High application rates of biochar to mitigate N2O emissions from a N-fertilized tropical soil under warming conditions.

Biochar application has been suggested as a strategy to decrease nitrous oxide emissions from agricultural soils while increasing soil C stocks, especially in tropical regions. Climate change, specifically increasing temperatures, will affect soil environmental conditions and thereby directly influence soil N2O fluxes

Legacy effects of intercropping and nitrogen fertilization on soil N cycling, nitrous oxide emissions, and the soil microbial community in tropical maize production

Maize-forage grasses intercropping systems have been increasingly adopted by farmers because of their capacity to recycle nutrients, provide mulch, and add C to soil. However, grasses have been shown to increase nitrous oxide (N2O) emissions. Some tropical grasses cause biological nitrification inhibition (BNI) which could mitigate N2O emissions in the maize cycle but the reactions of the N cycle and the microbial changes that explain the N2O emissions are little known in such intercropping systems. With this in mind, we explored intercropping of forage grasses (Brachiaria brizantha and Brachiaria humidicola) with distinct BNI and yield potential to increase N cycling in no-till maize production systems compared to monocrop with two N rates (0 and 150 kg ha−1) applied during the maize season. These grasses did not strongly compete with maize during the period of maize cycle and did not have a negative effect on grain yield. We observed a legacy of these grasses on N mineralization and nitrification through the soil microbiome during maize growth. We observed that B. humidicola, genotype with higher BNI potential, increased net N mineralization by 0.4 mg N kg−1 day−1 and potential nitrification rates by 1.86 mg NO3-N kg−1 day−1, while B. brizantha increased the soil moisture, fungi diversity, mycorrhizal fungi, and bacterial nitrifiers, and reduced saprotrophs prior to maize growth. Their legacy on soil moisture and cumulative organic inputs (i.e., grass biomass) was strongly associated with enhanced mineralization and nitrification rates at early maize season. These effects contributed to increase cumulative N2O emission by 12.8 and 4.8 mg N2O-N m−2 for maize growing after B. brizantha and B. humidicola, respectively, regardless of the N fertilization rate. Thus, the nitrification inhibition potential of tropical grasses can be outweighed by their impacts on soil moisture, N recycling, and the soil microbiome that together dictate soil N2O fluxes

Legacy effects of intercropping and nitrogen fertilization on soil N cycling, nitrous oxide emissions, and the soil microbial community in tropical maize production

Maize-forage grasses intercropping systems have been increasingly adopted by farmers because of their capacity to recycle nutrients, provide mulch, and add C to soil. However, grasses have been shown to increase nitrous oxide (N2O) emissions. Some tropical grasses cause biological nitrification inhibition (BNI) which could mitigate N2O emissions in the maize cycle but the reactions of the N cycle and the microbial changes that explain the N2O emissions are little known in such intercropping systems. With this in mind, we explored intercropping of forage grasses (Brachiaria brizantha and Brachiaria humidicola) with distinct BNI and yield potential to increase N cycling in no-till maize production systems compared to monocrop with two N rates (0 and 150 kg ha−1) applied during the maize season. These grasses did not strongly compete with maize during the period of maize cycle and did not have a negative effect on grain yield. We observed a legacy of these grasses on N mineralization and nitrification through the soil microbiome during maize growth. We observed that B. humidicola, genotype with higher BNI potential, increased net N mineralization by 0.4 mg N kg−1 day−1 and potential nitrification rates by 1.86 mg NO3-N kg−1 day−1, while B. brizantha increased the soil moisture, fungi diversity, mycorrhizal fungi, and bacterial nitrifiers, and reduced saprotrophs prior to maize growth. Their legacy on soil moisture and cumulative organic inputs (i.e., grass biomass) was strongly associated with enhanced mineralization and nitrification rates at early maize season. These effects contributed to increase cumulative N2O emission by 12.8 and 4.8 mg N2O-N m−2 for maize growing after B. brizantha and B. humidicola, respectively, regardless of the N fertilization rate. Thus, the nitrification inhibition potential of tropical grasses can be outweighed by their impacts on soil moisture, N recycling, and the soil microbiome that together dictate soil N2O fluxes

Alterations in soil pH emerge as a key driver of the impact of global change on soil microbial nitrogen cycling: Evidence from a global meta‐analysis

