Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 368484
Title Simulating seasonal patterns of increased greenhouse crop production by conversion of direct radiation into diffuse radiation
Author(s) Jongschaap, R.E.E.; Dueck, T.A.; Hemming, S.; Marcelis, L.F.M.; Marissen, A.
Source Acta Horticulturae 718 (2006). - ISSN 0567-7572 - p. 315 - 321.
Department(s) Agrosystems
Wageningen UR Greenhouse Horticulture
Wageningen UR Greenhouse Horticulture
Publication type Refereed Article in a scientific journal
Publication year 2006
Abstract The conversion of direct solar photosynthetically active radiation (PARDir) into diffuse radiation (PARDif) and its effects on greenhouse crop production were analyzed with simulation models. PARDir can be converted into PARDif by increasing the haze of greenhouse covers with a minimal loss of radiation transmission. At specific sun incidence angles, PARDif penetrates more deeply into the canopy than PARDir, thereby decreasing saturation effects in upper, and increasing photosynthesis rates at deeper layers. Increased profits can be realized if the crop is intercepting more incoming radiation at more efficient parts of the canopy. A dynamic crop growth model was used to quantify the yearly production of tomato, cucumber and sweet pepper, calculated on a daily basis. For different degrees of haze, six virtual leaf compartments were simulated in the canopy. These layers were analyzed for PAR availability, PAR absorption and photosynthesis rates. Model results showed that the conversion of direct to diffuse radiation shifted the vertical distribution of PAR to deeper canopy layers. Total photosynthesis in the top layer of the canopy was reduced by 0.5%, but photosynthesis per MJ absorbed PAR increased. Deeper canopy layers received and absorbed more PAR, thereby increasing total canopy photosynthesis. If all incoming PARDir was converted to PARDif, cucumber photosynthesis increased by 1.5% (winter), 4.0% (summer) and 3.4% (fall). For sweet pepper it was 1.5% (winter), 4.3% (summer) and 4.2% (fall) and for tomato it was 1.4% (winter), 3.5% (summer) and 2.6% (fall). Different reactions between crop types were related to differences in leaf area index evolution in the course of the growing season. About 55% of all benefits were obtained in summer months (May-June-July), when the amount of PARDir is the greatest and leaf area index (LAI) is sufficiently high.
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