Performance of flooded rice grown in succession to winter cover crops

Mean grain yield of flooded rice in southern Brazil has increased in recent years due to the use of high-yield cultivars and improvement of crop management practices. Nevertheless, stagnation in grain yields has been observed in some riceproducing regions. Adoption of conservation tillage systems based on cover crops may be a strategy to increase rice grain yield potential. The objective of the present study was to evaluate the effect of winter cover crops on initial establishment, development, and grain yield of flooded rice (Oryza sativa L.) grown under different fertilization levels and no-tillage. A field experiment was carried out for three consecutive years (2010/11, 2011/12, and 2012/13) in Cachoeirinha, Rio Grande do Sul, South Brazil. Treatments included three winter cover crops [ryegrass (Lolium multiflorum Lam.), native serradella (Ornithopus micranthus Benth.), and a ryegrass-serradella mixture] and fallow, and three fertilization levels for rice grown in succession. More than 3 Mg ha-1 of serradella aboveground residue or 4 Mg ha-1 of ryegrass residue limited rice emergence in the first year when rainfall in the sowing-emergence period was higher than in the second and third years In contrast, a large amount of residue (serradella >2 Mg ha-1; ryegrass >3 Mg ha-1) was beneficial to rice emergence when rainfall was low in the sowing-emergence period of the second and third years. The serradella cover crop increased rice aboveground biomass at anthesis by 22 % compared to the ryegrass cover crop. Furthermore, rice grain yield was 15 % higher in succession to serradella than to ryegrass in the third year. Continuous cultivation of flooded rice in succession to ryegrass over three years reduced grain yield by around 1.4 Mg ha-1, regardless of fertilization level. Fertilization for very high production expectations increased rice grain yield in all years, especially in the second year, when solar radiation was higher than normal. The use of winter cover crops affected plant emergence, aboveground biomass, and grain yield of flooded rice. Rice grain yield increased with increases in fertilization level, and this response was not affected by the previous cover crop