Aim: Soil nitrogen (N) cycling is critical to the productivity of terrestrial ecosystems. However, the impact of global change factors (GCFs) on the microbial mediators of N cycling pathways has yet to be synthesized, and it also remains unclear whether the response of the abundance of N-cycling genes can predict changes in their corresponding processes. Location: Global. Time period: 2000–2021. Major taxa studied: Archaea, bacteria. Methods: We synthesized 8322 paired observations of soil microorganisms related to N cycling from field experiments in which GCFs (climate change and nutrient addition) were manipulated. Results: We found that the abundance of soil microbes and most N-cycling genes were resistant to elevated CO2, experimental warming and water addition/reduction; however, N addition and the combination of N addition with other GCFs significantly increased the abundance of ammonia oxidizer bacteria (amoA-AOB). The results indicated that in steady-state (natural) conditions, the main factors driving the global abundance of soil bacteria, archaea and N-cycling genes varied in terms of the contributions of climatic and edaphic factors. However, upon manipulation of GCFs, the induced change in soil pH was the most essential factor associated with changes in the abundance of soil microbes and N-cycling genes. Notably, the changes in ammonia-oxidizing archaea (amoA-AOA) and amoA-AOB genes, in addition to genes involved in denitrification (nirS and nirK), were significantly correlated with the rates of their corresponding processes, but GCF-induced shifts in the potential nitrification rate (PNR) were explained well by changes in the abundance of the amoA-AOB gene under GCFs. Main conclusions: Our study highlights how ongoing GCFs impact the abundance of soil microbes and N-cycling genes, which might have a profound impact on terrestrial N cycling. Our field-based results provide new insights into the drivers of the abundance of soil microbes and N-cycling genes

Table_2_Edaphic mesofauna responses to land use change for sugarcane cultivation: insights from contrasting soil textures.docx

Land use change (LUC), specifically the cultivation of monoculture sugarcane, can negatively impact soil biodiversity, leading to a decline in soil health and ecosystem functioning. However, while studies focusing on macrofauna and microorganisms are more frequent in the literature, the impacts of LUC on mesofauna are still little known. Therefore, this study aimed to investigate the impacts of the predominant LUC for sugarcane production in Brazil on the diversity of edaphic mesofauna in soils with contrasting textures. In addition, we assessed correlations between biodiversity and soil properties chemical, biological, and physical attributes. We took samples from two sites (clayey and sandy soils) in southeastern Brazil. The sequence of LUC included i) native vegetation (NV), ii) pasture (PA), iii) sugarcane (SC), and iv) sugarcane ratoon (SCr). In the rainy season, monoliths (25 x 25 x 10 cm), soil samples were collected at 0-10, 10-20, and 20-30 cm to assess soil mesofauna, soil chemical (pH, soil organic matter, phosphorus, sulfur, potassium, calcium, magnesium, potential acidity, cation exchange capacity), physical (soil porosity) and biological (microbial biomass carbon and nitrogen) properties. The mesofauna taxonomic groups were quantified after the classification. Briefly, a total of 22 taxonomic groups were classified. The most predominant groups were non-oribatid mites, oribatid mites, and Collembola. Richness and abundance were lower in the three land uses studied (PA, SCr, SC) compared to the intercept (NV). In clayey soil, diversity decreased from NV to PA (-0.68 ± 0.27) and SC (-0.55 ± 0.27) but not to SCr. In sandy soil, land use significantly impacted the mesofauna diversity and evenness index, significantly reducing these indexes in SCr in relation to NV. Although land use change towards more intensified systems resulted in a loss of richness and abundance of soil mesofauna, sugarcane cultivation over the years can recover the diversity of mesofauna in clay-textured soils. These results provide a scientific background to better understand the LUC effects on sugarcane cultivation and support the establishment of sustainable practices that enhance soil health and biodiversity in different soil textures. This study highlights the need for tailored land management considering soil texture and biodiversity for improved ecosystem services.</p

Table_1_Edaphic mesofauna responses to land use change for sugarcane cultivation: insights from contrasting soil textures.docx

Land use change (LUC), specifically the cultivation of monoculture sugarcane, can negatively impact soil biodiversity, leading to a decline in soil health and ecosystem functioning. However, while studies focusing on macrofauna and microorganisms are more frequent in the literature, the impacts of LUC on mesofauna are still little known. Therefore, this study aimed to investigate the impacts of the predominant LUC for sugarcane production in Brazil on the diversity of edaphic mesofauna in soils with contrasting textures. In addition, we assessed correlations between biodiversity and soil properties chemical, biological, and physical attributes. We took samples from two sites (clayey and sandy soils) in southeastern Brazil. The sequence of LUC included i) native vegetation (NV), ii) pasture (PA), iii) sugarcane (SC), and iv) sugarcane ratoon (SCr). In the rainy season, monoliths (25 x 25 x 10 cm), soil samples were collected at 0-10, 10-20, and 20-30 cm to assess soil mesofauna, soil chemical (pH, soil organic matter, phosphorus, sulfur, potassium, calcium, magnesium, potential acidity, cation exchange capacity), physical (soil porosity) and biological (microbial biomass carbon and nitrogen) properties. The mesofauna taxonomic groups were quantified after the classification. Briefly, a total of 22 taxonomic groups were classified. The most predominant groups were non-oribatid mites, oribatid mites, and Collembola. Richness and abundance were lower in the three land uses studied (PA, SCr, SC) compared to the intercept (NV). In clayey soil, diversity decreased from NV to PA (-0.68 ± 0.27) and SC (-0.55 ± 0.27) but not to SCr. In sandy soil, land use significantly impacted the mesofauna diversity and evenness index, significantly reducing these indexes in SCr in relation to NV. Although land use change towards more intensified systems resulted in a loss of richness and abundance of soil mesofauna, sugarcane cultivation over the years can recover the diversity of mesofauna in clay-textured soils. These results provide a scientific background to better understand the LUC effects on sugarcane cultivation and support the establishment of sustainable practices that enhance soil health and biodiversity in different soil textures. This study highlights the need for tailored land management considering soil texture and biodiversity for improved ecosystem services.</p

