NC1186: Water Management and Quality for Specialty Crop Production and Health

(Multistate Research Project)

Status: Active

NC1186: Water Management and Quality for Specialty Crop Production and Health

Duration: 10/01/2020 to 09/30/2025

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Water conservation and quality are high priority issues in agriculture and society as a whole. Irrigation management issues, specifically access to high quality water, irrigation scheduling, salinity, runoff water quality, and urban surface- and stormwater management are topics of major concern to the green industry and specialty crop producers. The green industry includes ornamental plant producers, landscape and ecosystem service providers, urban farmers, and green infrastructure managers. Production systems in this specialty crop sector includes ornamental and edible crop production in soilless substrates in containers, hydroponics, engineered substrates (for example roof-top plantations), and field nurseries. Climate change will likely influence rainfall patterns, fresh water reserves, and the frequency and severity of drought events. Drought and flood events, competition for water resources, urban expansion into previously rural production areas, production of crops within urban boundaries, demand for lower environmental impacts, and increasing legislation at state and county levels increase the need for these sectors to conserve water, manage stormwater runoff, and use alternative water sources with lesser quality. Water quality aspects relevant to irrigation include chemical components (such as alkalinity, salinity, nitrogen and phosphorus, pesticide residues), biological components (including plant pathogens, algae, biofilm, and human food safety pathogens), and physical components (such as suspended particulates, and turbidity).

Specialty crop producers are highly productive per unit area and require intensive inputs including water, fertilizer, pesticides, energy, and other resources. The waste stream from this production, which can include particulates, agrichemicals, heat, and plant diseases, could be transported by irrigation and storm runoff into containment ponds and/or off-site into groundwater or surface water (Camper et al., 1994; Hong and Moorman, 2005; Warsaw et al., 2009b; Wilson and Foos, 2006; Wilson and Boman, 2011). Irrigation water management affects nutrient uptake by crop plants and runoff of leached nutrients into local water systems (Pershey et al., 2015; Ross et al., 2002; Tyler et al., 1996; Warsaw et al., 2009b). Emerging constraints on water use and quality mean that the green industry needs to identify ways to manage water without negatively impacting marketable yields per area and per year.

A multistate, multidisciplinary research and extension group is therefore necessary to address the broad range of water quantity, quality and plant production issues in the green industry. To help solve these research and extension needs, this project has identified five principal areas of concern. These include (1) the quality of irrigation water sources, (2) irrigation management and water conservation, (3) crop production runoff management, (4) urban stormwater, and (5) soilless culture.

1. Water quality of irrigation sources

Water sources can have quality issues that require treatment and management before use for irrigation (Cabrera et al., 2018). Primary water sources available for specialty crops include groundwater, surface water, municipal reclaimed water, and recycled tailwater from runoff and drainage (Duncan et al., 2009).Water resources can become contaminated by infiltration of pollutants from nearby industrial, urban (Bale et al., 2017), and agricultural operations (Majsztrik et al., 2017). In some regions of the U.S., groundwater is impaired by natural geological features. Surface water is even more vulnerable to contamination and significant changes in its chemical, physical, and biological quality because it has no protective over-layer of soil. Municipal reclaimed water, or highly treated wastewater, is an additional source of irrigation water, but it can sometimes contain problematic levels of organic and chemical contaminants (Tanji et al., 2007). Plant producers must therefore use tools and techniques to systematically monitor key chemical parameters, employ technologies to remove harmful contaminants when necessary, modify horticultural and irrigation management practices, and/or select crops which are tolerant of lower quality water sources.

2. Irrigation management

Water inputs (total water volume required for crop production) and waste outputs (runoff) can be substantially reduced by precision irrigation management, and improving water use efficiency is the first step to reduce waste of this resource. Irrigation use accounts for 62% of surface and groundwater use in the United States (Kenny et al., 2009) while only supplying around 10% of plant needs, with rainfall supplying the remaining 90% (Assouline et al., 2015). Nursery and greenhouse producers vary greatly in their application practices (Majsztrik et al., 2018a). Supplemental irrigation (in addition to rainfall) is beneficial in nursery production in field soils. In contrast, supplemental irrigation is essential for production in soilless substrates, as they are typically characterized by high levels of porosity, low water holding capacity and container-produced plants have smaller root and soil volumes, compared to field-grown plants. The majority (75%) of nursery crops in 17 of the major nursery-producing states are grown in containers (USDA, 2007), and most floriculture crops are grown in greenhouses under rain cover (USDA, 2019). Improved irrigation efficiency is necessary because containerized systems provide little buffering capacity to reduce leaching of nutrients or pesticides, which in turn can become a source of surface or ground-water contamination.

