that the response of diatoms to nutrient enrichment is context-dependent, and that intraspecific generalisations of diatom ecologies between geographic locations or through time should be made with caution. To apply diatoms to making nutrient inferences, more work focusing on how physiochemical and biological factors influence diatom nutrient requirements is required.

Nutrient Control of Phytoplankton Abundance and Biomass, and Microplankton Assemblage Structure in the Lower Columbia River (Vancouver, Washington, USA)

Nutrient limitation of phytoplankton is common but by no means universal in large temperate rivers. Previous field studies in the Columbia River, USA, are suggestive of nutrient limitations of phytoplankton, especially during summer, but this has never been tested experimentally. We therefore undertook monthly 5-day nutrient amendment incubation experiments from May–September 2018 using Columbia River water collected at Vancouver, Washington, USA. We compared replicate treatment bottles containing natural microplankton assemblages and amended nutrients (NO3, PO4 and SiO4 in combination) with replicate control bottles containing natural microplankton assemblages and ambient nutrients. Phytoplankton abundance and biomass were compared between treatments and controls on each day of each experiment, and microplankton assemblage structure was evaluated using Permutational Multivariate Analysis of Variance and Non-Metric Multi-Dimensional Scaling ordination on Day 0 (ambient) and Day 5 of each experiment. Nutrient amendment significantly affected phytoplankton abundance and biomass, particularly in June–August, although this varied between taxa (e.g., cyanobacteria, dinoflagellates, flagellates and ciliates showed more frequent positive responses than chlorophytes and diatoms did). Abundance-based microplankton assemblage structure was significantly correlated with PO4, SiO4 and NO3 concentrations, and BIOENV procedure in R revealed that the best subset of explanatory variables included SiO4 and NO3 concentrations. Biomass-based assemblage structure was significantly correlated with SiO4 and NO3, although BIOENV explanatory variables included only SiO4. These results are suggestive of summertime nutrient control of phytoplankton abundance and biomass, as well as microplankton composition, in the lower Columbia River, at least during some months. Since eutrophication is increasing in the watershed, this could have important implications for higher level consumers (e.g., zooplankton and out-migrating juvenile salmon).

Cashew Seedlings Nursery Production in University of Abuja Nigeria and its Response to Different Organic Amendments

Organic waste materials are embedded with plant nutrients augmented to contain nutrients used for plant use and raising cashew seedlings in the nursery. This study aims to observe the effect of organic materials as soil amendments in the growing of cashew seedlings. The treatments consisted of two cashew nut types (Jumbo and Medium size) and three organic materials: Cocoa pod husk-Biochar, Rice husk, Maize barn, and a control. These planting materials were arranged as Jumbo Nut-Control, Medium Nut-Control, Jumbo nut+Biochar, Medium nut+Biochar, Jumbo nut+Maize Bran, Medium nut+Maize Bran, Jumbo nut+Rice Husk, Medium nut+Rice Husk, Jumbo nut+Biochar+Maize Bran+Rice Husk and Medium nut+Biochar+Maize Bran+Rice Husk laid in a Complete Randomized Design with three replications. The seedlings were raised with a 10kg topsoil mix with 9.0g (5t/ha) of organic materials and control. Data collected include plant height, stem girth, numbers of leaves, leaf area, fresh and dry offshoot weight, root weight, and taproot length, analyzed with SAS statistical package and Mean separation using Tukey’s Studentized Range Test at (P≤0.05). The pre-and post-soil were analyzed for chemical properties. The result showed that the organic amendments improved the chemical properties of the soil. Although these nutrient amendments improved crop productivity, their effectiveness was pronounced in the medium cashew nut. At termination, the control treatments had the least fresh and dry shoot, root weight and shortest Root length when compared to other treatments. Conclusively, Cocoa pod husk-Biochar, Rice Husk and Maize Barn should be considered in cashew nursery and field trial upon transplanting.

