Ademir de Oliveira Ferreira

Desempenho de genótipos de milho cultivados com diferentes quantidades de palha de aveia-preta e doses de nitrogênio

The objective of this work was to assess the performance of corn (Zea maysL.) genotypes as affected by inputs of black oat (Avena strigosa Schreb.) residues applied on the soil surface and nitrogen fertilization under no-tillage system in a Typical Haplustox. The experiment was carried out in a complete randomized block design, arranged in split-split plots with three replicates. The main plots consisted of the amount of crop residues on the soil surface (no crop residue, 5.16 and 10.32 mg ha-1). The split plots were three corn genotypes, and the split-split plots were five nitrogen rates: 0, 60, 120, 180, and 240kg ha-1. An increase in the nitrogen rates decreased nitrogen deficiency and provided an adequate nitrogen supply for corn, under all the amounts of black oat residues. The corn genotypes grown with different amounts of black oat residues and nitrogen rates had different grain yield responses, use of mineralized nitrogen from crop residues, and root growth.

Alterações nos atributos físicos de um latossolo vermelho sob plantio direto induzidas por diferentes tipos de escarificadores e o rendimento da soja

Soil compaction at high intensity degrees is a hardly reversible process in the no-till system (NT), mainly in clayey soils. Generally, its occurrence in croplands is often irregular and restricted to areas with a previous history of pressures associated to intensive traffic of agricultural machineries. The purpose of this study was to investigate changes in soil physical properties of a red Oxisol with clayey texture (450 g kg-1) and soybean yield, caused by two site-specific chisels and conventional (random) chisel tillage. For this work, a 50.6 ha cropland area under long-term no-till and site-specific farming was selected in the Municipality of Victor Graeff, located in the plateau region of Rio Grande do Sul. The climate is a subtropical Cfa with annual rainfall ranging from 1500 to 1750 mm, average temperature of 20 °C, at 490 m asl. Based on three crop yield maps, the field was subdivided in three management zones with distinct yield potential where the soil physical properties were investigated. The following treatments were established in the low yield zone (LZ): (a) conventional chiseling at fixed soil depth (0.30 m) (CC); (b) site-specific chiseling with Fox® equipment at fixed soil depth (0.30 m) (SSCF); (c) site-specific chiseling with Fox® equipment at variable soil depth (0.10 to 0.30 m) based on maximum soil penetration resistance maps (SSCV); and (d) control without chiseling (CWC). The high yield zone (HZ) was used as a reference to evaluate treatment effects on soybean grain yield. Treatments were arranged in parallel strips of 100 x 20 m, in a randomized block design. In three evaluations, the soil water infiltration and bulk density, macro and microporosity and total porosity were evaluated in the layers 0.0-0.05, 0.05-0.10, 0.10-0.15 and 0.15-0.20 m. The results of the initial soil characterization showed higher bulk density and lower soil porosity in the 0.15-0.20 m layer, in the LZ in relation to HZ. Treatments showed an immediate increase of water infiltration after chiseling. The increase in water infiltration in treatments CC and SSCV was four times the water infiltration observed in the CWC. However, the chiseling effect, regardless of the chisel type, was ephemeral and after seven months there was a decrease of water infiltration in chiseled soil, similar to CWC. Of the chisel types, the SSCV was superior to CC by maintaining higher soil coverage and by increasing soybean yield. Although, in a crop season with high rainfall, no positive effects of chiseling on soybean yield were noticed, in relation to CWC.

Carbon balance and crop residue management in dynamic equilibrium under a no-till system in Campos Gerais

A adocao do sistema plantio direto e a manutencao dos residuos culturais na superficie do solo resultam, com o passar dos anos, em adicao de carbono (C) ao sistema, o que promove o sequestro de C e a mitigacao de emissoes de C-CO2 para a atmosfera. O objetivo deste trabalho foi avaliar a taxa de sequestro de C e a quantidade minima de residuos culturais necessaria para manter o equilibrio dinâmico (dC/dt = 0) de dois solos (Latossolo) com classes texturais diferentes. O delineamento experimental utilizado foi blocos ao acaso em arranjo fatorial 2 x 2 x 2. Os fatores analisados foram: (a) dois solos: Latossolo Vermelho distrofico tipico, com classe textural franco-argiloarenosa (LVTM), e Latossolo Vermelho distrofico tipico, com classe textural franco-argilosa (LVTA); (b) profundidades de amostragem: 0-0,05 e 0,05-0,20 m; e (c) epocas de amostragem (E1-outubro de 2007; E2-setembro de 2008). As lavouras onde foram coletadas as amostras vinham sendo manejadas em SPD por longo prazo (20 anos), com as seguintes rotacoes de cultura: trigo/soja/aveia-preta + ervilhaca/milho (LVTM) e trigo/milho/aveia-preta + ervilhaca/soja (LVTA). A taxa de sequestro anual de C foi de 0,83 e 0,76 Mg ha-1 para o LVTM e LVTA, respectivamente. A estimativa da quantidade minima de residuos culturais necessaria para manter o equilibrio dinâmico (dC/dt = 0) foi de 7,13 e 6,53 Mg ha-1 ano-1 para o LVTM e LVTA, respectivamente. A taxa de conversao de C em ambos os solos foi inferior a encontrada em outros estudos regionais, resultando numa elevada taxa de remanescente de palha na superficie do solo.

