One of the most difficult times to balance crop nitrogen (N) requirements with concerns about nitrate-N leaching occurs during crop establishment, when root systems are poorly developed and not widely distributed in the growing medium. This dilemma can be exacerbated when producing a slow-growing plant such as leatherleaf fern (Rumohra adiantiformis [Forst.] Ching) on sandy soils in shadehouses in areas with significant rainfall. Rhizomes were planted in 36 drainage lysimeters containing Tavares fine sand located in a shadehouse. Nitrogen fertilizer was applied at nine rates using liquid and/or controlled-release fertilizer. Nitrogen application rates were varied as the rhizomes became established and spread into unplanted areas of the lysimeters. Irrigation and rainfall were monitored and the amount of water not lost to evapotranspiration was determined. Nitrogen (ammoniacal, nitrate/nitrite, total Kjeldahl) concentrations in leachate collected below the rootzone were determined. Stipe sap nitrate and frond total Kjeldahl nitrogen (TKN) were determined to try to develop a production monitoring technique. Initially, only leachate samples from controlled-release fertilizer plots treated at 21 and 42 kg of N/ha per year and liquid fertilizer at 28 kg of N/ha per year were consistently below the maximum contamination level (MCL) of 10 mg·L–1. As the fern became established, leachate nitrate/nitrite-N concentrations from higher N application rate treatments also remained below the MCL. Leachate N concentrations decreased as rainfall increased. Fern growth increased with increasing N application rate. Stipe sap nitrate-N and frond TKN concentrations were not well-correlated during establishment.
Ilex ×meserveae `Blue Princess' plants were grown in a pot-in-pot using container media consisting of pine bark-peat-sand at 90:0:10, 75:15:10, and 60:30:10 by volume. During the summer season, plants were irrigated using a cyclic irrigation regime consisting of two and three irrigation applications and were compared to a traditional irrigation regime with one irrigation application that equaled the total volume applied in the cyclic regime. Nitrate concentrations in leachates were three times lower, whereas ortho-phosphate levels were two times lower in three irrigation application than those in one irrigation application. Increasing the percentage of bark in container media increased nitrate levels and reduced orhto-phosphate levels in leachates. There was no significant difference in growth index among treatments.
Ninebark [Physocarpus opulifolius (L.) Maxim] was grown on troughs under greenhouse conditions in 2.5-L containers filled with 100% composted pine bark and fertigated with drip irrigation using the following nutrient solutions: 1) a complete (control) solution, electrical conductivity (EC) of 1.75 dS·m–1, nonrecirculated; 2) solution as in treatment 1 but recirculated; 3) unamended municipal solid waste compost (MSW) leachate, EC 1.75 dS·m–1, recirculated; 4) solution as in treatment 3 amended in order of priority with NO3-N, NH4-N, P, K, Ca and/or Mg, to match the concentrations in the complete solution, EC 2.60 dS·m–1, recirculated; 5) unamended turkey litter compost (TLC) leachate, EC 1.75 dS·m–1, recirculated; and 6) solution as in treatment 5 amended as in treatment 4, EC 2.40 dS·m–1, recirculated. Among the four recirculated compost leachate treatments, shoot (stems and leaves) dry weight of ninebark was least with the unamended MSW, intermediate with amended MSW, and greatest but similar with both unamended and amended TLC. The most growth occurred with the recirculated control solution. Among the four leachate treatments, ninebark grew acceptably well only with recirculated unamended TLC, and was similar to that with the nonrecirculated control solution. Three treatments (nonrecirculated control, recirculated control and unamended TLC) showed no nutrient toxicity or deficiency symptoms. Poorer growth responses in the other treatments (amended TLC, amended MSW and unamended MSW) were related primarily to excess salts and/or nutritional disorders due to imbalance(s) in one or more nutrients.
