Effect of Planting Dates and Humic Acid on Vegetative Growth Traits and Yield of Two Varieties of Safflower (Carthamus Tinctorius L.)

Abstract

The field experiment was carried out during the winter season of 2024-2025 in two sites: Al-Hawi and Al-Ashiq village in Nineveh Governorate to study the effect
of three planting dates (1/11, 15/11, and 30/11), four humic acid levels (0, 5, 10, and 15 g/L), and two safflower varieties (Gila and Rabie 500) on growth traits and
yield. The three-factor factorial experiment was conducted using a randomized complete block design (RCBD) with a three-block Split-Split Plot Design. The
results showed a significant superiority of the early date (1/11), the humic acid level (15 g/L), and the variety (Gila) for all studied traits, including plant height.
As for the varieties, the variety (Gila) was significantly superior in most of the studied traits, as the level (15 g/L) gave the highest average for plant height (cm),
chlorophyll content (Spad), head weight (g), number of empty seeds (seed/head), fertilization percentage (%), seed yield (g.m-2
), and oil percentage (%). As for the
interaction between humic levels and planting dates, the level (15 g/L) and the planting date (1/11) were superior in giving the highest average in the traits of plant
height (cm), head weight (g), and number of empty seeds (seed/head) in the study site Al-Hawi. As for the study site Al-Ashiq, there was a significant superiority
in all the studied traits except for the traits of chlorophyll content and fertilization %. Regarding the interaction between humic levels and varieties, the level (15
g/L) with the Gila variety was superior in giving it the highest average plant height (cm), seed yield (g.m-2
) and oil percentage (%) in the study site of Al-Hawi,
while Al-Ashiq site was significantly superior in the head weight (g), seed yield (g.m-2
) and oil %. Concerning the bilateral interaction between planting dates and
varieties, the date (1/11) with the variety Gila showed superiority, with the highest average plant height, head weight, and seed yield at the Al-Ashiq study site, but
did not reach significance at the Al-Hawi study site. Furthermore, the triple interaction between humic acid levels, dates and varieties, the level (15 g/L), the date
(1/11) and the variety Gila gave the highest averages for the studied traits, but did not reach significance except for the plant height (cm) which was significantly
superior in the study site of Al-Hawi, and the chlorophyll content (Spad), head weight (g) and number of empty seeds (seed/head) in the study site of Al-Ashiq.