Gabriel Maltais-Landry

• PhD Biology
• Professor (Assistant) at University of Florida

Inefficient P use in agriculture results in soil P accumulation and losses to surrounding ecosystems, highlighting the need to use P inputs more efficiently. Composts reduce the need for mineral fertilizers by recycling P from wastes at the regional scale, whereas cover crops reduce soil P losses and have the potential to increase internal soil P r...

Phosphorus (P) is a key limiting factor in many terrestrial ecosystems because most soil P is bound to soil minerals or organic matter. Increasing P cycling rates can increase P availability, including in agricultural soils that receive external P inputs. For example, cover crops may increase P cycling rates via plant uptake and P release during mi...

Evaluating the contribution of weather and its individual components to recent yield trends can be useful to predict the response of crop production to future climate change, but different modeling approaches can yield diverging results. We used two common approaches to evaluate the effect of weather trends on maize (Zea mays L.) and wheat (Triticu...

Increasingly, private firms are focusing on environmental sustainability. However, such entities continue to experience difficulty in operationalizing sustainable practices in management decisions. For firms that own natural ecosystems, part of the difficulty stems from their inability to balance the environmental value of conserving these ecosyste...

Nitrogen (N) processing in constructed wetlands (CWs) is often variable, and the contribution to N loss and retention by various pathways (nitrification/denitrification, plant uptake and sediment storage) remains unclear. We studied the seasonal variation of the effects of artificial aeration and three different macrophyte species (Phragmites austr...

Soil health assessment is critical for understanding and promoting sustainable soil management practices. Soil health assessment methods incorporate a variety of inherent environmental and edaphic properties, including climate variables and texture, as well as cropping system. However, these inherent properties often vary systematically among cropp...

Cabbage (Brassica oleracea var. capitata) is an important vegetable crop grown in the sandy soils of Florida. The availability of phosphorus (P), an essential nutrient for cabbage growth and yield, can be limited by soil pH, aluminum (Al), iron (Fe), and calcium (Ca). This study assessed the response of cabbage plant P uptake and yield to different...

The objective of this study was to evaluate potato growth, phosphorus (P) uptake, total and marketable yield response to multiple rates of P fertilizer applied at planting, emergence, and tuber initiation stages in 2019 and 2020. Varying pre-plant (Ppp) rates (0, 25, 49, 74 kg ha−1 P) and two supplementary liquid P applications (0 and 12 kg ha−1 P)...

Polymer-coated controlled-release fertilizers’ (CRFs) unique nutrient release mechanism has the potential to mitigate the leaching of mobile soil nutrients, such as nitrate-nitrogen (NO3-N). The study aimed to evaluate the capacity of a polymer-coated CRFs to maintain maize (Zea mays L.) crop growth/health indicators and production goals, while red...

With rising food demand, sandy soils are increasingly used in agriculture. Carbon nanomaterials (CNMs) are a potential soil amendment that can enhance soil fertility and health in sandy soils, but most studies have been conducted in controlled greenhouse or laboratory environments. Therefore, there is limited information on the effect of CNMs on so...

In 2010, the Mehlich 3 (M3) soil extractant replaced Mehlich 1 (M1) as the official soil test for Florida. While a linear expression was initially established to reasonably estimate M3-P values based on M1-P recommendations for acid-mineral soils in Florida, Florida farmers have been skeptical of revised P recommendations and reported lower yields...

Synthetic fertilizers are the main nitrogen (N) input used in specialty crop systems established on sandy soils of Florida, although organic amendments and fertilizers can be used as a substitute. Organic N contained in these products must be mineralized before crop uptake, which is affected by amendment properties, soil properties, and temperature...

Carbon nanomaterials (CNMs) — amendments with carbon in nanoscale form —could potentially enhance fertilizer delivery efficiency in agriculture, but their interaction with soil properties and nutrient co-mobility, especially in coarse-textured soils, remain poorly understood. We conducted a column leaching study in repacked soil columns to compare...

