Assessing heat management practices in high tunnels to improve organic production of bell peppers

Abstract

Thermal energy conservation and heat management of the crop growth environment inside high tunnels (HTs) can provide high production efficiency and better yield with low operation cost, hence extending the growing seasons and increasing the sustainability of organic farming. This study assessed the beneficial effects of independent and combined practices on temperature changes inside the HT systems located in eastern Tennessee and further examined the impact of temperature changes on crop production. Specific practices included mulching (polyethylene and biodegradable plastic films and vegetative), row covers, cover crops, and irrigation with collected rainwater or city water. Sweet pepper (Socrates) was grown in the spring seasons of 2011, 2013 and 2015, and statistical differences were analyzed in a randomized complete block design (RCBD) for total marketable yield regarding pepper weight and fruit number per plant, as well as the changes in soil and air temperature. The employment of black polyethylene mulch produced the highest pepper yield by warming the soil, but not excessively, during the day when compared with clear polyethylene mulch. While the black biodegradable mulch did not generate as much soil warming as black polyethylene, its total marketable yield was statistically similar to that for the latter mulch treatment. Also, row covers continuously provided protection from freezing during the cold nights; but, black polyethylene can act alone as an insulator of soil, evidenced by soil temperature and crop yield results. Cover crops allowed for greater heat transfer to soil and increased soil temperatures, but lead to reduced overall yield. Rainwater irrigation not only enhanced water conservation, but also it warmed the soil and tended to increase the overall pepper production, because rainwater was warmer than municipal water except when the pepper were first transplanted in the cold early spring period.