ABSTRACT
The objective of this work was to study the effect of four levels of low available water (3%, 23%, 43% and 63%) on growth and development of two cotton cultivars, CNPA Precoce 1 and CNPA 7H, from the seed germination stage until the opening of the fruits. The experiment was carried out under greenhouse conditions, using PVC pots, containing 10 kg of a dry sandy soil, in a random block experimental design, with 3 replications and factorial scheme (2x4). The factors were 2 cultivars and 4 water stress levels. At the sowing time, the soil moisture content in all pots was kept at field capacity, until the start of treatments, that happened when the water soil lowered to the available water levels, listed above. After this time, the available water levels were maintained by weighing the pots, with suplemental irrigation when it was necessary, until the tested levels. The results obtained showed that both cultivars have low requirements of water at the initial stage of growth (1,58 mm/day for cv. Precoce 1 and 1,66 mm/day for CNPA 7H). The requirements are higher at the flowering stage (6,48 mm/day and 7,07 mm/day, respectively) and at the yield formation (11,03 mm/day and 11,75 mm/day, respectively). The CNPA 7H is more efficient in converting water into vegetative parts, while CNPA Precoce 1 has more water use efficiency in relation to flowering and fruitage. In the text regression equations are presented, correlating vegetative/reproductive variables and available water levels in soil.
Key words:
evapotranspiration; available water; water stress; phytomass