Changes in electrical conductivity and moisture content of substrate and their subsequent effects on transpiration rate, water use efficiency, and plant growth in the soilless culture of paprika (Capsicum annuum L.)

Abstract

The moisture content (MC) and electrical conductivity (EC) in substrates are major root-zone environmental factors that affect the transpiration rate and subsequent plant growth in soilless culture. For maintaining optimum root-zone environments, efficient real-time irrigation control is required based on the substrate EC, substrate MC, and transpiration. The objectives of this study were to clarify the relationship between substrate MC and EC and analyze the changes in substrate EC, plant growth, and water use efficiency under different moisture control regimes. Irrigation systems maintaining three regimes of substrate MC (70-85, 60-85, and 50-85%) were set as treatments, and a conventional irrigation using accumulated radiation served as a control. Subsequent changes in the substrate EC and transpiration rate were continuously measured at different substrate MCs, and the relationships between these variables were derived. The transpiration rate was most sensitive to substrate EC at general cultivation conditions of a substrate EC of 2.5 to 4.5 dS·m -1 and a substrate MC of 60 to 85%. The transpiration rate tended to decrease with increasing substrate EC and decreasing substrate MC. More water was consumed in a higher substrate MC, which was controlled within a narrow range of MC. However, substrate EC was well-controlled below 4.5 dS·m -1 in a substrate MC of 70 to 85%.The relationship between the range of substrate MC and the increase in substrate EC was obtained using equations. Although more water was supplied for the control with a substrate MC of 70 to 85%, fruit productivity tended to increase compared to the other substrate MC treatments (60-85 and 50-85%). From the results, it is hypothesized that precise control of root-zone environments can be used to increase fruit productivity and water use efficiency and to minimize plant water stress as well.

Moisture-Induced Pattern of Gases and Physicochemical Indices in Corn Straw and Cow Manure Composting

“…Subsequently, the initial decline in EC was attributed to the emission of NH 3 (results shown) in the early stages of composting [47]. The substrate EC generally decreases with increases in moisture content [48]. High compost moisture influences higher neutralization of soluble salts than compost with low moisture.…”

Development of a Cucumber Transpiration Model Based on a Simplified Penman-Monteith Model in a Semi-closed Greenhouse

“…In soilless cultivation, an increase in substrate EC due to insufficient moisture content is one of the main factors that interferes with transpiration, so a drainage rate of 30% per day was recommended to prevent the accumulation of salt in the substrate (Hellemans 2006). The salt accumulation causes less transpiration due to salinity/drought stress (Shin and Son 2015a). Salinity rinsing of drainage water would help maintain an adequate balance of substrate EC; thus, maintaining a drainage rate at $30% in bell peppers was suggested in soilless bell pepper (Capsicum annuum L.) cultivation (Shin and Son 2015b).…”

Moisture-Induced Effects on Lignocellulosic and Humification Fractions in Aerobically Composted Straw and Manure

“…These ions have electrical charges that can conduct electricity, increasing the EC of the compost. Conversely, EC decreased with increasing moisture content could be due to an increase in moisture content which might have influenced greater neutralization and leaching of soluble salts [30]. As water moves through the compost, it inevitably carries soluble salts with it, reducing the overall concentration of salts in the compost and lowering its EC.…”