The natural chemical qualities of the subsoil of Oxisols often restrict root growth, water use efficiency, and crop yield. The practice of continuous no-till farming creates a fertile topsoil but generally does not affect the subsoil. This study aimed to evaluate the effectiveness of gypsum in improving the chemical attributes of the subsoil and increasing crop yields. To this end, the experiment was conducted at two sites in distrophic Red Oxisols located in southern Brazil. The experimental design was a randomized complete block with three replications. Treatments consisted of broadcast gypsum rates of 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.5 Mg ha -1 . Soil samples were collected from the root zone at the beginning of the experiment and after six and 22 mo to evaluate soil pH and extractable P, K + , Ca 2+ , Mg 2+ , Al 3+ , and SO 4 -S concentrations. After 6 mo of gypsum application, an increase in exchangeable bases associated with a decrease in Al 3+ concentrations in the subsoil was noted, and this improvement was intensified further by 22 mo. An increase in crop yields was related to the increase in base saturation and Ca 2+ saturation and a decrease in Al 3+ saturation in the 25-to 40-cm soil depth. Surface application of gypsum was an effective method of improving the chemical quality of the rooting zone in Oxisols under continuous no-till farming and resulted in a higher impact on corn (Zea mays L.) grain yield than soybean [Glycine max (L.) Merr.] yield.

Modern maize, wheat, and soybean cultivars are usually characterized by a short cycle, high shoot-root ratio, and high responsiveness to nutrient input. Continuous no-tillage management (NTS) frequently leads to a steep gradient in soil chemical quality with depth, thus decreasing yield under conditions of acid subsoil and water stress. This study aimed to evaluate the effect of gypsum, applied separately or in combination with lime, on the yield of cultivars used in the state of Rio Grande do Sul, Brazil. The study consisted of four experiments conducted on a typic Hapludox under NTS. The experiment was arranged in a randomized block design with three replications. Experiments I and II were carried out on soils with a satisfactory chemical soil quality and tested treatments of gypsum applications ranging from 0.0 to 6.5 Mg ha -1 . The other experiments were carried out on acid soil (experiment III) and a soil with an abrupt drop in chemical quality (experiment IV). Experiment III was arranged in a split plot design, where plots corresponded to gypsum rates between 0.0 and 5.0 Mg ha -1 , and subplots to two lime rates (0.0 and 2.0 Mg ha -1 ). Experiment IV was conducted in a split plot design, with plots consisting of gypsum rates from 0.0 to 6.0 Mg ha -1 and subplots of lime rates from 0.0 to 4.8 Mg ha -1 . Of a set of 17 harvests investigated during the experimental period, 82 % responded with yield increases to gypsum and lime inputs. The gypsum rate that induced the highest grain yield was high (4.7 Mg ha -1 ) and similarly, the maximum technical efficiency of lime was higher than the currently recommended. Furthermore, the combined application of lime and gypsum increased yield. There was a correlation between grain yield with the chemical quality of the soil layer 0.25-0.40 m in experiment I, 0.00-0.40 m in experiment II, and the 0.00-0.25 m in experiment IV. Only in experiment III, where the surface layer was acidic, the diagnostic layer usually sampled (0.00-0.10 m) was correlated with grain yield. Therefore, the use of the 0.00-0.25 m soil layer with critical base saturation values of 65 % and maximum Al saturation of 5 % could improve the current recommendations for soil correction. To exploit the yield potential of modern grain cultivars on dystrophic Oxisol, the formation of a thicker layer with high chemical quality is an efficient strategy.

Resumo -O objetivo deste trabalho foi avaliar as relações da condutividade elétrica aparente (CEa), determinada por sensoriamento em tempo real, com os atributos do solo e com a produção vegetal, além de espacializar de forma indireta e em alta resolução os componentes da acidez de um Latossolo Vermelho distrófico no Sul do Brasil. O sensoriamento do solo foi realizado em duas áreas agrícolas, com o sensor Veris 3100. O solo foi amostrado à profundidade de 0,00-0,15 m, com trado calador. Avaliou-se o índice de vigor do milho (IV) com um sensor óptico, e a produtividade com sensores de produtividade e umidade. A associação dos atributos da acidez do solo com a produtividade do milho e com a CEa foi determinada por meio de análises de correlação e de componentes principais. A CEa relacionou-se ao IV e à produtividade de milho. Além disso, na área com qualidade química inferior, a CEa apresentou relação positiva com os conteúdos , matéria orgânica do solo e teor de argila.Termos para indexação: agricultura de precisão, condutividade elétrica, fertilidade do solo, manejo sítio-específico, matéria orgânica do solo, variabilidade espacial. High-resolution spacialization of an Oxisol's acidity attributes by on-the-go sensingAbstract -The objective of this work was to evaluate the relationships between the apparent electric conductivity (ECa), measured by on-the-go sensing, with soil attributes and plant production, besides indirectly mapping with high resolution, the main acidity attributes of an Oxisol in South Brazil. Soil sensing was performed in two crop fields using the Veris 3100 sensor. Soil was sampled at the 0.00-0.15-m soil depth using a hand auger. The corn vigor index (VI) was measured with an optical sensor, and yield was determined using grain yield and moisture sensors. contents, soil organic matter, and clay content.

