Weed Management in Sprinkler-Irrigated Rice: Experiences from Southern Brazil

Sprinkler rice saves water compared to paddy rice. However, in paddy fields, the water table is efficient for weed suppression. In sprinkler rice, there is no water table on soil; thus, weed management used in paddy rice may not be suitable for sprinkler rice, since herbicides and water table are expected to interact. Weed pressure in sprinkler rice is higher than in paddy rice; annual grasses are the main weeds in both paddy and sprinkler rice. Barnyardgrass, goosegrass, crabgrass and Alexandergrass show vigorous growth in sprinkler rice. A 3-year study shows that weeds in sprinkler rice reduce grain yield between 11 and 95%. Herbicides used in conventional and Clearfield® rice (clomazone, imazethapyr + imazapic, imazapyr + imazapic, pendimethalin and penoxsulam) were tested, contrasting paddy and sprinkler rice. Additionally, the technique locally called “needle-point” (glyphosate applied over the first-day emerging rice) was combined with pre- and postemergence herbicides. When using only pre- or postemergence, weeds reduced rice grain yield; a combination of products was the best option for sprinkler-irrigated rice. The Clearfield technology was efficient in controlling most weeds. However, using it combined to the needle-point promoted the best results. The main approaches for weed management in sprinkler-irrigated rice were summarized

Soil and Water Management for Sprinkler Irrigated Rice in Southern Brazil

Rice is grown in lowland paddies, which is flood irrigated. In the most undulating areas, continuous flooding is difficult and some farmers seek alternative irrigation methods. Grain yield in sprinkler irrigated rice ranges between 80 and 100% of that obtained under flooding, but for this, fertilizer and water should be properly managed. For sprinkler irrigated rice, fertilizer should be corrected by adding 10 kg/ha of P2O5 and 15 kg/ha of K2O for every expected additional ton of grains, over the standard recommendation. Regarding nitrogen fertilizer, it is recommended to be applied about 20 kg/ha of N at planting and the rest as topdressing. This can be done via soil, split into two applications: 50–60% of the topdressing dose at tillering start and the rest at panicle initiation. When N is applied by fertigation, 25% of the recommended topdressing N should be applied at tillering start; the remainder of the dose may be partitioned into four to six weekly applications through irrigation water. For water management, soil water tension should be kept below 10 kPa. At the vegetative stage, irrigation can be applied aiming to avoid water tensions in soil above 30 kPa at any moment

Atributos químicos e biológicos de um solo de várzea afetados pela sistematização do terreno

The objective of this work was to evaluate the relationship between soil chemical and biological attributes and the magnitude of cuts and fills after the land leveling process of a lowland soil. Soil samples were collected from the 0–0.20 m layer, before and after leveling, on a 100 point grid established in the experimental area, to evaluate chemical attributes and soil microbial biomass carbon (MBC). Leveling operations altered the magnitude of soil chemical and biological attributes. Values of Ca, Mg, S, cation exchange capacity, Mn, P, Zn, and soil organic matter (SOM) decreased in the soil profile, whereas Al, K, and MBC increased after leveling. Land leveling decreased in 20% SOM average content in the 0–0.20 m layer. The great majority of the chemical attributes did not show relations between their values and the magnitude of cuts and fills. The relation was quadratic for SOM, P, and total N, and was linear for K, showing a positive slope and indicating increase in the magnitude of these attributes in cut areas and stability in fill areas. The relationships between these chemical attributes and the magnitude of cuts and fills indicate that the land leveling map may be a useful tool for degraded soil recuperation through amendments and organic fertilizers.O objetivo deste trabalho foi avaliar a relação entre os atributos químicos e biológicos do solo e as magnitudes de cortes e aterros após sistematização de um solo de várzea. Foram coletadas amostras de solo na camada de 0–0,20 m, antes e depois da sistematização, em uma malha de 100 pontos estabelecida na área experimental, para avaliar os atributos químicos do solo e o carbono da biomassa microbiana (CBM). A sistematização alterou a magnitude dos atributos químicos e biológicos do solo. Valores de Ca, Mg, S, capacidade de troca catiônica, Mn, P, Zn e matéria orgânica do solo (MOS) diminuíram no perfil do solo, enquanto os de Al, K e CBM aumentaram após a sistematização. A sistematização reduziu em 20% o conteúdo médio de MOS na camada de 0–0,20 m. A maior parte dos atributos químicos não apresentou relação com as magnitudes de corte e aterro. A relação foi quadrática para MOS, P e N total, e linear para K, mostrando inclinação positiva e aumento das magnitudes destes atributos em áreas de corte e estabilidade em áreas de aterro. As relações entre estes atributos químicos e as magnitudes de cortes e aterro indicam que o mapa de sistematização pode ser uma ferramenta útil para a recuperação de solos degradados por meio da aplicação de corretivos e fertilizantes orgânicos

