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John A. Biernbaum and William R. Argo

Impatiens were planted in media containing either hydrated or carbonate dolomitic lime and subirrigated for 17 weeks using four irrigation water qualities (IWQ) and three water-soluble fertilizers (WSF). Micronutrients (Fe, Mn, Zn, Cu, B, and Mo) were incorporated into all root media at planting with fritted trace elements (FTE 555) at 0.07 kg·m–3 and were added to all WSF treatments with a commercially available chelated material (Compound 111) at a constant 50 mg·liter–1. Root-medium pH obtained from the various IWQ/WSF solutions at 4, 8, 12, and 17 weeks after planting were used to determine relationships with shoot tissue micronutrient concentrations. Tissue Fe concentrations decreased linearly as root-media pH increased from 5.0 to 8.5. Below pH 5.0, the tissue Fe concentration increased at a rate indicating greater nutrient availability in the root medium. However, between pH 4.0 and 7.5, tissue Fe was within acceptable levels. A linear relationship also was found with tissue Zn and B, but without the rate increase below a pH of 5.0. Tissue Mn decreased to a minimum as the rootmedium pH increased from 4.0 to 6.0 and increased again as the root medium pH increased from 6.0 to 8.5. Tissue Mo concentrations increased as root medium pH increased. Tissue Cu concentrations were unaffected by medium pH.

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William R. Argo, John A. Biernbaum, and William C. Fonteno

Medium CO2 and O2 partial pressures were measured at three locations [3.8 (top layer), 7.5 (middle layer), and 10.3 (bottom layer) cm below the rim] in 15-cm-tall pots containing flowering chrysanthemums [Dendranthem×grandiflorum (Ramat.) Kitamura] grown in one of three root media. Average ambient medium CO2 and O2 partial pressures were 63 Pa and 21 kPa, respectively, and were similar in the three sampled layers in root media with an average moisture content of 50% to 60% of container capacity. Within 10 minutes after a drip-irrigation application of well water containing a titratable alkalinity to pH 4.5 of 320 mg CaCO3/liter, the partial pressure of medium CO2 increased to ≤1600 Pa and medium O2 decreased to 20.5 kPa in the top and middle layers of the pot. With subirrigation, medium CO2 partial pressures increased to ≤170 Pa and medium O2 remained at 21 kPa. When reverse-osmosis purified water (titratable alkalinity to pH 4.5 of <20 mg CaCO3/liter) was used instead of well water, the large increase in medium CO2 did not occur, indicating that the bicarbonate alkalinity in the irrigation water was the source of CO2. The high medium CO2 partial pressure measured after irrigation was not persistent; within 180 minutes, it returned to levels averaging 45% higher (100 Pa) than that measured before the irrigation. Medium O2 also had returned to ambient levels 180 minutes after the irrigation.

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William R. Argo, John A. Biernbaum, and Darryl D. Warncke

Chemical analyses of 4306 randomly selected greenhouse water samples for 1995 from the United States and Canada were obtained from four analytical laboratories and graphically characterized using a distribution analysis. For pH, electro-conductivity (EC), and nutrient concentrations, a mean and median value and the percentage of samples with concentrations above or below those generally considered acceptable are presented for all samples and the 10 leading states in floricultural production. The median nutrient concentrations were more representative of the type of water found throughout the United States and Canada than that of the mean values because of the unequal distribution of the data. The overall median water source had a pH of 7.1; an EC of 0.4 dS·m−1; an alkalinity of CaCO3 at 130 mg·L−1; (in mg·L−1) 40 Ca, 11 Mg, 8 SO4−S, 13 Na, 14 Cl, 0.02 B, and <0.01 F; a Ca: Mg ratio of 3.2, and a sodium adsorption ratio (SAR) of 0.7. The information presented characterizes irrigation water and may assist in developing more refined fertilizer recommendations for greenhouse crop production.

