Vimala Nair

University of Florida | UF · Department of Soil and Water Sciences

Agroforestry—the practice of growing trees and crops in interacting combinations—is recognized worldwide as an integrated approach to sustainable land-use. It is estimated to be practiced over 1 billion hectares in developing countries, and to a lesser extent in the industrialized countries. Agroforestry systems (AFSs) are believed to have a higher...

The risk of phosphorus loss from agricultural soils can have serious implications for water quality. This problem has been noted particularly in sandy soils in several parts of the world including Europe (e.g., the Netherlands, Italy, and UK) and the southeastern USA. However, the capacity of a soil to retain P is limited and even non-sandy soils h...

Interest in the use of biochar in agriculture has increased exponentially during the past decade. Biochar, when applied to soils is reported to enhance soil carbon sequestration and provide other soil productivity benefits such as reduction of bulk density, enhancement of water-holding capacity and nutrient retention, stabilization of soil organic...

Off‐site transport of excess soil P from repeated P fertilizer applications constitutes waste of a vital resource and poses an environmental risk. Excess P can be mined by growing crops without P addition until it is exhausted to the point of P deficiency. This study evaluated the utility of the “soil phosphorus storage capacity” (SPSC) as an indic...

Biochar, a carbonaceous solid material obtained from the pyrolysis of biomass, has received considerable research attention because of its unique properties and potential to improve crop yields and soil carbon (C) sequestration while reducing environmental degradation and carbon footprints (CF). This paper summarizes the available results on severa...

Animal manures such as poultry litter supply plant‐available phosphorus (P), but P loss can occur following manure application to crops, particularly in sandy soils. The transformation of poultry litter biochar (PLB) reduces P losses upon application to crops while providing essential plant nutrients. Our objectives were to evaluate: (1) the effect...

Silvopastoral systems (SPS) incorporating non-native tree species such as Eucalyptus are increasingly being adopted in the Cerrado region of Brazil. The climate-change mitigation potential of the practice, although hypothesized, has not been assessed vigorously. The objective of this research was to measure the extent of SOC accumulation under SPS...

Oligotrophic wetlands of the Everglades are often the final recipients of nutrients from adjacent ecosystems and tend to accumulate phosphorus (P) in their soils. Understanding P source and sink dynamics in wetlands is critical for managing wetland ecosystems and protecting downstream resources. This study evaluated the soil P storage capacity (SPS...

Biosolids have been long used as a soil amendment to promote nutrient recovery. The readily releasable forms of nutrients present in this biowaste, such as phosphorus (P), along with their over application, can be detrimental to the environment, causing eutrophication. Pyrolysis, the thermal decomposition of organic materials at elevated temperatur...

During the past few decades, commercial silvopastoral systems (SPS) with exotic Eucalyptus (hybrid) trees have become popular in the Brazilian Cerrado (savanna). With the increasing awareness about the role of carbon (C) storage in soils as a climate-change mitigation strategy and the relationship between the nature of soil aggregates and the soil’...

Oligotrophic wetlands of the Everglades are often the final recipients of nutrients from adjacent ecosystems and tend to accumulate phosphorus (P) in their soils. Understanding P source and sink dynamics in wetlands are critical for managing wetland ecosystems and protecting downstream resources. In this study, soil P storage capacity (SPSC) was ev...

Tropical soils usually lack phosphorus (P) availability due to the high P retention associated with these soils, limiting plant productivity. Brazil is the largest tropical country and worldwide exporter of beef, where overgrazing and frequent slash and burn practices resulted in large areas of degraded pastures. Land degradation and lack of releas...

This chapter discusses the significant role agroforestry systems (AFS) play in realizing ecosystem services other than soil productivity improvement, climate change mitigation, and biodiversity conservation. Such “other” services include the improvement of hydrological characteristics and water quality, socio-cultural and recreational services, and...

