Influência da água disponível do solo em dois cultivares de mamona, nos primeiro e segundo ciclos de produção.

Abstract

This study examined different aspects of management of castor bean in the field, aiming to optimize water use and yield of castor bean in the first and second cycle, obtained under conditions of regrowth through pruning. The research was conducted at the Centro de Ciências Agrárias e Ambientais - CCAA, Campus II da Universidade Estadual da Paraíba - UEPB, located on the Sitio Imbaúba, s/n, Rural Zone, Lagoa Seca, PB, Micro region of Campina Grande, Paraiba Agrestic, with an average altitude of 634 m in the period October 2008 to October 2009. It was used a sandy loam soil with low organic matter content. The experimental design was randomized blocks in factorial 2 x 4 , consisting of two castor bean cultivars (BRS 149 - Nordestina and BRS 188 - Paraguaçu) and four leveis of available soil water (40, 60, 80 and 100 %), distributed in three blocks. Each plot had a surface area of 100 square meters where they were cultivated 50 plants, spaced 2m x lm. The soil was fertilized with triple superphosphate in foundation in the amount of 120 kg ha"1 P2O5 and included 100 kg.ha"1 K2O and 100 kg.ha"1 N in the forms of potassium chloride and urea, split in equal portions at intervals of 10 days via fertigation, with the first application occurring 20 days after sowing. The experiment was conducted for two consecutive cycles of 180 days, and the second cycle performed from a drastic pruning of the plants to a height of 30 cm from the ground levei. The available water content of soil was detected and replaced at intervals of two days through a segmented TDR probe. The data were statistically analyzed using the program SISVAR - ESAL - Lavras, MG, which was made through the analysis of variance (ANOVA), applying the F test and Tukey test for comparison of treatment means and regression analysis for the quantitative factors available water. They were evaluated: height, stem diameter, leaf area, flowering, days to issue their lst and their respective height and total number of inflorescences, biomass, leaf area ratio, consumption and efficiency of water use, production of fruits and seeds and oil content in seeds. It was found that increased soil water availability has increased ali índices of growth and / or development of plants with substantial increases in productivity and quality of the final product. The second cycle of the culture obtained from the drastic pruning, showed growth patterns and/or development and production capabilities similar to the first cycle, with high standards of product quality, demonstrating the feasibility of conducting a second round os castor from a drastic prining os the plants.