A sorghum sudangrass (SSG) cover crop grown after a cash crop could take up residual nitrogen (N) before it is lost. As in‐field monitoring of SSG properties is laborious, predicting biomass and N concentrations with spectral sensors could be useful. At two sites in Live Oak, Florida, we evaluated the response of SSG to residual N from previous N f...

Organic producers have few certified organic options to meet crop nitrogen (N) demand. Poultry-based amendments, including manures and processed fertilizers from livestock waste (e.g., feather meal), are commonly used in these systems, but synchronizing nutrient release with plant demand is challenging. Cover crop residues are also used in organic...

Widespread use of soluble mineral fertilizers derived from non-renewable sources has raised concerns about environmental impacts, energy expenditures, and sustainability. Combining biosolid and mineral sources of phosphorus and potassium to produce organomineral fertilizers (OMF) can be used as an alternative nutrient source while reducing the envi...

Cover crops have been widely adopted to improve soil functions in agroecosystems, including providing carbon (C) inputs that can contribute to soil C sequestration. However, soil C changes may be slow after introducing cover crops in unfavorable environments for soil organic matter (SOM) accumulation, like the Southeast United States subtropical re...

Integrating a perennial forage grass like bahiagrass (Paspalum notatum Flugge) into the traditional rotation of cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) increases yields and reduces irrigation needs in the Southeast United States. However, the long‐term effects of this sod‐based rotation (SBR) on soil properties remain unclea...

Pastureland contributes a large share of the global soil C stock, much of which derives from root systems. Management practices like fertilization and the introduction of improved forages have clear benefits to aboveground forage production, but their impacts on belowground biomass (BGB) and hence soil C are less clear, especially in relatively und...

Background and aimsCover crops are an integral constituent of sustainable subtropical agroecosystems. Using grass/legume mixtures as opposed to monocultures has the potential to maximize their multifunctionality. This project aimed to understand temporal patterns of nitrogen (N) release of cover crop monocultures and mixtures in a subtropical veget...

Abstract: A significant bottleneck of current agricultural systems remains the very low agronomic efficiency of conventional agrochemicals, particularly in sandy soils. Carbon nanomaterials (CNMs) have been proposed to address this inefficiency in sandy soils, which could potentially improve soil fertility and enhance crop growth and physiological...

Fruit orchards are a major part of agricultural production, and planting cover crops (CCs) in the row middles of these agroecosystems can increase soil nutrient availability. However, it is largely unknown how different mixtures of CCs may impact soil carbon (C) and nitrogen (N) concentrations, greenhouse gas emissions (GHG), and the soil microbiom...

Cover crops are typically grown during the summer in Florida’s organic vegetable systems, where they can affect nutrient cycling, soil health, and pests/pollinators. We compared the effects of five summer cover crops and a weedy fallow on marketable yields and the cycling of phosphorus, potassium, and carbon. Weed, nematode, and insect pollinator a...

Growers in the United States (US) southeast are often recommended to reduce nitrogen (N) fertilization after peanut (Arachis hypogaea L.) by cooperative Extension services. However, these guidelines are not supported by the scientific literature. An experiment was conducted to quantify N contributions from peanut residues to a subsequent carinata (...

As a recently introduced crop in the United States, there are limited data regarding temporal nutrient accumulation and partitioning dynamics of Brassica carinata (carinata). A four site‐year study was conducted in Jay, FL and Salisbury, NC during the 2018–2019 and 2019–2020 growing seasons. Three carinata genotypes (DH‐157.715, M‐01, and Avanza 64...

PurposeImproving crop yields by increasing fertilizer-use-efficiency is essential to minimizing agriculture's environmental impact. Water-dispersible carbon nanomaterials (CNM) have emerged as an innovative material to improve crop yields by increasing nutrient utilization and enhancing crop physiological processes. However, the optimum dose of CNM...

