RESUMO: A descompactação do solo é uma alternativa para o cultivo da soja em áreas de arroz, mas pode afetar o desenvolvimento do arroz irrigado em rotação. O objetivo do estudo foi avaliar o efeito remanescente da escarificação do solo realizada antes do cultivo da soja, sobre o uso da água de irrigação, o rendimento de grãos e parâmetros operacionais da semeadura do arroz, realizada na safra seguinte. A escarificação do solo foi feita no mês de setembro de 2017, anteriormente à soja na safra 2017/18 e o experimento de arroz foi conduzido na safra 2018/19. Os tratamentos foram:escarificação e não escarificação do solo. A escarificação aumentou a macroporosidade, a microporosidade e a porosidade total e diminuiu a densidade do solo. O cultivo do arroz reduziu a macroporosidade e aumentou a microporosidade. Não se observou influência do manejo de escarificação do solo sobre os parâmetros operacionais na semeadura do arroz. O solo escarificado necessitou 5,3 % a mais de água para irrigação do arroz, em relação ao solo não escarificado. Conclui-se que a escarificação do solo antes do cultivo da cultura da soja tem efeito remanescente em arroz na safra seguinte, mantendo maior porosidade do solo em relação à área não escarificada e elevando a quantidade de água necessária para irrigação do arroz cultivado na sequência. Não se verificou interferência da escarificação em parâmetros operacionais da semeadura e sobre o rendimento de grãos do arroz.

ABSTRACT: Soil decompaction is an alternative for soybean cultivation in rice areas, but it can affect the growth of irrigated rice in rotation. The objective of the study was to evaluate the effects of soil deep tillage performed before soybean cultivation on rice irrigation water, grain yield, and operational parameters of rice sowing carried out in the following crop season. Soil scarification was implemented in September 2017, prior to soybean crop season in the 2017/18 crop, and the rice experiment was conducted in the 2018/19 season. Treatments were: soil with scarification and soil without scarification. Deep tillage decreased soil density and increased macroporosity, microporosity, and total porosity. Rice cultivation decreased macroporosity and increased microporosity. Soil scarification management had no influence on operational parameters in rice sowing. Soil with scarification required 5.3% more water for rice irrigation than soil without deep tillage. In conclusion, soildeep tillage before the cultivation of soybean crop has effects on rice in thefollowing crop season, maintaining greater soil porosity in relation to the non-deep tillage area and increasing the amount of water needed for irrigation of rice cultivated in the sequence. Deep tillage did not affect sowing operational parameters and rice grain yield.

ABSTRACT The objective of this paper was to evaluate the quality of water drained after the use of the knife-roller (an implement used to incorporate rice residues after harvest), the partial global warming potential (pGWP) and straw decomposition as a result of postharvest field management of irrigated rice. The experiments were conducted during the 2018 and 2019 offseason and the treatments consisted of several water drainage periods (0, 3, 6, 9 and 12 days) after a field pass with a knife-roller. In addition, a nonflooded harvest treatment without straw management was included. Analysis of drainage water three days after a pass with the kniferoller showed a reduction in total soluble solids by 94% compared to zero days. Nitrogen and soluble phosphorus were not influenced by the treatments. However, potassium levels increased as the drainage period increased, which is related to the period between harvest and drainage. As the electrical conductivity is influenced by the concentration of ions, it showed the same response curve as the potassium levels and, for pH, there were small oscillations influenced by the temperature. The total CH4 emission and the pGWP were higher when the water depth remained for a longer period. However, the N2O emissions were higher in the absence of soil submersion. Water should be drained three days after a pass with the knife-roller in order to reduce potassium loss and suspended solids as well as pGWP. The use of the knife-roller accelerated the process of straw decomposition in relation to the unmanaged straw treatment.