A wide variety of irrigation systems are used in intensive plant and crop production systems, including recirculating sub-irrigation systems, drip irrigation / low-volume spray stakes, and overhead sprinklers. In general, the more efficient irrigation systems are more expensive to install and maintain. There is little information available on differences in water use among these different irrigation approaches for container production, even less information about differences on the economy of their use, or the compatibility of these systems with the quality of water sources.

Options for precision irrigation management to improve irrigation efficiency include controlling the timing, volume, and delivery of water through sensor-based measurement of soil moisture status, climate-based evapotranspiration modeling, and micro-irrigation. However, successful adoption of these methods requires science-based knowledge, cost-effective tools and the training of practitioners.

3. Crop production runoff management

In many areas of the country, specialty crop producers have begun to recycle tailwater and stormwater runoff from their facilities. This process can potentially reduce production input costs, because fertilizers and water in the runoff are re-used. However, recycled runoff water contain agrichemical residues that can have phytotoxic effects (Briggs et al., 2002; Riley et al., 1994; Warsaw et al., 2012; Willis, 1982; Wilson et al., 2006, 2010). Phytotoxicity problems may result when recycled water contains agrichemicals with high water solubility, or when a persistent agrichemical is extensively used and the recycled water is applied to plants sensitive to that compound (Bhandary et al., 1997). Herbicide effects can occur at 1 to 10 parts per million (ppm) and the plant growth regulator paclobutrazol at 5 parts per billion (ppb) have been found to be detrimental to growth and quality of several ornamental crops (Baz and Fernandez, 2002; Bhandary et al., 1997; Fernandez et al., 1999; Million et al., 1999). Other drawbacks of recycling include the need to invest in infrastructure to collect, capture and treat irrigation water runoff (Pitton et al., 2018). However in areas such as California, recycling of tailwater has been practiced since the 1970s (Skimina, 1986), and growers throughout the US have successfully adopted containment as a strategy for reducing water and nutrient runoff (Lea-Cox and Ross, 2018).

Managing runoff is a challenge for container producers. The volume of water applied and the amount of runoff generated is much greater than from field production. However, issues associated with runoff from field or container production areas are similar and can have a major impact on water resources. Runoff of rain and irrigation water is an important avenue for the movement of agrichemicals from production sites into nearby receiving water bodies (Bjorneberg et al., 2002; Taylor et al., 2006; White, 2013). Assessment and management of runoff plays a critical role in minimizing the environmental impacts of specialty crop production operations (White, 2013). Runoff can be substantially reduced by effective irrigation management (Pershey et al., 2015; Warsaw et al., 2009b). Capturing and treating or recycling are other options (Grant et al., 2018; Majsztrik et al., 2017; White, 2013). Many larger greenhouses have addressed the issue of runoff by using closed irrigation systems. Although subirrigation systems can substantially reduce runoff from greenhouses, they are cost-prohibitive and impractical for many operations, especially nurseries. 

Plant pathogens in irrigation water were recognized early in the last century as a significant crop health issue (Bewley and Buddin, 1921). Plant pathogens threaten the sustainability and profitability of the ornamental plant industries as much as water shortages. Recycling irrigation conserves water but it may also spread pathogens from a single point to an entire enterprise and from a single farm to other facilities sharing the same water resource (Hong et al., 2008a, 2008b, 2008c; Nyberg et al. 2014). This could result in severe crop losses. At least 26 species of Phytophthora, 26 species of Pythium, 5 species of Phytopythium, 27 genera of fungi, 8 species of bacteria, 10 viruses, and 13 nematode species have been identified in water sources (Hong and Moorman, 2005; Redekar et al., 2019). Among those pathogens are Phytophthora ramorum, the causal agent of sudden oak death (SOD), and Ralstonia solanacearum, one of the USDA select agents under the Agricultural Bioterrorism Protection Act of 2002. Therefore, there is an urgent need to assess the risk posed by recycling waterborne pathogens, to evaluate pathogen mitigation strategies, and to develop extension programs disseminating this information to growers (Lamm et al., 2017). A wide range of water treatment technologies can be effective for biological contaminants, including chlorination, chlorine dioxide, copper ionization, hydrogen peroxide, ozone, surfactants, and ultraviolet radiation (Raudales et al., 2014a), but there are many economic, crop management, and other factors involved in their successful adoption in addition to plant pathology (Raudales et al., (2014b).

