WATER AND NUTRIENT DYNAMICS IN CONTAINER-NURSERY PRODUCTION SYSTEMS

Water quality remains a predominant issue within the Chesapeake Bay watershed, and nutrient loading continues to undermine the progressive recovery of this ecosystem. Until recently, the ornamental plant industry has had little information to develop better management practices to increase the efficiency of water and nutrient applications. This research used an integrated approach to examine container- production systems, to develop recommendations to increase nutrient uptake efficiency and reduce runoff. A 40-month field study examined the effects of various cultural practices on irrigation and nutrient uptake efficiencies. Under cyclic scheduling, drip irrigation applied 3 to 4.5 times less water than overhead irrigation and had significantly less runoff when plants were spaced at low densities. While drip irrigation is significantly more efficient, overhead irrigation is more practical and economically feasible for most small container-nursery stock. Time Domain Reflectometry (TDR) was examined as an alternative to cyclic scheduling and when used with overhead irrigation, water applications were half that of cyclic irrigation scheduling. . This research simultaneously documented nitrogen (N) and phosphorus (P) dynamics by examining nutrient applications, uptake and leaching over the forty months. In most cases, N and P uptake efficiency and runoff was negatively affected by overhead irrigation, particularly when soluble nutrients were applied via fertigation and at low plant densities. Nitrogen and P efficiencies ranged between 10 and 30% and were dependent upon methods of irrigation and fertilization, plant density and water use. The use of both drip and TDR-scheduled overhead irrigation reduced nutrient runoff to half that of the overhead irrigation program Intensive spring nutrient uptake studies showed that N influences the total growth of Rhododendron (azalea) and P uptake is a function of P fertilization rate and growth, influenced by N rate. Moderate N rates maintained optimal growth, while total P was only required at 1/20 of this N rate. Periodicity in nutrient uptake suggests seasonal timing of fertilizers may increase N and P uptake efficiency. Novel management strategies in the area of irrigation, fertilization, and cultural practices should be adopted by the ornamental industry to improve upon low efficiencies and reduce nutrient pollution in our watersheds

Chilling Requirements to Relieve Bud Dormancy in Black-fruited Aronia Taxonomic Groups Is Related to Ploidy and Geographic Origin

The genus Aronia Medik., also known as chokeberry, is a group of deciduous shrubs in the Rosaceae family, subtribe Malinae. The two commonly accepted black-fruited Aronia species are black chokeberry [Aronia melanocarpa (Michx.) Elliott] and aroniaberry [Aronia mitschurinii (A.K. Skvortsov & Maitul)]. The geographic range of wild A. melanocarpa is the Great Lakes region and the northeastern United States, with a southerly extension into the higher elevations of the Appalachian Mountains. Wild A. melanocarpa found in New England are diploids, whereas plants throughout the rest of the range are tetraploids. A. mitschurinii is a cultivated hybrid between ×Sorbaronia fallax (C.K.Schneid.) C.K.Schneid. and A. melanocarpa and exists as a tetraploid. There is currently limited diversity of Aronia genotypes in the ornamental and fruit industries, and many of the current cultivars are not adapted to the southern United States and similar environs with limited chilling to break winter dormancy. The goal of this study was to determine 1) the chilling requirements for A. mitschurinii ‘Viking’ and 2) the range of chilling requirements for wild A. melanocarpa genotypes from different geographic origins. Two experiments were conducted in which plants were subjected to various chilling accumulation treatments and then moved to a greenhouse for observation of budbreak and subsequent growth. Expt. 1 was conducted at the University of Maryland at Wye, MD, and focused solely on the commercial cultivar A. mitschurinii ‘Viking’. Outdoor, ambient fall and winter temperatures were used to achieve the chilling treatments. In Expt. 1, we determined the optimal chilling requirements for A. mitschurinii ‘Viking’ to be greater than 900 h using the single temperature model. Expt. 2 was conducted at the University of Connecticut and focused on wild genotypes, plus A. mitschurinii ‘Viking’. A fixed temperature cold room was used to achieve chilling treatments. In Expt. 2, we found A. melanocarpa genotypes from southern regions in the United States required chilling accumulation of 600 h (single temperature model), compared with genotypes from northern regions that required more than 900 h of chilling accumulation. Tetraploid A. melanocarpa required 900 h of chilling to break bud, but diploid A. melanocarpa required 1200 h of chilling to break bud. Expt. 2 confirmed the 900-h chilling requirement for A. mitschurinii ‘Viking’. For both experiments, the rate of budbreak and shoot growth was positively correlated with increasing amounts of chilling

