NC_temp1186: Water Management and Quality for Specialty Crop Production and Health
(Multistate Research Project)
Status: Draft Project
NC_temp1186: Water Management and Quality for Specialty Crop Production and Health
Duration: 10/01/2025 to 09/30/2030
Administrative Advisor(s):
NIFA Reps:
Non-Technical Summary
Statement of Issues and Justification
Accelerated population growth and climate change have positioned the availability and quality of freshwater resources as most crucial for society at the local, regional and national scales. In United States, irrigated agriculture and urban/public supply account for 37% and 12%, respectively of the total daily water use (Dieter et al., 2015). Specialty crop producers and the green industry, which includes ornamental plant producers, urban landscape & green infrastructure managers, and urban farmers, have become significantly affected by accessibility to high quality water resources and the concomitant issues of water use efficiency, irrigation management, salinity and drought, among others.
The production systems in this specialty crop sector, with an annual farmgate value of $11.8 billion dollars (NASS, 2020), traditionally have included ornamental growers, but it has diversified to include edible crops in soilless culture, including controlled-environment greenhouses and buildings (plant factories, vertical farming). The urban component of the green industry also extends to include outdoor urban gardening/farming. Altogether, these commodities are known for their intensive management and use of good quality water sources (Cabrera, 2021; Fulcher et al., 2016). Thus, their profitability and sustainability are jeopardized when challenged with water availability and quality issues due to pervasive issues of seasonal and extended droughts (McCabe et al., 2022), reduced allocations (Milman and Canon, 2023), restrictions/prohibitions on urban potable water use (Nemati et al., 2023), and regional salinity issues (i.e., saltwater intrusion, deicing salts) (Burga, 2023; Kaushal et al., 2023). Furthermore, the intensive use of fertilizers and agrichemicals in these commodities (Abdi et al., 2021; Cabrera, 2021) coupled with poor water use efficiencies lead to high pollution potential from their tailwater effluents into local water bodies (surface and ground), triggering local and regional scrutiny, pervasive monitoring and challenging environmental regulations and enforcement (California Water Boards, 2024; Majsztrik and Lea-Cox, 2013).
Under these scenarios, a range of water management and conservation practices need to be implemented by specialty crops and green industries, including increases in applied water use efficiency and reduced water footprints; use of alternative water sources of lesser quality; capture, treatment and recycling of drainage and on-farm stormwater effluents; development and use of improved/engineered soilless substrates; and management of field soils. Water quality aspects relevant to use of alternative and recycled water sources for irrigation include chemical (alkalinity, salinity, emergent environmental contaminants, nitrogen, phosphorus, pesticide residues, pharmacological residues, etc.), biological (plant pathogens, algae, biofilm, human food safety pathogens, coliform bacteria, etc.), and physical components (suspended particulates, turbidity, micro- and nanoplastics, etc.).
These challenges support the continuation of a multistate, multidisciplinary research and extension group that addresses the broad range of water quantity, quality and plant production issues affecting the profitability and sustainability of specialty crops. To address these challenges and produce tangible and practical solutions to these issues through research and extension activities, this multistate project has identified four principal areas of concern: (1) quality of irrigation sources, (2) irrigation management and efficiency, (3) runoff management, and (4) substrates and soilless culture.
1. Quality of irrigation water sources
The aesthetic requirements of ornamental specialty crops place constraints on the chemical quality of the water used for their irrigation, particularly when this is largely accomplished with overhead sprinkler systems. Furthermore, a broad majority of ornamental species, woody plants and edible specialty crops in particular, are fairly sensitive to moderate concentrations of total soluble salts and specific ions like sodium (Na), chloride (Cl) and boron (B) (Duncan et al., 2009; Grieve et al., 2012; Niu and Cabrera, 2010). Thus, traditional water sources can have local/regional quality issues that require treatment and management before their use for irrigation.
The traditional water sources used in specialty crops include surface and groundwater, but their increasing regional scarcity due to severe droughts and competition by other priority uses are giving way to alternative sources like municipal reclaimed water and recycled agricultural tailwater from runoff and drainages (Cabrera et al., 2018; Duncan et al., 2009). Although the quality of groundwater sources are often impaired by natural geological features, their chemical footprint is often stable over time. Conversely, surface waters are fairly vulnerable to contamination and significant changes in their chemical, physical, and biological quality because they do not have a protective over-layer of soil. Non-traditional irrigation sources like municipal reclaimed water often are contaminated by salts, pollutants from industrial, commercial and residential activities (Bale et al., 2017; Tanji et al., 2007) and emerging environmental contaminants (e.g., microplastics, PFAS, pharmaceutical residues; Donley et al., 2024; Fork et al., 2021; Thornton-Hampton et al., 2022). Agricultural tailwaters (drainages) can also fluctuate significantly in their quality, often containing significant residues of fertilizer salts and organic pesticides (Abdi et al., 2021; Alexandrino et al., 2022; Majsztrik et al., 2017).
