An Investigation of a Root Zone Heating System and Its Effects on the Morphology of Winter-Grown Green Peppers

Muhammad Ameen,Wei Lu,Muhammad Memon,Xiaochan Wang,Rana Noor,Zhuo Zhang,Fahim Ullah,Muhammad Yaseen,Muhammad Umair,Khurram Yousaf

doi:10.3390/en12050933

Abstract

The winter season in Nanjing is from December to February, with extremely low temperature and high humidity due to seasonal snowfall. During these extreme cold climatic conditions, plants have to survive severe heat stress conditions, even if they are being kept in greenhouses. The objective of this study was to investigate a heating system that can provide heat directly to the root zone instead of heating the entire greenhouse, which is a viable option to reduce energy consumption. Root zone heating could be an effective alternative for the sustainable development of plants during the winter. A novel type of root zone heating system was applied to evaluate the energy consumption during different greenhouse ambient temperature conditions, the effects of root zone heating systems on pepper plant morphology, and heat transfer rates to plant canopy in the greenhouse. The temperature treatments in root zone heating system were T-15, T-20, T-25, T-30, and a control treatment (TC) at 15 °C, 20 °C, 25 °C, and 30 °C, respectively, while TC received no heat. A simulation study was carried out to validate the root zone temperature. The results of the current investigation revealed that energy consumption has an inverse relationship to the ambient temperature of the greenhouse, while temperature gradients to the plant canopy observed from the lower to the upper part of the plant and the upper canopy experienced less temperature fluctuation as compared to the lower part of the plant. The results also showed that treatment T-20 had the maximum in terms of the leaf dry weight, stem diameter, and the number of leaves, while T-25 showed the maximum root dry weight and stem dry weight; T-30 and T-15 had minimum dry weights of plant segments among all treatments. Control treatment (TC) showed a minimum dry mass of plant. The root zone heating with optimal root zone temperature was found to be a viable and adaptable option as this leads to improved energy consumption patterns for the sustainable growth and development of plants in greenhouses during extremely low temperatures.

Highlights

Agriculture, as a production-oriented division, requires energy as an important input
The simulated results show ab increased root zone temperature in image A of Figure 2 after one hour. This root zone temperature incline continued up to image I in Figure 2, while the heat flux throughout the pot showed a continuous expansion, which can be observed during the last hour, as shown in image
The increasing trend of root zone temperature in both methods is shown in Figure 3 from 12 p.m. to 6 p.m., while after this increase the experimental root zone temperature showed a slight decline from 6 p.m. to 12:00 a.m

Summary

Introduction

Agriculture, as a production-oriented division, requires energy as an important input. The Yangtze River Delta is one of China’s most advanced, dynamic, densely inhabited industrial areas and is growing into a prominent world-class metropolitan area and performing a vital role in China’s commercial and social growth [1]. It is famous for the intensive cultivation of crops [2] and faces extreme low temperature for one month with poor light and weather conditions. These severe conditions have a significant impact on horticultural productivity in non-heated greenhouses [3]. Some other factors of the environment, i.e., temperature and light, influence the growth and development of plants [1,2,3,4]

Objectives

Results

Conclusion