Application of selected nutrient amendments to regulate soil properties for reducing arsenic accumulation in rice

ABSTRACT Arsenic (As) contamination in rice and the deleterious effects of its consumption on human health is a major concern. To decrease the bioavailable fractions of arsenic in soil for achieving subsequently reduced accumulation of arsenic in rice grains, a pot experiment was conducted using arsenic-laden soil. The effects of different nutrient amendments viz., ZnSO4, FeSO4, Ca2SiO4, Murate of Potash (MOP), Di-Ammonium Phosphate (DAP) independently and in combination (as a mix) at low, mid, and high doses were evaluated concerning arsenic accumulation in rice variety Muktoshree IET-21845. Changes in bioavailable fractions of soil arsenic were measured by the sequential extraction procedure. The total arsenic in the control treatment without any amendment was 19 mg kg−1. The maximum concentration of total arsenic in grains in the control treatment without any amendment was 1.02 mg kg−1. It was found that the combined (mid-dose of the mix) amendments enhanced rice growth by 55%, and decreased arsenic accumulation in the grain by 89%, which was the minimum total arsenic reached with the suitable amendments. The bioavailable fractions of soil arsenic were decreased to 79% and 88% in the case of mid-dose application of the DAP and the mix (combined amendments) treatments to the soil, respectively. These nutrient amendments in defined doses may be highly effective in reducing arsenic toxicity to rice cropping in the arsenic-contaminated soils.

ROLE OF BIOCHEMICAL AND BIOPHYSICAL CHARACTERISTICS IN MANAGEMENT OF O3 INJURY IN PLANTS THROUGH SOIL NUTRIENT AMENDMENTS

The present study focuses on mitigative measurements adopted to manage ozone (O3 ) stress by application of different doses of nutrient (N, P, K) treatments. Two cultivars of maize (Zea mays L. var HHM-1 and Malviya hybrid2) growing under ambient O3 stress conditions were treated with three doses of nutrients (NPK); recommended (N1 ), 1.5x recommended (N2 ) and 2x recommended (N3 ) in near natural condition. The antioxidant pool, secondary metabolites, photosynthetic efficiency and gas conductance parameters were assessed. Results of our experiment suggest that the plants treated with nutrients responded better than the plants without nutrient, which served as control. Increased antioxidant activities in both the maize cultivars upon nutrient treatment resulted in decline of O3generated superoxide radicals and H2O2 contents, indicating a reduction in O3 stress. It was observed that the antioxidant response upon treatment was more prominent in HHM-1, as compared to MH-2, in which major proportions of antioxidant stimulations were observed during the vegetative period only. SOD and CAT played an important role in defining the plant’s defense and regulating the SOR and H2O2 contents in both the maize cultivars at both vegetative and reproductive stages. The results of the present experiment clearly suggest that nutrient amendments can be effectively used in partially mitigating ambient ozone stress, however more experimentation with different crop varieties is required to prove the expediency of nutrient amendments.

Changes in Microbiome Activity and Sporadic Viral Infection Help Explain Observed Variability in Microcosm Studies.

The environmental conditions experienced by microbial communities are rarely fully simulated in the laboratory. Researchers use experimental containers (“bottles”), where natural samples can be manipulated and evaluated. However, container-based methods are subject to “bottle effects”: changes that occur when enclosing the plankton community that are often times unexplained by standard measures like pigment and nutrient concentrations. We noted variability in a short-term, nutrient amendment experiment during a 2019 Lake Erie, Microcystis spp. bloom. We observed changes in heterotrophic bacteria activity (transcription) on a time-frame consistent with a response to experimental changes in nutrient availability, demonstrating how the often overlooked microbiome of cyanobacterial blooms can be altered. Samples processed at the time of collection (T0) contained abundant transcripts from Bacteroidetes, which reduced in abundance during incubation in all bottles, including controls. Significant biological variability in the expression of Microcystis-infecting phage was observed between replicates, with phosphate-amended treatments showing a 10-fold variation. The expression patterns of Microcystis-infecting phage were significantly correlated with ∼35% of Microcystis-specific functional genes and ∼45% of the cellular-metabolites measured across the entire microbial community, suggesting phage activity not only influenced Microcystis dynamics, but the biochemistry of the microbiome. Our observations demonstrate how natural heterogeneity among replicates can be harnessed to provide further insight on virus and host ecology.