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Paul R. Fisher, William R. Argo, and John A. Biernbaum

Two experiments were run to validate a “Nitrogen Calcium Carbonate Equivalence (CCE)” model that predicts potential fertilizer basicity or acidity based on nitrogen (N) form and concentration for floriculture crops grown with water-soluble fertilizer in containers with minimal leaching. In one experiment, nine bedding plant species were grown for 28 days in a peat-based substrate using one of three nutrient solutions (FS) composed of three commercially available water-soluble fertilizers that varied in ammonium to nitrate (NH4 +:NO3 ) ratio (40:60, 25:75, or 4:96) mixed with well water with 130 mg·L−1 calcium carbonate (CaCO3) alkalinity. Both the ammonium-nitrogen (NH4-N) content of the FS and plant species affected substrate pH. Predicted acidity or basicity of the FS for Impatiens walleriana Hook.f. (impatiens), Petunia ×hybrida E. Vilm. (petunia), and Pelargonium hortorum L.H. Bailey (pelargonium) from the Nitrogen CCE model was similar to observed pH change with an adjusted R 2 of 0.849. In a second experiment, water alkalinity (0 or 135.5 mg·L−1 CaCO3), NH4 +:NO3 ratio (75:25 or 3:97), and N concentration (50, 100, or 200 mg·L−1 N) in the FS were varied with impatiens. As predicted by the N CCE model, substrate pH decreased as NH4 + concentration increased and alkalinity decreased with an adjusted R 2 of 0.763. Results provide confidence in the N CCE model as a tool for fertilizer selection to maintain stable substrate pH over time. The limited scope of these experiments emphasizes the need for more research on plant species effects on substrate pH and interactions with other factors such as residual limestone and substrate components to predict pH dynamics of containerized plants over time.

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David S. Conner, Kurt B. Waldman, Adam D. Montri, Michael W. Hamm, and John A. Biernbaum

Relatively low-cost season extension structures have the potential to contribute to farm economic viability in temperate climates by providing a means to continue sales beyond the limits of outdoor-only field production. These structures, commonly called hoophouses, high tunnels, passive solar greenhouses, or unheated greenhouses, allow for the extension of heat-tolerant (warm season) crops on both ends of the production time frame and at winter harvesting of cold-tolerant (cool season) crops. In this study, results are presented from a multiyear investigation into the economic impacts of year-round production and harvesting, with a focus on profitability of the structure and crop production as a whole. The results of case studies from nine Michigan farms reveal a very broad range of outcomes across farms in construction time, labor allocation and returns, and gross and net revenue. The economic implications of farmer use, including projected investment payback time, are discussed.

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William R. Argo, Brian J. Weesies, Erica M. Bergman, Michelle Marshal, and John A. Biernbaum

The rhizon soil solution sampler (RSSS) currently is being used for in situ extraction of the soil solution for nutrient analysis of mineral soils used to produce field-grown crops. In this study, laboratory and greenhouse experiments were conducted to test the effectiveness of the RSSS for in situ solution extraction from soilless container root media and to compare an RSSS extraction method for measuring root-medium pH, electrical conductivity (EC), and NO3-N and K concentrations with that measured with the saturated media extract (SME) method. A near 1:1 correlation was found between the pH, EC, and NO3-N and K concentrations measured in the extracted solution of the RSSS and SME method in media without plants and in media from ten species grown using three water-soluble fertilizer concentrations applied by subirrigation. More testing is needed with the RSSS, perhaps using composite samples form several pots for analysis. The RSSS shows promise for nutrient extraction in container-grown crops because it is fast, nondestructive, simple, economical, and has minimal effect on the nutritional status of the medium in the pot.