4. Urban stormwater

Urban horticulture and production of specialty crops in controlled environments are significant emerging trends. Plant production within cities using roof-top farms and greenhouses, vertical farms, and other urban growing systems can provide local fresh food production; green roofs and green infrastructure can reduce energy inputs for heating and cooling, reduce stormwater runoff from rainfall events; and provide additional social, economic and environmental benefits. The need to conserve water and limit runoff is even more acute in urban environments, where runoff water volume and quality can be highly regulated and can have major economic impacts.  The subject of recent investigations, thermal pollution in runoff may be particularly detrimental to natural receiving waters (LeBleu et al., 2019). While typically associated with urban systems, Green Infrastructure Technologies and Low Impact Development (LID) systems have direct application to production systems as well as they can guide recommendations for producers (Morash et al., 2019) The management of urban growing systems would benefit from the application of science and technologies that have been successfully developed and implemented by rural and large-scale plant production systems. There is a need to further develop and improve existing methods and technologies that facilitate the reduction, infiltration, remediation, and reuse of tail-and stormwater runoff, targeting both urban and rural specialty crop producers.

5. Substrates and nutrients

Selection and design of container and urban crop production soilless substrates, with physical and chemical properties that are well-matched to plant needs and irrigation practices, can further reduce fertilizer and pesticide inputs and runoff. Nursery and greenhouse and food producers typically purchase or blend soilless substrates by screening single components or combining two or more inorganic or organic components. Substrates provide anchorage for stabilizing the plant in the container and provide a reservoir for water, mineral nutrients, and oxygen. Scientists have often approached substrate development or evaluation by focusing on either substrate chemical properties (pH, electrical conductivity) or static physical properties (water, oxygen, and anchorage). However, less attention has been applied to dynamic changes in the complete root zone system, where physical and chemical properties change over time during the crop cycle. These changes affect plant health, growth and crop time, root development, profitability, and resource efficiency (i.e., the amount of water and mineral nutrients required to produce a marketable crop).

Scientists are beginning to delve into dynamic physical properties of containerized substrates, in addition to conventionally-measured static substrate properties. Similarly, nutrient management has evolved beyond evaluation of "the best fertilizer" for a particular crop to studying and supplying crop nutrient needs through engineering substrate blends, components and amendments in order to increase nutrient use efficiency and reduce nutrient leaching. Furthermore, there is an increasing need to understand the economic and environmental sustainability of new and traditional substrates, especially in regards to source availability and quality for urban and specialty food crop production.

Related, Current and Previous Work

This large multistate team has strong contacts with colleagues working on related areas. We plan to continue to actively collaborate with related teams. This has included shared annual meetings with the NE1335 group (now NE1835) in 2016 and S1065 group in 2018, and the multi-disciplinary Clean WateR3 USDA-SCRI grant project.

A CRIS search of multistate projects was undertaken to avoid duplication and identify potential collaborators. The NC1186 team provides over-arching focus specifically on water, substrates and nutrients and there is overlap with several other teams. The aforementioned NE1835 group (Resource Optimization in Controlled Environment Agriculture) has potential collaboration because that project includes water and fertilizer as key resources in soilless media and hydroponics for greenhouse and indoor production systems. Our team actively collaborates with members of S1065 (Sustainable Practices, Economic Contributions, Consumer Behavior, and Labor Management in the U.S. Environmental Horticulture Industry) on economic analysis of water and nutrients. SERA17 (Organization to Minimize Nutrient Loss from the Landscape) has potential for new collaboration on the landscape sector of the greenhouse industry. There are many other multistate teams that have a component related to technology and policy related to irrigation water quality and conservation in specific sectors or geographic regions, and the NC1186 team will continue to actively identify opportunities for joint meetings.

1. Water quality of irrigation sources

We surveyed commercial greenhouse operations and estimated that the cost per 1000 gal of irrigation water ranged from $0.02 to $6.43 for pond and municipal sources, respectively (Raudales et al., 2017). Public water and rain water sources, which are considered high quality because of low levels of chemical, biological and physical contaminants, were the most expensive sources (> $2.50 per 1000 gal). In contrast, the cost of well water was between $0.09 and $0.64 per 1000 gal, and pond water was between $0.02 and $0.25 per 1000 gal. For growers using fertigation, the fertilizer value of the nutrient solution further increased value of recycled irrigation. Water treatment costs varied widely in terms of initial capital and ongoing operating cost. The return on investment for capture, treatment, and reuse of runoff is highest for high-cost water sources that include fertilizer nutrients or when an existing water quality issue is causing significant crop losses.

One group of NC1186 members in New Jersey, Texas and Ohio has been funded by USDA-ARS (FNRI) on "Alternative irrigation water sources for sustainable nursery production and urban landscapes". Their objectives are to evaluate the long-term effects of irrigation with municipal reclaimed water and residential greywater on nursery, greenhouse crops and landscape plants and on the substrates/soils where they grow, as compared to municipal potable or other high-quality water sources. Results to date indicate that some specific chemical quality parameters are more challenging to plant growth and quality, and also affect physical, chemical and microbiological properties of soils and substrates (Cabrera et al., 2018). Among the most challenging chemical parameters of these alternative water sources on crop nutrition are salinity, alkalinity, sodicity, sodium chloride salt, and boron concentrations (Grieve et al., 2012; Niu and Cabrera, 2010; Tanji et al., 2007). The quality of water sources can also affect the incidence of clogging of irrigation systems by blocking irrigation emitters or pipes.

