Worldwide, a significant increase in watermelon (
Citrullus lanatus
[Thunb.] Matsum. & Nakai) growing areas has been
registered in the last few years. In-row plant spacing has a significant effect on the growth and yield of watermelon, and can
enhance competition for water and nutrients. The aim of this study was to investigate the effects of in-row plant spacing
(1.0, 1.5, 2.0 and 2.5 m) and arbuscular mycorrhiza (AM) fungi
Glomus mosseae
inoculations on watermelon growth
and yield under field conditions during 2003, 2004, and 2005 year. In 2003, the main vine length, number of leaves, and
number of lateral branches were increased quadratically as the in-row plant spacing increased from 1.0 to 2.5. With an
increase in the in-row plant spacing the early yield of watermelon decreased in 2004, while the fruit number decreased in
2003 and 2004. The total yield and fruit number decreased with an increase in the in-row plant spacing in all 3 yr; however,
the fruit mass increased at wider plant spacings in 2003. Mycorrhizal inoculation increased the main vine length and
the number of lateral branches in 2003. Compared to non-mycorrhizal plants, mycorrhizal plants presented higher early
yield in 2005 and a higher early fruit number in 2003 and 2005. Mycorrhizal inoculation increased total yield in 2005;
however, the fruit weight was not affected by mycorrhizal inoculation during early or total harvest. In this study, an in-row
plant spacing of 1.0 m provided the best early and total yield while maintaining high fruit weight. The growth and yield
enhancement of watermelon due to mycorrhizal colonization was not consistent; therefore, mycorrhizal inoculation could
not be recommended as a standard production practice.
