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A segment of the greenhouse crop market would like to obtain vegetables and herbs that are certified organic. The technology for the use of biological controls for insects and diseases is well-developed and a significant part of greenhouse vegetable production. Organic fertilizers, however, have not been well-utilized in organic greenhouse vegetable production. Common organic fertilizers were analyzed for the levels of nutrients when mixed with water for use in greenhouse fertigation. Products derived from algae-Algamin (liquid) and Ohrstrom's Garden Maxicrop (powder), Bat Guano, and products derived from fish waste-GreenAll Fish Emulsion (liquid) and Mermaid's Fish Powder, demonstrated nutrient levels comparable to typical water-soluble fertilizers used for greenhouse plant production. Although the organic fertilizers could not be used as a concentrate for injector systems, readings from a conductivity meter were directly related to nitrate nitrogen levels and could be used for fertilizer management in the capillary mat subirrigation system used for plant production.

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Valley, MN, USA). The ground tissue was placed in vials containing ∼3 g of tissue and submitted for a nutrient analysis of N, P, K, Ca, Mg, S, B, Cu, Zn, Fe, and Mn concentrations (Waters Laboratory, Warsaw, NC, USA). Dried plant material (0.5 g) was

Open Access

This research was carried out from 2004 to 2005 in two commercial ‘Hass’ avocado orchards cultivated under rainfed conditions in a hot subhumid climate of the state of Nayarit, Mexico. The objectives of this study were to: 1) establish the patterns in nutrient concentrations during the lifespan of winter and summer vegetative flush leaves; and 2) validate a methodology based on mathematical functions to identify the appropriate period for leaf sampling to diagnose plant nutrition in avocado considering its two major vegetative flushes. Leaf samples were taken monthly for each vegetative flush, starting when leaf length was 5 cm or greater and concluding at leaf abscission. Starting at vegetative budbreak, winter and summer leaves lived 12.5 and 7.8 months, respectively. Summer flush leaves grew faster and attained greater length than winter leaves. A mathematical model based on the concentration of macro- and micronutrients through the lifespan of avocado leaves was evaluated. This model was used to determine the period when nutrient concentrations became stable and, consequently, to identify the proper leaf sampling period. For the ‘Hass’ avocado in Nayarit, the period for sampling winter flush leaves corresponded to 6.6- to 7.9-month-old leaves (4 Sept. to 13 Oct.). For summer leaves the optimum period was shorter and occurred when leaves were 3.9 to 4.9 months old (5 Dec. to 5 Jan.). The procedure and sampling time obtained here should be tested in other regions.

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date were pooled together for mineral nutrient tissue analysis at the Cornell Nutrient Analysis Laboratory (Ithaca, NY). EBCs were observed under ×16 magnification (field of view or field size is equal to 1.44 mm). A random plant was selected from each

Open Access

rate because the nutrient analysis did not match the percent of N as stated on the product label. Feather meal was applied in two equal split-applications in March and May. In weed mat plots, the feather meal was concentrated in the openings in 2007

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fractions of total Si compared with roots and shoots. Because sap analyses using petiole tissue are becoming more frequent for nutrient analysis, the quantification technique needs to be sensitive enough to detect Si in these ranges. Interestingly, Si

Open Access

Abstract

Macadamia (Macadamia integrifolia, Maiden et Betche) husks, a waste product of the industry, could serve a useful purpose as a mulch (8). However, uncomposted husks have been shown to be toxic to germinating corn (Zea mays L.) seedlings when mixed with vermiculite as a potting medium. In a composting study, unamended heaps of macadamia husks retained potent phytotoxic compounds for at least 209 days (unpublished data). Observations (H. Ooka, personal communication) indicated that mature macadamia trees could be killed with high levels of fresh husks used as a mulch around the base of plants. The objective of this study was to measure the yield, growth, and leaf nutrient levels of mature macadamia trees in response to increasing amounts of uncomposted husks applied as a surface mulch.