A hazard/risk assessment of low quality water sources can be matched with management strategies to remediate or cope with each irrigation water source (Duncan et al., 2009; Grieve et al., 2012; Tanji et al., 2007). Distinctive chemical quality footprints of ground, surface and municipal reclaimed waters have been anecdotally acknowledged across some specialty crop growing regions of the country. However, there is a pressing need to integrate grower and scientific knowledge of practical and effective strategies to successfully grow crops using inferior quality water sources. Based on this information, recommendations can be developed related to plant selection, irrigation practices and equipment suitable to the chemical footprints of water sources available in each region. 

2. Irrigation management 

Irrigation systems must be designed and maintained for optimal performance (Ross, 2008a, 2008b). Scheduling irrigation is a complex daily decision, often based upon subjective information (Lea-Cox et al., 2009). Controlling the water available to the plant may allow for more direct control of physiology and growth (Alem et al., 2015). Jones (2004; 2008) argues that measuring soil water status is better suited for irrigation control than measuring plant water status. Capacitance sensor technology accurately measures water content of a wide variety of substrates, via the dielectric constant (Bayer et al., 2013, 2015; Nemali and van Iersel, 2006, 2008). The SCRI-MINDS team (Lea-Cox et al., 2013; Kohanbash et al., 2013) developed advanced wireless sensor networks that can be used to both monitor and control irrigation events throughout an operation.

The use of sensor networks can realize significant (40-70%) savings in water use (Belayneh et al., 2013; Chappell et al., 2013; van Iersel et al., 2013) and benefit commercial specialty crop producers by reducing production times and improving yield (Oki et al., 2001). This can lead to significant economic value, including both private (Lichtenberg et al., 2013; Majsztrik et al., 2013a) and public (Majsztrik, et al., 2013b) benefits. There is also a potential increased market value for plant products grown with water conservation methods (Behe et al., 2018). To upscale the wireless sensor network technology, efficient operational methods for categorizing plants into functional groups for irrigation are needed to schedule irrigation events for a broad range of specialty crops/cultivars. Research continues to evaluate strategies and technologies to minimize chemical (fertilizer, pesticide, fungicide etc.) runoff through better irrigation practices (Abdi and Fernandez, 2019; Del Castillo Múnera et al., 2019; Hoskins et al., 2013, Hoskins et al., 2014b, Pershey et al., 2015; Warsaw et al., 2009a, 2009b, 2012). Other emerging technologies such as small unmanned aircraft systems (sUAS) provide opportunities to optimize irrigation, although specialty crops present challenges such as a relatively small area of production and diversity of plant species (de Castro et al., 2018).

3. Crop production runoff management

Management of contaminants by water containment and recycling systems is critical to reduce environmental impacts and optimize intensive plant production. Grower concerns about the presence of plant pathogens, pesticide residues, and salinity potentially limit the willingness of growers to recycle water. Several ongoing research projects in FL, MI, OR, SC, VA address our capacity to know when, where, and how a contaminant (whether sediment, agrichemical, or pathogen) needs to be managed to optimize plant health in the production setting. Treatment technologies to manage sediment and some agrichemical contaminants exist and have been optimized for other applications. Development and evaluation of treatment technologies (such as bioreactors, filter socks, floating wetlands, activated carbon filters, particle filters, sedimentation ponds, carbon bioreactors, slow-sand filtration etc.) for their utility in mitigation of contaminants (sediment, agrichemical, and pathogen) in high-intensity production systems is ongoing (Bell et al., 2018; Grant et al., 2018; Garcia Chance et al., 2019; Garcia Chance and White, 2018; Huang and Fisher, 2019; Lee and Oki, 2013; Majstrik et al., 2018, 2019; Nyberg et al., 2014; Oki et al., 2016; Oki et al., 2017; Ridge et al., 2019; Spangler et al., 2019a, 2019b; White, 2018; White et al., 2019).

Surveys of water quality in nursery recycling and tailwater recovery ponds have been conducted by NC1186 members in CA, FL, MD, NC, SC, and VA (Garcia Chance et al., 2019b). Members in MI and VA have developed model production areas and determined how runoff flows are influenced by irrigation method. Over the past 5 years, NC1186 members from SC, FL, VA, CA, MD, and MI collaborating in the Clean WateR3 project (SCRI 2014-51181-22372) have developed information related to which treatment technologies can be used both effectively and economically by green industry producers to contain and recycle water (Pitton et al., 2018; Bell et al., 2018; Garcia Chance et al., 2018, 2019a; Majstrik et al., 2018, 2019; Ridge et al., 2019; White, 2018; White et al., 2019). The long-term goal is to integrate physical, chemical, and biological technologies in treatment chains in order to reduce contaminant presence in production runoff. NC1186 members are collaborating to develop research projects to address these gaps in knowledge.