Efeito do sistema de cultivo e manejo do solo no estabelecimento de soja em terras baixas/ Effect of the growing and soil management system on soybean establishment

Objetivou-se com o trabalho avaliar a resposta das plantas da soja implantada em diferentes sistemas de cultivo e manejo do solo, no estabelecimento da cultura em terras baixas de clima temperado. Quatro tratamentos de manejo de solo foram avaliados em condições de terras baixas, em áreas de arroz, para implantação da cultura da soja: camalhão escarificado (CE), onde implantou-se a soja no sistema sulco-camalhão construído em solo previamente escarificado; sulco-camalhão (C), com plantio de soja em camalhão construído em solo não escarificado; escarificado (E) com plantio de soja em solo escarificado mas sem sulco-camalhões; e convencional (Convencional), com plantio de soja em sistema usual, sem camalhão ou escarificação do solo. Foram avaliados a área foliar, altura, diâmetro do caule e conteúdo de água das plantas. As avaliações foram efetuadas quinzenalmente da emergência à maturação dos grãos. A utilização de camalhão e escarificação favorecem o crescimento e desenvolvimento da planta, diminuindo o estresse causado pelo encharcamento do solo e permitindo melhor ambiente para o desenvolvimento do sistema radicular das plantas

Effect of land leveling on the physical, chemical and biological soil attributes in lowland.

Land leveling is the process of alteration of natural surfer of land into a plan. This practice is relatively common in the lowland of the RS, because it increases the efficiencies of the agricultural practices mainly the uniformity of irrigation. However, for its implementation has great movement of soil with cut in relatively high point and filled in the lower part. The objectives of this study were to (i) know the effect of the land leveling on behavior of average of physical, chemical and biological soil attributes (ii) identify the different patterns of behavior and spatial distribution of soil attributes before and after land leveling, and (iii) know the relationship between the magnitude of cuts and fills with soil attributes. To this end, in typical irrigated rice area in the county of Capão do Leão, RS, in a grid of 100 points in equidistant arrangement of 10 x 10m, soil samples were collected before and after the land leveling, with the purpose of obtaining physical, chemical and biological soil attributes. The results showed that land leveling affects the spatial variability and distribution of almost all the attributes of the soil studied. Adversely affect the physical attributes of soil, especially the mean size distribution of aggregate stability and macroporosity. The land leveling also adversely affect the fertility of the soil, since there is greater need for application of lime due to the increase in the average value of the SMP and fertilizer due to the decrease in mean levels of nutrients such as phosphorus, calcium, magnesium, sulfur, probably the available nitrogen, except the average of potassium that to increase. The area where the soil was cut the correction of the acidity and fertility, with the application of chemical fertilizers and/or organic, should be conducted according to the magnitude of the cuts caused by the land leveling.A sistematização consiste no processo de adequação da superfície natural do terreno de forma a transformá-lo num plano. Esta prática é relativamente comum nas várzeas arrozeiras do RS, pois aumenta a eficiência de várias práticas agrícolas, principalmente a uniformidade da irrigação. Entretanto, para sua execução há grande movimento de solo com cortes nas partes relativamente altas e aterros nas partes mais baixas. Este trabalho objetivou (i) conhecer o efeito da sistematização sobre o comportamento médio dos atributos físicos, químicos e biológico do solo (ii) identificar padrões de comportamento e distribuição espacial dos atributos do solo antes e depois da sistematização, e (iii) determinar a relação entre a magnitude dos cortes e/ou aterros com os atributos do solo. Para tal, em área típica de arroz irrigado no município do Capão do Leão, RS, foram coletadas amostras de solo, antes e após a sistematização, numa malha de 100 pontos, em arranjo eqüidistante de 10 x 10m, com a finalidade de se obter atributos físicos, químicos e biológicos. Os resultados mostraram que a sistematização alterou a variabilidade e distribuição espacial de quase todos os atributos do solo. Afetou negativamente os atributos físicos do solo, principalmente o diâmetro médio ponderado dos agregados e a macroporosidade. A sistematização do terreno afetou também negativamente a fertilidade do solo, pois há maior necessidade de aplicação de calcário devido ao aumento do valor médio do índice SMP e de fertilizante devido à diminuição nos teores médios dos principais nutrientes tais como fósforo, cálcio, magnésio, enxofre e provavelmente do nitrogênio disponível, com exceção do valor médio do potássio que aumentou. Na zona em que o solo foi cortado a correção da acidez assim como da fertilidade, com a aplicação de fertilizantes químicos e/ou orgânicos, deverá ser realizada em função da magnitude dos cortes provocados pela sistematização do terreno