Specialty crop producers must therefore know which tools and techniques to use to systematically monitor key water quality parameters, employ technologies to remove harmful contaminants, adopt/modify irrigation management practices and production systems, and/or select crops that are tolerant of lower quality water sources. There may also be opportunity to use specialty crop production to mitigate emerging environmental contaminants from waters, whether recycled or used only once, and help improve water quality and protect communities and water users around them.
2. Irrigation management and use efficiency
Efficient use of water is key to reduce waste of this resource. Sound irrigation management practices are required to reduce both water inputs (volumes required to grow a crop) and outputs (drainage and runoff). While container nursery and greenhouse growers vary in their water application practices (Majsztrik et al., 2018a), water application rates from these commodities are 4 to 5-fold higher than irrigated agronomic crops (for example 84” vs 18” per year; Cabrera et al., 2013). Under the assumption of similar overall water use efficiencies in both agronomic and specialty cropping systems, the latter generate significantly higher drainage output volumes per unit area. An intensive and frequent irrigation program is essential for crop production in soilless substrates, as these have high levels of porosity and low water holding capacity, and they have significantly smaller rootzone volumes compared to field-grown plants (Caron and Michel, 2021). Most nursery and floriculture crops in the US are grown in containers (NASS, 2020), and thus require daily (often several times a day) irrigation applications. Increases in irrigation use efficiency are necessary in containerized production systems because soilless substrates provide little buffering capacity to reduce leaching of nutrients and pesticides.
While overhead sprinklers are the traditional method to irrigate container nursery crops (Spinelli et al., 2024), other more efficient micro-irrigation options are available, including micro-sprinklers, low-volume spray stakes and drip irrigation, and recirculating sub-irrigation systems in greenhouse crops. In general, the more efficient irrigation systems are more expensive to install and maintain. There is limited information available on differences in water use among these different irrigation approaches for container crop production, on the economics of their use, and their compatibility with the quality of alternative water sources.
In addition to advances in equipment, improvements in irrigation management and efficiency require knowledge on how, when, and how much water to apply (Basiri-Jahromi, et al., 2020), namely control of timing, volume, and delivery of water based on measurement of soil/substrate moisture status, potential crop water use through evapotranspiration modeling (climate-based or from a proxy reference crop), and/or measurement of crop water stress. However, successful use and adoption of these methods requires science-based knowledge, cost-effective tools and the training of practitioners.
3. Runoff management
Specialty crop producers across the US have begun to capture, treat and recycle tailwater and stormwater runoff from their facilities. Procedures can significantly increase water use efficiency (WUE), potentially reduce production costs, and mitigate pollution associated with fertilizer runoff when water is recycled. However, recycled runoff effluents often contains agrichemical residues with phytotoxic effects (Abdi et al., 2021; Baz and Fernandez, 2002; Warsaw et al., 2012). Phytotoxicity problems are often due to residues of agrichemicals with high water solubility, or when persistent agrichemicals are extensively used, and the recycled water is applied to crops sensitive to that compound. Phytotoxic effects of preemergent herbicide residues of 1-10 parts per million (ppm) and the growth retardant paclobutrazol at 5 parts per billion (ppb) have been reported in several ornamental crops (Baz and Fernandez, 2002; Raudales et al., 2024).
The costs of infrastructure to collect, capture and treat irrigation water runoff discourages adoption of recycling practices (Gottlieb et al., 2022; Pitton et al., 2018). Managing runoff is a major challenge for container crop growers, as the volumes of water applied and the generated runoff are significantly higher than from field production; thus, when compounded with increased agrichemical loads can have a major impact on nearby receiving bodies of water (Lea-Cox and Ross, 2018). Thus, assessment and management of runoff play a critical role in minimizing the environmental impacts of specialty crop operations (White, 2013). Runoff can be substantially reduced by effective irrigation management (Pershey et al., 2015), and its capture, treatment and recycling help increase WUE and reduce pollution (Majsztrik et al., 2017). Large greenhouse operations have addressed runoff by using closed (sub)irrigation systems, but these are cost-prohibitive and impractical for smaller operations and outdoor container nurseries. Several promising treatment technologies (activated carbon, bioreactors, floating treatment wetlands, cold plasma-activated water) have been developed at the laboratory scale and are in various stages of investigation at the production scale.