Agroforestry homegardens consist of multispecies combinations of a variety of economically useful plants including trees, shrubs, vines, and herbaceous species, often grown in association with livestock, in small landholdings around or adjacent to the home. These unique farming systems founded on generations of experience and traditional knowledge...

This chapter briefly explains the fundamental processes that support plant production on Earth and clarifies the several terms and methods used for measuring and expressing plant productivity. Photosynthesis is the process by which green plants and some other organisms use sunlight (solar energy) to synthesize carbohydrates (chemical energy) from c...

The multipurpose tree (MPT) is a term that is used almost exclusively in tropical agroforestry. In a general sense, the perennial and taller plant components of agroforestry systems (AFS) are referred to as trees, but the MPTs are woody species that are deliberately kept and managed for more than one preferred use, product, or service. Such species...

Silvopasture is a broad term encompassing different forms of integrating trees, forage, and domesticated animals on the same unit of land. The practice ranges from the traditional, extensive animal grazing under woodlots and forests to modernized intensive forms of tree–animal integration. These can broadly be grouped under two categories: grazing...

Recognized for long as the kingpin of agricultural soil management, soil organic matter (SOM) has attained added importance lately because of its significant role as a carbon sink. This chapter will focus on the issues related to SOM in soil productivity enhancement, which is of special relevance to the nutrient-depleted tropical soils; issues rela...

Since its modest beginning in the late 1970s, agroforestry has become widely recognized and accepted as a sustainable approach to land management the world over. Although the international investments in agroforestry research and development have been comparatively meager, those investments have paid off extremely well. The role and potential of ag...

The term agroforestry was coined in 1977 as part of the early international efforts to initiate research on integrated production systems involving crops and trees. Numerous discussions and arguments were held during those early days to define and characterize agroforestry, and several definitions were proposed. This chapter reviews the development...

This chapter examines the role of agroforestry in carbon sequestration (CS) and climate-change mitigation (CCM) based on the scientific hypotheses, research results, and observations accumulated so far. Since the emergence of climate change (CC) as a prominent global issue in the late twentieth century, agroforestry has received immense attention a...

This introductory chapter traces the historical evolution and development of agriculture and forestry as separate disciplines and chronicles how the demands and challenges of the post-World War II era led to the emergence of agroforestry as an interface between the two. The Green Revolution technologies of the late 1900s paved the way for increasin...

The main purpose of a classification scheme is to provide a practical framework for the synthesis and analysis of the information about existing agroforestry systems (AFS) and the development of new and promising ones. During the early stages of AF development in the tropics, a substantial database was generated from a global inventory of tropical...

Biological Diversity, or biodiversity, refers to all living things and the interactions among them, including the diversity within species, between species, and of ecosystems. Agricultural biodiversity or agrobiodiversity is a subset of biodiversity including all crops and livestock and all interacting species of pollinators, symbionts, pests, para...

Biological nitrogen fixation (BNF) refers to the process by which the nitrogen that is present abundantly in the atmosphere as non-reactive molecular dinitrogen (N2) is converted into reactive forms that become available to plants and thereby to all life forms. The key process of BNF is the conversion of N2 to ammonia (NH3) catalyzed by the enzyme...

The shaded perennial systems, also called plantation-crop combinations, include managed multistrata tree-crop associations predominantly in the tropics, in which the main crops are perennials that are harvested periodically like arable crops. These tree crops are economically and socially very important to the countries where they are cultivated be...

This chapter examines the role of agroforestry systems (AFS) in fulfilling the demands and expectations of food security and the related United Nations Sustainable Development Goals (SDGs). These issues are particularly focused on developing countries, where the predominance of small farms is a distinguishing feature. The definition of a small farm...

Plant component interactions refer to the effect of one plant (component) on another or the whole system. In agroforestry systems (AFS), since the woody perennials are dominant components, these interactions are usually referred to as tree–crop interactions or tree-animal interactions. Early assessments of the potential interaction effects in agrof...