Industrial Hemp Remains Illegal to Cultivate In Maryland Until Final Regulations and Research Programs Finalized

In 2016, the Maryland General Assembly first passed legislation allowing for the development of an Industrial Hemp Pilot Program in the state. That program was recently updated this year by House Bill (HB) 698 to allow farmers contracting with the Maryland Department of Agriculture (MDA) or Institutions of Higher Education (IHE) in Maryland to grow industrial hemp for research purposes. Production of hemp under the program must further either agricultural or academic research. While HB 698 becomes effective on July 1, MDA is currently developing regulations and applications required under this new law and IHE have not had sufficient time to develop research programs for industrial hemp production, which conform to the regulations. Until then, any grower attempting to produce industrial hemp in Maryland is still producing it illegally and faces potential criminal penalties.Department of Agricultural and Resource Economics, University of Maryland Extension, Agriculture Law Education Initiative, and Maryland Department of Agricultur

A Comparison of Irrigation-Water Containment Methods and Management Strategies Between Two Ornamental Production Systems to Minimize Water Security Threats

Water security in ornamental plant production systems is vital for maintaining profitability. Expensive, complicated, or potentially dangerous treatment systems, together with skilled labor, is often necessary to ensure water quality and plant health. Two contrasting commercial ornamental crop production systems in a mesic region are compared, providing insight into the various strategies employed using irrigation-water containment and treatment systems. The first is a greenhouse/outdoor container operation which grows annual ornamental plants throughout the year using irrigation booms, drip emitters, and/or ebb and flow systems depending on the crop, container size, and/or stage of growth. The operation contains and recycles 50–75% of applied water through a system of underground cisterns, using a recycling reservoir and a newly constructed 0.25 ha slow-sand filtration (SSF) unit. Groundwater provides additional water when needed. Water quantity is not a problem in this operation, but disease and water quality issues, including agrochemicals, are of potential concern. The second is a perennial-plant nursery which propagates cuttings and produces field-grown trees and containerized plants. It has a series of containment/recycling reservoirs that capture rainwater and irrigation return water, together with wells of limited output. Water quantity is a more important issue for this nursery, but poor water quality has had some negative economic effects. Irrigation return water is filtered and sanitized with chlorine gas before being applied to plants via overhead and micro-irrigation systems. The agrochemical paclobutrazol was monitored for one year in the first operation and plant pathogens were qualified and quantified over two seasons for both production systems. The two operations employ very different water treatment systems based on their access to water, growing methods, land topography, and capital investment. Each operation has experienced different water quantity and quality vulnerabilities, and has addressed these threats using a variety of technologies and management techniques to reduce their impacts

Parameterizing a Water-Balance Model for Predicting Stormwater Runoff from Green Roofs