Soil physical quality in cropping systems at Mato Grosso

Brazilian agriculture receives great contribution of the Midwest region of Brazil, which is under the cerrado biome and responsible for much of the Brazilian production of grains and cotton fiber. On the other hand, crop yields have shown stagnation, which may indicate a problem related to the inappropriate use of some technologies. Despite the fact that soil physical quality (SPQ) is important to the quality of an agricultural production system, its study is not yet widespread, especially in the Cerrado production systems. This study tested the hypothesis that the physical quality of a dystrophic Latossolo Vermelho, located in the Midwest of Brazil, is influenced by soil tillage systems and production systems with use of succession or crop rotation. We determined soil physical properties in no tillage (NT) and conventional tillage (CT), at the 0.0-0.1 m, 0.1-0.2 and 0.2-0.4 m layers of an Oxisol under 5 different production systems composed of cotton crop succession and rotation strategies in Itiquira-MT. The experimental design is a randomized block with 4 replications and split plots. We measured soil Air permeability (Ka), Pores continuity index (K1),Moisture at field capacity (FC), porosity at the macropores domain (PORm) , porosity at the soil matrix domain(PORs), soil air capacity (CASOLO), air capacity of the soil matrix (CAMAT), the relationship between moisture at FC and total porosity (FC/TP ), Bulk density (BD) as well as the yield of cotton and soybean crops. The NT 0-0.1 m layer had higher BD and FC than the CT. Differently, the CT had greater macroporosity, gaseous conductivity and better continuity of pores. The production systems of cotton monoculture and cotton/millet succession showed lower values of PORm. At the 0-0.2 m layer, PORs was greater under PC in the production systems that included the soybean crop. The 0.2-0.4 m layer of CT had higher FC and POMAT, while K1 was lower. The NT resulted in 10.2% higher soybean yield than the one found for PC, attributed to the better water supply to the crop under NT. The cotton yield of fiber and seeds was lower in the cotton monoculture, although it is not possible to link this result to SPQ differences between the production systems. We conclude that the different cultivation schemes and tillage systems affected the soil physical quality. However, the effect of soil physical quality in crop yields was only observed when the plants were subjected to water deficit, as in the case of the soybean crop.A agricultura brasileira recebe grande contribuição da região Centro Oeste do Brasil, que está sob o bioma do cerrado, a qual é responsável por grande parte da produção brasileira de grãos e fibra de algodão. Por outro lado, as produtividades das culturas têm apresentado estagnação, o que pode indicar um problema relacionado ao uso inadequado de algumas tecnologias. Apesar da qualidade física do solo (QFS) ser importante para a qualidade de um sistema de produção agrícola, o seu estudo é pouco difundido, principalmente nos sistemas de produção da região dos cerrados. Esta pesquisa testou a hipótese de que a qualidade física de um Latossolo Vermelho distrófico, localizado no Centro-Oeste do Brasil, é influenciada pelos sistemas de preparo do solo e pelo sistema de produção com utilização de sucessão ou rotação de culturas. Foram determinadas as propriedades físicas do solo em plantio direto (PD) e preparo convencional do solo (PC) nas camadas de 0,0-0,1 m, 0,1-0,2 m e 0,2-0,4 m de um Latossolo Vermelho distrófico sob 5 diferentes sistemas de produção compostos por estratégias de sucessão e rotação de culturas utilizados para a produção de algodão em Itiquira-MT. O delineamento experimental é de blocos casualizados com 4 repetições e parcelas divididas. Foram medidos a permeabilidade do solo ao ar (Ka), índice de continuidade de poros do solo (K1), umidade do solo na capacidade de campo (CC), porosidade no domínio dos macroporos do solo (POMAC), porosidade no domínio da matriz do solo (POMAT), a capacidade de ar do solo (CASOLO), capacidade de ar da matriz do solo (CAMAT), a relação entre a capacidade de retenção de água e a porosidade total (CC/PT), densidade do solo (DS), bem como as produtividades das culturas do algodoeiro e da soja. Na camada de 0-0,1 m o PD apresentou maior densidade do solo e umidade na capacidade de campo (CC) que o PC; já o PC teve maior macroporosidade, condutividade gasosa e melhor continuidade de poros. O sistema de produção com monocultura do algodão e a sucessão com o algodoeiro e milheto apresentaram menores valores de porosidade no domínio dos macroporos. Na camada de 0-0,2 m verificaram-se menores valores de porosidade no domínio da matriz do solo (POMAT) sob PC nos sistemas de produção que incluíam a cultura da soja. Já na camada de 0,2-0,4 m verificaram-se maiores valores de CC e POMAT no PC, enquanto a conectividade dos poros foi reduzida. O PD teve produtividade de soja 10,2% maior que o PC atribuído ao melhor suprimento hídrico à cultura sob PD. O rendimento de algodão em caroço foi menor sob a monocultivo de algodão, não sendo possível associar este resultado à diferença de QFS entre os sistemas de produção. Conclui-se que os diferentes sistemas de produção e sistemas de preparo influenciaram a qualidade física do solo. Todavia, o efeito da qualidade física do solo na produtividade somente foi observado quando as plantas foram submetidas a déficit hídrico, como no caso da cultura da soja.71