Impacts of land leveling on lowland soil physical properties

The practice of land leveling alters the soil surface to create a uniform slope to improve land conditions for the application of all agricultural practices. The aims of this study were to evaluate the impacts of land leveling through the magnitudes, variances and spatial distributions of selected soil physical properties of a lowland area in the State of Rio Grande do Sul, Brazil; the relationships between the magnitude of cuts and/or fills and soil physical properties after the leveling process; and evaluation of the effect of leveling on the spatial distribution of the top of the B horizon in relation to the soil surface. In the 0-0.20 m layer, a 100-point geo-referenced grid covering two taxonomic soil classes was used in assessment of the following soil properties: soil particle density (Pd) and bulk density (Bd); total porosity (Tp), macroporosity (Macro) and microporosity (Micro); available water capacity (AWC); sand, silt, clay, and dispersed clay in water (Disp clay) contents; electrical conductivity (EC); and weighted average diameter of aggregates (WAD). Soil depth to the top of the B horizon was also measured before leveling. The overall effect of leveling on selected soil physical properties was evaluated by paired "t" tests. The effect on the variability of each property was evaluated through the homogeneity of variance test. The thematic maps constructed by kriging or by the inverse of the square of the distances were visually analyzed to evaluate the effect of leveling on the spatial distribution of the properties and of the top of the B horizon in relation to the soil surface. Linear regression models were fitted with the aim of evaluating the relationship between soil properties and the magnitude of cuts and fills. Leveling altered the mean value of several soil properties and the agronomic effect was negative. The mean values of Bd and Disp clay increased and Tp, Macro and Micro, WAD, AWC and EC decreased. Spatial distributions of all soil physical properties changed as a result of leveling and its effect on all soil physical properties occurred in the whole area and not specifically in the cutting or filling areas. In future designs of leveling, we recommend overlaying a cut/fill map on the map of soil depth to the top of the B horizon in order to minimize areas with shallow surface soil after leveling

