Effect of nitrogen on Safflower physiology and productivity.

Abstract

Safflower (Carthamus tinctorius L.) is an oil-crop suitable for semi-arid agriculture, but its physiological response to agronomic inputs has yet to be fully evaluated. The effect of fertiliser on the physiology and production of Safflower grown in pots filled with standard grade perlite inside a semi-controlled glass house was studied.Plants were initially irrigated with 20-100 ml standard hydroponic solution and then one month after germination plants were irrigated using 50-200 ml complete Hoagland’s solution, supplemented with one of eight levels of nitrogen (0, 25, 50, 75, 100, 125, 150, 175 kg N ha^-1) in the form of ammonium nitrate. Elevating nitrogen to 100kg N ha-1 significantly increased the assimilation rate by about 42 %, transpiration rate by 32%, stomatal conductance by 52% and LAI by 42% compared with the control. The above ground dry weight, seed yield andWater Use Efficiency (WUE) increased incrementally with increases in nitrogen rate. Above ground dry weight increased by an average of 42%, seed yield by 76% and WUE by 41% at harvest compared with the control.This study clearly demonstrates how nitrogen fertilisation can affect physiology of Safflower leading to improvementin seed yield.

Key Words: Stomatal conductance, transpiration, water use efficiency