Particulate soil organic carbon and stratification ratio increases in response to crop residue decomposition under no-till

O aporte continuo de residuos na superficie do solo, conduzidos sob sistema plantio direto (SPD), leva ao acumulo de carbono (C). Os objetivos deste estudo foram avaliar a decomposicao dos residuos de aveia-preta (Avena strigosa Schreb.) e relacionar o efeito da decomposicao sobre o carbono orgânico do solo (COS), o carbono orgânico particulado (COP) e a taxa de estratificacao (TE) de C do solo em um Cambissolo Haplico sob SPD na regiao dos Campos Gerais - PR. As avaliacoes foram realizadas durante sete datas de coleta (t0 a t6) em 160 dias, em tres transectos, com seis pontos de coleta para cada um. A produtividade inicial de biomassa de aveia foi de 5,02 Mg ha-1, restando, apos 160 dias, 17,8 % da materia seca inicial. O conteudo de COT foi superior (38 %) na camada de 0-5 cm em comparacao a de 5-20 cm, variando, na primeira, de 27,56 a 30,07 g dm-3 (t0 para t6). A TE aumentou de 1,33 para 1,43 durante os 160 dias. Alem disso, houve aumento do estoque de COP nesse periodo, o qual variou de 8,1 a 10,7 Mg ha-1. O aumento de COS na camada de 0-5 cm, durante os 160 dias, ocorreu principalmente devido ao aumento do COP derivado da decomposicao dos residuos da aveia. A relacao linear entre o COS e o COP mostrou que 21 % do primeiro teve contribuicao da fracao mais labil. Os resultados sao um indicativo de que a entrada continua de residuos pode ser intensificada, como forma de aumentar o estoque e sequestro de C em solos sob SPD.

Nitrogen fertilizer (15N) leaching in a central pivot fertigated coffee crop

Nitrogen has a complex dynamics in the soil-plant-atmosphere system. N fertilizers are subject to chemical and microbial transformations in soils that can result in significant losses. Considering the cost of fertilizers, the adoption of good management practices like fertigation could improve the N use efficiency by crops. Water balances (WB) were applied to evaluate fertilizer N leaching using 15N labeled urea in west Bahia, Brazil. Three scenarios (2008/2009) were established: i) rainfall + irrigation the full year, ii) rainfall only; and iii) rainfall + irrigation only in the dry season. The water excess was considered equal to the deep drainage for the very flat area (runoff = 0) with a water table located several meters below soil surface (capillary rise = 0). The control volume for water balance calculations was the 0 - 1 m soil layer, considering that it involves the active root system. The water drained below 1 m was used to estimate fertilizer N leaching losses. WB calculations used the mathematic model of Penman-Monteith for evapotranspiration, considering the crop coefficient equal to unity. The high N application rate associated to the high rainfall plus irrigation was found to be the main cause for leaching, which values were 14.7 and 104.5 kg ha-1 for the rates 400 and 800 kg ha-1 of N, corresponding to 3.7 and 13.1 % of the applied fertilizer, respectively.

Relação de estratificação como indicador do sequestro de carbono em macroagregados de Latossolo sob plantio direto

The decrease in soil organic carbon (SOC) content in deeper layers indicates the occurrence of stratification between the surface layer and subsurface layer of soil due to continuous C addition by crop residues. The objective was to evaluate the change (delta) of stratification (RE) of carbon (C) as an indicator of C sequestration and soil total and particulate soil in macroaggregates of two soils (Typic Hapludox) with different textures, managed in no-tillage system. The tests were developed in completely randomized design twelve repetitions.Analyzed factors were: (a) two soils: Oxisol with medium texture and Oxisol with clay texture, (b) sampling depth: 0-5 and 5-20cm, (c) two sampling times (October 2007-T1, September 2008-T2). The results were submitted to variance analysis by program SISVAR 5.3, using the Tukey test at 5% significance. There was a significant linear relationship between the ∆ RE and carbon sequestration rate total macroaggregates Oxisol with medium texture (R²=0.78**) and Oxisol with clay texture (R²=0.81**) indicating that there was C sequestration confirming to be a sensitive indicator of the rate of C sequestration in soil macroaggregates.