This study was conducted to determine if changes in the raffinose: sucrose ratio in embryos of shrunken-2 sweet corn (Zea mays L.) hybrids were related to differences in seed leachate conductivity between two hybrids harvested at four maturities and artificially dried to 0.10 g H2O/g fresh weight. The ratio of raffinose: sucrose differed for `Crisp N' Sweet 710' (CNS) and `How Sweet It Is' (HSII). The mass ratio of raffinose: sucrose in CNS was >0.3 in seed harvested between 0.44 to 0.64 g H2O/g fresh weight and increased as seed dried from the initial harvest moisture to 0.10 g H2O/g fresh weight. Raffinose: sucrose ratios of HSII were <0.3 at all harvests between 0.55 to 0.72 g H2O/g fresh weight, but changes during desiccation were not as pronounced. Leachate conductivity of whole seeds of CNS and HSII decreased as seeds were harvested at progressively lower moisture contents. We suggest that a higher raffinose: sucrose ratio may be indicative of increased seed vigor in shrunken-2 hybrids.
Poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch `V-14 Glory') were grown in a greenhouse for 70 days in 1.3 liters of medium (13 cm deep in 15-cm pots) with a leaching fraction (LF) of ≈ 0, 0.1, 0.2, or 0.4. Plants were fertigated with 300 mg N/liter from 20 N-4.4P-16.6K. The electrical conductivity (EC) of the fertigation solution was 2.1 dS·m-1. The leachate EC increased from 2 dS·m-1 initially to plateaus of ≈ 6, 9, and 15 dS·m-1 for LFs of 0.4, 0.2, and 0.1, respectively. Poinsettia height, shoot fresh and dry mass, and leaf and bract areas were not significantly different among the LF treatments. Leachate pH decreased from 6.1 initially to 5.1 at the end, but there was no significant difference among the LF treatments. The EC of a saturated medium extract (ECe) was between 17% and 48% higher in the lower third of the medium than in the middle third. The difference was greater with a lower LF. The EC, was 8.9, 7.3, 5.2, and 3.4 dS·m-1 in the lower third of the pot for a LF of 0, 0.1, 0.2, and 0.4, respectively. Under conditions of this study, container poinsettias required no leaching.
Poinsettias (Euphorbia pulcherrima 'Gutbier V-14 Glory'), chrysanthemums (Dendranthema grandiflora 'Tara') and geraniums (Pelargonium xhortorum 'Orbit') were grown using various ratios of controlled release:constant liquid fertilization as a percentage of recommended rates (%CRF:%CLF). While plants grown under the 100:0 CRF:CLF regime produced significantly less nitrates, phosphates and total soluble salts in the leachate than 0:100 or 50:50 CRF:CLF, quality rating, plant diameter, and leaf, bract and flower dry weight of poinsettias and chrysanthemums were reduced. Geraniums grown under 100:0, 50:50 or 0:100 CRF:CLF regimes were similar in quality rating, height, diameter, dry weights and days to anthesis. Poinsettias and chrysanthemums grown under 50:50 CRF:CLF were similar in height, days to anthesis, plant diameter, flower and stem dry weights and quality rating but produced less nitrates, phosphates and total soluble salts in the leachate than plants grown under 0:100 CRF:CLF. However, chrysanthemums grown under 50:50 CRF:CLF had lower leaf and root dry weights and poinsettias had lower leaf and bract dry weights than under 0:100 CRF:CLF regime.
Experiments were conducted to determine the effect of varying solution N concentrations on fruit yield and NO3-N concentration in leachate from rockwool-grown `Midal' peppers (Capsicum annuum L.) in Florida. Treatment 1 plants received a series of nutrient solutions containing N at 60, 90, and 120 mg·liter–1 (60–90–120 mg·liter–1) during their growth cycle. Plants in treatments 2 and 3 were grown with N at 120 or 175 mg·liter–1, respectively, throughout their entire growth cycle. Two trials were conducted; trial 1 from 17 Nov. 1991 to 1 July 1992, and trial 2 from 31 July 1992 to 23 Feb. 1993. In both trials, total marketable fruit weight was significantly (P ≤ 0.05) higher (16% to 67%) for plants grown with N at 175 than with 60–90–120 mg·liter–1. In trial 2, plants receiving N at 175 mg·liter–1 produced significantly more fruit (8%) and 14% higher total fruit weight than plants receiving N at 120 mg·liter–1. The trend toward higher yield with N at 175 rather than 120 mg·liter–1 also occurred during trial 1, but differences were not significant. Nitrogen concentration did not significantly affect the percentage of total fruit having blossom-end rot in either trial (41% in trial 1; 13% in trial 2). Nitrogen at 175 mg·liter–1 resulted in 10% to 40% increases in total nutrient solution use and 2.5- to 3.5-fold increases in leachate NO3-N concentration compared to N at 120 mg·liter–1.