Chemical and biological attributes of a lowland soil affected by land leveling

The objective of this work was to evaluate the relationship between soil chemical and biological attributes and the magnitude of cuts and fills after the land leveling process of a lowland soil. Soil samples were collected from the 0 - 0.20 m layer, before and after leveling, on a 100 point grid established in the experimental area, to evaluate chemical attributes and soil microbial biomass carbon (MBC). Leveling operations altered the magnitude of soil chemical and biological attributes. Values of Ca, Mg, S, cation exchange capacity, Mn, P, Zn, and soil organic matter (SOM) decreased in the soil profile, whereas Al, K, and MBC increased after leveling. Land leveling decreased in 20% SOM average content in the 0 - 0.20 m layer. The great majority of the chemical attributes did not show relations between their values and the magnitude of cuts and fills. The relation was quadratic for SOM, P, and total N, and was linear for K, showing a positive slope and indicating increase in the magnitude of these attributes in cut areas and stability in fill areas. The relationships between these chemical attributes and the magnitude of cuts and fills indicate that the land leveling map may be a useful tool for degraded soil recuperation through amendments and organic fertilizers

State-space approach to evaluate effects of land levelling on the spatial relationships of soil properties of a lowland area

Land levelling is an agricultural practice to correct soil surface irregularities turning the area more efficient for management of agronomic inputs. The technique has been adopted mainly in lowland areas used for flood irrigation of rice. As a result sub-surface soil layers may be exposed with possible impact on crop production by changing soil properties. This study aimed to evaluate the effects of land levelling on the spatial relationships of soil properties. Relations among them were quantified using a state-space approach in different scenarios constructed from data sets in a 1 ha lowland area sampled as a grid. The grid consisted of 100 sampling points (10 m × 10 m), with samples collected from the 0–0.20 m soil layer, before and after levelling, totalizing 200 samples. Soil water contents at field capacity (θFC) and permanent wilting point (θPWP) were taken as response variables due to their importance on rice water management. Sand, silt and clay contents, soil microporosity (Micro) and bulk density (BD), cation exchange capacity (CEC), organic carbon content (Corg), and the depth of the top of the B horizon in relation to soil surface (DTB) were used as co-variables through an evaluation of their spatial auto- and cross-correlation behaviors with θFC and θPWP. Eight data-array scenarios were tested. Results showed that levelling induced negative effects on soil quality since this procedure decreased θFC and θPWP, Corg, and CEC as well as increased BD. Using the state-space approach, we concluded that its performance in estimating θFC and θPWP was affected by the scenarios after levelling, the best performance being for the vertical scenarios. DTB and CEC contributed to the estimation of both soil water contents for all scenarios after levelling. The main problem associated to the levelling is the cutting of shallow soils which decreases their capacity to store water and to exchange cations in the effective arable depth which will be explored by the crop root system. As DTB is directly related to the spatial distribution of taxonomic soil profile properties, the state-space approach, which considers sampling location coordinates, may be a potential on-site-specific tool aiming at the recuperation of degraded soils through amendments since it opens the possibility for farmers to manage a crop field based on local environmental properties, with their spatial association and localized variation being a function of the distance between their measurements145135147CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESSem informaçãoSem informaçã

Spatial variability of the chemical, physical and biological properties in lowland cultivated with irrigated rice

In the areas where irrigated rice is grown in the south of Brazil, few studies have been carried out to investigate the spatial variability structure of soil properties and to establish new forms of soil management as well as determine soil corrective and fertilizer applications. In this sense, this study had the objective of evaluating the spatial variability of chemical, physical and biological soil properties in a lowland area under irrigated rice cultivation in the conventional till system. For this purpose, a 10 x 10 m grid of 100 points was established, in an experimental field of the Embrapa Clima Temperado, in the County of Capão do Leão, State of Rio Grande do Sul. The spatial variability structure was evaluated by geostatistical tools and the number of subsamples required to represent each soil property in future studies was calculated using classical statistics. Results showed that the spatial variability structure of sand, silt, SMP index, cation exchange capacity (pH 7.0), Al3+ and total N properties could be detected by geostatistical analysis. A pure nugget effect was observed for the nutrients K, S and B, as well as macroporosity, mean weighted diameter of aggregates, and soil water storage. The cross validation procedure, based on linear regression and the determination coefficient, was more efficient to evaluate the quality of the adjusted mathematical model than the degree of spatial dependence. It was also concluded that the combination of classical with geostatistics can in many cases simplify the soil sampling process without losing information quality