Estrese salino na germinação, produção de mudas e produção de arroz irrigado (Oryza sativa L.).

Abstract

Two experiments were installed in the experimental area of the Department of Agricultural Engineering of the Federal University of Paraíba, Campina Grande-PB. First Experiment was carried out under greenhouse conditions with the purpose of studying the deleterious effects of irrigation water salinity on the germination and seedling vigor of the 'Formoso' rice cultivar (Oiyza saliva L.). Second Experiment conducted in rhizotrons under plastic protection had the objective to evaluate the growth, development and production of the cultivar. Crop was sown in small plastic pots containing 314 g of substrate (3 parts of soil and 1 part of organic matter). In the Experiment I the germination and vigor were studied adopting a completely randomized design with 5 leveis of salinity of the irrigation water ECw (0.50, 2.50, 4.50, 6.50 and 8.50 dS m"1) and 5 replications. Cultivar was shown to be tolerant to the salinity in the germination stage, reaching leveis of germination above 87 % (14 days after sowing - 14 DAS) in ali the treatments. For the seedling vigor a completely radomized design was adopted in 5x2 fatorial scheme with 5 replications. The salinity leveis studied were the same and vigor was evaluated on 2 dates (Ej - 8 DAS, E2 - 13 DAS). Vigor was evaluated through the variables - index of emergency speed, growth rate and the relative growth rate of the root and shoot, height of seedling, root length, root and shoot dry weight and root/shoot relationship. Most of the seeds germinated at the 4 DAS, the growth rate and relative growth rate of the shoot were larger in comparisons to roots. The Experiment II carried out in 30 drainage rhizotrons containing 22 kg of soil adequately fertilized and corrected for acidity. Seedlings were transplanted on 18 DAS; plots were irrigated daily with 57 mm water depth. A completely randomized design was adopted in a 5x2 fatorial scheme with 3 replications, the 5 salinity leveis used were 1.00, 2.00, 3.00, 4.00 and 5.00 dS m"1 and, 2 types of seedlings (So- seedlings without saline stress irrigated with ECw equal to 0.50 dS m"1 and Si - seedlings produced under saline stress irrigated with ECw of 8.50 dS m"1). In this experiment evaluations were made for duration of phenological stages, height of plants, root and shoot dry matter, root/shoot relationship, number of tillers and panicles, components of the panicles, 100 grains weight, grain yield, real evapotranspiration and root growth. Irrigation water salinity delayed the vegetative period and duration of phenological cycle. Heading stage had duration shortened with the increase of salinity, however effective filling period for grains did not suffer alteration. Increase of the saline levei of irrigation water induced signifícant reduction in growth of the two types of seedlings. Height of plants, root and shoot dry matter weight, number of tillers and panicles, components of the panicle (grain sterility, length, density, number of ramifications and dry weight), 100 grains weight, grain yield and real evapotranspiration rate reduced with the increase of the saline concentration. The factor types of seedlings (S0 and Si) did not influence grain yield and 100 grains weight; plants originated of seedlings produced under conditions of saline stress (Si) presented real evapotranspiração rate significantly smaller and larger efficiency of use of water. Therefore, it is advantageous to use low quality water (saline water) for production of rice seedlings.