Certified organic farmers who grow mixed vegetables often rely on composted manure as their primary nutrient source to build soil organic matter and long-term fertility, but this can result in excessive phosphorus inputs relative to processed organic fertilizers. We established a two-year experiment to compare two certified organic fertilizers − 13...

High-throughput sequencing has become a critical tool for studying microbiomes by measuring relative microbiome profiling, although this typically overlooks the absolute abundance of microbiomes. Consequently, pathological, physiological, and ecological roles of microbial communities may be represented inaccurately. To address this, we estimated ab...

Rapid urbanization results in the accumulation of food wastes that can be composted and diverted from landfills. Previous lab incubations demonstrated that food-based composts can increase soil N relative to manure-based composts, but these benefits were not tested within a crop system. We assessed soil fertility and yield of spinach (Spinacia oler...

Soil health is a promising lens through which to approach land management, having the potential to serve as a descriptor of biophysical processes and as an effective communication tool across stakeholders. However, this potential has been largely unrealized due to difficulty in quantitatively assessing soil health and linking those assessments to o...

Cover crops can improve internal nitrogen (N) cycling in agroecosystems while increasing crop yield, with mixtures potentially providing more benefits than monocultures. Cover crops may be especially useful for organic vegetable producers that have few options to meet crop N demand with certified organic products. We established a two-year experime...

Cotton root microbiomes were investigated in two long-term rotation systems established in 2000, a bahiagrass (Paspalum notatum Flugge)-bahiagrass-peanut (Arachis hypogaea L.)-cotton (Gossypium hirsutum L.) rotation (sod-based rotation, SBR) and a peanut-cotton-cotton rotation (conventional rotation, ConR), from 2017 to 2019. Our results demonstrat...

Integrating two years of bahiagrass (Paspalum notatum Flugge) into the peanut (Arachis hypogea L.) and cotton (Gossypium hirsutum L.) cropping system improves soil quality and crop production as compared to a conventional peanut-cotton-cotton rotation (CR). However, it is unclear if this system, known as a sod-based rotation (SBR), affects soil bio...

Citrus production has been declining in Florida since 2004, mainly because of Huanglongbing (HLB), a deadly disease that is affecting an increasingly large proportion of worldwide citrus production. Nutrients such as nitrogen, calcium, and magnesium play an important role in defense mechanisms and could extend the productive life of HLB-affected ci...

Optimizing nitrogen (N) input rates for vegetable production is crucial in Florida to reducing production costs and enhancing environmental sustainability. Asian vegetables emerging and expanding in Florida not only increase profit for growers, but also enhance food diversity for consumers. The objective of this study was to gain a better understan...

The discovery of nanocarbon forms and their potential application presents new opportunities in agriculture to enhance crop growth and quality. While the application of carbon nanomaterial (CNM) in agriculture is steadily rising, its fate on soils biogeochemistry isn’t well documented yet. Our study aims to evaluate the effect of novel CNM at diffe...

Brassica carinata, a non-food oilseed feedstock mainly used for biofuel, is a potential alternative winter crop for the southeastern (SE) US. Data on carinata C and N mineralization dynamics are essential in lifecycle analyses (LCA) studies for sustainability certifications. Decomposition pattern of Brassica carinata (carinata) determines availabil...

There are limited data regarding temporal nutrient accumulation and partitioning dynamics of carinata (Brassica carinata). As a recently introduced crop in the US, such studies inform the rate of macro and micronutrient accumulation and will aid fertility management decisions in carinata. The objective of this study was to quantify nutrient uptake...

Farmers in the US southeast are often recommended to reduce nitrogen (N) fertilization after peanut (Arachis hypogaea L.) by co-operative Extension services. However, these guidelines are not supported by the scientific literature. An experiment was conducted to quantify the N credit from peanut to a subsequent carinata (Brassica carinata) crop. A...

