João Carlos de Souza Maia

Crescimento da parte aérea de plantas cultivadas em vaso, submetidas à irrigação subsuperficial e a diferentes graus de compactação de um Latossolo Vermelho-Escuro distrófico

Compaction is a process that can occur in soils managed inadequately, affecting crop growth and yield directly or indirectly. The shoot development was evaluated as a function of different degrees of subsoil compaction in soybean, corn, cotton, and Brachiaria brizantha plants grown in pots filled with soil material from a dystrophic Dark-Red Latosol, with water supply through subsurface irrigation. The experiment was carried out in screened greenhouse at the School of Agronomy and Veterinary Medicine of UFMT, in rigid PVC pots with 195 mm internal diameter in a completely randomized design in a 4 × 5 factorial scheme (four species and five soil densities - 1.0; 1.2; 1.4; and 1.5 Mg m-3). The water content in the soil/pot system was maintained above 60% of its maximum water retention capacity. At the end of the experiment, the plant height was measured and the plants cut at ground level; the leaf area estimated, and cotton, corn and soybean yield and the shoot dry matter evaluated. Soil densities above 1.4 Mg m-3 led to significant reduction in the development of shoot growth of cotton, corn, and soybean, while in Brachiaria brizantha plants the reduction was verified only at a density of 1.5 Mg m-3. Soybean presented the largest increment of the evaluated characteristics at a density of 1.2 Mg m-3. Brachiaria brizantha presented higher tolerance to compaction, whereas cotton plants were the most sensitive to effects of soil compaction. In general, the quadratic model adequately explained the growth of the studied plants as a function of soil compaction.

Uso do penetrômetro eletrônico na avaliação da resistência do solo cultivado com cana-de-açucar

This work aimed to evaluate soil resistance to penetration by means of a constant-speed electronic penetrograph, in two soils: a clay-textured Rhodic Haplustox and a loamy-textured Typic Haplustox, under mechanization and transportation processes in a sugarcane crop as a function of different numbers of cuts and different working depths. The data were statistically analyzed under two formats: (a) by means of conventional statistics, in which the treatment means were compared by Tukey test at 5% probability level, and (b) by geostatistical analysis, in which semivariance was used to produce models that would represent the spatial dependence of the data. The resistance to penetration results showed distinct behaviors for the studied depths, indicating that the weight of vehicles and machinery and the rotating wheel pressure caused alterations in the soil profile.

The use of two penetrometers in the evaluation of soil strength in a distrophic red latosol

Soil compaction is a problem that interferes in root growth and crop production. This study was conducted in the experimental station of Centro Federal de Educacao Tecnologica of Cuiaba (CEFET), in Santo Antonio do Leverger - MT, Brazil. The aim was to evaluate the cone index of the Distrophic Red Latosol in function of different water levels in two depths, by using a constant speed penetrometer and an impact one, correlating them with the soil density. The design was made of randomized blocks with eight treatments and five replications, arranged by split plots, with four bands of soil water content in the plots: range 1 (0.1883 to 0.2354 m3 m-3); range 2 (0.2355 to 0.2544 mm-3); range 3 (0.2545 to 0.2702 mmand range 4 (0.2703 to 0.3177 m3 m-3), and two depths of sampling like subplots (0.05 to 0.10 m and 0.15 to 0.20 m). From the results it was found that: i) the penetrometers showed significant positive correlation with the soil density; ii) the impact penetrometer presented the highest soil strength.

Penetrógrafo eletrônico automático

This paper presents the development of an automatic recording penetrometer, which operates at the touch of a button. It incorporates a data acquisition system, which can store data of 187 tests and has a serial PC interface. The test characterization such as dates, location (latitude and longitude) can be recorded as well. The maximum working depth may be set and the load cell calibration can be verified through a keyboard with 2 lines display. A speed variation error of < 5% compared to ASAE standard was verified for cone indices between 500 and 5,684 kPa. The equipment is compact, easy to handle and can realize one test every minute.

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.

Eficiência técnica na suinocultura: efeitos dos gastos com meio ambiente e da renúncia fiscal

Swine creation on an industrial scale results in intense production of dejections in the rural properties, consequences that reveal in the soil, air, fauna, flora and socio-economic environment; in this context, negative externalities can interact with other variable or economic actions, represented, for example, by the expenses with the conservation of the environment and, in particular, in Mato Grosso, by participation in the Program of Quality Farm, a state instrument of fiscal renunciation. After estimating the technical efficiency indices with data of ten properties situated in Mato Grosso from production functions, whose dependent variable is represented by the production of swine and the independent ones are the consumption of water, electricity and the amount of workers directly tied with the productive process. It was verified that the expenses with the conservation of the environment exert a positive effect on technical efficiency indices, while the participation in the Program of Quality Farm, differently from the previous variable, shows itself to be statistically not significant.

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.

Demanda tractiva en función de la resistencia mecánica del suelo a la penetración

In this study, empirical models were developed to determine the tensile force demanded by disc plows, harrows and planters fertilizers, as function of soil mechanical resistance to penetration. The mean of the referred resistance was determined until 25, 35 and 15 cm depths, according to the regulations for the disc plow, springs harrow and fertilizer seeder. The adjustment was verified based on the coefficient of determination, dispersion graphics, residual analysis and t test (Student). It was confirm the normality of the residuals and to establish intervals of confidence with 95% of probability. The estimated and experimentally obtained values did not differ significantly. It was concluded that the associated exponential functions presented appropriate precision and reliability to predict the traction force being considered the soil mechanical resistance to penetration and that the models can be a useful tool for planning and management of mechanized farming operations in soils with texture similar to those of this research.

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.