Growing horticultural crops in high tunnels requires that growers develop some new ideas
about how to provide for plants’ needs. The growing season is typically longer and growing
conditions more conducive to plant health and vigor. Both plant biomass production and
yield are greatly increased. Nutrient needs of high tunnel plantings can be much greater
than needs of field-grown crops.
The planting environment inside the tunnel has much in common with a container: the root
zone can be quite limited. Since rain is not falling over the entire area, and moisture is only
being applied to the soil in a strip down the center of the row, root growth can be restricted
by dry soil even though there is apparently plenty of space for root development. Soils with
high organic matter allow moisture to move away from the drip irrigation emitters, and allow
roots to grow out farther. For this reason, all high tunnels should have abundant compost
tilled into the soil at the beginning of the season, not just tunnels for certified organic
produce. This is especially important in sandy soils with low water-holding capacity.