Estimation of the effects of phosphorus in organic fertilizers and supplementary irrigation on the yield and nutrient quality of barley grain by chlorophyll fluorescence

Abstract Purpose This study investigates the effects of phosphorus in organic fertilizers (a mixture of poultry and cow manure) and supplementary irrigation on the yield and nutrient quality of barley seeds under rainfed conditions. The experiment was conducted in the split-plot design, where supplementary irrigation served as the main factor with four levels (control (no irrigation), irrigation at the heading stage, irrigation at the seed milk stage, and irrigation at both heading + seed milk stage). Organic fertilizer constituted the sub-plot factor with six levels (Control (no fertilizer), 1ton ha −1 cow manure + 0.5ton ha −1 poultry manure, 2ton ha −1 of cow manure + 1ton ha −1 poultry manure, 3ton ha −1 cow manure + 1.5ton ha −1 poultry manure, 4ton ha −1 cow manure + 2ton ha −1 poultry manure, 5ton ha −1 cow manure + 2.5ton ha −1 poultry manure), respectively. The results showed that supplementary irrigation in the stage heading + seed milk and seed milk stage produced the highest values for the number spikes per plant (19 and 18), seed yield (3136 and 3032 kg h −1 ), harvest index (36.3 and 35.7%), Fm (28,600 and 28,319), Fv (21,918 and 21,582) and Fv/F0 (4.35 and 4.22The heading + seed milk stage also resulted in the highest seed nutrient contents, including nitrogen (1.39%), phosphorus (0.65%), potassium (1.66%), iron (52 mg kg −1 ), zinc (30 mg kg −1 ) and manganese (44) mg kg −1 ). Application of organic fertilizers significantly improved most measured traits of rainfed barley (except for F0 and F0/Fm). The combination of supplemental irrigation and organic fertilization-particularly 5ton ha −1 of cow manure and 2.5ton ha −1 of poultry manure applied during the heading and seed milk stages, resulted in the highest number of seeds per spike (35) and thousand seed weight (43 g). Overall, this integrated management practice effectively seed yield, seed nutrients quality and chlorophyll fluorescence parameters of barley in the Khorramabad region.