The bacterial disease Huanglongbing (HLB) has drastically reduced citrus production in Florida. Nutrients play an important role in plant defense mechanisms and new approaches to manage the disease with balanced nutrition are emerging. Nutrients like nitrogen (N), calcium (Ca), and magnesium (Mg) could extend the productive life of affected trees,...

Brassica carinata (carinata), a non‐food oilseed feedstock mainly used for biofuel, is a relatively new alternative winter crop in the southeastern (SE) United States (US). However, there are limited N rate and N application timing data available at the regional scale. These data are needed to expand production in the SE US. A N rate study was cond...

Agricultural intensification has substantially reduced soil biodiversity as well as agroecosystem functions and services. Sustainable agroecosystems that increase crop diversity through rotation may promote soil biodiversity and above-belowground interactions. Studying ecological networks, soil communities, and abiotic impacts simultaneously increa...

Sunn hemp ( Crotalaria juncea L.), as a summer leguminous cover crop, is often grown before fall planting of strawberries ( Fragaria × ananassa Duch.) in Florida. Although sunn hemp has been suggested as a green manure for supplying nitrogen (N) to subsequent crops, limited information is available regarding the contribution of sunn hemp biomass to...

There are limited data regarding temporal nutrient accumulation and partitioning dynamics of carinata (Brassica carinata). As a recently introduced crop in the SE US, such studies inform the rate of macro and micronutrient accumulation and aid fertility management decisions. The objective of this study was to quantify nutrient uptake and partitioni...

Farmers in the US southeast are often recommended to reduce nitrogen (N) fertilization after peanut (Arachis hypogaea L.) by co-operative Extension services. However, these guidelines are not supported by the scientific literature. An experiment was conducted to quantify the N credit from peanut to a subsequent carinata (Brassica carinata) crop. A...

Brassica carinata, a non-food oilseed feedstock mainly used for biofuel, is a potential alternative winter crop for the southeastern (SE) US. However, there are agronomic constraints to regional Brassica carinata production, including fertility optimization. An N rate study was conducted during the winter-spring growing season during 2017-2018 and...

Phosphorus(P) is a key macronutrient required by crops, and addition of P through fertilization is needed to maintain soil productivity. Phosphate rock, which is single largest source to develop P fertilizers, is a finite resource. Innovative technologies for utilizing relatively low-grade phosphate rock not only add economic benefit to the phospha...

Can Organically Activated Dolomite Phosphate Rock (DPR) fertilizer be Effective?

Nutrient concentrations and availability differ significantly among composts depending on the materials used and the production process. Our objective was to assess how different composts affect nitrogen (N), phosphorus (P), and potassium (K) availability and plant uptake. In a greenhouse experiment maintained between 10-27 ℃, we grew spinach (Spin...

Nutrient concentration and availability vary substantially among composts depending on the materials used and the production process. Composts produced from agricultural operations typically utilize animal wastes such as manures, whereas composts produced in urban areas mainly incorporate food and yard waste. Our objective was to assess how differe...

A core principle of organic farming is the reliance on internal nutrient recycling, favoring nutrient sources produced on farms (e.g.,manures) as opposed to those that are not (e.g., processed fertilizers, municipal compost). Soil fertility management varies tremendously among organic vegetable production systems, potentially with large effects on...

Nutrient concentrations and availability vary substantially among composts depending on the materials and processes used during production. As a general rule, agricultural operations compost mostly animal wastes such as manures, whereas composts produced in urban areas mainly incorporate food waste, sometimes mixed with yard waste. Our objective wa...

Optimal manure management can maximize agronomic benefits and minimize environmental impacts. Field experiments were conducted in the Pacific Northwest (Vancouver, Canada) to determine how chicken and horse manures that were fall-applied to meet nitrogen crop demand affect soil ammonium (NH4⁺) and nitrate (NO3⁻), apparent net mineralization (ANM) a...

