Root dynamics of muskmelon transplants as affected by nursery irrigation

Containerized 'Lavi' muskmelon [Cucumis melo L. (Reticulatus Group)] transplants were grown in a nursery with two irrigation systems: overhead irrigation (OI) and flotation irrigation (FI). Initially, root development was monitored during a 36-day nursery period. Thereafter, seedling root growth was monitored either in transparent containers inside a growth chamber, or through minirhizotrons placed in the field. During the nursery period, OI promoted increased early basal root growth, whereas FI promoted greater basal root elongation between 25 and 36 days after seeding (DAS). At 36 DAS leaf area, shoot fresh weight (FW) and dry weight (DW), and shoot to root ratio were greater for OI than for FI transplants, while root length and FWs and DWs were nearly the same. Total root elongation in the growth chamber was greater for FI than for OI transplants between 4 and 14 days after transplanting. Similarly, the minirhizotron measurements in the field showed a greater root length density in the uppermost layer of the soil profile for FI than for OI transplants. Overall, muskmelon transplants had greater root development initially when subjected to overhead compared to flotation irrigation in the nursery. However, during late development FI transplants appeared to have a greater capacity to regenerate roots, thus providing an adaptive mechanism to enhance postplanting root development and to withstand transplant shock in field conditions. At harvest, root length density and yield were closely similar for the plants in the two transplant irrigation treatments.