Feasibility of early fertilization of maize with 15N application to preceding cover crop

Early nitrogen (N) application on live cover crops or their residues is a potential alternative for supplying N demand while enhancing the yield of subsequent cash crops in tropical regions. The objective of applying N on live forage grasses or their residues to no-till (NT) systems is to promote the gradual release of N via straw decomposition to the subsequent crop. However, the N use efficiency by the subsequent crop under early fertilization has not been determined in the end of growing season. The aim of this study was to evaluate whether the most cultivated tropical forage grasses can supply the N demand and enhance the grain yields of maize via the N recovery when N is applied with different timings than the conventional method. A 3-year field experiment was performed using palisade grass [(Urochloa brizantha (syn. Brachiaria)] and ruzigrass (U. ruziziensis) as cover crops with four N application timings to agricultural system: (i) no-N, zero N application; (ii) CC+N, 120 kg N ha−1 applied on live cover crops 35 days before maize seeding; (iii) St+N, 120 kg N ha−1 applied on cover crops straw 1 day before seeding; and (iii) Nv4, conventional method of sidedress N application at the maize V4 (four leaf) growth stage. Except control, all N treatments received 40 kg N ha−1at maize seeding, totalizing 160 kg N ha−1. Straw decomposition and cover crop N accumulation were greater in the treatments in which N fertilizer was applied on palisade grass compared with ruzigrass. High maize yields were achieved with N application on palisade grass or its residues or according to the conventional method, with yields of 13.2, 13.2 and 13.6 Mg ha−1, respectively. Similarly, high maize yields were obtained when N was applied on ruzigrass residues or according to the conventional method (12.1 and 11.8 Mg ha−1, respectively). However, regardless of cover crop species, N recovery was highest when N fertilizer was applied via the conventional method. Additionally, most of the N in maize at harvest came from the soil when N fertilizer was applied to live palisade grass. Thus, best recovery of N fertilizer in the grain occurred in maize fertilized using the conventional method. Our results indicate that agricultural systems characterized by high dry matter from palisade grass have the potential to recycle and supply N to subsequent maize. Although palisade grass combined with early N fertilizer application may enhance maize response and yield, the current conventional method of N fertilizer application on maize allows higher recovery from N fertilizer while increasing the maize yield in tropical food production

LT‐Brazil: a database of leaf traits across biomes and vegetation types in Brazil

Motivation Leaf traits represent an important component of plant functional strategies, and those related to carbon fixation and nutrient acquisition form the leaf economics spectrum. However, observations of functional leaf traits are underrepresented in tropical regions in comparison with those in temperate areas. Brazil, a country with continental scale and vast biodiversity is a timely example, where many biomes are impacted by human activities and climate change. However, leaf traits relevant to understand vegetation responses to these impacts remain poorly quantified for many species found in the country. We compiled an extensive data set of four functional leaf traits for native woody species occurring in the Brazilian territory. In addition to trait observations, sampling dates and geo-references were compiled and climatic parameters and soil properties of each sampling site were extracted from several databases. Main types of variables contained The LT-Brazil data set contains 3,479, 1,216, 775 and 775 clean observations of leaf mass per area, leaf nitrogen (N) concentration per unit mass, leaf phosphorus (P) concentration per unit mass, and leaf N : P ratio, respectively, from native woody species, encompassing information of biome, vegetation, taxonomic data, geographical coordinates, climatic parameters, as well as soil properties. Spatial location and grain We compiled trait observations from 223 sites under native vegetation distributed in all main biomes (i.e., Amazônia, Caatinga, Cerrado, Mata Atlântica, Pampa and Pantanal) across the Brazilian territory. Time period and grain The data represent information published and/or sampled during the last 25 years. Major taxa and level of measurement Our compilation was focused on trait data observed for native woody species, excluding monocots, palm trees, herbs, and hemiparasitic plants. Thus, 108, 478 and 1,321 botanical families, genera and species were included, covering c. 9% of the woody angiosperm flora of Brazil. Software format Data are provided as comma-separated value (.csv) files

U.S. cereal rye winter cover crop growth database

Abstract Winter cover crop performance metrics (i.e., vegetative biomass quantity and quality) affect ecosystem services provisions, but they vary widely due to differences in agronomic practices, soil properties, and climate. Cereal rye (Secale cereale) is the most common winter cover crop in the United States due to its winter hardiness, low seed cost, and high biomass production. We compiled data on cereal rye winter cover crop performance metrics, agronomic practices, and soil properties across the eastern half of the United States. The dataset includes a total of 5,695 cereal rye biomass observations across 208 site-years between 2001–2022 and encompasses a wide range of agronomic, soils, and climate conditions. Cereal rye biomass values had a mean of 3,428 kg ha−1, a median of 2,458 kg ha−1, and a standard deviation of 3,163 kg ha−1. The data can be used for empirical analyses, to calibrate, validate, and evaluate process-based models, and to develop decision support tools for management and policy decisions