Effect of nitrogen fertilization on central tendency and spatial heterogeneity of soil moisture, pH and dissolved organic carbon and nitrogen in two bioenergy croplands#

AbstractBackgroundSoil moisture, pH, dissolved organic carbon and nitrogen (DOC, DON) are important soil biogeochemical properties in switchgrass (SG) and gamagrass (GG) croplands. Yet their spatiotemporal patterns under nitrogen (N) fertilization have not been studied.AimsThe objective of this study is to investigate the main and interactive effects of N fertilization and bioenergy crop type on central tendencies and spatial heterogeneity of soil moisture, pH, DOC and DON.MethodsBased on a 3‐year long fertilization experiment in Middle Tennessee, USA, 288 samples of top horizon soils (0–15 cm) under three fertilization treatments in SG and GG croplands were collected. The fertilization treatments were no N input (NN), low N input (LN: 84 kg N ha−1 in urea) and high N input (HN: 168 kg N ha−1 in urea). Soil moisture, pH, DOC and DON were quantified. And their within‐plot variations and spatial distributions were achieved via descriptive and geostatistical methods.ResultsRelative to NN, LN significantly increased DOC content in SG cropland. LN also elevated within‐plot spatial heterogeneity of soil moisture, pH, DOC and DON in both croplands though GG showed more evident spatial heterogeneity than SG. Despite the pronounced patterns described above, great plot to plot variations were also revealed in each treatment.ConclusionThis study informs the generally low sensitivity of spatiotemporal responses in soil biogeochemical features to fertilizer amendments in bioenergy croplands. However, the significantly positive responses of DOC under low fertilizer input informed the best practice of optimizing agricultural nutrient amendment.

The interactive effects of temperature and nutrients on a spring phytoplankton community

AbstractA complex interplay of environmental variables impacts phytoplankton community composition and physiology. Temperature and nutrient availability are two principal factors driving phytoplankton growth and composition, but are often investigated independently and on individual species in the laboratory. To assess the individual and interactive effects of temperature and nutrient concentration on phytoplankton community composition and physiology, we altered both the thermal and nutrient conditions of a cold‐adapted spring phytoplankton community in Narragansett Bay, Rhode Island, when surface temperature was 2.6°C and chlorophyll > 9 μg L−1. Water was incubated in triplicate at −0.5°C, 2.6°C, and 6°C for 10 d. At each temperature, treatments included both nutrient amendments (N, P, Si addition) and controls (no macronutrients added). The interactive effects of temperature and resource availability altered phytoplankton growth and community structure. Nutrient amendments resulted in species sorting and communities dominated by larger species. Under replete nutrients, warming tripled phytoplankton growth rates, but under in situ nutrient conditions, increased temperature acted antagonistically, reducing growth rates by as much as 33%, suggesting communities became nutrient limited. The temperature–nutrient interplay shifted the relative proportions of each species within the phytoplankton community, resulting in more silica rich cells at decreasing temperatures, irrespective of nutrients, and C : N that varied based on resource availability, with nutrient limitation inducing a 47% increase in C : N at increasing temperatures. Our results illustrate how the temperature–nutrient interplay can alter phytoplankton community dynamics, with changes in temperature amplifying or exacerbating the nutrient effect with implications for higher trophic levels and carbon flux.

