Effect of root zone cooling and evaporative cooling in greenhouse on the growth and yield of potato seed by aeroponics in tropical lowlands

Abstract

Temperature control of the rooting area with application of root zone cooling in an aeroponic system succeeded in maintaining the freshness of potato plant roots during planting to achieve tuber initiation. However, following the application of root zone cooling, many wilted plants that were burnt due to high temperatures above the plant surface remained. Therefore, effort is needed to improve the condition of the top of the plant, so that the growth of potato plants in the lowlands may be optimized. The results of some studies show that evaporative cooling can reduce the pressure of hot temperatures in the greenhouse and the area around the plant canopy. Therefore, integrated research on the aeroponic system for the application of root zone cooling and evaporative cooling is needed in order to improve the condition of the upper part of the plant. The purpose of this research was to determine the effect of evaporative cooling on the growth and yield of aeroponic potato plants in the lowlands planted with the application of root zone cooling. The evaporative cooling technique used was cold water and cold airbursts, with a temperature of 25 °C. Nutrients were used at a concentration of 1-2 mS/cm and acidity of nutritional solutions of 6 (pH). Two types of evaporative cooling were applied: cold-water spray and cold air conditioning. Two varieties, genotype 007 and granola, were used. A split-plot, randomized complete design was employed with evaporative cooling as the main plot and potato variety as the subplot. Growth data were analyzed by the F test followed by the DMRT test at the 5% level of significance. From the results of this research, we conclude that the evaporative cooling system can provide a decrease in air temperature in lowland greenhouses. However, the optimal humidity and temperature for the growth and development of aeroponic potato plants in the lowlands were not achieved when the air temperature in the greenhouse was high. A burst of cold air creates a more even temperature and humidity compared with the evaporative spray of cold water. The humidity level inside a greenhouse that is not exposed to cold-water bursts (far from the plant area) reaches 42%. The difference in air humidity achieved with two different evaporative cooling methods reached 2% at 13.00 and 6% at 16.00. The application of evaporative cooling with bursts of cold air resulted in a higher number of tubers and higher tuber weight compared with evaporative cooling with bursts of cold water. The average number of tubers produced from the application of evaporative cooling with bursts of cold air was 19.3 crop bulbs, and the average tuber weight was 10.4 grams per tuber, while the application of evaporative cooling with cold water bursts resulted in an average of 9.4 crop bulbs and an average tuber weight of 6.3 grams per tuber.

Keywords : aeroponics, potato seed, lowland, evaporative cooling, greenhouse, root zone cooling.