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Rice culture can suffer great damages due to fungal diseases which affect seeds, roots, leaves and panicles, among which the blast disease stands out. In this context, the chemical control through fungicide use takes a key role, promoting healing, protecting and eradicative effects of the disease. The great majority of fungicides recommended include active ingredients of systemic action ways, that is, capable of penetrating and moving inside plants, being able to exert its effect in a different location from that applied. This study presents a review about the systemic fungicide use for blast disease control. For this disease, there are 25 registered commercial products which include 12 different active ingredients, considering seed treatment and foliar application, involving a total of 6 distinct ways of systemic action. The treatment with systemic fungicides has been shown efficient in chemical control for promoting healing, protecting and eradicating effects of the disease.

Rice is the most important crop for the south and south-west region of the Rio Grande do Sul state (Brazil); as all commercial crops, irrigated rice is requiring the use of alternatives for increasing yield and quality of its product with less aggressive/toxic inputs in the environment. The aim of this study was to analyze the influence of the biofertilization in the rice crop yield and the parameter of its seed quality and grain quality. It was carried out a field experiment with two treatments (with and without biofertilization with 150 + 150 L CLC® ha-1) with 12 repetitions in an irrigated rice. Biofertilization did not influenced the percentages of whole grain, polished grain and no broken grain. There were no difference between the treatments for final seed germination, seed hectoliter weight and pH. The rice yield with biofertilization using continuous liquid composting was not statistically higher, an expected result for a first year of biofertilization. However, it provided 398 kg ha-1 grain yield increase, which is a very positive and a promising result considering being the first year of application. Therefore, a significant yield increase for the following years of application is expected.

Despite its relevance, nitrogen is poorly utilized by the plants when improperly applied. Thus, the objective of this study was to evaluate the yield and nitrogen use efficiency (NUE) in corn in response to doses and split application of nitrogen fertilization. The experimental design was a randomized block design, with three replications. Doses of nitrogen of 0, 30, 60 and 180 kg ha -1 were applied at sowing in order to create different nutritional status of corn plants and to obtain different values of Normalized Difference Vegetation Index (NDVI) measured with "Greenseeker ® " optical sensor. The subplots with nitrogen doses in topdressing of 0, 30, 60 and 90 kg ha -1 at V8 and a dose of 60 kg ha -1 at V12 were placed in experimental plots with doses of 0, 30, 60 and 180 kg ha -1 of nitrogen at sowing. Moreover, NUE was calculated in the experiment using agronomic indexes determined by applications of nitrogen in late topdressing (V8 and V12) and contrasted to the possible combinations at doses of 60, 90 and 120 kg ha -1 of total N applied. The results showed the occurrence of a linear relationship between nitrogen fertilizer dose and NDVI at V8 as well as at V12 stages. Late topdressing fertilizations (V12) did not cause a decrease in grain yield when combined with nitrogen fertilization at sowing, moreover resulted in higher NUE. Split the nitrogen dose showed better NUE than the combinations where nitrogen was not applied at sowing or in topdressing. The delay of nitrogen topdressing can be an alternative for the planning of the moment of the N fertilization according to the climate forecast in each region. Key words: Produtividade e eficiência nutricional do milho em resposta a doses e parcelamentos da adubação nitrogenadaApesar de sua relevância, o nitrogênio apresenta reduzido aproveitamento pela planta quando aplicado de forma inadequada. Assim, objetivou-se avaliar a produtividade e a eficiência do uso de nitrogênio (EUN) no milho em resposta a doses e parcelamentos da adubação nitrogenada. O delineamento experimental utilizado foi de blocos ao acaso, com três repetições. Foram aplicadas doses de 0, 30, 60 e 180 kg ha -1 de nitrogênio em semeadura visando criar diferentes condições nutricionais das plantas de milho e assim obter diferentes níveis de Índice de Vegetação por Diferença Normalizada (NDVI) medidos com sensor óptico "GreenSeeker ® ". As subparcelas com doses de nitrogênio em cobertura de 0, 30, 60 e 90 kg ha -1 em V8 e uma dose de 60 kg ha -1 em V12 foram alocadas experimentalmente nas parcelas com doses de 0, 30, 60 e 180 kg ha -1 de nitrogênio em semeadura. Além disso, foi calculado no experimento a EUN através de índices agronômicos determinados a partir das aplicações de N em cobertura tardia (V8 e V12) e contrastado às possíveis combinações nas doses de 60, 90 e 120 kg ha -1 de nitrogênio total aplicado. Os resultados mostraram que houve relação 352Telmo Jorge Carneiro Amado et al.

Embora sendo cada vez mais adotada no Brasil, existem poucos estudos sobre o processo de adoção e uso de tecnologias de AP no país. O objetivo deste estudo foi avaliar a percepção, grau de adoção e perfil dos produtores rurais quanto à utilização da técnica de AP na Região Noroeste do RS. O trabalho caracterizou-se como uma pesquisa exploratória quanto a sua finalidade. O público-alvo da entrevista foram produtores rurais assistidos pela Cooperativa Tritícola Regional São-Luizense Ltda. Para a obtenção das descrições experienciais de cada produtor foram utilizados questionários semiestruturados, sendo um com perguntas abertas e fechadas e outro utilizando-se a Escala Likert. Os dados foram analisados calculando-se a frequência das respostas dadas e análise de discurso, e a associação entre as variáveis e os produtores investigados foi identificada mediante o uso de análise estatística multivariada. A AP ainda é recente na Região Noroeste do RS, sendo utilizadas poucas ferramentas, restringindo-se à aplicação à taxa variável de insumos, muito centrada na produção de soja, principalmente. É utilizada por produtores de diferentes níveis de escolaridade, idade e tamanho de área.