Fabricio Tomaz Ramos

Curvas de compactação de um Latossolo Vermelho-Amarelo: com e sem reúso de amostras

The soil compaction curve is determined by the Proctor test, normal or modified, widely used in civil engineering, however, its use has agronomic limitations, since the configuration of the curved part of the reuse of a single sample, disregarding the original soil structure. In this context, the objective of the study was to evaluate the configuration of the compaction curve based on with and without reuse of samples of an Oxissol, considering different management systems. While comparing the procedure with and without reuse of the sample, it was found that regardless of managements and layers evaluated, curves of soil compaction obtained were different. Furthermore, the procedure to reuse samples increases the density of the soil due to fragmentation of the aggregates and reorganization of its particles. Thus, for agricultural purposes, the compaction curve is suitably characterized without reuse of samples, since with this test, the aggregates of the sample, are not fully fractionated, both aggregates from soil under native vegetation or anthropized areas.

Correlation of the least limiting water range with soil physical attributes, nutrient levels and soybean yield

and micronutrients analyzed, and also with the land slope, compared the correlation with the soybean yield data. Therefore, nutritional analysis of the grains complemented by physical analysis of the soil can be used to identify nutritional imbalances that are not otherwise observable and thus, the LLWR can be useful for planning corrective actions regarding soil and crop management, based on measurement of the Bdcritical.

Humic Substances on Soybeans Grown Under Water Stress

ABSTRACT Hypothetically, humic substances (HSs) can improve the response of plants in sandy soils. The objective was to assess the effect of applying an organomineral fertilizer enriched with HSs on soybean plants grown with and without water stress. The experimental design was entirely randomized, in a greenhouse, in a 2 × 5 factorial setup (two moisture levels and five fertilizer doses: 0, 1, 2, 4, and 8 mL dm−3), for a total of 10 treatments, with eight repetitions, using as substrate a Psamment. The organomineral fertilizer was applied in the soil 21 days after plant emergence, and the water regimes were established 1 week thereafter. Plant height, shoot and root dry mass, mineral nutrition, and grain yield were evaluated. There was a positive response to the doses, with the most efficient one under water stress being 6.5 mL dm−3 and HSs favored the uptake of micronutrients.

Soil organic matter doubles the cation exchange capacity of tropical soil under no-till farming in Brazil: Effect of organic matter on soil cation exchange capacity

BACKGROUND Agricultural conservation practices increase total organic carbon storage in soil (TOCS ), a factor that is correlated with the physical and chemical qualities of highly weathered soils. In this study, we investigated the effects of TOCS on the physicochemical attributes of a Latosol after 10 years of no-till management in Mato Grosso State, Brazil. RESULTS TCOS was highly correlated (r = 0.92) with cation exchange capacity (CEC, pH = 7) and soil density. In the top 0.2 m soil layer, CEC increased by 25% with every 1.8 kg m-2 of stored organic carbon. Eliminating soil organic matter reduced CEC from an already low value of 8.40 cmolc kg-1 to 4.82 cmolc kg-1 . Humus is therefore clearly important for the formation of a negative liquid charge in a predominantly electropositive but clayey soil. CONCLUSION We confirmed that TOCS is an indicator related to the physiochemical characteristics of weathered soils. Furthermore, our results demonstrate that the increased carbon storage under non-tilling systems is essential for guaranteeing weathered soil fertility in tropical climates.

DEFINIÇÃO DE ZONAS DE MANEJOS A PARTIR DE ATRIBUTOS DO SOLO E PRODUTIVIDADE DE SOJA

Demarcating soil management zones can be useful, for instance, delimiting homogeneous areas and selecting attributes that are generally correlated with plant productivity, but doing so involves several different steps. The objective of this study was to identify the chemical and physical attributes of soil and soybean plants that explain crop productivity, in addition to suggesting and testing a methodological procedure for defining soil management zones. The procedure consisted of six steps: sample collection, data filtering, variable selection, interpolation, grouping, and evaluation of management zones. The samples were collected in an experimental area of 12.5 ha cultivated with soybean during the 2013/14 crop in Dystrophic Red Latosol, in Mato Grosso, Brazil. A total of 117 pairs of plant and soil samples were collected. Student’s t-test was used (α = 0.02) to verify that the number of samples was adequate for correlation analysis. Results showed that only the P and Mn content in the grains explained (based on R values) the variation in soybean grain productivity the area. Based on the interpolation of these contents by ordinary kriging, the fuzzy C-means algorithm was used to separate them into groups by similarity. Division into two groups was the best option, which could be differentiated by Mann–Whitney test (P < 0.05), resulting in a map with 10 management zones.

CARBONO ORGÂNICO E NITROGÊNIO TOTAL NAS FRAÇÕES DENSIMÉTRICAS DA MATÉRIA ORGÂNICA SOB DIFERENTES MANEJOS DO SOLO

The evaluation of land use and management by the measurement of soil organic matter and its fractions has gained attention since it helps in the understanding of the dynamics of their contribution to soil productivity, especially in tropical environments. This study was conducted in the municipality of Colorado do Oeste, state of Rondônia, Brazil and its aim was to determinethe quantity of organic carbon and total nitrogen in the light and heavy fractions of organic matter in the surface layers of a typic hapludalf under different land use systems: Native Forest: open evergreen forest, reference environment; Agroforestry System 1: teak (Tectona grandis LF) and kudzu (Pueraria montana); Agroforestry System 2: coffee (Coffea canephora), marandu palisade grass (Brachiaria brizantha cv. Marandu), “pinho cuiabano” (Parkia multijuga), teak and kudzu.; Agroforestry System 3: teak and cocoa (Theobroma cacao); Silvopasture System: teak, cocoa and marandu palisade grass; and Extensive Grazing System: marandu palisade grass. The experimental design was a randomized block in split-split plots (use systems versus soil layers of 0-0.05 and 0.05-0.10 m) with three replications. The results showed that relative to Native Forest, the Agroforestry System 2 had equaland greater amounts of organic carbon and total nitrogen respectively (light and heavy fractions) in the soil organic matter, with the light fraction being responsible for storage of approximately 45% and 70% of the organic carbon and total nitrogen, respectively. Therefore, the light densimetric fraction proved to be useful in the early identification of the general decline of the soil organic matter in the land use systems evaluated.