ATRIBUTOS FÍSICOS DO SOLO, REGIME HÍDRICO E RESPOSTA BIOLÓGICA DO FEIJOEIRO (Phaseolus vulgaris L.) SOB AMBIENTE PROTEGIDO

Abstract

Crop yield is affected by the environmental conditions under which plants grow and develop. Water is the main factor to be controlled under protected environments aiming at maximization of yield and grade of agricultural products. The productive potential of a crop is extremely conditioned by the local atmospheric conditions along with requirements for water and nutrients in the soil. The aim of the current work was to scrutinize the effect of soil water status on the yield components of two cultivars of beans (Phaseolus vulgaris L.), as well as characterize soil physical attributes and correlate them to the biological responsiveness of the plants under protected environmental conditions. The experiment was carried out in March of 2016 at a greenhouse belonging to the Agronomic Institute of Paraná (IAPAR) with beans. The experimental design taken into account here in was a completely randomized design at a factorial scheme with six replications for yield components and four replications for both soil physical attributes and crop ecophysiological parameters. For such a crop, yield components of two genotypes under the influence of four levels of soil humidity were assessed for agronomical purposes. Soil humidity within the stipulated levels at this trial was monitored by means of a Time Domain Reflectometer (TDR). For each wooden bed set up in the greenhouse soil samples were collected to characterize the soil physical attributes. Such samples were used for laboratory analyses of soil bulk density (DS), total porosity (PT), macroporosity (MA), microporosity (MI), hydraulic conductivity (K0), water retention curve (CRA) and pores distribution curve (CDP). The ecophysiological parameters were analyzed at four different times through a LICOR Infrared Gas Analyzer (IRGA), model 6400-XT. By means of such an equipment net photosynthesis, stomachic conductance, intercellular carbon concentration, transpiration, photosynthetic water use efficiency, and carboxylation efficiency were evaluated. Number of pods per plant and grain mass per plant were to be affected linearly as a function of soil water status. A thousand grain mass for the cultivar Tuiuiú were higher than those related to the cultivar Campos Gerais, regardless of soil water conditions. DS and MI depicted an increasing linear behavior as a function of water treatments. PT and MA showed a decreasing linear behavior faced with adequate or inadequate soil water requirements. The cultivar factor affected DS, PT and MA. Soil samples from suitable water supply treatments resulted in a greater soil water retention under the lowest matric potentials along with a lower frequency of pores. A part from transpiration rates, all other ecophysiological parameters did not detect effect of the studied treatments on the biological response of the crop. CRA did not reflect remarkably both growth and development of the crop as a function of soil water conditions and also genotypes of beans in study. CDP featured changes in soil structure as a result of the filling of the beds with soil under the protected environment, as well as due to the impact of water and crop genotypes treatments considered in this study.