Many nutrient recommendations for greenhouse production of vegetable crops were developed in northern climates and may not be optimum for Florida production. Experiments were designed to determine nitrogen (N) levels that would maximize yield of rockwool-grown peppers (Capsicum annuum `Midal') in Florida, while reducing nitrate leaching. Treatment 1 plants were fed 60, 90, and 120 ppm N during vegetative, early fruit, and late fruit stages, respectively. Plants in Treatments 2 and 3 were grown at 120 and 175 ppm N, respectively, throughout their entire growth cycle.
In Trial 1, increasing N did not affect the number of marketable fruit produced, but increased fruit size. Marketable fruit weight was significantly greater for plants in Treatment 3 compared to Treatment 1. However, there was not a significant difference in marketable yield between plants grown at 120 ppm N and 175 ppm N. Excess N provided by the 175 ppm N treatment caused a 10% increase in total water use and a 250% increase in nitrate-N in the leachate compared to the 120 ppm N treatment. Nitrogen level did not affect blossom end rot (BER) occurrence. Early results of Trial 2 indicate higher occurrence of BER with increasing N concentration and are again showing that 120 ppm N will maximize yield and reduce environmental impact of greenhouse pepper production in Florida.
Poinsettia (Euphorbia pulcherrima `Gutbier V-14 Glory') were grown using commercially available poinsettia fertilizer of various combinations of controlled-release (CRF) and constant liquid fertilizer (LF). At the end of the production period, plants treated with 83, 165 or 250 mg/l LF only were 10% taller than plants treated with the same concentrations of CRF. The total number of cyathia and the number of open cyathia at harvest was 18% and 50% higher for plants treated with LF only compared to plants treated with CRF only. Plants treated with 165 CRF/ 83 LF or 83 CRF/250 LF were not different compared to 250 CRF/0 LF or 0 CRF/ 250 LF in height, number of cyathia at anthesis, and total number of cyathia at the end of the production period. When LF was changed to clear water 5 weeks before the end of production, nitrate runoff from 83 CRF/250 LF treatment was reduced 30% for the last two weeks, and from the 165 CRF/83 LF treatment nitrate leachate was reduced gradually from 33 to 66% over the 5-week period.
Understanding the possible influence of inorganic soil amendments on salt leaching and deposition is helpful in selecting soil amendments when salinity is a problem. Greenhouse experiments were conducted to: 1) evaluate the effects of isolite and zeolite on turf quality of Kentucky bluegrass (Poa pratensis L.) under three salinity levels; and 2) determine if soil amendments affected leachate composition, salt deposition, and soil sodium absorption ratio (SAR). `Challenger' Kentucky bluegrass was grown in columns filled with 100% sand, 50 sand: 50 isolite, and 50 sand: 50 zeolite (v/v). Irrigation waters with three levels of salinity [0.25 (control), 3.5, or 6.5 dS·m-1] were applied daily for 3 months in Study I and for 6 months in Study II. Saline water reduced turf quality compared with control. Amendment of sand with isolite increased turf quality only during the third month of treatment with the most saline water in Study I. However, zeolite increased turf quality during both the second and third months at both salinity levels in both studies. The beneficial effects of zeolite on turf quality diminished 5 and 6 months after salinity treatments. Amending sand with zeolite reduced leaching of Na+ and K+, but increased the leaching of Ca2+ and Mg2+. Amending sand with zeolite increased SAR values by 0.9, 1.6, and 6.3 units in Study I and 0.9, 3.6, and 10.9 units in Study II, under control, 3.5, and 6.5 dS·m-1 salinity treatments, respectively. Isolite increased SAR by 1.1-1.6 units with 3.5 dS·m-1 and by 2.5-3.5 units with 6.5 dS·m-1 salinity treatments. Results indicate that amending with zeolite may buffer soil solution Na+ concentration in the short-term. In the long-term, however, a substantial amount of Na+ may be retained concurrent with Ca2+ and Mg2+ exchange, thereby increasing sodicity and salinity problems.