Sowing Dates and Cultivars Mediated Changes in Phenology and Yield Traits of Cotton-Sunflower Cropping System in the Arid Environment

Cotton-sunflower cropping system is a unique oilseed-based rotation. The real problem is overlapping sunflower-maturity with cotton-sowing. Investigations aim to tackle cotton-late-sowing through sowing-time-adjustment and cultivar-selection at cropping-system-level. Cotton (May 10th to June 24th) and sunflower (December 20th to February 03rd) sowing-dates were maintained biweekly. Maturity-time based cultivars were selected (early, medium, late) and variations in ambient-temperature through sowing-dates from 33.2 to 33.9 °C, 32.2 to 33.6 °C and 29.2 to 32.6 °C, length of emergence-squaring, squaring-flowering and flowering-maturity differed by 3.1, 1.5 and 5.1 days, respectively. Likewise, sunflower-sowing-dates based ambient-temperature ranged 13.7–18.1 °C, 16.3–17.5 °C and 23.8–28.5 °C at emergence-budding, budding-anthesis and anthesis-maturity, resulted in a difference of 13.5, 4.8 and 1.0 days. Results revealed that cotton late-sowing (May 10th to June 24th) and sunflower (December 20th to January 19th) resulted in reduces seedcotton, lint and achene yield by 19.9, 8.2 and 8.8 kg ha−1 day−1. Oil productivity was the highest in cotton vide June 24th and in sunflower 04th January. In this cropping system, cotton is highly sensitive to sowing-dates for yield losses (35%) and sunflower less sensitive (14.4%). Meanwhile, yield variations in cotton-cultivars (12.5%) and sunflower-hybrids (10.0%). It was realized that sunflower December 20th hold great importance to assure minimum cotton yield-losses than looking for hybrids.