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Neufahrn bei Freising, Germany

Carrillo L.,Staatliche Forschungsanstalt fur Gartenbau | Jauch M.,Staatliche Forschungsanstalt fur Gartenbau | Meinken E.,Weihenstephan-Triesdorf University of Applied Sciences
Acta Horticulturae | Year: 2012

The presented study focuses on the quality review of substrates from the German market designed for extensive greening, according to the German FLL guideline (2008). They were mainly made up of broken bricks, lava, pumice, broken expanded clay, broken expanded slate, oil shale cinder, coal cinder, etc. and mostly mixed with compost material. In total, 22 substrates designed for either single layer or multi-layer systems were studied. The maximum water capacity ranged between 13.6 and 55.4 % (vol.). The permeability ranged from 12.7 mm/min to more than 440 mm/min for broken expanded clay substrate. Referring to grain size distribution, the values of the studied substrates were mainly beyond the FLL requirements, due to a too high proportion of fine particles often present in the organic part of the substrates. Concerning chemical parameters, pH values ranged from 5.2 to 10.6; moreover substrates displayed a non-buffered pH, which is expected to be reduced over the time. With regard to nutrients, nitrogen (N), phosphorus (P) and potassium (K) were extracted in CaCl2/DTPA (CAT) and calcium-acetate-lactate (CAL). N values ranged from 0.5 to 246 mg/L, whereby substrates containing high amounts of organic matter mostly displayed the highest values, and to the contrary, substrates with a high level of mineral content (broken expanded clay, lava, zeolite) generally displayed very low measurable nitrogen. Therefore, concerning those substrates, a suitable N-fertilisation seems to be fundamental to ensure satisfactory plant growth. Concerning P and K, the values ranged from between 1 to 107 mg/L for P with values exceeding FLL limits and 13 to 972 mg/L for K. Regarding the heavy metal analysis, only the values for Ni gave unsatisfactory results for some substrates (the values ranged from 2.8 to 106 mg/kg). In each examined substrate, one parameter at least exceeded the FLL limits, indicating the difficulties of fulfilling the FLL requirements.

Amberger-Ochsenbauer S.,Staatliche Forschungsanstalt fur Gartenbau | Taylor M.,Longwood Gardens Inc. | Lohr D.,Staatliche Forschungsanstalt fur Gartenbau | Meinken E.,Weihenstephan-Triesdorf University of Applied Sciences
Acta Horticulturae | Year: 2012

Fertilizers containing urea-N are recommended for horticultural crops because of the lower EC of the nutrient solution compared to solutions with ammonium or nitrate fertilizers, but high supply of urea raises the risk of plant damage and of gaseous N loss. Plants of Pelargonium × hortorum 'Merkur' were potted in partially decomposed peat with low nutrient supply from a complete water soluble fertilizer (0.75 g L-1, N+P 2O5+K2O = 14+16+18). Plants were fertigated in an ebb-flow-system with nutrient solutions containing (mg L-1): 100 N, 16 P, 83 K, 8 Mg plus micro-nutrients. Nitrogen was applied as urea and ammonium nitrate at ratios of 0+100, 33+67, 67+33 and 100+0 per cent. The experiment was a factorial design with deionized water and tap water (electrical conductivity 0.7 dS m-1, acid capacity 5.8 mmol L-1, equivalent to 290 mg CaCO3 per litre) used with each fertilizer treatment. Increasing ratios of urea caused pH to increase and EC to decrease in the nutrient solutions. There was only a small effect (with tap water) or no effect (with deionized water) of urea on salt content and pH of the growing medium. Even with 100% urea in the nutrient solution, urea was rapidly decomposed in the growing medium. The fresh mass of plants was significantly impaired with increasing ratios of urea, if deionized water was used for fertigation. Even with 33% urea, plant growth was reduced compared to plants fertilized with 100% ammonium nitrate. In the tap water treatments urea only had a small negative effect on plant growth. Although the use of urea is an effective way to reduce EC in nutrient solutions, there is little or no influence on the content of soluble salts in the growing medium and even small amounts of urea may have a negative effect on growth of pelargonium.

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