Investigation of cotton morphological traits, water use efficiency and yield as influenced by different tillage systems and wheat residue managements.

Repeated tillage, in addition to the burning of post-harvest crop residues in recent decades, has caused various problems, including reduced soil fertility and increased soil water losses, resulting in reduced water use efficiency. To study the effects of type of tillage system and how to manage wheat residues on yield, and cotton water use efficiency, a field experiment was conducted in 2016 and 2017 in a randomized complete block design with four replications in Hashemabad cotton research station of Gorgan was executed. The tillage system consisted of four levels of tillage: no-tillage (NT), conventional tillage (CT), disk (DK), combinate (ComT), and crop residues management of wheat including three levels of complete removal of the remains (CRR), straw removal (SR), and preservation of residues (PR). According to the results, the average total yield in two years of the experiment was 1183 kg/ha in the land preparation with disk (DK) and complete removal of residues (CRR) up to 2563 kg/ha in the land preparation with combinates (ComT) and preservation of residues (PR) was variable. In all tillage systems, the highest yield is related to (PR) and (SR). (CRR) significantly reduced the yield compared with those treatments. Also, the effect of treatments on water use was very similar to their effect on total yield. The average water use efficiency of 0.33 kg / m 3 of water consumed in the treatment of CRR, in addition to conventional tillage (CT) up to 0.77 kg / m3 of water consumed in the treatment (PR) Also, planting with (ComT) was variable. In all soil tillage systems, water use efficiency in the removal of residues was significantly less than the (PR) and (SR). Besides, the results of this study clearly showed that: a) Regardless of the tillage systems, preservation of wheat residue in the soil after harvesting can significantly improve the yield and water use efficiency of cotton, and (b) among the tillage systems, in conventional tillage (CT) system, the lowest yield and water use efficiency are obtained.