Proper management of soils has been central to the welfare of human society since very early times. An understanding of the nature and properties of soils is, indeed, critical to the success of any land-use system. Since the beginning of agricultural research in the mid-1800s, soils and soil-related aspects including plant nutrition were dominant t...

In land-use parlance, the terms tropical and temperate are used loosely as approximate synonyms for developing countries and industrialized regions, respectively. From the agroforestry perspective, the arid and semiarid lands, and the subhumid and humid lowlands and highlands recognized in the FAO reports are considered as tropical developing regio...

Shifting Cultivation or swidden farming is considered the oldest form of agriculture. It refers to the traditional, centuries-old farming system, in which land under natural vegetation is cleared, cropped – usually with food crops – for a few years, and then left untended allowing the natural vegetation to regenerate; a few years later, the farmer...

The concept of soil conservation has evolved over several decades to include both the prevention of soil loss and reduction of its productive capacity. Land degradation, an allied term, refers to any change or disturbance to the land perceived to be deleterious or undesirable. Both these terms are prominent components of soil health, a term that ha...

The temperate countries/regions considered in this chapter include the USA and Canada, Europe, southern Australia and New Zealand, parts of China, and the southern regions of South America, with the primary focus on North America and Europe where agroforestry has made significant strides. Historically, natural forests and woodlands were used for gr...

Alley cropping is an agroforestry practice of growing an arable crop between rows of trees or perennial shrubs. In tropical alley cropping, the perennial species, usually leguminous trees or shrubs, are planted and managed as hedgerows less than 10 m apart with the crop planted in the interspaces or alleys between the hedgerows. The trees are prune...

Agroforestry – the practice of growing trees and crops in interacting combinations – is recognized the world over as an integrated approach to sustainable land-use. Agroforestry systems, being multifunctional, facilitate not only the production of food and wood products but also provide a variety of ecosystem services such as climate-change mitigat...

Ecosystem services (ES) are the benefits that people obtain from ecosystems. The term became popular in both scientific literature and common parlance around the turn of the century. The concept of ecosystems as the organisms and the non-living environment with which they interact has been popular for a long time, but it was not until the latter pa...

This chapter deals with a vast array of complex and diverse systems and practices that are little known outside the limited regions where they are practiced but are revered by the local inhabitants for their multiple products, outputs, and services. The term Cinderella agroforestry systems is used to refer to such “downtrodden” or little-explored s...

Agricultural wastes from plant and animal operations are often land applied to recycle and manage residues. Compositional variability among these wastes is vast. Some waste components can potentially represent a threat to the environment and humans depending on their nature, application loads, and soil type. Biochar, the product obtained by biomass...

Background and aims Agroforestry systems combining trees with crops or pastures have been widely used to reduce water, soil, and nutrient losses and associated water pollution from agricultural lands in both temperate and tropical regions. However, reviews on improvement/efficiency and the scope of such reductions by soil, management, climate, and...

Growing shade-tolerant perennial crops under trees is an economically attractive land-use activity in the tropics; but the importance of these systems in facilitating ecosystem services such as soil carbon sequestration is seldom recognized. We assessed soil carbon stock at various depths (0-10, 10-30, 30-60, and 60-100 cm) in shaded perennial agro...

Shaded perennial agroforestry systems (AFS) are regarded as desirable land-use practices that improve soil carbon sequestration. However, most studies assume a positive correlation between above ground and below ground carbon without considering the effect of past and current land management, textural variations (silt and clay percentage), and such...

Phosphorus (P) loss models use Langmuir isotherms to calculate P bonding strength (KL), equilibrium P concentration (EPC0), and P sorption maximum (Smax). A protocol has been developed for Florida sandy soils allowing the estimation of isotherm parameters using simple extraction techniques without generating time- and resource-consuming isotherms....

Planting and managing native fodder trees and shrubs on degraded lands offers a promising approach to establishing resilient silvopastoral systems (SPS) in the semiarid Caatinga region of Brazil (Pinheiro & Nair, 2018). Although several examples of such successful smallholder initiatives are available, their experience is seldom known or recognized...

