Broad bean (Vicia faba L.) crop growth and yield response to humic acid and phosphorus fertilizer

A field experiment was conducted during the winter growing season in the field of the directorate of agriculture in Kirkuk Governorate, Iraq to investigate the two broad bean cultivars (Fava da Orto and Luz de Otono) crop growth and yield response to three levels of humic acid (0, 20 and 40 kg ha-1 Potassium humate) as soil application and three phosphorus fertilizer levels (80,120 and 160 kg P2O5 ha-1). A randomized complete block design (RCBD) with three replications was used in this experiment laid out. The results showed that the two cultivars did not differ significantly in most of the studied traits, Luz de Otono cultivar is significantly superior in the leaf content of chlorophyll a and b, while the Fava da Orto cultivar is significantly superior in plant seed yield. An increasing application of humic acid up to 40 kg ha-1 Potassium humate and phosphorus fertilizer levels up to 160 kg P2O5 ha-1 significantly reduced the number of days to 50% flowering and first pod appearance. In contrast, significantly increased leaf area and leaf area index, leaves the content of chlorophyll a, b and total, plant dry matter, leaves nitrogen and phosphorus percentage, pod length, plant seed yield, seeds nitrogen and phosphorus percentage and seeds protein percentage. Binary interaction between Fava da Orto cultivar with 40 kg ha-1 Potassium humate and 160 kg P2O5 ha-1, 40 kg ha-1 Potassium humate with 160 kg P2O5 ha-1 and triple interaction among Fava da Orto cultivar, 40 kg ha-1 Potassium humate and 160 kg P2O5 ha-1 significantly gave the highest value in most of the studied traits, especially plant seed yield and seeds protein percentage. We can conclude that crop growth and seed yield for two tested broad bean cultivars were a high response to the high levels of humic acid and phosphorus fertilizer used in this study at the experiment location due to the low soil content in organic matter and mineral elements.