Evaluation of the Effects of Foliar Sulfur Applications on Yield, Evapotranspiration and Water Use Efficiency of Cotton (<i> Gossypium</i><i> hirsutum</i> L.) Under Different Irrigation Regimes

In this study, it was aimed to determine the effects of foliar sulphur applications on cotton plants exposed to water stress. It was carried out on 'Carisma' variety cotton plant with 3 irrigation level, 3 sulfur doses and 3 replicates, except for control treatments, in split plots experimental design in randomized blocks. Sulfur in elemental form was applied at doses of 150 ml da-1 (S1), 250 ml da-1 (S2) and 350 ml da-1 (S3), except for the control (S0) and I 100 , I66, I 33 irrigation levels of the available capacity and in the non-irrigated treatment (I0). Irrigation water amounts varied between 332-1006 mm and 306-928 mm in the 2015 and 2016, and evapotranspiration ranged between 299-1096 mm and 247- 995 mm, respectively. Evapotranspiration decreased slightly in the first year increased in the second year as the sulphur doses increased. The highest yields were 5871 kg ha-1 (I100S0) 6148.7 kg ha-1 (I100S1) in 2015 and 2016, respectively. In comparison to I 100 , yield decreased by 70%, 39% 14% in 2015, 67%, 33% and 8% in 2016 in I0, I 33 and I66, respectively. Sulphur doses caused yield to decrease 2015 and increase in 2016. Compared to S0 treatment, yield increased by 14%, 1.9% and 8.6% at S1, S2 and S3 2016. With the decrease in ET, yield (relative to I 100 ) decreased by 73%-70% at I0, 52%-39% at I 33 and 26%-15% at I 66 in the first year, by 75%-67% at I0, 44%-33% at I 33 and 20%-8% at I 66 in the second year, and by 74%-68% at I0, 48%-36% at I 33 and 23%-11% at I66. Water use efficiency (WUE) was approximately the same in sulfur doses, while the lowest was determined at I 100 and the highest was determined at I0 and I33. WUE increased as the amount of irrigation water increased in the second year, but did not show a stable change in the first year. The highest WUE was calculated in the first year on I 33 (6.3 kg ha-1mm-1) and in the second year on I0 (7.5 kg ha-1mm-1). Sulphur doses did not cause a significant difference in WUE and the highest WUE was determined at S0 (6.0 ha-1mm-1) in the first year and in the second year at S1 (6.5 kg ha-1mm-1). Sulphur doses did not affect leaf sulphur concentration in the first year, but statistically in the second year. Mean of two years, the highest leaf sulphur concentration was measured in S3.