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Kenneth G. McCabe, James A. Schrader, Christopher J. Currey, David Grewell, and William R. Graves

bioplastics containing soy could allow for reduced fertilizer inputs during production of plants with short production cycles. To test this hypothesis, our objectives were to grow a common greenhouse-grown crop in various soy-composite biocontainers under a

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Youbin Zheng*, Thomas Graham, Stefan Richard, and Mike Dixon

Pot gerbera (Gerbera jamesonii Var. `Shogun') plants were subirrigated with one of four nutrient solutions (10, 25, 50, and 100% of full strength) in order to determine whether currently used commercial nutrient solution concentrations can be reduced without negative impact on crop production. Nutrient concentration levels did not affect leaf area, flower number and appearance, and plant total dry weight. There were no significant differences in leaf chlorophyll content between the plants that received the 50 and 100% strength nutrient solutions. It is concluded that nutrient solution concentrations typically used in commercial greenhouse, for pot gerbera production, can be safely reduced by at least 50% without adversely affecting crop production. Nutrients accumulated in the top section of the growth substrate under all treatment levels; however, no phytotoxic effect was observed. Fertilizer inputs were reduced in the 50%, 25%, and 10% treatments by 54%, 75%, and 90% respectively. After 4 weeks recirculating, the quality of the nutrient solutions was still within acceptable limits.

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T.L. Schultz and U.K. Schuch

Nitrate nitrogen is becoming a major pollutant in much of our nation's water supply. High levels of nitrate runoff are commonly found to occur from intense agricultural areas such as container nurseries. The objective of this study was to investigate combinations of liquid fertilizer (LF) plus controlled-release fertilizer (CRF) that would both minimize nitrate runoff and provide nutrient levels for optimum growth of Ilex verticillata L. The experiment was established in 1998 at the Iowa State Univ. Horticulture Research Station, Ames. Six fertilizer treatments were arranged in a randomized block design with eight replications. Treatment combinations of liquid fertilizer (LF) and controlled-release fertilizer (CRF) were [LF (mg/L)/CRF (g)]: 90/0, 90/8.5, 90/17, 180/0, 180/8.5, 180/17 (Peter's Excel 21-5-20 and Osmocote 18-6-12, 9-month release, respectively). Analysis of nitrate leaching showed that in 12 out of 16 weeks, the 180 mg/L LF treatments resulted in twice the amount of nitrate leached compared to the 90 mg/L LF. In 3 out of 16 weeks, treatments containing 0 g CRF leached significantly less nitrate than those containing 17 g CRF. None of the treatments produced a difference in total dry weight or caliper of Ilex verticlillata L. This data suggests that plant growth remains similar over a range of fertilizer input and higher rates of applied LF result in higher nitrate leaching.

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N.R. Rice, M.W. Smith, R.D. Eikenbary, D.C. Arnold, W.L. Tedders, B.W. Wood, G.G. Taylor, B.S. Landgraf, and G.E. Barlow

Annual legume ground covers were evaluated in pecan (Carya illinoinensis) orchards to supply nitrogen and increase beneficial arthropods. Treatments were established at two sites, each with 5 ha of a `Dixie' crimson clover (Trifolium incarnatum) /hairy, vetch (Vicia villosa) mixture and 5 ha of grass sod. Data indicated that the legume mixture supplied over 100 kg·ha-1 N to the pecan trees. Beneficial arthropods were greater in orchards with legume ground covers than in orchards with a grass groundcover. Lady beetles and green lacewings were the most important spring predators, and green lacewings were the most important fall predator. The Species distribution on the ground covers differed from that in the canopy. Coleomegilla maculata lengi, Hippodamia convergens and Coccinella septempunctata were the most abundant lady beetle species in the legume ground covers, and Olla v-nigrum, Cycloneda munda, and Hippodamia convergens were the most abundant species in the pecan canopies. Beneficial arthropods appeared to suppress injurious pecan aphids.