Effect of contour rainwater-harvesting and integrated nutrient management on sorghum grain yield in semi-arid farming environments of Zimbabwe

ABSTRACT The application of insufficient amounts of mineral fertiliser, coupled with unreliable precipitation, has caused a drastic reduction in the yield of sorghum in the smallholder-farming areas of Zimbabwe. This calls for innovative interventions to improve production under changing climatic conditions. This study evaluated the effect of contour-based rainwater-harvesting methods and the use of cattle manure + N nutrient amendment on sorghum yield. A split-split plot experiment was conducted where rainwater-harvesting practice, sorghum variety, cattle manure + N and distance from rainwater-harvesting structure were treatment factors. The results showed that the yield of sorghum was significantly higher under the tied contour and infiltration pits than standard contour at all distances from rainwater-harvesting practices and seasons. In all seasons sorghum varieties Macia and Sc Sila showed higher yield under the tied contour and infiltration pits than standard contour. However, regardless of the distance from rainwater-harvesting practice and season the sorghum variety, Macia showed a higher grain yield than Sc Sila. At each incremental level of N application to cattle manure, Macia had a higher grain yield than Sc Sila, and no significant grain yield benefits were shown in each variety at N application to cattle manure above 50 kg N ha−1.

Effects of soil nutrient amendments on growth and grain yield performances of quality protein maize grown under water deficit stress in Ibadan, Nigeria

Drought and poor soil fertility are major limitations to crop production, globally. To investigate the impacts of water deficit stress (WS) and soil nutrient amendment (SA) on growth and yield performances of maize. A two years factorial field study was carried out, using a quality protein maize (QPM) (ILE-1-OB) and a non QPM–drought tolerant check (TZPBSR-W) varieties in Ibadan. Treatments include; six fertilizer application rates; 50 and 100 (kg N ha-1) ofNPK-20-10-10, 10.7 kg N ha-1of Tithonia Poultry Compost (TPC), 50 N + 10.7TPC and 100 N + 10.7TPC (kg N ha-1), three WS; the control (FW), WS at vegetative stage (STR1), and WS at reproductive stage (STR2). Leaf area (LA) and grain yield (GY) were measured using standard procedures. From the results, across WS, LA ranged from STR1 (458.90 ± 12.4) to FW (598.81 ± 13.1 cm2), GY varied from STR2 (2.94 ± 0.2 t ha-1) to FW (6.59 ± 0.2 t ha-1), across fertilizers, LA varied from 0 N (397.65 cm2) to 100N + 10.7TPC (622.71 cm2) and 50 N + 10.7TPC (611.03 cm2), respectively. The GY varied from 0 N (2.37 t ha-1) to 100 N + 10.7TPC (5.82 t ha-1) and 50N + 10.7TPC (5.26 t ha-1). Drought stress reduced growth and GY performances of QPM, while SA with 50 kg N ha-1 of inorganic fertilizer and 10.7 kg N ha-1 of TPC enhanced growth and grain yield of maize under WS.

Soil carbon stocks in temperate grasslands differ strongly across sites but are insensitive to decade-long fertilization.

Enhancing soil carbon (C) storage has the potential to offset human-caused increases in atmospheric CO2 . Rising CO2 has occurred concurrently with increasing supply rates of biologically limiting nutrients such as nitrogen (N) and phosphorus (P). However, it is unclear how increased supplies of N and P will alter soil C sequestration, particularly in grasslands, which make up nearly a third of non-agricultural land worldwide. Here, we leverage a globally distributed nutrient addition experiment (the Nutrient Network) to examine how a decade of N and P fertilization (alone and in combination) influenced soil C and N stocks at nine grassland sites spanning the continental United States. We measured changes in bulk soil C and N stocks and in three soil C fractions (light and heavy particulate organic matter, and mineral-associated organic matter fractions). Nutrient amendment had variable effects on soil C and N pools that ranged from strongly positive to strongly negative, while soil C and N pool sizes varied by more than an order of magnitude across sites. Piecewise SEM clarified that small increases in plant C inputs with fertilization did not translate to greater soil C storage. Nevertheless, peak season aboveground plant biomass (but not root biomass or production) was strongly positively related to soil C storage at seven of the nine sites, and across all nine sites, soil C covaried with moisture index and soil mineralogy, regardless of fertilization. Overall, we show that site factors such as moisture index, plant productivity, soil texture, and mineralogy were key predictors of cross-site soil C, while nutrient amendment had weaker and site-specific effects on C sequestration. This suggests that prioritizing the protection of highly productive temperate grasslands is critical for reducing future greenhouse gas losses arising from land use change.