Carbono do solo e atributos de fertilidade em resposta à calagem superficial em plantio direto

The objective of this work was to evaluate the effect of surface liming on the content of total organic carbon (TOC) of a soil under no‑tillage, and to identify the relationship between that content and other fertility attributes. The experiment was carried out on a medium‑textured Oxisol in Ponta Grossa, PR, Brazil. The treatments consisted of the application of 0 and 6 Mg ha -1 of dolomitic lime on soil surface in 1993 and of the reapplication of 0 and 3 Mg ha -1 in 2000, on plots with or without lime. The soil was collected in 2008, and the TOC content and fertility attributes were evaluated. Liming increased TOC content and base saturation, and decreased aluminium saturation. TOC content showed a linear relation with the effective cation exchange capacity and correlation with the levels of P and K. The potential CEC showed correlation with TOC, and the effective CEC with pH. Liming under no‑tillage, for a long period of time, increases TOC and total N contents.

VARIAÇÃO NA RESISTÊNCIA TÊNSIL DE AGREGADOS EM FUNÇÃO DO CONTEÚDO DE CARBONO EM DOIS SOLOS NA REGIÃO DOS CAMPOS GERAIS

Macroscale soil behavior depends on the mechanical properties of individual aggregates. Tensile strength (TS) of soil aggregates has been used as an indicator of management effect on soil quality as related to land use. The objective of this study was to evaluate the change of TS in relation to the variation of soil organic carbon (SOC) content in two soils (Typic Hapludox) with different textures under a long term no-tillage system. The experiment was arranged in a completely randomized 2 x 2 x 2 factorial design with 12 treatments. The analyzed factors were: (a) two soils: Oxisol with medium texture and Oxisol with clay loam texture, (b) two sampling layers: 0-5 and 5-20 cm, (c) two sampling dates (October 2007-T1, September 2008-T2). To determine TS, 1440 soil blocks were sampled. The TS and SOC contents were measured in 1920 aggregates for each sampling time. RT decreased as SOC content increased, with a greater impact on Oxisol with clay loam texture. The clay content affected the TS behavior, to which it was inversely proportional. The impact of SOC content on TS was greater in the soil surface (0-5 cm) than in the 5-20 cm layer.

No-till corn performance in response to P and fertilization modes

No-tillage systems provide soil changes that affect nutrient dynamics, hence, changing rates and forms of fertilizer application. This study aimed to evaluate the effect of phosphorus (P) and modes of nitrogen (N) and P application in corn under long-term no-tillage in a clayey Oxisol. Two experiments were carried out in the same experimental area and in the same year, in a randomized blocks design with four replications. In experiment I, the treatments consisted of five doses of phosphorus (0, 40, 80, 120 and 160 kg ha -1 of P 2 O 5 ) applied in the sowing furrow. In experiment II, the treatments consisted of the N and P application modes (topdressing, in the sowing furrow and control - without N and P). Experiment I evaluated the root length, P uptake and grain yield and, the Experiment II, the firing height and yield. The P rates provided linear increases in root length in the 0-10 cm layer , P uptake and grain production. The different modes of application provided differences in the firing height and corn yield. The control treatment (0 kg ha -1 of N and P) provided the highest firing height, superior than those of topdressing and application in the furrow , which were not significantly different. The topdress application of N and P provided an increase in corn yield that exceeded 16 and 42% of the application in the furrow and the control, respectively . Thus, the results confirmed that increasing rates of P 2 O 5 , in soil with high initial P content, influence positively corn production factors, but with little significant responses, and the topdress application of N and P on soil with high P content, without water restriction, provided increased grain yield in relation to the application in the furrow .

Nitrogen dynamics in soil management systems: II - mineralization and nitrification rates

Nitrogen is the main limiting factor in crop productivity and thereby soil management systems may change the mineralization and nitrification rates. In an experiment on soil management systems implemented in 1988 at the experimental station Fundacao ABC, Ponta Grossa, in the central South region of the State of Parana, inorganic N dynamics were examined to find a soil management strategy with a view to a sustainable environment. The objective of this study was to calculate the net mineralization and nitrification rates of soil N and the correlation with soil pH under management systems. Randomized complete block design was used, in split plots, in three replications. The following soil management systems (SMSs) were adopted in the plots: 1) conventional tillage (CT); 2) minimum tillage (MT); 3) no-tillage with chisel plow every three years (NTCH); and 4) continuous no-tillage (CNT). To evaluate the dynamics of inorganic N, samples were collected from sub-plots at different times (11 sampling times - T1 to T11). In the CNT and NTCH, the net mineralization rates were higher in the MT and CT systems in the 0-2.5 cm soil layer, while the nitrification rate was higher in the 2.5-5 cm layer. Soon after implementing the white oat management, the mineralization and nitrification rates in all soil layers were higher in the MT and CT systems. In the period of soybean development, in the 0-2.5 and 2.5-5 cm soil layers, the mineralization and nitrification rates were higher in the CNT and NTCH than in the MT and CT systems.