Influência do uso de gesso e matéria orgânica no desenvolvimento e produção de arroz (Oryza sativa L.) irrigado, num solo salino-sódico.

Abstract

The objectives of the present study were to determine influence of gypsum and organic matter application on growth and production of different cultivars of irrigated rice (Oryza sativa,L.) in a saline sodic soil as well as to observe effects of these amendments and rice crop on some chemical characteristics of soil. A field experiment was carried out at the Experiment Station Farm of Irrigated Perimeter of São Gonçalo, Sousa-PB with four treatments {30 & 60 t/ha gypsum, 10 t/ha organic matter and control} and four cultivars of rice (IR-2053-436-1-2, IR~2058-78-l-3~2-3, Pokkali and BR-IRGA-409} in a split plot design with three replications. For the evaluation of rice cultivars, besides yield results, parameters like plant height, no of plants/m linear, no of tillers / plant, weight of panicles, % of filled grains, root length and total duration of crop were considered. The treatments studied generally showed beneficial effect on growth, development and yield of rice. The analysis of variance of final plant height measurements revealed significant differences at 0.01 level due t o treatments and cultivars. The maximum height being attained by TR-2053-436--1-2 with organic matter. Regarding the no. of plants/m linear, the treatments of gypsum presented on .an average 45% superiority over control while for weight of panicles/m2 no s i g n i f i c a n t differences were observed. On the other hand, variation in rice yields due to treatments were found to be significant at 0,05 level, and comparison of means by Tukey's test showed no significant differences between organic matter and gypsum levels and the latter in relation to control. Independent of amendment application, the following decreasing sequence of production was observed for the cultivars: IR-2058-78-1-3-2-3 (6.67t/ha), IR-2053-436-1-2 (6.44 t/ha), BR-IRGA-409 {6,19 t/ha)fPokkali(5,17 t/ha). A high index of lodging was verified in cultivar IR-2053-436-1-2. The cultivar BR-IRGA-409, recommended for the Irrigated Perimeter of São Gonçalo and at present being introduced in other irrigated areas of northeast, showed good performance under all the treatments including control where its yield was found to be better than other cultivars thereby indicating relatively higher tolerance to salinity and exchangeable sodium. The soil analysis after 168 days, at depth intervals of 0-30 and 30-60 cm showed appreciable reduction of exchangeable sodium percentage (ESP) and pH of soil with the application of gypsum upto 30 cm depth, although the reduction in ESP was not found to be proportional to rate of gypsum application. The application of 30 t/ha of gypsum seems to be more economical as the yield differences between the two treatments were not significant. In the case of organic matter and control a decrease in electrical conductivity of saturation extract and pH was observed without any corresponding decrease in ESP of soil. The best yields were obtained with organic matter althougt its effect in reclamation os soil was not found to be satisfactory at least in the short period.