Manures allow for nitrogen (N) and phosphorus (P) recycling but low N:P ratios result in P over-fertilization when applying manures to meet crop N demand. Such stoichiometric imbalances can result in inefficient use of non-renewable P resources as well as aquatic eutrophication. On average, P surpluses in wheat (Triticum aestivum L.) and corn (Zea...

Manure‐based soil amendments (MBSAs) must be managed optimally to maximize N concentration and availability while minimizing environmental impacts (e.g., greenhouse gas [GHG]) emissions. We conducted an 83‐d incubation study to determine the effects of different moisture (60 or 120% of water‐holding capacity [WHC]) and temperature (4 or 20°C) condi...

Implications: We monitored the impact of rainfall protection on nutrient losses and greenhouse gas emissions during the decomposition of broiler chicken, turkey and horse manure-based soil amendments. We found large ammonium and potassium losses when amendments were exposed to rainfall, resulting in a 37-74% decrease in N inputs when compared to a...

Background and aims Plants affect phosphorus (P) cycling through uptake and the mobilization of P from several soil pools into soil solution. The effects of seven cover crop species – three legumes (variable morphology), three cereals (variable domestication degree), one mustard (non-mycorrhizal) – on P cycling were compared in a greenhouse experim...

Background and aims Cover crops provide benefits in agricultural systems with high P availability (i.e., optimal or excessive soil P for plant growth) by reducing losses of soil phosphorus (P) via erosion and leaching, and potentially by increasing soil P availability when P is released during residue decomposition. We quantified P transfer from co...

The effects of design and operational factors on the dynamics of ciliated protozoa in constructed wetlands (CWs) treating wastewater remain poorly known, although bacterivory by ciliates could have important implications for nutrient cycling in these systems. We conducted a greenhouse experiment with eight wetland mesocosms (1 m(2)) fed with synthe...

Submerged aquatic vegetation (SAV) may serve as an integrative proxy of spatial and temporal nitrogen (N) availability in aquatic ecosystems as plants are physiologically capable of storing variable amounts of N. However, it is important to understand whether plant species behave similarly or differently within and among systems. We sampled differe...

One of the key challenges to many alternative energy options is land use competition, such as conflict with food production (e.g., corn or sugar cane ethanol) or natural resource protection (e.g., solar panels in desert habitat). Wind power has largely avoided these conflicts by leasing land from farmers and maintaining a small footprint on the lan...

Hydroponics culture generates large amounts of wastewater that are highly concentrated in nitrate and phosphorus but contains almost no organic carbon. Constructed wetlands (CWs) have been proposed to treat this type of effluent, but little is known about the performance of these systems in treating hydroponic wastewater. In addition, obtaining sat...

Constructed wetlands (CWs) are efficient at removing excessive nutrients from wastewaters. However, this removal often results in the flux of important greenhouse gases (GHG), such as nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) that could mitigate the environmental benefits of CWs. We studied the efficiency of artificial aeration an...

Greenhouse gas (GHG) emissions by constructed wetlands (CWs) could mitigate the environmental benefits of nutrient removal in these man-made ecosystems. We studied the effect of 3 different macrophyte species and artificial aeration on the rates of nitrous oxide (N(2)O), carbon dioxide (CO(2)) and methane (CH(4)) production in CW mesocosms over thr...

We studied the contribution of artificial aeration, loading rate, and macrophyte species on pollutant removal in horizontal subsurface flow constructed wetlands (HSSFCWs) treating reconstituted trout farm wastewater. Twelve 1 m2 mesocosms located in a controlled greenhouse environment were used to test two species of macrophytes (Phragmites austral...

The effect of organic loading, season and plant species on the treatment of fish farm effluent was tested using three-year old mesocosm wetland systems. During one year, nine 1 m2 mesocosms (horizontal subsurface flow), located in a controlled greenhouse environment, were fed with a reconstituted fish farm effluent containing a high fraction of sol...