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Youbin Zheng, Thomas Graham, Stefan Richard, and Mike Dixon

To determine whether currently used commercial nutrient solution concentrations can be reduced during the final stage (last 4 to 5 weeks) of production of potted gerbera (Gerbera jamesonii `Shogun') under recirculating subirrigation conditions, plants were grown under one of four nutrient levels (10%, 25%, 50%, and 100% of full strength). Nutrient concentration levels did not affect leaf area, flower number and appearance, and plant total dry weight. There were no significant differences in the greenness (as measured by SPAD meter) of leaves from plants that received the 50% and 100% strength nutrient solutions. However, leaves from plants that received the 10% and 25% strength solution showed significantly less greenness than that of the plants that received 50% and 100% strength nutrient solutions. There were interveinal chlorosis symptoms on the younger leaves of some plants in the 10% and 25% strength nutrient treatments. It is suspected that this interveinal chlorosis was due to iron (Fe) deficiency caused by the increased substrate pH. It is concluded that the nutrient solution concentrations typically used for potted gerbera production in commercial greenhouses at the final stage (4 to 5 weeks) under recirculating subirrigation conditions, can be safely reduced by at least 50% without adversely affecting crop production. Nutrient salts accumulated in the top section of the growth substrate under all treatments levels; however, no phytotoxic effects were observed. No differences in water use (141 mL per plant per day) were observed amid the various nutrient levels. Fertilizer inputs were reduced in the 50%, 25%, and 10% treatments by 54%, 75%, and 90% respectively, relative to the 100% treatment. After 4 weeks under recirculating conditions, the qualities of the nutrient solutions were still within acceptable limits.

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Youbin Zheng, Diane Feliciano Cayanan, and Mike Dixon

○ K □ Mg △ Ca Water consumption of the production system (average 147 mL per pot per day) was unaffected by nutrient solution concentration, but fertilizer inputs were reduced at lower nutrient feeds. Compared with the 100% treatment

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Pablo R. Hidalgo, Richard L. Harkess, and Frank Matta

Earthworm castings were evaluated to determine the effect of earthworm castings on growth of Poinsettia `Freedom Bright Red'. Castings derived from cow (CC), horse (HC), or sheep (SC) manure were combined with peatmoss at 1:0, 1:3, 1:1, 3:1, or 0:1 peat: castings (v/v). One plant was potted per 1.5-L container and were fertilized at 0, 50, 200, or 350 mg/L N in a RCB arrangement. Plant growth index at all fertilizer rates was greatest when grown in SC at 0:1, 1:3, and 1:1 and CC at 0:1 and 1:3 (peat: castings) ratios. For each of the three animal sources, no differences in growth index were observed among fertilizer rates when 100% castings was used as the substrate. Bract area was greatest on plants grown in SC at 1:0, 1:3, and 1:1 (peat: castings) ratios at all four fertilizer rates. Bract area on plants grown in CC at 0:1 and 1:3 (peat: castings) was less than SC, but better than CC at 1:1, 3:1, or 1:0 or any of the HC substrates. Plants grown in substrates with 75% or more castings all had similar bract area regardless of fertilizer rate. As castings in the substrate decreased, bract area increased as fertilizer rate increased. When fertilized at 0, 50, or 200 mg/liter N plant dry weight decreased as castings increased in the substrate. Fertilization at 350 mg/liter did not affect dry weight between substrates.

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Jeffrey G. Williamson and Jonathan H. Crane

-volume irrigation technology will allow for fertigation, which, if properly managed, will reduce fertilizer inputs by minimizing losses from leaching and/or runoff. Critical issues facing the temperate fruit industry include limited land availability, availability

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Ross C. Braun, Jack D. Fry, Megan M. Kennelly, Dale J. Bremer, and Jason J. Griffin

fewer pesticide and fertilizer inputs compared with cool-season turfgrasses ( Fry and Huang, 2004 ). However, cool-season turfgrasses remain green late into the autumn and also green up earlier in the spring, whereas warm-season grasses turn brown after

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Martin M. Maboko and Christian P. Du Plooy

decrease NC in open-bag hydroponic system will reduce nutrient leaching, and at the same time decrease fertilizer input costs by 25% and 50% on cherry and FM tomatoes, respectively, with a reduced risk associated with soil and soil water pollution. Further