In Brazil, silvopastoral systems (SPS) are practiced in about 2 million hectares with Eucalyptus hybrids as the main tree species, and the area is increasing because of governmental incentives. To understand the influence of such systems on soil organic carbon (SOC) storage, we studied C content in three aggregate size classes in four land-use syst...

Excess phosphorus (P) loading due to anthropogenic activities has been identified as a primary cause of surface water eutrophication, but it is controversial whether P is a contributor to groundwater contamination. In this study, subsurface transport of P to groundwater and its environmental risk across different land uses was investigated in a kar...

Global phosphate reserves are being depleted at an alarming rate even as excess phosphorus (P) application has resulted in surplus (“legacy”) soil P. Legacy P can be recovered by crops if excess fertilizer application is avoided. We conducted a field experiment for a typical regional cropping system at three sites on three different soil types in F...

Determination of Langmuir isotherms and subsequent calculation of KL, the phosphorus (P) bonding strength, and the equilibrium P concentration (EPC0) of a soil is a tedious and time-consuming process. A protocol using simple extraction techniques has been developed for Florida sandy soils allowing the estimation of isotherm parameters without gener...

Poster presented at the USDA-NIFA Project Directors Meeting at the University of Delaware, October 01 - 03, 2018

Core Ideas Establish a common threshold in P saturation across a geographic diversity of soils. Predict water‐soluble P from soil P storage capacity to guide fertilizer strategies. Relate runoff P concentration with soil P storage capacity. Loss of legacy soil phosphorus (P) due to historical over‐application of fertilizers and manures can result...

Use of biochar as a fertilizer has gained prominence recently as an alternative to inorganic phosphorus (P), supplies of which are dwindling. Biochar prepared from different feedstocks behaves differently with respect to P retention and release. We evaluated P release from biochars from different feedstocks, including mixed hardwoods, poultry litte...

Although several studies on carbon sequestration under agroforestry systems (AFS) are reported in the literature, they are highly variable in the study procedures as well as the nature of systems and study locations. This makes it difficult to extrapolate the results to broader contexts of systems and locations outside the specific locations of the...

Soil management practices and land-use systems (LUS) have considerable influence on the soil’s aggregate hierarchy. We evaluated the relative distribution of three soil aggregate-size classes: macroaggregates (MA: 250–2000 μm), microaggregates (MI: 53–250 μm), and silt + clay size-fraction (<53 μm), in four soil-depth classes (0–10, 10–30, 30–60, a...

Agricultural production systems have become highly dependent on chemical products and technological inputs resulting in ecosystem degradation on a massive scale. To minimize external fertilizer inputs, use of biochar that can be obtained from locally available farm materials could substitute or complement the use of synthetic products. Wide differe...

The contribution of agroforestry systems (AFS) to enhance soil organic carbon (SOC) storage in soil layers due to the presence of deep tree roots are of interest in the context of promoting carbon sinks and greenhouse gas mitigation. To quantify the relative soil C contribution from trees in agroforestry systems (AFS), this study assessed the repor...

Please see the complete paper, pages 351-354, in the Conference Proceedings. Using biochar from sewage sludge and other feedstocks in European agroforestry: Opportunities and challenges. p 351-354. 4th European Agroforestry Conference - Agroforestry as Sustainable Land Use. Nijmegen, Netherlands. May 2018.

Poster presented at the USDA-NIFA Project Directors Meeting, Washington DC, January 29-31, 2018

Mapping soil nutrients can help smallholder farmers identify soil nutrient status and implement site-specific soil management schemes. In the past, Digital Soil Mapping has seldom been utilized to guide soil nutrient management in smallholder farm settings in South India. The objective of this research was to analyze the spatial resolution effects...

Background and Aims Silvopastoral management of tree plantations is becoming popular in Brazil. The impact of this practice on carbon dynamics of these soils is unknown, and predicting it is difficult because historical land-use records of the region do not exist. The objective of the study was to quantify the relative soil organic carbon (SOC) con...