4. Urban stormwater

Stormwater management systems are designed to reduce sediment, agrichemicals, thermal, and other contaminants present in the first flush of runoff, keeping them from entering containment (recycling) ponds or natural water bodies. The sizing and efficiency of contaminant removal of a receiving body of water is significantly affected by practices implemented in the watershed to reduce both the volume of water and mass of agrichemical contaminants present. Contaminant mitigation practices paired with containment ponds form an integral part of a treatment train approach, designed to improve water quality for recycling purposes and aquatic health. A similar approach is used with emerging urban green infrastructural stormwater management systems (Lea-Cox et al., 2016; Price et al., 2011; Starry et al., 2016), which link stormwater reduction structures on rooftops (green roofs) to micro-infiltration sites (rain gardens, tree pits) and pervious pavements, providing stormwater ecosystem service benefits (Lea-Cox et al., 2019), by reducing impacts to combined sewer systems and local water bodies.

NC1186 participants have considerable experience in various aspects of stormwater management. Members from CA, MD, MI and VA have been developing cost-effective methods to map and measure the volume and intensity of stormwater runoff, to aid the design of structures and capacity of remedial systems. Working groups in FL, MI, MS, NJ, OH, SC, TX and VA have been working on substrate, bioreactor and other remediation technologies, to reduce agrichemical (fertilizer and pesticide) and greywater (salinity) issues. The NC1186 group is active in a range of water treatment technologies, including plant-based remediation in AL (Morash et al., 2019) and SC (Garcia Chance et al., 2019b; Garcia Chance and White, 2018; Spangler et al., 2019b), together with physical treatment system work on slow-sand filtration (CA, SC) (Lee and Oki, 2013; Nyberg et al., 2014; Oki et al., 2016; Oki et al., 2017) and activated carbon systems (FL and CT). The research capacity within the NC1186 group therefore provides us with a unique opportunity to develop a full suite of treatment technologies to improve stormwater management, in both horticultural production and urban landscape settings.

5. Soilless culture and nutrient management 

Historically, physical and chemical properties have been measured utilizing porometer analysis (Fonteno and Bilderback, 1993), moisture characteristic curves (Dane and Hopmans, 2002; Verdonck et al., 1978), and soil sampling methods such as the saturated media extract (Warncke, 1990) or pour through (LeBude and Bilderback, 2009). These analyses focus on samples taken at a single point in time and have been used to formulate and model substrates with "ideal" conditions for specific vessels or containers with a given geometry (Milks et al., 1989).

New dynamic parameters that describe water, air, pH, and nutrient flux (Altland and Jeong, 2016, Altland et al., 2018), transport gradients (Hoskins et al., 2014a, 2014b; Fields et al., 2017), or consumption (Fields et al., 2018) throughout plant root development are needed to assess and select soilless substrates to deal with increasing challenges facing producers (Caron et al., 2014). There is a need for increased yield or biomass with limited resources. Parameters which deserve greater attention include, but are not limited to, creating and testing advanced substrates, root interactions, gas diffusion, hydraulic conductivity, solute transport and mineral incorporation to remediate and supply nutrients. Measuring and modeling these parameters in situ, in real-time, can provide inferences into electrochemical flux, infiltration of oxygen and replacement of carbon dioxide from root respiration, water movement and connectivity, chemical equilibria and both agrichemical and water availability as well as environmental fate during crop production. New tools (e.g. HYdraulic PROPerty analyzer; Schindler et al., 2010; Fields et al., 2018) and models (e.g. HYDRUS; Šimůnek et al., 2012; Fields et al., 2015) that use models or in-situ measurements [for example, O'Meara et al. (2014)] are needed to make inferences from these dynamic phenomena. Utilizing new methodology and tools will allow scientists to continue to assist crop producers that utilize soilless substrates to improve resource use efficiency and subsequent economic growth.

Despite a number of review papers on green roof systems (Berndtsson et al., 2009), few quantitative data exist on the impact of urban crop production practices on the ability of modified green roofs to retain stormwater and mitigate any nutrient runoff from these impervious surfaces. Agricultural rooftop farms are modifying green roof substrates with additional organic matter to enhance water and nutrient retention; crops are also fertilized and irrigated during the growing season, possibly contributing to nutrient runoff issues if not carefully managed (Howard et al., 2019). Urban farmers using vacant lots also face similar issues, as they typically cannot grow in native urban soils which are generally infertile, and are often contaminated with rubble and pollutants such as heavy metals. Raised beds, using sustainable organic substrates with composted material additions are typically used. Correct substrate formulation and nutrient management practices, timely irrigations and the leaching of nutrients from raised beds with rainfall, are common issues facing urban farmers of all backgrounds. Research into substrate amendments such as alumina and biochar to increase phosphorus retention, increase cation-exchange and water-holding capacity, and reduce nutrient runoff from urban farming systems are ongoing (Howard et al., 2019).