Open Access

Many abiotic factors impact the yield and growth of Cannabis sativa (cannabis). Cannabis has been reported to be a bio-accumulator of heavy metals. For growers who are targeting floral production and other byproducts for human consumption, this is a concern. Silicon (Si) has been examined as a beneficial plant element to limit the uptake of heavy metals in a variety of crops. The objective of this study was to determine the impact of Si on heavy metal micronutrient uptake and plant growth for greenhouse-cultivated cannabis at varying Si substrate amendments. ‘Auto CBG’ plants were grown in a 70:30 peat:perlite substrate with one of three varying calcium silicate (CaSiO3) (Si) substrate amendment rates, Si0X, Si0.5X, or Si1X (of 0.0, 1.04, and 2.07 kg⋅m−3 CaSiO3), and one of three micronutrient fertility treatments, M1X [0.49 boron (B), 0.19 copper (Cu), 4.02 iron (Fe), 0.99 manganese (Mn), 0.01 molybdenum (Mo), and 0.20 zinc (Zn) mg⋅L−1], M2X, or M4X, using a modified Hoagland’s solution, creating a 3 × 3 factorial. Plants grown with a Si1X substrate amendment exhibited a significantly lower iron concentration in the foliage and root tissue when compared with those grown in a substrate without Si. After 6 weeks of growth, Si0X plants that received a M4X fertility rate exhibited greater foliar micronutrient concentrations of B, Mn, Zn, Fe, and Cu than plants that received a Si substrate amendment when provided a M4X fertility rate. Additionally, lower micronutrient concentrations in floral tissue were observed in plants that received a Si substrate amendment for M2X and M4X when compared with plants that did not. Silicon substrate amendments had no impact on the cannabinoid concentration or plant growth metrics after 12 weeks of growth. This research suggests that using a Si substrate amendment in a greenhouse production system can limit excessive uptake and accumulation of micronutrients in the foliage, roots, and floral material of cannabis without negative impacts on plant growth or cannabinoid concentrations.

Open Access

Triplicate water samples were collected monthly from nine waterways [eight runoff containment basins (RCBs) and one stream] on four commercial ornamental plant nurseries from February to July, and from one RCB and nursery from April to October. Four RCBs, one per nursery, were actively used as an irrigation water source. Analysis was done for 18 water quality variables, including ammonium–nitrogen (NH4 +–N), nitrate–nitrogen (NO3 –N), ortho phosphate–phosphorus (PO4–P), total-phosphorus (T-P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), aluminum (Al), boron (B), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), pH, total alkalinity (T-Alk), electrical conductivity (EC), and sodium (Na). The degree and rate of monthly change varied considerably between RCBs. Macronutrients generally increased at most nurseries in 1–2 months after fertilizer application particularly in three RCBs (MD21, VA11, and VA12), with levels of N- and P forms exceeding preferred criteria for irrigation water by June and July in VA11 and VA12. Micronutrients fluctuated less but did vary per RCB with the most monthly change occurring in MD21. Even though pH fluctuated, pH tended to remain alkaline or neutral to acidic respective of the RCB during the entire sample period. T-Alk tended to increase over the summer. EC primarily fluctuated in RCBs with high macronutrient levels. Although levels of N- and P forms were mostly suitable by irrigation water criteria, they were frequently above U.S. Environmental Protection Agency (USEPA) nutrient criteria for promoting healthy water environments of lakes and reservoirs, and are discussed.

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Nine runoff containment basins (RCBs), used directly or indirectly for irrigating plants in ornamental plant nurseries, and one adjacent stream were sampled for water quality between Feb. and July 2013 in Maryland (MD), Mississippi (MS), and Virginia (VA). Triplicate water samples were taken monthly. Analysis was done for 18 water quality variables including nitrate-nitrogen (NO3 -N) and ammonium-nitrogen (NH4 +-N), orthophosphate-phosphorus (PO4-P) and total-phosphorus (T-P), potassium, calcium, magnesium, sulfur, aluminum, boron (B), copper (Cu), iron (Fe), manganese, zinc (Zn), pH, total alkalinity (T-Alk), electrical conductivity (EC), and sodium. Additionally, 15 RCBs from 10 nurseries in Alabama (AL), Louisiana (LA), and MS were sampled in 2014 and 2016. Most prevalent correlations (P = 0.01) were between macronutrients, EC, B, Fe, and Zn, but none were prevalent across a majority of RCBs. Water quality parameter values were mostly present at low to preferred levels in all 25 waterways. Macronutrient levels were highest for a RCB that receives fertility from fertigation derived runoff. Water pH ranged from acidic to alkaline (>8). Results of this study show water quality in RCBs can be suitable for promoting plant health in ornamental plant nurseries, but also shows levels will vary between individual RCBs, therefore demonstrates need to verify water quality from individual water sources.

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