Digital soil mapping (DSM) is gaining momentum as a technique to help smallholder farmers secure soil security and food security in developing regions. However, communications of the digital soil mapping information between diverse audiences become problematic due to the inconsistent scale of DSM information. Spatial downscaling can make use of acc...

The importance of subsurface phosphorus (P) transport in deterioration of surface water quality is well documented. Practices and treatments have been identified and modeling approaches have been implemented to decrease the subsurface P load to surface waters. Soil phosphorus storage capacity (SPSC) is a site-assessment tool that predicts the poten...

This 4-page fact sheet is part of the Soil Phosphorus Storage Capacity (SPSC) for Phosphorus Risk Assessment and Management series. This series is intended for use by those who are interested in management practices and policies that minimize the risk of phosphorus loss from soils. Written by Biswanath Dari, Vimala D. Nair, and Willie G. Harris and...

The paradox of biochar with high cation exchange capacity and at its ability to adsorb phosphorus (P) at the same time has puzzled scientists. Our research has shown that: i) biochars can constitute a P source when applied to minimally P-impacted sandy soils, and ii) biochar- enhanced P sorption at elevated solution concentrations may be reversible...

Biochar is obtained by biomass heating in the complete absence or low concentrations of oxygen, through the process known as pyrolysis. The diversity in biochar feedstocks may confer different abilities in desorption of phosphorus (P). Therefore, biochar application at the same rate to soils would have different P release properties that are a func...

Biochar as a soil amendment in land-use systems has attained prominence recently; numerous studies in different parts of the world have reported a variety of beneficial effects of biochar. Considering that several soil constraints limit agricultural production in Brazil and that biochar occurs naturally in the Brazilian Amazon (locally known as “Te...

Properties of biochar are thought to determine whether phosphorus (P) sorption or increased P availability occur following biochar application to sandy acidic soil; the effect of soil properties on P retention in biochar-amended acid soils remains largely unexplored. Our objective was to determine effects of hardwood biochar and poultry litter bioc...

Purpose Seasonal fluctuating water tables are common in sandy coastal plain soils, but their role in soil organic carbon dynamics is uncertain. Seasonal saturation influences biogeochemical processes that affect fate of organic matter and metals. A column study was conducted to test hypotheses that shallow water table (SWT) fluctuations reduce CO2...

http://www.agroforestry.eu/conferences/III_EURAFConference#Programme

The use of sewage sludge as fertiliser is a common practice in Europe, where sewage sludge is usually applied on a plant-available N or total metal concentration basis; as a result, phosphorus (P) concentrations can be well above crop needs. The objective of the study was to evaluate the effect of three doses of sewage sludge (0, 200, and 400 kg to...

Equilibrium models used for predicting phosphorus (P) loss from a site often use the Langmuir strength of P bonding, KL and the P sorption maximum, Smax, or the Freundlich adsorption coefficient, KF, obtained from traditional isotherms, as model input parameters. The overall objective of the study was to develop a protocol to allow estimation of is...

To better manage legacy phosphorus (P) in watersheds, reliable techniques to predict P storage and release from uplands, ditches, streams and wetlands must be developed. Techniques such as the P saturation ratio (PSR) and the soil P storage capacity (SPSC), originally developed for upland soils, are hypothesized to be applicable to wetland soils as...

Soil testing is a multistep process starting with the collection of a sample that adequately represents the area or field to be tested. Due to wide-ranging soil conditions across Florida and the United States, multiple soil test methods exist. During the 1970s, Florida along with several other southeastern US states adopted Mehlich-1 (M1) as the of...

Reliable techniques must be developed to predict phosphorus (P) storage and release from soils of uplands, ditches, streams, and wetlands in order to better understand the natural, anthropogenic, and legacy sources of P and their impact on water quality at a field/plot as well as larger scales. A concept called the “safe” soil phosphorus storage ca...