An Irrigation Scheduling Model for Summer Squash
| Autor: | M. Jane Hayes, Doyle A. Smittle, W. Lamar Dickens |
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| Rok vydání: | 1992 |
| Předmět: | |
| Zdroj: | Journal of the American Society for Horticultural Science. 117:717-720 |
| ISSN: | 2327-9788 0003-1062 |
| DOI: | 10.21273/jashs.117.5.717 |
| Popis: | An irrigation scheduling model for summer squash (Cucurbita pepo L.) was developed and validated during 1986, 1987, and 1989. The model is represented by the equation: 12.7(i - 4) × 0.5ASW = D i-1 + (E(0.14 + 0.015) - P - I) i, where crop age in days is i; effective root depth is 12.7(i - 4) with a maximum of 381 mm; usable water (cubic millimeter per cubic millimeter of soil) is 0.5ASW, deficit on the previous day is D i-1; evapotranspira tion is pan evaporation (E) times 0.14 + 0.015i; rainfall (in millimeters) is P; and irrigation (in millimeters) is I. The model was validated during the three years using a line-source irrigation system with irrigation depths ranging from 5% to 160% of the model rates. Nitrogen rates were 50%, 100%, and 150% of the recommended rate. Marketable fruit yields increased as the irrigation depths increased up to the model rate then decreased with greater water application depths. Marketable fruit yields increased as the N rate increased in 1987 and 1989, but yields were similar at all N rates in 1986. The shelf life of marketable fruits was not influenced by irrigation or N rates. Summer squash has been classified as moderately sensitive to water stress. The blossom and fruit development stage of growth has been classified as more sensitive than the preblossom stage of growth (Bruce et al., 1980). Most researchers agree that irrigation should be applied before 50% of the available soil water has been depleted from the root zone (Bruce et al., 1980; Hansen et al., 1980; Smittle and Threadgill, 1982; Stan- sell and Smittle, 1989; Vittum and Flocker, 1967). However, Portas (1968) noted that the root zone was not uniformly per- meated by roots and that the root zone was a dynamic rather than a static system. Therefore, the fraction of the available soil water depletion necessary to cause a yield reduction depends on the depth at which soil water is measured and the rooting depth of the crop (Bruce et al., 1980). The root system and water extraction zone generally expand at the rate of 12 to 15 mm·day -1 |
| Databáze: | OpenAIRE |
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