Recycled irrigation water can contain and spread pathogens from a single infected plant to an entire operation, resulting in severe crop losses (Nyberg et al. 2014). Dozens of species of fungi, oomycetes, bacteria, viruses, and nematodes have been identified in recycled water sources (Redekar et al., 2019). Thus, there is a need to assess the risk posed by pathogens in recycled waters and evaluate mitigation strategies. While there are several water treatment technologies for waterborne pathogens, their eventual adoption involves several economic and crop management factors, along with extension/outreach education to growers (Raudales et al., 2014).
4. Substrates and soilless culture
Continued reductions of water, fertilizer and pesticide inputs, and runoff from specialty crop production can be accomplished with the proper selection, design and management of container substrates and soilless culture methods, which have the potential for higher yields than soil-based production. However, because of their small rootzone volumes, soilless systems provide a limited and dynamic reservoir capacity of water, mineral nutrients and oxygen (Caron and Michel, 2021), thus requiring systematic monitoring and management to minimize plant stress and ensure maximum crop growth potential.
Recent research demonstrates that substrate components can be stratified (layered) within a container to improve irrigation and fertilizer efficiency while producing plants with similar yield and quality to those grown in conventional systems (Fields et al., 2021; Owen et al., 2022). Further exploration into substrate stratification has revealed additional benefits for growers including reducing weed growth (Yvraj et al., 2022) and reducing reliance on peat moss, which can also lower substrate-related costs (Fields and Criscione, 2023). The engineering of new substrates and soilless systems require further refinement to improve supply and delivery of nutrients to increase nutrient use efficiency and reduce leaching and volatilization losses.
The traditional approaches to substrate evaluation and development have focused on static physical (water holding and air-filled porosity) and chemical properties (pH, electrical conductivity, selected ions). However, limited attention has been applied to the dynamic changes in these physical and chemical properties that occur over the relatively short time intervals that substrate systems remain in flux (s, min. hr.), or with continuous root growth over the crop production cycle (Judd et al., 2015). These dynamic root environments affect plant growth and development, crop timing, profitability, and resource efficiency (Caron and Michel, 2021). Additionally, little is known about the biological properties of soilless substrates, as historically, they were considered of minor importance (Giuffrida et al., 2021); though recent research has highlighted the complex dynamics and relationships of microbial communities of various substrates and how they are affected by the crop plants and fertilization inputs (Quijia-Pillajo et al., 2024; Valles-Ramirez et al., 2023).
Proposed participating stations and other project members:
Land Grant States/Institutions: AR, CA, FL, GA, LA, MA, MD, MI, MO, NC, NJ, OH, OR, SC, TN, UT, VA
Non-Land Grant Participating States/Institutions: USDA-ARS Application Technology Unit, Wooster, OH; USDA-ARS National Arboretum, McMinnville, TN
Related, Current and Previous Work
Objectives
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Water quality of irrigation sources. Characterize the quality of conventional and alternative or non-traditional water sources in different regions of the country. Determine water quality (chemical, physical and biological) parameters and levels that are most limiting for specialty crop production systems and evaluate suitable treatment and irrigation management options.
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Irrigation management and use efficiency. Determine the water quantity requirements of distinct crop production systems with different container types and environmental conditions. Compare irrigation methods and their effects on crop water use, plant growth and quality, runoff volume and quality. Identify methods and techniques that reduce water use, leaching, and runoff, leading to enhanced crop water use efficiency (WUE) and reduced water footprints. Develop and optimize irrigation methods that can be easily deployed and modulated in intensive crop production systems using real-time information on plant and substrate water status and environmental conditions.
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Runoff management. Evaluate methods and practices that enhance the containment of irrigation drainage and reduce contaminants in irrigation return flow. Identify improvements to recycled water management, characterizing critical control points within production systems. Develop chemical, physical, and biologically-based water treatment technologies and BMP guidelines that help mitigate the undesirable effects of sediments, agrichemicals, emerging environmental contaminants, and pathogens found in captured runoff intended for recycling in specialty crops.
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Substrates and soilless culture. Assess physical, chemical, and biological properties of conventional and engineered soilless substrates and components and their impacts on plant growth and quality, water use and recycling, WUE, nutrient delivery and retention, crop fertility and pollution potential in intensively managed specialty crops. Expand knowledge of how soilless substrate systems affect crop biomass and yields, root growth, pathogen and weed pressures, and dynamic physicochemical properties including hydraulic conductivity, pH, cation and anion exchange, plant-water availability, gas exchange and moisture retention.