  1. Water quality of irrigation sources. Characterize the quality of alternative or non-traditional water sources in different regions of the U.S. Determine water quality parameters and levels that are most limiting for intensive plant production systems and evaluate treatment and management options to overcome the limiting factors.
  2. Improved irrigation management. Determine the water quality and quantity requirements of different plant production systems with varied container sizes and environmental conditions. Compare irrigation methods (e.g. overhead, spray stakes, drip irrigation, subirrigation) to determine how they affect total water use, plant growth and quality, and runoff water quality. Identify methods to reduce water use, leaching, and runoff and quantify results from more efficient techniques. Develop new and optimize existing irrigation methods that are easily deployed in intensive plant production systems to provide growers with real-time information regarding water requirements and environmental conditions of their crops. Evaluate the compatibility of low-quality water with irrigation methods and systems.
  3. Crop production runoff management. Address research and extension needs related to enhancing containment of production runoff and improving recycled water management by identifying and characterizing critical control points within production systems, further developing chemical, physical, and biologically-based water treatment technologies and providing BMP guidelines to mitigate adverse effects of sediment, agrichemicals, and pests in production runoff, irrigation reservoirs, and other water sources.
  4. Urban stormwater. Improve the design of biological urban stormwater systems to better reduce and remediate stormwater runoff from various sources, addressing issues of water volume, intensity, quality, and reuse. Focus on the use of novel biological and engineered systems and materials (e.g. organic/inorganic substrates and amendments) which mitigate runoff and pollutants, as well as the use of woody and herbaceous plants, in single or combined (treatment train approach) systems in greenhouse, nursery, and urban production environments.
  5. Soilless culture and nutrient management. Assess physical, chemical, and biological properties of soilless culture systems or components for their impact on plant health and vigor, water reuse and subsequent use efficiency, nutrient delivery and retention, crop fertility, and environmental impact for a variety of important controlled environment and urban crops throughout the U.S. Expand our knowledge of how soilless culture systems affect plant productivity, root growth, plant pathogen or weed pressure, and dynamic physicochemical properties including hydraulic conductivity, pH, cation and anion exchange, plant-water availability, gas exchange and moisture retention.


This is a highly collaborative team with many years of experience in multistate projects together in NC1186. Bullets present significant priority areas, and a few illustrative examples are provided at the bottom of objectives for projects specific to certain locations.

Objective 1. Water quality of irrigation sources

  • Work with external collaborators to gather, collate, model, and interpret runoff-related water quality data from nursery and greenhouse operations across the U.S., and analyze on a regional basis.
  • Assess risks associated with water quality parameters that influence plant growth and categorize their potential impacts on plant production through plant studies.
  • Assess water quality factors that affect accumulation of biofilm, algae, and plant pathogens on irrigation systems.
  • Evaluate commercial practices and emerging research-based technologies in order to identify best management strategies to:
    • monitor and interpret water quality;
    • manage high levels of salts, alkalinity and specific ions;
    • remediate agrichemical, pesticide, and other contaminants in conventional and alternative irrigation water sources;
    • provide geographic analyses and visualization of water quality issues for specialty crops;
    • successfully produce crops and maintain urban landscapes and gardens with low quality water sources, selecting plants/crops, irrigation practices and equipment most suitable to the chemical, physical and biological profiles of water sources available in each region.
  • SC has constructed replicated beds to measure water infiltration vs surface flow for 3 common bed materials
  • SC will continue to evaluate slow sand filters for plant pathogen and agrichemical removal
  • CA, FL, MD, and MI, and MISC will evaluate commercial irrigation reservoirs to develop case studies and best management practices on monitoring, including chemical quality, pesticide contaminants, turbidity, dissolved oxygen, and recommended remediation methods.
  • Lead collaborators: CA, CT, FL, MD, MI, NC, NJ, SC, TX


Objective 2. Improved irrigation

  • Determine the irrigation efficiency and economic returns of various impact, micro, and drip irrigation systems.
  • Quantify water demand by plants based on evapotranspiration (ET) and other micrometeorological measurements.
  • Measure plant responses to drying substrates and detect the early onset of drought stress to determine when irrigation is needed. Plant parameters to be measured could include changes in stem caliper, leaf temperature, leaf reflectance, leaf transpiration, photosynthesis, and plant growth indices.
  • Quantify the effects of water-related biotic and abiotic stress on plant anatomical, morphological, and physiological responses to determine how plant quality is affected.
  • MD will lead multi-location efforts using soil moisture and EC sensors to measure real-time substrate water and nutrient status, to control irrigation, reduce application volumes and reduce nutrient leaching.
  • SC will test irrigation system efficiency for a number of impact, micro irrigation and drip irrigations systems. Distribution uniformity, wear over time, influence of wind and other parameters will be tested.
  • Lead collaborators: CA, CT, MD, MI, OR, SC, USDA-ARS