Crop coefficients (kc) were calculated for three different species of common green roof succulents from March to November in 2011, to parameterize the Food and Agricultural Organization of the United Nations (FAO) Penman-Monteith equation for use in a mechanistic green roof water-balance model. Seasonally averaged kc values for each species for 2011 were used to predict plant evapotranspiration (ET) in 2012. The adjusted FAO Penman-Monteith equation predicted the total annual ET within 3–13 mm, a substantial improvement over model predictions with kc set to 1, which overpredicted ET by 100 mm or more, depending on the species. The adjusted equation was inserted in water-balance models, which predicted runoff within 2–13% of measured totals for 2012. This discrepancy may be explained by variability in maximum water-holding capacity, which is difficult for two-dimensional models to predict. Nevertheless, these results provide increased confidence in the use of models to predict stormwater runoff from green roofs, and evaluate performance. Monitoring multiple green roof installations with cost-effective sensor networks will increase the ability to identify the key components to enhance green roof function, reduce stormwater runoff, and inform future design

A Comparison of Irrigation-Water Containment Methods and Management Strategies Between Two Ornamental Production Systems to Minimize Water Security Threats

Water security in ornamental plant production systems is vital for maintaining profitability. Expensive, complicated, or potentially dangerous treatment systems, together with skilled labor, is often necessary to ensure water quality and plant health. Two contrasting commercial ornamental crop production systems in a mesic region are compared, providing insight into the various strategies employed using irrigation-water containment and treatment systems. The first is a greenhouse/outdoor container operation which grows annual ornamental plants throughout the year using irrigation booms, drip emitters, and/or ebb and flow systems depending on the crop, container size, and/or stage of growth. The operation contains and recycles 50–75% of applied water through a system of underground cisterns, using a recycling reservoir and a newly constructed 0.25 ha slow-sand filtration (SSF) unit. Groundwater provides additional water when needed. Water quantity is not a problem in this operation, but disease and water quality issues, including agrochemicals, are of potential concern. The second is a perennial-plant nursery which propagates cuttings and produces field-grown trees and containerized plants. It has a series of containment/recycling reservoirs that capture rainwater and irrigation return water, together with wells of limited output. Water quantity is a more important issue for this nursery, but poor water quality has had some negative economic effects. Irrigation return water is filtered and sanitized with chlorine gas before being applied to plants via overhead and micro-irrigation systems. The agrochemical paclobutrazol was monitored for one year in the first operation and plant pathogens were qualified and quantified over two seasons for both production systems. The two operations employ very different water treatment systems based on their access to water, growing methods, land topography, and capital investment. Each operation has experienced different water quantity and quality vulnerabilities, and has addressed these threats using a variety of technologies and management techniques to reduce their impacts.https://doi.org/10.3390/w1112255

Comparative Analysis of Water Quality between the Runoff Entrance and Middle of Recycling Irrigation Reservoirs

Recycling irrigation reservoirs (RIRs) are an emerging aquatic ecosystem of critical importance, for conserving and protecting increasingly scarce water resources. Here, we compare water quality between runoff entrance and middle of four RIRs in nurseries in Virginia (VA) and Maryland (MD). Surface water temperature (T) and oxidation-reduction potential (ORP) were lower in the middle than at the entrance, while the trend was opposite for dissolved oxygen (DO), pH and chlorophyll a (Chla). The magnitude of these differences between the entrance and middle decreased with increasing depth. These differences were magnified by water stratification from April to October. Minimum differences were observed for electrical conductivity (EC), total dissolved solids (TDS) and turbidity (TUR). Cluster analyses were performed on water quality difference data to evaluate whether the differences vary with respect to reservoirs. Two clusters were formed with one consisting primarily of VA reservoirs, and the other consisting mostly of MD reservoirs in both years. Water quality in the middle and at the entrance of RIRs was expected to vary greatly because of runoff inflow. The two-point water quality differences observed here, although statistically significant, are not large enough to cause significant impact on crop health and productivity for most water quality parameters except pH. Additional analysis of outlet data shows that the range and magnitude of water quality difference between the middle and the outlet are comparable to those between the middle and entrance of RIRs. These results indicate that monitoring at a single point is sufficient to obtain reliable water quality estimates for most water quality parameters in RIRs except pH. This is important when considering the cost of labor and equipment necessary for documenting water quality in agricultural production systems. However, additional pH measurements are still necessary to make practical water quality management decisions