Evaluation of irrigation levels and soil fertility management on seed and oil yield of sesame (Sesamum indicum L.)

Introduction Undr the condition of simoultaniousley irrigation of some crops, there is a shortage of water for irrigation. In this conditions, scheduling of the irrigation is crucial. In irrigation programs, evaporation pan is widley used. There are some reports for the effet of deficit irrigation on grain yield of sesame, where drought stress reduced growth and grain yield of sesame from 1212 to 624 kg ha-1 (Mehrabi and Ehsanzadeh, 2012). Application of fertilizers with ecological source, including animal manure and compost, can be used instead of chemical fertilizers, where application of such fertilizers can supply nutrients for crops, increase soil fertility and also maintain organic matter of the soil. Since the effect of fertilizer on the grain yield of sesame under different irrigation conditions is not well documented, the current research was aimed to determine the response of sesame to the source of nutrient under drought stress conditions. Materials and Methods A field experiment was conducted in Shadegan, Khuzestan province, during 2016-17 growing season to evaluate the effect of chemical and organic fertilizers on yield and yield components of seasame under different irrigation conditions. The experiment was conducted as a split plot based on RCBD with three replication where irrigation levels (irrigation after 100, 200 and 300 mm evaporation from evaporation pan) were assigned as main plot and fertilizer type (control, chemical fertilizer including 250 and 100 kg ha-1 phosphorous and nitrogen fertilizers, respectively, 30 t ha-1 animal manure and 30 t ha-1 compost) were allocated to sub plots. All compost, animal manure and ammonium phosphate and half of nitrogen fertilizer were applied before planting. At harvest time, plant height, leaf number per plant, branch per plant, capsule per plant, grain per capsule, 1000-grain weight and grain yield were measure. Harvest index and oil percentage were also determined. Results and discusions The highest plant highet was achieved in 100 mm evaporation from evaporation pan which was not significantly difference with the irrigation interval of 200 mm mm evaporation from evaporation pan. The lowest plant height was recorded in control treatment which was 25, 20 and 10 percent lower than that of chemical fertilizer, animal manure and composr, respectively. the most leaf number was recorded in 100 mm evaporation from evaporation pan. Application of chemical fertilizer produced the highest leaf number. Irrigation interval of 100 mm evaporation from evaporation pan had the highest branch per plant. Sesame had the highest capsule per plant and 1000-grain weight in 100 mm evaporation from evaporation pan which was not significantly difference with 200 mm evaporation from evaporation pan. Application of chemical and animal fertilizers produced highest capsule per plant. However, compost had no significant effect on this trait. Irrigation after 300 mm evaporation from evaporation pan resulted in te highest harvest index. The lowest oil percentage (47.5%) of sesame was achieved in 300 mm evaporation from evaporation pan and no application of fertilizer. The highest oil yield of sesame was recorded in 100 mm evaporation from evaporation pan which was 17% and 43% more than that of 200 and 300 mm evaporation from evaporation pan. Application of animal manure and compost resulted in 35.5% and 16% increase of oil yield.