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Rhuanito S. Ferrarezi, Alan L. Wright, Brian J. Boman, Arnold W. Schumann, Fred G. Gmitter, and Jude W. Grosser

a breach may not be detected for several years—which is a serious issue for the production system. Our hypothesis is antipsyllid screen houses and container-grown cultivation would allow rapid young plant growth, playing a role in developing new

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Bryan K. Sales, David R. Bryla, Kristin M. Trippe, Jerry E. Weiland, Carolyn F. Scagel, Bernadine C. Strik, and Dan M. Sullivan

anion) and, when added to soil, improve porosity and aeration and increase retention of water and nutrients ( Bruun et al., 2014 ; Knowles et al., 2011 ; Nemati et al., 2015 ; Sohi et al., 2010 ). Plant growth and productivity have been shown to

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Maynard E. Bates

A simple plant growth model has been developed based on the analysis of growth curves of lettuce and spinach in numerous controlled environment experiments. The model incorporates elements for genetic potential, plant spacing, photosynthetic photon flux, photoperiod, environment, and morphology. Predicted parameters are relative growth rate, mean plant weight, and plant growth efficiency. Prediction may be on an hourly or daily basis. Examples drawn from data on various species and cultivars will be presented.

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Mark T.F. Highland*, Daniel C. Sclar, Elaine R. Ingham, Karen L. Gartley, and James E. Swasey

Compost has great potential for use in horticulture; however, the relationship between compost feedstock materials and resultant compost characteristics must be well understood. Research examining plant growth response from the addition of compost to container growing media is limited. This research had two parts: the first part examined the relationship between compost feedstock materials and resultant mature compost characteristics. The second part investigated plant growth responses when compost replaced the peat component of container growing media. Two feedstock treatments were aerobically composted in turned windrows. Compost characteristics examined include pH, EC, C:N Ratio, Solvita Maturity, and several biological characteristics (total and active bacteria, total and active fungi, protozoa, spore forming bacteria, E. coli O157:H7, and total coliformic bacteria). To examine plant growth response, compost was substituted for peat (from 0%-40% by total volume) in container growing media. Crops tested were Antirrhinum majus `Rocket White', Viola × wittrockiana `Crown Azure', Oriental Hybrid Lilium `Siberia', and Chrysanthemum × grandiflorum `Yellow Kodiak'. Quantitative plant growth response measurements (shoot fresh and dry weight, percent root necrosis, flower number, and flower size) were recorded and compared by treatment. Despite initial feedstock differences between the two compost treatments, both resulted in similar compost biology and species richness. Coliformic bacteria and E. coli O157:H7 levels were below detection limits in final compost. Choice of compost feedstock materials had a significant effect on the chemical characteristics of the finished product. Compost replacement for peat resulted in plant growth greater than or equal to those of the control treatment.

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Bruno Casamali, Marc W. van Iersel, and Dario J. Chavez

, likely because there were enough nutrients in the soil to support the initial plant growth. However, fertilized trees had greater yield in the third year of fruit production, likely because the long-term lack of fertilization started to induce negative

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Soohyun Kang, Yating Zhang, Yuqi Zhang, Jie Zou, Qichang Yang, and Tao Li

Plant growth and development are largely affected by spectra properties of light through mediating photosynthesis and photomorphogenesis. UV radiation critically influences terrestrial plants, and many studies are now available concerning the effect

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Marco Volterrani, Nicola Grossi, Monica Gaetani, Lisa Caturegli, Aimila-Eleni Nikolopoulou, Filippo Lulli, and Simone Magni

seeding is routinely adopted for several field crops. Properly sized sprigs could fit precision seeding machinery thus with the potential of being planted at a defined depth and spacing. Plant growth regulators (PGRs) are known for their ability to modify

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Juan Carlos Díaz-Pérez

vegetable production in the southeast United States over the past 40 years ( Boyhan et al., 2008 ; Roberts and Anderson, 1994 ; Russo, 1993 ). Studies in Israel report that shading increases plant growth and yield in bell pepper ( Rylski and Spigelman

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E. Jay Holcomb and Paul N. Walker

Coal gasification slag is an ash byproduct remaining after the volatization process. This material is currently under utilized. A series of experiments were conducted to determine the suitability of coal gasification slag as a growing medium or growing medium amendment. Chrysanthemums, lettuce, poinsettias and some bedding plants were grown in slag or slag amended media in an ebb and flow fertigation system. Slag alone has a high pH and initial slag samples had some very small particle sizes. Plant growth in slag alone was poor because of high pH and low aeration. When slag was amended with moss peat, the pH was lowered to an acceptable range and the aeration was better. Plant growth in peat-slag media was equal to plant growth in a peat-perlite mix. Media composed of peat-slag and bark were also successful in producing crop growth equal to peat-perlite. There were no nutritional problems growing in slag amended media except that boron uptake by chrysanthemum was greater than in other media. Eliminating the small particle sizes by washing the slag makes the slag easier to handle, but does not produce crop growth equal to slag amended media.

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J.W. Buxton and T.D. Phillips

Students in plant science courses have difficulty thoroughly understanding the effect of water stress on net photosynthesis and its consequences—reduced plant growth, productivity, quality, and profit. A laboratory demonstration utilizing a controlled water table irrigation system (CWT) provides a nearly constant plant water potential. Pots are placed on a capillary mat with one end suspended in a trough with nutrient solution. The vertical distance from the solution surface to the pot bottom determines the water potential; the water potential is 0 when the pot bottom is at the same level as the nutrient solution. The greater the vertical distance from solution to the pot bottom, the lower the water potential. For this demonstration, the bench was sloped from 0 to 10 cm above the solution over a distance of 90 cm. Corn, squash, soybean, fescue, and marigold seed were directly sown to either 9- or 15-cm pots and then placed on the CWT sloped bench at five vertical distances above the solution. Weekly, students observed plant growth and at the end of 8 weeks evaluated root and shoot growth. For all species, plant growth was indirectly related to the distance above the nutrient solution. Plants at near 0 water potential were much larger than those grown 8 to 10 cm above the solution.