Growth, yield and fruit quality of specialty banana in response to yeast extract and potassium amendments

Nutrient and bio-stimulant amendments are important for growth, yield, and quality of fruit crops under environmentally stressed site conditions. Our field study was conducted to evaluate the effect of potassium fertilization and yeast extract on growth, yield and finger quality of banana grown under arid and semi-arid marginal site conditions in Egypt. Using different levels of Potassium at 500 & 1000 mg as a foliar application and yeast extract at one & two liters per plant as a drench soil application and their combinations doses added monthly six times during the period from October to March. The obtained results showed a positive correlation between the values of the studied parameters (growth, productivity and fruit quality) and the yeast and potassium levels. As a result, the parameters values increased as the yeast and the K2SO4 levels increased to a higher level during the two growing seasons. Herein, yeast extract 2000 ml + K2SO4 1000 mg/l/plant was statistically the superior. In addition, yeast extract 2000 liters + K2SO4 500 mg/l/plant statistically ranked 2nd after the above-mentioned superior treatment. On the contrary, the lowest values of these parameters were obtained by Control yeast extract 1 liter/plant. The remaining treatments have occupied an intermediate position between the treatments mentioned above in both seasons.

Soil initial bacterial diversity and nutrient availability determine the rate of xenobiotic biodegradation.

SummaryUnderstanding the relative importance of soil microbial diversity, plants and nutrient management is crucial to implement an effective bioremediation approach to xenobiotics‐contaminated soils. To date, knowledge on the interactive effects of soil microbiome, plant and nutrient supply on influencing biodegradation potential of soils remains limited. In this study, we evaluated the individual and interactive effects of soil initial bacterial diversity, nutrient amendments (organic and inorganic) and plant presence on the biodegradation rate of pyrene, a polycyclic aromatic hydrocarbon. Initial bacterial diversity had a strong positive impact on soil biodegradation potential, with soil harbouring higher bacterial diversity showing ~ 2 times higher degradation rates than soils with lower bacterial diversity. Both organic and inorganic nutrient amendments consistently improved the degradation rate in lower diversity soils and had negative (inorganic) to neutral (organic) effect in higher diversity soils. Interestingly, plant presence/type did not show any significant effect on the degradation rate in most of the treatments. Structural equation modelling demonstrated that initial bacterial diversity had a prominent role in driving pyrene biodegradation rates. We provide novel evidence that suggests that soil initial microbial diversity, and nutrient amendments should be explicitly considered in the design and employment of bioremediation management strategies for restoring natural habitats disturbed by organic pollutants.

The Potential of Termite Mound Spreading for Soil Fertility Management under Low Input Subsistence Agriculture

Termites can play a localized prominent role in soil nutrient availability and cycling because mound materials are often enriched in nutrients relative to surrounding soil. Mound materials may thus prove to be useful amendments, though evidently mound spatial arrangement needs to be considered as well. Furthermore, it is not known if gradients of soil properties exist from termite mound to interspace sites. Studying both aspects would be required to decide whether spreading of mounds or spatially differentiated management of surrounding crop to accommodate soil fertility gradients would be valid nutrient-management strategies. Mound abundance and mass were estimated at 9 and 4 mounds ha−1, representing 38.9 and 6.3 t ha−1 on Nitisols and Vertisols, respectively. Soil physical and chemical properties were measured on samples collected from internal and external parts of mounds and adjacent soils at 0.5, 1 and 10 m away from mounds. In general, termite mounds were enriched in plant nutrients and SOC on Vertisols but not on Nitisols. Termite mounds constituted only 0.3 to 1.3% of the 0–15 cm SOM stock on a per ha basis but nevertheless the immediate vicinity of termite mounds was a relative fertile hotspot. Hence, under the studied condition, we suggest spatial arrangement of crop around termite mounds according to soil fertility gradient and spatially differentiated nutrient management strategies. Our result suggests recommendation of termite mound spreading for soil nutrient amendment has to consider plant nutrient stock in termite mounds on per ha basis besides their nutrient enrichment. Interesting topics for future investigation would be growth experiment for different crops with mound materials treatment. It would also be interesting to study the effect mound building termite on soil properties under different soil conditions, slope class and land use.

