Growth characteristics of cabbage plug seedlings due to mutual shading among neighbouring seedlings

Plug seedlings are increasingly used in vegetable cultivation in Japan, because they are suitable for machine operations and are disease resistant; however, in cabbage cultivation, variation in seedling growth affects plant growth after transplanting to the field, and eventually, harvesting all the cabbages at the same time is not possible. In this paper, a simulation model used to express the growth variation in cabbage plug seedlings is proposed to reveal their cultivation characteristics and consider a cultivation technique that would produce uniform growth among seedlings. In this simulation model, the mutual shading among neighbouring plug seedlings resulting from high-density planting, which is one of the factors of variation in seedling growth, was modelled. The model parameters were obtained from the results of a cultivation experiment comparing growth against the light quantity that seedlings could receive; however, there were differences between the growth of a single seedling in the cultivation experiment and the growth of the plug seedlings. It is believed that growth rate and mass would be greater for a single seedling than for the plug seedlings. This simulation was able to express the growth variation of the actual plug seedlings by adjusting the model parameters.