The effects of irrigation regimes, row spacing and phosphorous fertilizer on yield and yield components of Nigella sativa L.

Water is one of the environmental factors which has high impact on the growth and the essential oil content of medicinal plants. Plants are faced with various environmental stresses during their growing period. Each of these stresses have different effects on growth, metabolism and yield according to the sensitivity level and stage of the plant growth. Management of nutrients consumption along with water consumption management influences the quantitative and qualitative yield of crops and medicinal plants. Phosphorus is an essential nutrient required for plant growth. It helps in root development, plant maturation, and seed development. Along with nitrogen and potassium, phosphorus is one of the most important elements for plant life. Soil gets depleted of phosphorus due to several reasons including being washed away by rain. Therefore, modern farming is reliant on the use of phosphorus based fertilizers. This investigation was conducted to the effects of irrigation regimes, row spacing and phosphorous fertilizer on yield and yield components of Nigella sativa L.

A split plot factorial layout was carried out based on a randomized complete block design with three replications at the research farm of Ziba andishan Company of Esfahan during 2017. The main factor was three levels of irrigation regimes including: 50, 100 and 150 mm evaporation from the surface of evaporation basin while 3 levels of phosphorous fertilizer application including: 1) no amended fertilizer (control), 2) 75 and 3) 150 Kg ha-1 Super phosphate triple and 3 levels of row spacing 20, 30 and 40 cm were used as subplots.

The results showed that the triple interaction effects of irrigation regimes, phosphorous fertilizer and row spacing treatments on all studied characteristics expect seed weight/ capsule weight were significant at P≤0.01. The maximum no. seeds in capsule, 1000- seed weight and seed yield per plant was observed in 50 mm irrigation regimes, 150 Kg ha-1 phosphorous and 30 cm row spacing, the maximum seed yield and biological yield was observed in 50 mm irrigation regimes, 150 Kg ha-1 phosphorous and 20 cm row spacing and the maximum harvest index observed in 100 mm irrigation regimes, control phosphorous and 40 cm row spacing.

Although, by increasing the row spacing and decreasing the density, the portion of each plant from water, nutrients and light increases and this causes that the number of seeds per capsule, 1000-seed weight and seed yield per plant increase, but according to the point that in agronomy, seed yield is the most evaluation index, therefore, in similar conditions, irrigation regimes of 50 mm, phosphorus of 150 kg per hectare and planting row spacing of 20 cm is recommended.