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  • Author or Editor: D.M. Cole x
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Improving the quality of water released from containerized production nurseries and greenhouse operations is an increasing concern in many areas of the United States. The potential pollution threat to our ground and potable water reservoirs via the horticultural industry needs to receive attention from growers and researchers alike. `Orbit Red' geraniums were grown in 3:1 peat:perlite medium with microtube irrigation to study the effect of fertilizer source on geranium growth, micronutrient leaching, and nutrient distribution. Manufacturer's recommended rates of controlled-release (CRF) and water-soluble fertilizers (WSF) were used to fulfill the micronutrient requirement of the plants. Minimal differences in all growth parameters measured between WSF and CRF were determined. A greater percentage of Fe was leached from the WSF than CRF. In contrast, CRF had a greater percentage of Mn leached from the system than WRF during the experiment. Also, regardless of treatment, the upper and middle regions of the growing medium had a higher nutrient concentration than the lower region of medium.

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`Formosa' azalea (Rhododendron indicum) was grown for 4 months in 7.6-L (2 gal) containers in four substrate blends: 100% pine bark (PB) (by volume), 1 PB: 1 cotton gin compost (CGC), 3 PB: 1 CGC, and 3 PB: 1 peat (PT) at three irrigation levels [600, 1200, and 1800 mL·d-1 (20.3, 40.6, and 60.9 floz/d)] in a polyethylene-covered greenhouse. Plants were evaluated for growth on a biweekly basis using a growth index. Roots were evaluated visually at the end of the study using a 0 (no root growth) to 5 (root bound) scale. Initial physical properties were determined and leachates were collected every 30 days. There was no difference in percent increase in growth across irrigation and substrate treatments. Visual root rating was greatest (4.5) for azaleas grown in 3 PB: 1 PT and least (3.5) in 1 PB: 1 CGC. The two PB/CGC blends improved water-holding capacity (WHC) in comparison to 100% PB, with 1 PB: 1 CGC exhibiting the greatest WHC among all four substrates. Bulk density was greatest with the CGC-amended substrates. Leachate pH tended to increase and electrical conductivity (EC) tended to decrease with increasing irrigation volume. Leachates from the CGC-amended substrates were less acidic and EC tended to be similar or greater than leachates from the 100% PB and 3 PB: 1 PT substrates.

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Abstract

Fruit production and tree size were measured and yield efficiency was computed for 11-year-old trees of ‘Washington’ navel and ‘Olinda Valencia’ oranges [Citrus sinensis (L.) Osbeck], ‘Minneola’ tangelo (C. paradisi Macf. × C. reticulata Blanco), and ‘Lisbon’ lemon (C. limon Burm. f.) on 21 rootstocks in the San Joaquin Valley of California. Performance of most rootstocks was similar over all scions, and several rootstocks produced trees with higher yields than ‘Troyer’ and ‘Carrizo’ citranges [C. sinensis × Poncirus trifoliata (L.) Raf.], the current standard rootstocks. ‘Yuma Ponderosa’ lemon (× C. limon) had the highest yields, but several trees on this rootstock died or were declining. Trees on ‘C-32’ citrange (C. sinensis × P. trifoliata) were largest, and yielded nearly as much as those on ‘Yuma Ponderosa’ lemon. ‘C-35’ citrange (C. sinensis × P. trifoliata) produced smaller trees with excellent yield efficiencies, and should be suitable for higher-density plantings with most scions, except perhaps navel orange, because this combination yielded poorly at other locations. ‘Rangpur’ lime (C. limonia Osbeck) was promising only with lemon scion, and ‘Swingle’ citrumelo (C. paradisi × P. trifoliata) only with ‘Minneola’.

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