Objective 3. Crop production runoff management

  • Identify, adapt, and assess select filtration and chemically- and biologically-based treatment technologies to manage nutrient, pesticide, particulate, pathogenic, and biological contaminants in production runoff.
  • Develop and evaluate treatment technologies at laboratory, pilot, and commercial scales, focusing on the performance of individual and integrated treatment systems.
  • Evaluate bioreactors hydraulic retention times and placement to improve water quality as appropriate to recycling (remove pesticides but retain nutrients).
  • Determine ideal combination and placement of treatment technologies in series to remove/remediate various agrochemicals from discharged water.
  • FL will evaluate efficacy of physical particle filters and flocculation to remove suspended particles and increase water clarity in case study commercial irrigation reservoir sites.
  • SC will use medium scale slow sand filters to determine their effectiveness at removing plant pathogens and agrichemicals from runoff water following protocols established by members of the group.
  • USDA-ARS will develop Fe-enriched substrates that sorb or to filter phosphates from container leachates or other off-site release (remove all agrochemicals).
  • Lead collaborators: CA, CT, FL, MI, SC, USDA-ARS


Objective 4. Urban stormwater

  • Identify research priorities and needs related to urban stormwater management, based on survey responses and stakeholder input.
  • Develop and integrate treatment technologies for urban/green infrastructural stormwater management systems, which link stormwater reduction structures on rooftops (e.g., green roofs and urban farms) to micro-infiltration sites (e.g., bioretention cells and functional landscapes) at ground level.
  • This approach would combine precision irrigation management techniques (Obj. 2) with novel soilless culture techniques (Obj. 5) to maximize stormwater retention and minimize agrichemical runoff (Obj. 3).
  • Lead collaborators: CA, MD, SC


Objective 5. Soilless culture and nutrient management

  • Systematically assess static and dynamic physical or chemical properties of soilless culture systems, components or formulations employing existing and new techniques.
  • Develop an integrated model for soilless culture chemical or physical properties, crop nutrient requirements, irrigation regime, root development and plant water uptake, and agrichemical transport to maximize resource use efficiency and minimize environmental impact.
  • Incorporate emerging bioassay technologies to identify the microbial communities within soilless culture systems and understand the dynamic nature of these populations and subsequent influence on plant production.
  • Determine how irrigation or water management methods affect plant-water availability, runoff, and reuse.
  • Develop sustainable-substrate matrices utilizing existing and novel substrate components for specialty crop production in accordance with current market costs.
  • Assess the use of suitable organic and inorganic amendments for urban crop production and green infrastructure mitigation systems, to maximize stormwater retention and minimize agrochemical runoff.
  • Provide regional recommendations and best management practices for sustainable, affordable soilless culture systems that maximize resource efficiency, optimize crop growth, and minimize environmental impact.
  • Quantify mass balance, ion concentration, and nutrient delivery in recirculating hydroponic systems with varying water quality and discharge fractions.
  • USDA-ARS will develop techniques for extracting and purifying DNA or RNA from soilless substrates, and using these samples to quantify and visualize microbial communities in the substrate.
  • USDA-ARS and OH will evaluate the stability of bacterial and other microbial communities when intentionally added to substrates for plant-growth-promoting or plant-protection purposes.
  • FL will develop management strategies for maintaining pH, salt accumulation, and maintenance of nutrient solutions of reused or discharged solutions used in hydroponics.
  • KY will research nutrient delivery to container-grown ornamental and edible crops using compost amendments.
  • Lead collaborators [Add to this list if participating]: CA, FL, KY, LA, MD, MI, USDA-ARS

Measurement of Progress and Results


  • Improved strategies for irrigation management, which reduce water and fertilizer use, while maintaining or improving plant quality and minimizing environmental impacts of agrichemicals.
  • System integration and design guidelines for integration of treatment technologies on-farm, whether installed individually or as integrated treatment systems.
  • Develop and/or improve economically-feasible strategies to manage stormwater runoff from specialty crop production and urban systems, including identifying and eliminating barriers to the adoption of treatment technologies.
  • Guidelines for growers on the optimal irrigation approach for their operation.
  • Presentations at grower meetings, symposia, colloquia, and workshops. Refereed journal publications for the scientific community and extension articles and factsheets readily available for stakeholders. Serve as a clearinghouse for articles and speakers from members to national and state trade journals, conferences, workshops and other presentations. Existing and new websites will be used to disseminate information from this group.
  • Apply for state, regional, and national grants to fund research, graduate student, outreach, and other activities.