Time-dependent theory of optical electro- and magnetostriction

Electrostriction, the deformation of dielectric materials under the influence of an electric field, is of continuous interest in optics. The classic experiment by Hakim and Higham [Proc. Phys. Soc. 80, 190 (1962)] for a stationary field supports a different formula of the electrostrictive force density than the recent experiment by Astrath et al. [Light Sci. Appl. 11, 103 (2022)] for an optical field. In this work, we study the origin of this difference by developing a time-dependent covariant theory of optical force densities in photonic materials. When a light pulse propagates in a bulk dielectric, the field-induced force density consists of two parts: (i) The optical wave momentum force density f_owm carries the wave momentum of light and drives forward a mass density wave of the covariant coupled field-material state of light. (ii) The optostrictive force density f_ost arises from the atomic density dependence of the electric and magnetic field energy densities. It represents an optical Lorentz-force-law-based generalization of the electro- and magnetostrictive force densities well known for static electromagnetic fields and derived from the principle of virtual work. Since the work done by f_ost is not equal to the change of the field energy density during the contraction of the material, we have to describe this difference with optostriction-related dissipation terms to fulfill the energy conservation. The detailed physical model of the dissipation is left for further works. The optostrictive force density can be understood in terms of field-induced pair interactions inside the material. Because of the related action and reaction effects, this force density cannot contribute to the net momentum transfer of the optical field. The theory is used to simulate the propagation of a Gaussian light pulse through a dielectric material. We calculate the electric and magnetic fields of the Gaussian light pulse from Maxwell's equations and simultaneously solve Newton’s equation of motion of atoms to find how the velocity and displacement fields of atoms develop as a function of time under the influence of the field-induced force density.Peer reviewe

Applying the angular spectrum representation to calculate the optical force density generated in dielectrics by tightly focused laser beams

The Angular Spectrum Representation (ASR) is applied to describe semi-analytically the optical force densities acting on linear dielectric media when a quasi-monochromatic tightly focused Gaussian beam is applied. This method is seen to be inherently faster than conventional finite-difference schemes. Numerical simulations of the optical force densities were also performed and found to be in agreement with the literature, providing a complementary tool for the study of opto-mechanical effects in matter

Recovery of physical attributes of an ultisol as affected by soil tillage and sowing time in no-tillage

A melhoria da qualidade estrutural do solo pelo uso continuado do sistema semeadura direta ocorre junto com o processo de sua (re)acidificação. Em algumas circunstâncias, ocorre também compactação superficial devido ao tráfego de máquinas, que necessita ser corrigida pela mobilização do solo. Assim, em experimento conduzido há 12 anos sob diferentes sistemas de manejo do solo, avaliou-se o tempo necessário para o solo readquirir os atributos físicos iniciais, alterados no processo de revolvimento do solo, por ocasião da reaplicação de calcário. O experimento foi realizado na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul - RS, em um Argissolo Vermelho distrófico típico. Os sistemas de manejo avaliados foram: (a) preparo convencional durante 12 anos, (b) sistema semeadura direta com revolvimento do solo para incorporar calcário a cada quatro anos, (c) sistema semeadura direta durante oito anos e (d) sistema semeadura direta durante 12 anos. Determinaram-se, imediatamente antes e 6, 12, 24, 36 e 48 meses depois da terceira reaplicação de calcário, a densidade, a porosidade total, a macroporosidade, a microporosidade, a estabilidade de agregados e o teor de C orgânico em três camadas (0,0–2,5; 2,5–7,5 e 7,5–15,0 cm) de solo. O revolvimento do solo para incorporação do calcário no sistema semeadura direta de quatro anos propiciou condições mais favoráveis de densidade e porosidade do solo, mas diminuiu a estabilidade de agregados. Houve necessidade de um período de quatro anos de cultivo do solo no sistema semeadura direta para o retorno da estabilidade de agregados à condição original. Os atributos físicos do solo foram mais uniformes no perfil no preparo convencional, porém com menor estabilidade de agregados na camada superficial, que foi relacionada ao teor de C orgânico.The improvement in the structural soil quality under continuous no-tillage occurs concomitantly to soil (re)acidification. Surface compaction can sometimes occur, owing to machinery traffic, which has to be corrected by soil tilling. In a 12-year experiment under different soil management systems we evaluated the time it takes to recover the initial soil physical attributes that are affected by soil tillage by the occasion of lime reapplication. The experiment was set up on a Rhodic Paleudult (Ultisol) at the Agronomical Experimental Station-UFRGS, in Eldorado do Sul, state of Rio Grande do Sul, Brazil, for 12 years under conventional and 4, 8 and 12 years under no-tillage systems. The soil physical attributes (bulk density, porosity and aggregate stability) and organic carbon content were evaluated in three (0–2.5, 2.5–7.5 and 7.5–15.0 cm) soil layers, just before and 6, 12, 24, 36 and 48 months after the third lime application. By tilling the soil at lime incorporation after four years of notillage, bulk density and porosity improved, but the aggregate stability decreased. Four years under no-tillage were necessary to recover the original aggregate stability condition. Soil physical attributes were more uniform in conventional tillage, but the aggregate stability in the surface layer was lower, and was related to the organic carbon content

