Iowa High Tunnel Fruit and Vegetable Production Manual
High tunnels are valuable assets to growers enabling them to produce high yields of quality horticultural crops. However, different strategies and more detailed management are required with this method of production. The objective of this workbook is to provide growers with the information and resources to use high tunnels effectively, enhance productivity and net income, and learn from the experience of other high tunnel users.
Although they resemble greenhouses, high tunnels, also referred to as “hoop houses,” are quite different. High tunnels are simple, plastic-covered, passivesolar- heated structures in which crops are grown in the ground. Typically, they are ventilated by manually rolling the sides up or down as needed. They are designed to extend the growing season and intensify production.
High tunnel production facilitates the diversification of farming operations, requires less capital expenditure than greenhouse production, and for relatively low investment, often yields high returns. Unlike commercial greenhouses that may cost $20 per square foot or more, depending on the covering, high tunnels cost as little as $3 to $5 per square foot, depending on the size, covering, frame material and end wall construction (Spaw et al. 2004). For the purposes of property assessment and taxation, high tunnels are usually classified as temporary agricultural structures because they lack a concrete foundation or footings and are moveable.
High tunnels are used by the horticulture industry to extend the harvest season of many high-value crops. Because they are primarily used in Iowa for early season production, they are like row covers. However, high tunnels are larger and taller, allowing room for the crop to grow to maturity, cultural practices to be performed and equipment to be operated under them, such as tilling and laying plastic. Thus, the descriptive name -“high tunnel.” High tunnels and row covers also differ in the length of time they are left in place; row covers are often removed before the end of the season, and high tunnels may remain in the same place for several cropping seasons before being moved.
High tunnels have been extensively used for several years in many regions of the world where the growing season is short or the climate is not conducive to the production of quality fruits, vegetables, herbs and flowers. China and Spain currently have the largest concentration of high tunnels. They were not widely used in the United States until the last decade, when an increasing number of farmers began using them to enhance their existing production system and increase marketing opportunities.
Existing fruit and vegetable growers add high tunnels to their operations to increase marketing opportunities. High tunnels help growers extend the season on both ends and provide a steady supply of fruits, vegetables and cut flowers for the market. High tunnel production requires a combination of cultural practices unique to high tunnels and typical of field production, such as proper variety selection (adaptable varieties for early and main season) and sequence of planting dates (Taber et al. 2006).