Rows and rows-end border effect at two levels of nitrogen on four cultivars of rice in Southeast Rio Grande do Sul, Brazil

Abstract

The objective of this research was to determine the occurrence of rows border effect and the extension of rows-end border effect on the yield of four rice cultivars (Oryza sativa L.) grown in the field, at two levels of nitrogen: 30 kg/ha and 60 kg/ha. IAS 12-9 Formosa showed the most outstanding reaction to the different cultivars in border rows, followed by IRGA-408 and EEA-406; Bluebelle was the less sensitive lo border effect. The average yield of the four cultivars in middle rows was statistically greater with 60 kg/ha than with 30 kg/ha of nitrogen when IRGA-408 was at the border rows; conversely, the mean yield was significantly smaller under 60 kg/ha of nitrogen, with EEA-406 at the border rows. As to the rows-end border effect, the results indicated that in the first 0,25 m of every row the higher yields were similar for the four cultivars. However, on IAS 12-9 Formosa, 0,50 m of rows-end trimming is sufficient to remove border effect; for Bluebelle the extension of the rows-end trimming necessary to eliminate that effect could not be clearly established (0,50 m or 0,75 m); on EEA-406 and IRGA-408 there is rows-end border effect up to 0,75 m. Therefore, the use of rows-end trimming in rice yield trial plots is indicated and the extension of the end-trimming should vary according to the cultivar. The rows border effect varied according to the cultivar in the middle rows.