Intervalo hídrico ótimo e crescimento inicial da cultura da cana-de-açúcar

Abstract

The land use and management practices of the soil alter its structure and, consequently, its physical-water properties. In order to understand this relationship between physical characteristics (resistance to penetration, soil density and porosity) and water characteristics (available water) the concept of Optimum Water Interval (IHO) was developed. A study was carried out with the objective of determining and evaluating the IHO and its relationship with the initial development of sugarcane according to soil density levels and the presence or absence of salinity. Thus, an experiment was carried out in a protected environment at the Experimental Station in Irrigated Agriculture Ronaldo Freire de Moura at the Federal Rural University of Pernambuco (UFRPE) from June to September 2016. The study was carried out in pots of 15 dm3, which were filled with a layer of Spodosol collected at a depth of 0 - 0.40 m. A completely randomized design was used in a 5 x 2 factorial scheme with five replications, with five levels of soil density (1400, 1500, 1600, 1700 and 1800 kg m-3), two salinity levels (0 and 3 dS m-1). For this research, 240 undisturbed soil samples was collected in 98 cm³ rings, at a depth of 0.0-0.1 m, to obtain the following parameters: soil density; penetration resistance curve; Water retention curve, total porosity, macroporosity and soil microporosity. The critical soil density was reached at the intersection of the upper and lower limits of the optimum water interval (IHO). Morphological parameters (stem height and diameter), fresh matter and dry matter of the aerial part of the plants and dry root matter) where evaluated. From the results, it was observed that the density influenced in a negative way the growth and yield variables in the sugarcane. For the level of salinity adopted only the variable total fresh matter had a positive effect up to the level of density 1530 kg m-3 and from that level onwards there was a negative effect. The treatment that was submitted to the salinity there was an increase of the IHO when compared to the treatment that did not receive salinity.