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Kurt B. Waldman, David S. Conner, John A. Biernbaum, Michael W. Hamm, and Adam D. Montri

Quantitative and qualitative data from a group of 12 novice hoophouse farmers over a 3-year period in Michigan were analyzed to better understand factors associated with profitable use of these structures. There was wide variation in labor inputs and effective wages. We used regression analysis and semistructured interviews to better understand the variation in performance. Not all farmers were making use of the hoophouse between outdoor seasons when supply is low and prices are high, as economic theory would predict. However, high wage earners were more likely to push production into the extended season months, hire labor at higher wages, and spend less time in maintaining crops and appeared to harvest more efficiently. Markets played a role in farmers’ success as some farmers were able to make significant profits by organizing community-supported agriculture (CSA)/direct sales or by finding new markets.

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John A. Biernbaum, William R. Argo, Brian Weesies, Allen Weesies, and Karen Haack

A series of experiments was conducted to quantify the rate of nutrient loss from a container medium in a 15-cm-wide (1.3-liter) pot with a container capacity (CC) of 0.7 liter/pot under mist propagation and to determine the effectiveness of reapplying fertilizer to medium at 90% of CC with either top watering or subirrigation. Reducing the volume of water applied per day decreased the rate of nutrient leaching. Based on CC leached (CCL), the rate of nutrient loss was similar for all treatments. Differences in the rate of macronutrient removal from the media were measured, but, by 2 CCL, the concentration of all nutrients tested was below acceptable levels for the saturated media extract. With top watering, reapplying water-soluble fertilizer (WSF) at volumes under 0.2 liter/pot did not affect the nutrient concentration in the lower half of the pot at WSF concentrations up to 86 mol N/m3. Applying up to 0.8 liter/pot did increase nutrient concentrations in the lower half of the pot, but the media nutrient concentrations were lower than that of the applied WSF concentration. Applying WSF with subirrigation was limited by the moisture content of the media prior to the irrigation.

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Mark V. Yelanich, James E. Faust, Royal D. Heins, and John A Biernbaum

The measurement of evaporation and transpiration from container-grown crops is labor intensive and expensive if measurements are made by periodic weighing of the plants with electronic scales. Thin-beam load cells (LCL-816G, Omega Engineering) measured with a datalogger provides a method of making continuous mass measurements over time. Four load cells were tested to determine the feasibility for use in greenhouse studies. The sensors were calibrated to an electronic scale at a range of air temperatures. The electrical signal (μV) was a linear function of mass from 0 to 816 g. The change in mass per change in electrical signal (i.e. the slope) was the same for all four load cells (1.26 g ·μV-1), however the absolute electrical signal (the intercept) was unique for each sensor (-246 to + 101 g). The effect of temperature on sensor output was unique for each sensor in terms of both the magnitude and direction of change. A two-point calibration of mass performed at a range of temperatures is required to properly use thin-beam load cells to continuously measure evapotranspiration of container-grown crops.

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Erica M. Bergman, Michelle Marshal, Brian Weesies, William R. Argo, and John A. Biernbaum

A small suction lysimeter tube (SLT) was used to extract media solution samples for twelve pot plant species in peat-based media subirrigated with 50, 100, or 200 mg · liter-1 N and K2O. Media samples from different pots were also tested using the saturated media extract (SME) procedure. Sample solution pH, EC, NO3 --N and K+ were measured with Cardy flat electrode meters. Averaged over crops, solution pH was similar for SLT and SME (after extraction) at each N concentration. The mean (12 crops × 3 reps at each N level) SME and SLT solution EC and K+ concentrations were similar for samples collected from the 50 and 100 mg · liter-1 N treatments. NO3 --N values were lower with the SLT than SME method at 50 mg·liter-1 N. SLT levels for EC, NO3 --N, and K+ were 27, 39, and 24% higher than SME values for samples collected from the 200 mg·liter-1 N treatments. Sample variation between replicates and between methods for the single pot samples was unacceptable. More testing is needed with SME and SLT samples from the same pot and composite samples from several pots, but SLT sampling is fast, nondestructive, simple, and economical at $6-7 per tube.