ABSTRACT The concept of a no-tillage system (NTS), or “Sistema Plantio Direto,” was established in Brazil from the evolution of no-tillage (NT) or “Plantio Direto,” given the edaphoclimatic conditions and the need to promote chemical, physical and biological improvements in cultivated soils. While “Plantio Direto” is a conservationist practice, “Sistema Plantio Direto” presents itself as an agricultural production system based on the simultaneous adoption of minimum soil disturbance, maintenance of permanent soil cover and crop rotation. This study reviews the concepts of “Plantio Direto” and “Sistema Plantio Direto” in the Brazilian literature and uses two case studies in Paraná State to demonstrate the practical implications of these concepts. These two terms and their variations are recurrent themes in Brazilian scientific research and the professional environment, and may occur erroneously, hindering their adoption, results and implications. Regarding the “Sistema Plantio Direto,” we highlight the need to clarify the concepts of its basic practices to parameterize and characterize this process. The definition of crop rotation, for example, requires limits on the number of species along a given time scale, thus enabling their identification. Regarding the case studies, most grain crops conducted in Paraná State did not adopt the “Sistema Plantio Direto,” mainly neglecting the component of crop rotation. Nevertheless, the use of the “no-tillage system participatory quality index” (PQI) tool can contribute to the assessment and monitoring of the quality of the “Sistema Plantio Direto.” However, it requires adjustments to differentiate the “Sistema Plantio Direto” from the “Plantio Direto.”

ABSTRACT The susceptibility of soil to compaction, evaluate by the Proctor test, is a measure that has been studied in agricultural production systems, aiming at a more detailed study of the degree of compression that can be achieved in a given soil. This study was aimed to compare different locations, (Guarapuava, Pinhão and Candói) at different depths (0-10, 10-20 and 20-40 cm for Guarapuava, 0-10, 10-25 and 25-40 cm for Pinhao and 0-15, 15-25 and 25-40 cm for Candói) as the maximum density of these soils. The samples were subjected to the normal Proctor test, determining the maximum density and the critical moisture for compaction. The accumulation of organic matter in the surface layer of soil provided a reduction of the maximum density and increased the critical moisture to soil compaction, increasing compression as there is an increase in depth.

RESUMO A susceptibilidade do solo à compactação, avaliada pelo ensaio Proctor, é uma medida que vem sendo estudada nos sistemas agrícolas de produção visando um estudo mais detalhado sobre o grau de compactação que é possível obter em um determinado solo. O presente trabalho teve objetivo comparar diferentes locais, (Guarapuava, Pinhão e Candói) em diferentes profundidades (0-10; 10-20 e 20-40 cm para Guarapuava, 0-10; 10-25 e 25-40 cm para Pinhão e 0-15; 15-25 e 25-40 cm para Candói) quanto à densidade máxima destes solos. As amostras foram submetidas ao ensaio Proctor normal, determinando-se a densidade máxima e a umidade crítica para compactação. O acúmulo de matéria orgânica na camada superficial dos solos proporcionou uma redução da densidade máxima e aumentou a umidade crítica para compactação do solo, aumentando a compactação conforme há um aumento na profundidade.

ABSTRACT Applications of phosphogypsum (PG) provide nutrients to the soil and reduce Al3+ activity, favoring soil fertility and root growth, but allow Mg2+ mobilization through the soil profile, resulting in variations in the PG rate required to achieve the optimum crop yield. This study evaluated the effect of application rates and splitting of PG on soil fertility of a Typic Hapludox, as well as the influence on annual crops under no-tillage. Using a (4 × 3) + 1 factorial structure, the treatments consisted of four PG rates (3, 6, 9, and 12 Mg ha-1) and three split applications (P1 = 100 % in 2009; P2 = 50+50 % in 2009 and 2010; P3 = 33+33+33 % in 2009, 2010 and 2011), plus a control without PG. The soil was sampled six months after the last PG application, in stratified layers to a depth of 0.8 m. Corn, wheat and soybean were sown between November 2011 and December 2012, and leaf samples were collected for analysis when at least 50 % of the plants showed reproductive structures. The application of PG increased Ca2+ concentrations in all sampled soil layers and the soil pH between 0.2 and 0.8 m, and reduced the concentrations of Al3+ in all layers and of Mg2+ to a depth of 0.6 m, without any effect of splitting the applications. The soil Ca/Mg ratio increased linearly to a depth of 0.6 m with the rates and were found to be higher in the 0.0-0.1 m layer of the P2 and P3 treatments than without splitting (P1). Sulfur concentrations increased linearly by application rates to a depth of 0.8 m, decreasing in the order P3>P2>P1 to a depth of 0.4 m and were higher in the treatments P3 and P2 than P1 between 0.4-0.6 m, whereas no differences were observed in the 0.6-0.8 m layer. No effect was recorded for K, P and potential acidity (H+Al). The leaf Ca and S concentration increased, while Mg decreased for all crops treated with PG, and there was no effect of splitting the application. The yield response of corn to PG rates was quadratic, with the maximum technical efficiency achieved at 6.38 Mg ha-1 of PG, while wheat yield increased linearly in a growing season with a drought period. Soybean yield was not affected by the PG rate, and splitting had no effect on the yield of any of the crops. Phosphogypsum improved soil fertility in the profile, however, Mg2+ migrated downwards, regardless of application splitting. Splitting the PG application induced a higher Ca/Mg ratio in the 0.0-0.1 m layer and less S leaching, but did not affect the crop yield. The application rates had no effect on soybean yield, but were beneficial for corn and, especially, for wheat, which was affected by a drought period during growth.

