ABSTRACT One of the challenges in rice areas is the sustainable post-harvest system, which involves using rice straw management and cover crop species. In this context, this study aimed to evaluate the emission of methane (CH4) and nitrous oxide (N2O) with the use of different post-harvest management of rice straw as well as with the combined use of ryegrass. A field experiment was conducted during the 2016 off-season and 2016/17 rice crop season with different post-harvest rice straw management: maintaining rice straw on the soil surface (No-tillage); incorporating straw into dry soil with a disc (Disc); incorporating straw into flooded soil with a roller crimper (Roller Crimper); maintaining rice straw on the soil surface with subsequent rolling of the soil with a roller (Roller). In each straw management, treatments with and without ryegrass were established. The results demonstrate that incorporating rice straw in flooded soil with a roller crimper increases CH4 emissions in the off-season, and used in combination with ryegrass, proved to be the most significant contributor to partial global warming potential. Most annual N2O emissions occur in the off-season for all management treatments, especially for the no-tillage treatment, which showed increased emissions when combined with the use of ryegrass. However, as global warming potential is influenced mainly by emissions of CH4, the no-tillage system showed the best mitigation potential on greenhouse gas emissions.

Resumo: O objetivo deste trabalho foi avaliar os efeitos da adubação com nitrogênio em cobertura e silicatos, bem como da utilização de fungicidas, sobre a ocorrência de brusone nas panículas, a renda do benefício e os grãos inteiros, vítreos e gessados, em cultivar de arroz irrigado por inundação sensível à doença. Foram conduzidos dois experimentos em delineamento de blocos ao acaso, em arranjo fatorial 4×4×2, com quatro repetições: no experimento 1, quatro doses de nitrogênio × quatro doses de silicato de cálcio e magnésio via solo × com e sem uso de fungicidas; e, no experimento 2, quatro doses de nitrogênio × quatro doses de silicato de potássio via foliar × com e sem fungicidas. Nas doses acima de 60 kg ha-1 de nitrogênio sem fungicidas, houve aumento da severidade de brusone nas panículas, redução do percentual de grãos inteiros e vítreos, e aumento de grãos gessados e área gessada. Os maiores efeitos dos silicatos ocorreram sem aplicações de fungicidas. O uso de fungicidas reduziu a severidade de brusone nas panículas. A renda do benefício oscilou entre 60 e 70%, em ambos os experimentos. O controle da brusone com fungicidas mantém elevadas a qualidade de grãos do arroz, a renda do benefício e as percentagens de grãos inteiros e vítreos.

Abstract: The objective of this work was to evaluate the effects of fertilization with nitrogen topdressing and silicates, as well as of the use of fungicides, on the occurrence of rice blast on panicles, milling yield, and whole grains, vitreous grains, and chalky kernels in a flood-irrigated rice cultivar sensitive to the disease. Two experiments were conducted in a randomized complete block design, in a 4×4×2 factorial arrangement, with four replicates: in experiment 1, four doses of nitrogen × four doses of calcium and magnesium silicate on soil × with and without fungicides; and, in experiment 2, four doses of nitrogen × four doses of potassium silicate applied on leaves x with and without fungicides. At the doses above 60 kg ha-1 nitrogen without fungicides, there was an increase of rice blast severity on panicles, a decrease in the percentage of whole and vitreous grains, and an increase in chalky kernels and chalky area. The greatest effects of silicates occurred without fungicides. Fungicide use reduced the severity of rice blast on panicles. Milling yield ranged from 60 to 70% in both experiments. The control of rice blast with fungicides maintains high rice grain quality, milling yield, and percentages of whole and vitreous grains.

RESUMO: O uso intensivo de produtos fitossanitários na lavoura de arroz irrigado ( Oryza sativa L.) tem causado preocupação quanto ao impacto ambiental sobre comunidades de organismos aquáticos não alvos que são habitantes naturais nesses agroecossistemas. O objetivo da presente revisão é analisar os dados atualmente existentes na literatura sobre alguns importantes fungicidas e inseticidas (tais como trifloxistrobina, tebuconazol, triciclazol, lambda-cialotrina e tiametoxam), os quais são usados para controlar pragas e doenças na lavoura de arroz irrigado, bem como seus efeitos sobre a comunidade de organismos aquáticos não alvos.

ABSTRACT: The intensive use of plant protection products in rice paddy fields ( Oryza sativa L.) has caused concern about the environmental impact on communities of non-target organisms that are natural inhabitants in these agroecosystems. The purpose of this review is to analyze the data currently available in the literature about some important fungicides and insecticides (such as trifloxystrobin, tebuconazole, tricyclazole, lambda-cyhalothrin, and thiamethoxam), which are currently used to control pests and diseases in rice paddy fields, as well as their effects on the community of non-target aquatic organisms.

ABSTRACT A compacted subsurface soil layer can be a limiting factor for soybean growing, reducing soybean yield. The aim of this study was to evaluate the effect of different tillage systems on the physical properties of two Albaqualf soils of the Central Plains region in the state of Rio Grande do Sul in southern Brazil. Two experiments were conducted: one in Santa Maria, RS, during the 2013/14 and 2014/15 crop seasons, and another in Formigueiro, RS, during the 2013/14 crop season. A randomized block experimental design with four replications was used. The treatments were: sowing using an offset double disc (T1); sowing using a fluted coulter disc (wavy disc with 12 waves) (T2); sowing with a knife runner opener (T3); sowing with a knife runner opener + press wheel mechanism for ground levelling (T4); sowing using a furrow opener upon a raised bed (T5); and chisel plough + sowing using an offset double-disc (T6). In the 2014/15 growing season, the T4 factor was changed using a knife runner opener 0.05 m from the planting row. A smaller reduction in the compacted subsurface soil layer was observed for both T1 and T2, which exhibited high soil bulk density values for the 2013/14 and 2014/15 crop seasons. Furthermore, T3, T5 and T6 led to a reduction in bulk density, and increasing total porosity and macroporosity in the soil, which consequently increased water infiltration, water storage capacity, and crop yield in areas with the presence of a compacted subsurface soil layer.