Abstract
As one of the trial projects aiming to reconstruct a food production area in the Tohoku region following the Great East Japan Earthquake and Tsunami in 2011, we conducted an empirical study on an integrated mechanical cultivation system for cabbages grown for processing. As a countermeasure against the lodging of cabbage heads, which is recognized as one of the problems associated with the mechanical harvesting of cabbages, we investigated the effect of transplant depth of plug-grown seedlings on the yield, head angle, and root system of cabbages. We compared three transplant depths: shallow (+4.0 mm from the soil surface), medium (-4.4 mm), and deep (-22.6 mm). The fresh weights of cabbage leaves and heads did not differ among the planting depths. The population of cabbages with a small head angle (\<20°) from the vertical position was significantly larger in the deep plantation than in the shallow plantation, indicating that the deep plantation of plug-grown seedlings could reduce the probability of lodging. We discuss the possible reasons for these results, focusing particularly on the form of main stem and root system. The ratio of stem length to stem weight was lower in the deep plantation than in the shallow plantation, suggesting that a thicker and more rigid stem could be developed by deep plantation. Root length density tended to be higher in the deep plantations than in the shallow plantation at depths of 5–10 cm. These properties may contribute to lodging resistance in cabbage.