Potenciais produtivos distintos têm sido verificados entre talhões, bem como dentro desses, em áreas sob muitos anos de plantio direto (PD). Ferramentas de agricultura de precisão (AP) podem auxiliar a identificar tais diferenças, mas para manejar eficientemente a fertilidade do solo nessas condições a amostragem deve ser representativa. Este trabalho teve como objetivo avaliar a influência de atributos químicos do solo, conforme a camada ou profundidade de amostragem, na produtividade da cultura do trigo, em uma área sob PD de longa duração, utilizando zonas de um talhão com potenciais produtivos distintos. O estudo foi feito em Reserva do Iguaçu, PR, em área com 25 anos de PD e cinco anos de adoção de técnicas de AP. A partir de mapas de colheita anteriores, identificaram-se duas zonas, Z1 (alta produtividade) e Z2 (baixa produtividade), onde se estabeleceram malhas com 16 unidades amostrais. A produtividade do trigo foi estimada em três pontos por unidade, coletando-se amostras de solo de 0,0-0,1 e de 0,1-0,2 m nos mesmos pontos. A produtividade do trigo foi 22 % maior em Z1 do que em Z2, de acordo com os mapas de colheita utilizados. Os teores de carbono orgânico do solo (Corg) foram maiores em Z1, nas duas camadas do solo. Na camada de 0,1-0,2 m, a saturação (m%) e os teores de Al3+ foram significativamente maiores em Z2; nessa camada, Z1 apresentou maiores valores de pH e saturação por bases (V%) e teores de Ca2+, Mg2+ e K+. Houve correlação positiva da produtividade com os teores de Corg nas duas camadas do solo. Considerando somente a camada de 0,1-0,2 m, a correlação foi positiva com os valores de pH e V% e com a disponibilidade de Ca2+, Mg2+ e K+; e negativa, com a disponibilidade de Al3+. As diferenças na fertilidade do solo entre Z1 e Z2 se deram principalmente na camada de 0,1-0,2 m e foram associadas à diferença de produtividade do trigo, indicando ser importante a presença desse estrato na amostragem do solo em áreas de PD de longa duração, visando representar corretamente o estado de fertilidade do solo.

Different yield potentials between plots and within them have been verified in areas managed under no-till (NT). Precision farming (PF) techniques can help in identifying these distinct areas, but for efficient soil fertility management in areas under long-term NT, there must be representative sampling. The aim of this study was to evaluate the influence of soil chemical properties on wheat yield in accordance with the sampling layer or depth in an area under long-term NT using zones of a plot with different yield potentials. The study was carried out at the Reserva do Iguaçu (Iguaçu Conservation Area), Parana, Brazil, in an area under NT for 25 years and with adoption of PF techniques for five years. Using data from yield maps of previous crops, two zones with distinct yield potentials were identified, named Z1 (higher yields) and Z2 (lower yields), in which sample grids with 16 units (50 × 50 m) were established. Wheat yield was estimated in three points per sampling unit, taking soil samples in the 0.0-0.1 and 0.1-0.2 m depths at the same points. Wheat yield was 22 % higher in Z1 as compared to Z2, in agreement with the yield maps from previous crops. Soil organic carbon contents (Corg) were higher in Z1 for both soil layers. In the 0.1-0.2 m layer, the aluminum saturation (m %) and the Al3+ contents were significantly higher in Z2. In this same layer, Z1 showed higher values of pH and base saturation (V %) and higher levels of Ca2+, Mg2+ and K+. There was positive correlation between wheat yield and Corg content in both soil layers, and considering only the 0.1-0.2 m layer, correlation was positive with pH, V % and Ca2+, Mg2+ and K+ contents, and negative with Al3+. The differences in soil fertility between Z1 and Z2 were mainly in the 0.1-0.2 m layer and were associated with the difference in wheat yield, indicating that the presence of this stratum is important for soil sampling in long-term NT areas aiming to correctly represent the status of soil fertility.