Recovery of physical attributes of an ultisol as affected by soil tillage and sowing time in no-tillage

A melhoria da qualidade estrutural do solo pelo uso continuado do sistema semeadura direta ocorre junto com o processo de sua (re)acidificação. Em algumas circunstâncias, ocorre também compactação superficial devido ao tráfego de máquinas, que necessita ser corrigida pela mobilização do solo. Assim, em experimento conduzido há 12 anos sob diferentes sistemas de manejo do solo, avaliou-se o tempo necessário para o solo readquirir os atributos físicos iniciais, alterados no processo de revolvimento do solo, por ocasião da reaplicação de calcário. O experimento foi realizado na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul - RS, em um Argissolo Vermelho distrófico típico. Os sistemas de manejo avaliados foram: (a) preparo convencional durante 12 anos, (b) sistema semeadura direta com revolvimento do solo para incorporar calcário a cada quatro anos, (c) sistema semeadura direta durante oito anos e (d) sistema semeadura direta durante 12 anos. Determinaram-se, imediatamente antes e 6, 12, 24, 36 e 48 meses depois da terceira reaplicação de calcário, a densidade, a porosidade total, a macroporosidade, a microporosidade, a estabilidade de agregados e o teor de C orgânico em três camadas (0,0–2,5; 2,5–7,5 e 7,5–15,0 cm) de solo. O revolvimento do solo para incorporação do calcário no sistema semeadura direta de quatro anos propiciou condições mais favoráveis de densidade e porosidade do solo, mas diminuiu a estabilidade de agregados. Houve necessidade de um período de quatro anos de cultivo do solo no sistema semeadura direta para o retorno da estabilidade de agregados à condição original. Os atributos físicos do solo foram mais uniformes no perfil no preparo convencional, porém com menor estabilidade de agregados na camada superficial, que foi relacionada ao teor de C orgânico.The improvement in the structural soil quality under continuous no-tillage occurs concomitantly to soil (re)acidification. Surface compaction can sometimes occur, owing to machinery traffic, which has to be corrected by soil tilling. In a 12-year experiment under different soil management systems we evaluated the time it takes to recover the initial soil physical attributes that are affected by soil tillage by the occasion of lime reapplication. The experiment was set up on a Rhodic Paleudult (Ultisol) at the Agronomical Experimental Station-UFRGS, in Eldorado do Sul, state of Rio Grande do Sul, Brazil, for 12 years under conventional and 4, 8 and 12 years under no-tillage systems. The soil physical attributes (bulk density, porosity and aggregate stability) and organic carbon content were evaluated in three (0–2.5, 2.5–7.5 and 7.5–15.0 cm) soil layers, just before and 6, 12, 24, 36 and 48 months after the third lime application. By tilling the soil at lime incorporation after four years of notillage, bulk density and porosity improved, but the aggregate stability decreased. Four years under no-tillage were necessary to recover the original aggregate stability condition. Soil physical attributes were more uniform in conventional tillage, but the aggregate stability in the surface layer was lower, and was related to the organic carbon content

On the formulations of the electromagnetic stress–energy tensor

In this work, we review the main existing theories for the electromagnetic stress-energy tensor in dielectric media - a problem directly related to the century-long debate regarding the correct momentum of light in dielectric media, known as Abraham-Minkowski controversy. The theoretical validity of the main existing formulations is analyzed in terms of symmetry and invariance requirements for the tensors. We also present position- and time-dependent numerical simulations of the related electromagnetic forces for a lossless nondispersive medium, highlighting the different expected spatial force distributions. The force densities of different formulations drive forward different momentum and atomic number density distributions of the medium contributing to the total momentum and energy densities associated with the coupled field-medium state of light.Peer reviewe