Soil Tillage, Rice Straw and Flooded Irrigated Rice Yield.

The objective of this study was evaluate the effect of soil management systems and straw levels in flooded irrigated rice grain yield. The experimental design was a completely randomized with three experiments and 10 replications in experiment 1 and 2 and 6 replications in experiment 3. The experiments were: E1 - no-till system (E1PD) and conventional system with two harrowings at 0.0–0.07 m layer and leveling with remaplam (E1PC), after three years of rice cultivation, with sowing of ryegrass in winter and grazing; E2 - no-till system (E2PD) and conventional system after native field (E2PC); E3 - no-till without straw on soil surface (E30P), current straw on soil surface of 3,726 kg ha^-1 (E31P), two times current straw of 7,452 kg ha^-1 (E32P) and three times current straw of 11,178 kg ha^-1 (E33P). Were evaluated the average geometric diameter of aggregates, soil bulk density, soil porosity, macro and microporosity, in 0.0-0.05 and 0.05-0.10 m layer. At the harvest were evaluated the number of panicles in 0.25 m² area, number of filled, empty an total grains in 10 panicles, thousand grains weight and rice grains yield in 2 m². In the conventional system macroporosity and total porosity was greater than no-till system, however, this not results in differences in production components and rice grain yield. Rice straw levels in no-till up to 11,178 kg ha^-1, before sowing, not reduces flooded irrigated rice grains yield.