Depth-resolved microbial diversity and functional profiles of trichloroethylene-contaminated soils for Biolog EcoPlate-based biostimulation strategy

This study explores the toxic effect of TCE at different depths of sub-surface soil and underpins microbial community-level suitable carbon (C)-sources that provided directionality to the in situ biostimulation effort via augmentation strategy for effective TCE remediation in soil. The impacts on resident microbial communities and their functional profiles that govern the TCE biodegradation process were identified. Highly contaminated PW01 soil (9 m depth) had severely limited microbial diversity and was enriched in Proteobacteria and Firmicutes. The abundance of TCE degradation-associated genera was observed in all contaminated samples, and the abundance of TCE-degradation-related taxa were positively correlated with soil TCE contamination levels. Community-level metabolic activity associated with the utilization of diverse external C-sources was directly influenced by TCE concentration and soil depth. Multivariate data analysis revealed that the functional genus, TCE concentration, and selected available C substrate uptake capacity correlated in soil samples. Pearson’s correlation tests revealed that C sources such as L-arginine, phenylethylamine and γ-hydroxybutyric acid utilization trait exhibited significant positive correlations with chloroalkane and chloroalkene degradation pathway abundance. Ultimately, depth and TCE contamination level-associated soil microbiota and their most preferred C-source understanding could add to facilitate effective biostimulation via external nutrient amendment for efficient in situ TCE degradation.

Response of water-bound fluxes of potassium, calcium, magnesium and sodium to nutrient additions in an Ecuadorian tropical montane forest

In the past two decades, the Amazon-exposed, tropical montane rain forests in south Ecuador experienced increasing deposition of reactive N mainly from Amazonian forest fires, episodic Ca and Mg inputs from Saharan dust, and a low but constant P deposition from unknown sources. To explore the response of this tropical, perhumid ecosystem to nutrient inputs, we established in 2007 a Nutrient Manipulation Experiment (NUMEX). Since 2008, we have applied 50 kg ha−1 year−1 of N as urea, 10 kg ha−1 year−1 of P as NaH2PO4·H2O, 50 kg ha−1 year−1 of N + 10 kg ha−1 year−1 of P and 10 kg ha−1 year−1 of Ca as CaCl2·H2O in a randomized block design at 2000 m a.s.l. in a natural forest of the south Ecuadorian Andes. Previous studies have shown that alkali and alkaline earth metals had beneficial effects on the functioning of N and P co-limited tropical forests occurring on acidic soils. Therefore, we determined the response of all major aqueous ecosystem fluxes of K, Ca, Mg and Na to nutrient amendments, to understand how increasing atmospheric deposition would affect their cycling in the future. Additions of N and P decreased K leaching from the organic layer and in the mineral soil, thus tightening K cycling. This suggests that increasing future N and P availability may result in K limitation in the long term. The leaching of Ca and Mg from the canopy increased in response to amendments of N and P and we observed an enhanced uptake of these nutrients also if Ca was amended alone. Although N was applied as urea, acidity of soil solutions and leaching of K, Ca, Mg and Na did not increase following separate N amendments. In spite of the acid soils and of its low cation-exchange competitivity, Na included in the P fertilizer was only partly leached from the organic layer. We suggest that it was probably required to cover an unmet Na demand of the soil fauna. Our results demonstrate the major role in the functioning of the tropical montane forests played by K, Ca and Mg as potential future growth-limiting elements and increasingly required nutrients in response to rising N and P availability, while they also support the importance of Na as a functional element in these ecosystems.

