Investigation of the effects of different fertilizer doses and forms on yield components in sunflower (Helianthus annuus L.)

This study aimed to investigate the effect of different fertilizer doses and forms (leonardite 100 kg/ha, humic acid 1lt/da, %100 DAP 42 kg/da, %100 Urea 12 kg/da, %50 reduced DAP 21 kg/da, %50 reduced Urea 6 kg/da) on the yield and yield components of sunflower variety Deray. The study also aimed to determine the optimal fertilizer dose and form in sunflower cultivation and examine the effects of fertilizers used in sunflower production on plant height, SPAD value, thousand grain weight (TGW), hundred grain weight (HGW), seed coat ratio, first leaf height, stem thickness, head diameter seed width seed length oil percentage protein percentage yield and nutrient content in leaves. The study was conducted in 2023 at Siirt University Faculty of Agriculture Field Crops department trial area according to a randomized complete block design. The applications of humic acid leonardite and chemical commercial fertilizers were statistically effective on the agronomic data of sunflower plants as well as macro- and micro-analysis results after harvest. The highest oil percentage was recorded at 35.65% with the control application while the highest protein percentage at 36.11% was achieved with leonardite application among soil conditioners. In terms of yield, the highest value of 335.68 kg/da was obtained from chemical fertilizer application with %100 Urea + %100 DAP. It can be concluded that organic fertilizer applications enhance nutrient availability for plants while improving soil chemical and physical conditions in soils deficient in organic matter resulting positively on both yield quantity & quality aspect in sunflower farming.