Outcomes or Projected Impacts

  • Increased profitability by reducing costs associated with irrigation (direct costs of water), reduced power use, savings on fertilizer cost, and labor savings.
  • Reduced water and fertilizer use, energy and labor (increased resource use efficiency). Substantial reductions in leaching and runoff of water, nutrients, pesticides from irrigation and rainfall (environmental benefits). Increased production and reduced need for pesticides (plant growth benefits).
  • Conservation of water resources. Decreasing the amount of water used by specialty crop growers will leave more water available for other uses. Improved water quality. Reducing runoff volume and contaminant loads will help protect the water quality of ground and surface water throughout the U.S. Decreased carbon and water footprints of operations.
  • Greater understanding of the link between measured substrate properties and irrigation use efficiency. Development of an integrated substrate/nutrition/irrigation model for crop management which will offer a new way of studying and growing crops.
  • Knowledge of plant responses to recycled water and other alternative water sources can help nursery, landscape professionals, and homeowners to choose appropriate plants for landscapes where low-quality water may be used. Increased use of reclaimed water or other alternative water sources for irrigating nursery crops and landscape plants, which can extend the supply of available freshwater for other beneficial uses.


(1):Develop survey framework to collect water quality and grower production practice data in a consistent way between regions. Carry out plant selection and growth response studies with different water contaminants (continued throughout 5-year period). Conduct surveys and focus groups to identify key producer and consumer issues surrounding stormwater runoff in urban, greenhouse, and nursery production systems. Identify key knowledge gaps in specific water quality issues, treatment technologies, and their integration. Develop modeling framework for substrate physical and chemical properties. Present online webinars on substrates and irrigation.

(2):Continue plant selection and growth response studies with reclaimed water and a range of chemical water qualities. Gather and interpret regional water quality and grower production practices data, identify key issues, and run targeted trials to identify and demonstrate appropriate remediation and management options. Evaluate treatment technologies at laboratory and commercial scale for managing chemical, physical, and biological water quality issues. Gather data to calibrate and validate substrate physical and chemical property models. Measure runoff /infiltration characteristics in production beds using various impact and wobbler sprinkler heads. Continue development of real-time irrigation techniques and strategies to reduce water requirements, improve efficiency and operational water security, and reduce contaminant runoff. Investigate and develop economic and effective reduction and remediation technologies, strategies and knowledge for reducing agrichemical and biological contaminant loads in recycled water for specialty crop production. Engage and inform consumers regarding the benefits of conserving and reducing the use of freshwater resources and the benefits and challenges of recycling and reusing irrigation and stormwater runoff for specialty crop production. Evaluate substrates in terms of static and dynamic physical and chemical properties, crop response, effect of time and plant-root interaction, and water and agrichemical transport and fate. Validate the integrated substrate/agrichemical/irrigation model.

(5):Focus on integrating knowledge and outreach, including development of case studies on water conservation and treatment options at selected grower sites. Develop peer-refereed and extension publications for disseminating the information to the green industry. Update best management practices guidelines for landscape irrigation and crop selection, stormwater management, runoff capture, water recycling and treatment, and soilless substrate selection and management.

Projected Participation

View Appendix E: Participation

Outreach Plan

This group will deliver face-to-face presentations to industry and academia at regional, national and international meetings. Examples of these meetings are Southern Nursery Association research conference, Annual conference of American Society for Horticultural Science, International Society for Horticultural Science, state grower association meetings, etc. Peer-reviewed publications and extension articles will be generated. Existing websites (including and new websites will be used to disseminate information. Online extension training courses (including Greenhouse Training Online (, Freyre et al., 2018) and webinars will be provided.


The project has an annual meeting, with location varying each year. There is a secretary, vice-chair, and chair who are elected by annual meeting participants, with one-year terms where responsibilities progress in order from secretary to vice-chair to chair. Minutes are prepared and distributed for corrections by the secretary. Annual reports are submitted by the chair into NIMSS. All members have voting rights.

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  • Wilson, P.C. and J.F. Foos. 2006. Survey of carbamate and organophosphorous pesticide export from a South Florida (USA) agricultural watershed: Implications of sampling frequency on ecological risk estimation. Environ. Toxicology Chem. 25:2847-2852.

  • Wilson, P.C., C. Riiska, J.P. Albano. 2010. Nontarget deposition and losses of chlorothalonil in irrigation runoff water from a commercial foliage plant nursery. J. Environ. Qual. 39:2130-2137.

  • Wilson, P.C. and B.J. Boman. 2011. Characterization of selected organo-nitrogen herbicides in south Florida canals: Exposure and risk assessments. Science of the total environment 412-413: 119-126.



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Michigan State University, University of Maryland
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