Network structure of resource use and niche overlap within the endophytic microbiome

Endophytes often have dramatic effects on their host plants. Characterizing the relationships among members of these communities has focused on identifying the effects of single microbes on their host, but has generally overlooked interactions among the myriad microbes in natural communities as well as potential higher-order interactions. Network analyses offer a powerful means for characterizing patterns of interaction among microbial members of the phytobiome that may be crucial to mediating its assembly and function. We sampled twelve endophytic communities, comparing patterns of niche overlap between coexisting bacteria and fungi to evaluate the effect of nutrient supplementation on local and global competitive network structure. We found that, despite differences in the degree distribution, there were few significant differences in the global network structure of niche-overlap networks following persistent nutrient amendment. Likewise, we found idiosyncratic and weak evidence for higher-order interactions regardless of nutrient treatment. This work provides a first-time characterization of niche-overlap network structure in endophytic communities and serves as a framework for higher-resolution analyses of microbial interaction networks as a consequence and a cause of ecological variation in microbiome function.

Improving Farmers’ Revenue in Crop Rotation Systems with Plot Adjacency Constraints in Organic Farms with Nutrient Amendments

The search for sustainable agriculture is leading many economies to turn to crop rotation systems and to abandon monoculture systems which generally require increased use of pesticides and synthetic fertilizers. But the optimization of crop rotation remains a challenge, especially when considering organic farming. This work tackles the optimization of crop rotation in traditional organic farms with plot adjacency constraints and nutrient amendments. In the present configuration, each farmer owns a certain quantity of rudimentary equipment and a number of workers, all considered as resources. Farms are subdivided into plots and each plot allows only one crop at a given period. At a given interval of time, each plot receives a certain quantity of nutrient. The generated rotations are of fixed durations for all plots and the objective is to maximize farmers’ income. A linear programming approach is used to determine the solution of the proposed farming model. Three levels of constraints are combined in the linear program to generate realistic rotations: (i) biophysical constraints including crop succession and plot adjacency; (ii) structural constraints including budget and resources; (iii) organizational constraints such as nutrient amendment and market demand. To evaluate the performance of the model, scenarios based on real-world data has been defined and solved using free solvers. The solutions obtained indicate that all the constrains are satisfied. In addition, farmers’ revenue is improved, reaching a stationary position when the quantity of available resources is equal or greater than the quantity of required resources. Finally, Cbc solver is faster than GLPK solver; and it provides solutions on larger instances where GLPK does not.

Enhancing food waste compost quality with nutrient amendments

Enhancing food waste compost quality with nutrient amendments

Nutrients cause consolidation of soil carbon flux to small proportion of bacterial community

Nutrient amendment diminished bacterial functional diversity, consolidating carbon flow through fewer bacterial taxa. Here, we show strong differences in the bacterial taxa responsible for respiration from four ecosystems, indicating the potential for taxon-specific control over soil carbon cycling. Trends in functional diversity, defined as the richness of bacteria contributing to carbon flux and their equitability of carbon use, paralleled trends in taxonomic diversity although functional diversity was lower overall. Among genera common to all ecosystems, Bradyrhizobium, the Acidobacteria genus RB41, and Streptomyces together composed 45–57% of carbon flow through bacterial productivity and respiration. Bacteria that utilized the most carbon amendment (glucose) were also those that utilized the most native soil carbon, suggesting that the behavior of key soil taxa may influence carbon balance. Mapping carbon flow through different microbial taxa as demonstrated here is crucial in developing taxon-sensitive soil carbon models that may reduce the uncertainty in climate change projections.