Preconditioning Cotton to Improve Water Use Efficiency and Conserve Irrigation Water

Water is often the major limiting factor to crop production in New Mexico. With the growing competition among industrial, urban and agricultural water users for the state’s limited water resources, conservation and water use efficiency are of priority interest. Preconditioning or hardening crop plants to water deficits has been proposed as a means of utilizing deficit irrigation for conserving irrigation water while minimizing yield reductions, thus improving water use efficiency. This approach, however, has not been explored as a water conservation tool. Greenhouse studies were conducted to determine the feasibility of preconditioning a crop to water deficits for the purpose of reducing subsequent water use with minimal impact on yield. Cotton (Gossypium hirsutum L.) was utilized as the experimental plant material.

Results suggest that cotton plants subjected to low levels of soil water potential (-1.50 MPa) during the preflowering stage used significantly less water than plants optimally irrigated [-0.17 MPa soil water potential at irrigation (SWPI)]. No significant differences in water use were observed, however, between -0.17 MPa SWPI and a moderate level of irrigation (-0.45 MPa SWPI) applied during the flowering stage. Furthermore, water-use efficiency was not significantly influenced by SWPI levels applied during either stage or by their interaction. The cotton crop, therefore, did not seem to lose its sensitivity to water stress during the flowering stage and the low (-1.50 MPa) SWPI level applied before flowering did not produce a preconditioning effect resulting in a reduction of water use during the flowering stage. Yet, the threshold leaf water potential for zero turgor and stomatal closure was lowered significantly when the plants were subjected to a stress level of -3.00 MPa leaf water potential during the preflowering stage. This lowered threshold may contribute to the earliness of crop maturity by allowing photosynthesis and assimilate transport to proceed at lower leaf water potentials and thus reduce the boll maturation period which may reduce water use by shortening the effective growing season. The results indicate that the -1,50 MPa SWPI level applied before flowering promoted the earliness of crop maturity without any significant reductions in yield. Furthermore, the results suggest that savings in irrigation water can be achieved.