O manejo influencia atributos químicos e físicos do solo; entretanto, os químicos têm sido mais estudados, negligenciando-se a relevância da física do solo para a produtividade das culturas. Os objetivos deste trabalho foram avaliar a produtividade do trigo e caracterizar a sua relação com os atributos físicos de um Latossolo Bruno, sob sistema plantio direto (NT). O estudo foi realizado entre 2010-2011 em Reserva do Iguaçu, Paraná, em um dos talhões da fazenda Campo Bonito, com 25 anos de NT. Os mapas de colheita de cevada (2006), trigo (2007) e milho (2009) permitiram identificar as zonas Z1 (potencial produtivo maior) e Z2 (potencial produtivo menor), em que se estabeleceram malhas amostrais com 16 unidades de 50 x 50 m e três pontos de amostragem por unidade. Em 2010, avaliaram-se a produtividade de grãos (GY) do trigo e a capacidade de infiltração de água no solo (WIC). Amostras de solo com estrutura deformada e indeformada foram coletadas nas camadas de 0,00-0,10 e 0,10-0,20 m. As primeiras serviram para determinar o teor de carbono orgânico (Corg) e as últimas para determinar: densidade do solo (BD), porosidade total do solo (TP), macroporosidade (Mac) e microporosidade (Mic). Avaliaram-se, também, a resistência do solo à penetração (PR) e o conteúdo de água do solo (SWC). A GY do trigo no talhão foi próxima da média regional e houve diferença significativa de rendimento entre zonas, sendo 22 % superior em Z1 em relação a Z2. Não houve variação significativa da Mic entre as zonas do talhão; Z1 apresentou teores de Corg, SWC, TP e Mac maiores e BD menor que Z2, nas duas camadas de solo avaliadas, além de PR menor que Z2, na camada de 0,00-0,10 m, havendo, portanto, condição física de solo mais restritiva em Z2, condizente com os resultados de produtividade do trigo e potencial produtivo delimitado a priori, a partir dos mapas de colheita. A WIC foi significativamente maior (30 %) em Z1 que em Z2, em acordo com os resultados de TP e Mac, também maiores em Z1, nas duas camadas de solo. Considerando-se essas duas camadas, a análise de correlação permitiu destacar relações positivas entre a GY do trigo e TP, SWC e WIC.

Soil management influences the chemical and physical properties of soil. Chemical conditions have been thoroughly studied, while the role of soil physical conditions regarding crop yield has been neglected. This study aimed to analyze the wheat yield and its relationship with physical properties of an Oxisol under no-tillage (NT). The study was carried out between 2010 and 2011, in Reserva do Iguaçu, State of Paraná, Brazil, on the Campo Bonito farm, after 25 years of NT management. Based on harvest maps of barley (2006), wheat (2007) and maize (2009) of a plot (150 ha), zones with higher and lower yield potential (Z1 and Z2, respectively) were identified. Sampling grids with 16 units (50 x 50 m) and three sampling points per unit were established. The wheat grain yield (GY) and water infiltration capacity (WIC) were evaluated in 2010. Soil samples with disturbed and undisturbed structure were collected from the 0.00-0.10 and 0.10-0.20 m layers. The former were used to determine soil organic carbon (Corg) levels and the latter to determine soil bulk density (BD), total porosity (TP), macroporosity (Mac), and microporosity (Mic). Soil penetration resistance (PR) and water content (SWC) were also evaluated. The wheat GY of the whole plot was close to the regional average and the yield between the zones differed significantly, i.e. 22 % higher in Z1 than in Z2. No significant variation in Mic was observed between zones, but Z1 had higher Corg levels, SWC, TP and Mac and lower BD than Z2 in both soil layers, as well as a lower PR than Z2 in the 0.00-0.10 m layer. Therefore, soil physical conditions were more restrictive in Z2, in agreement with wheat yield and zone yield potential defined a priori, based on the harvest maps. Soil WIC in Z1 was significantly higher (30 %) than in Z2, in agreement with the results of TP and Mac which were also higher in Z1 in both soil layers. The correlation analysis of data of the two layers showed a positive relationship between wheat GY and the soil properties TP, SWC and WIC.