Effects of low tunnels, plastic mulch and mineral nutrient treatments on chilling tolerance of snap bean plants

Abstract

Field experiments were carried out during two successive autumn seasons to study the response of snap bean plants (Phaseolus vulgaris L.) grown under plastic mulch, low tunnels and in the open field to foliar application of KCl and CaCl<inf>2</inf>. Bean seeds (cultivar: Giza 3) were sown in 6^th of November for two seasons (1996 and 1997). Plastic tunnels, black mulch, spraying with KCl (25mM) and CaCl<inf>2</inf> (25mM), and a control treatment were applied either individually or as a combination between treatments to protect bean plants from chilling injury. Plant growth, yield and quality of pods in addition to protein, carbohydrates and fiber content of pods were determined in response to the application of treatments compared to control. Treated plants showed increased plant growth parameters such as plant height, number of leaves, total leaf area in addition to the total yield of plants. This effect was significant especially when plastic tunnels or mulch were combined with the chemical applications of CaCl<inf>2</inf> or KCl. All treatments did not significantly affect carbohydrates and fiber content of pods. Using plastic tunnels significantly increased pods protein content. Low tunnels treatments had a significant effect on reducing pods malformation percentage and the effect was more pronounced when combined with spraying of CaCl<inf>2</inf> or KCl. Control plants had the highest malformation of pods. The results indicate that spraying with CaCl<inf>2</inf> or KCl increased the effectiveness of low tunnels and plastic mulch on protecting bean plants from chilling stress. The possible roles of mineral nutrients and covering treatments on chilling tolerance of bean plants are discussed.