Spatial variability of soil physical properties as a result of different tillage systems / Variabilidade espacial das propriedades físicas do solo em função do preparo de solo

Geostatistical tools allow soil physical properties to be monitored in order to describe the pattern of spatial variability and indicates the places with higher variation. Therefore, the purpose of this study is to assess the spatial variability of physical properties of soils under direct seeding and conventional tillage, using a native forest soil profile as reference. The areas where the samples were collected belong to the Federal University of Viçosa in the municipality of Viçosa in the state of Minas Gerais (Brazil). The studied soil physical properties were density, hydraulic conductivity, total porosity and moisture. The GS+ was used in order to do spatial distribution analysis and semivariograms. The spatial dependence index was fixed by the parameters based on the relative size of the nugget effect and sill. It was considered as strong spatial dependence when ? 25%, moderate spatial dependence between 26% and 74% and weak spatial dependence ? 75%. The range achieved in this study was higher than the distances between the sample points, proving the spatial continuity of the studied parameters. The forest area presented the lowest value of moisture and the highest value of hydraulic conductivity. Direct seeding area presented the highest density value and the lowest hydraulic conductivity when compared to the other two areas. Conventional tillage area had the highest total porosity in comparison to the other areas due to greater soil inversion.  The spatial dependence indexes were classified as moderate for the variables soil density, total porosity and saturated hydraulic conductivity. 

Soil lead availability as a result of corrective-residue and organic matter uses

Nos últimos anos, a utilização de resíduos na agricultura têm sido incrementada devido ao crescimento populacional e industrial. Os resíduos da mineração de zinco e chumbo, conhecido comercialmente por calcário de Paracatú, têm sido utilizados em algumas regiões como alternativa para a correção da acidez dos solos. Esses resíduos, além do Ca e do Mg, apresentam metais pesados em sua constituição, principalmente Pb, Cd e Zn. Desta forma, este estudo tem como objetivos: (i) avaliar o comportamento do Pb aplicado no solo via resíduo-corretivo, sob efeito da variação do pH e da influência da matéria orgânica; (ii) avaliar os teores de Ca, Mg e Al trocáveis, fitodisponibilidade do Pb, Ca e Mg, em função das doses aplicadas do resíduo-corretivo e da matéria orgânica. Para o estudo dos teores de Pb, Ca, Mg e Al trocáveis e Pb total, foram instalados experimentos de incubação, sob condições controladas de laboratório, mantendo-se a umidade do solo a 70 % da capacidade de campo, em um esquema fatorial completo 5 X 3, correspondentes a 5 doses do resíduo-corretivo (0, 2, 4, 8 e 12 t ha-1), e a 3 de matéria orgânica (esterco bovino 0, 13 e 26 t ha-1). Os materiais foram incubados por 90 dias. Após este período, montou-se um experimento tipo "Neubauer" para avaliar-se a fitodisponibilidade do Pb, Ca e Mg. As maiores doses do resíduo-corretivo, associadas às maiores de matéria orgânica, reduziram o Pb trocável no solo e aumentou os teores de Ca e Mg trocáveis, porém, o teor de Pb absorvido foi maior para a maior dose do resíduo-corretivo, devido a provável liberação de exsudados de raízes solubilizando o metal, sem que houvesse influência da matéria orgânica, porém, a presença da matéria orgânica aumentou a absorção de Ca e de Mg e impediu a relativa elevação do pH no solo. Observou-se diminuição no teor de Al trocável no solo causada pelo aumento do pH, e pelo aumento da matéria orgânica do soloIn the last years, the use of residues in the agriculture has increased due to the population growth in the world. Lead and zinc mining residue, known commercially as lime of Paracatú has been used in some Brazilian agricultural regions an alternative to the correct soils acidity. This residue, besides Ca and Mg, presents heavy metals in its constitution, mainly Pb, Cd and Zn. This study has the objective: (i) of evaluating the behavior of Pb applied in the soil via corrective-residue, as affected by pH and organic matter and (it) the amount of exchangeable Ca, Mg and Al, and Pb, Ca and Mg phythoavailability. To evaluate the amounts of exchangeable Pb, Ca, Mg and Al and total Pb, incubation experiments were installed, under laboratory controlled conditions, maintaining the soil water content at approximately in the field capacity, in a fatorial 5 X 3 statistical design, corresponding to 5 doses of the corretive-residue (0,248 and 12 t ha-1), and 3 doses of organic matter (bovine manure O, 13 and 26 t ha-1). Materials were incubated by 90 days and after this period, the incubated soil samples were used in a "Neubauer" experiment type to evaluate Pb, Ca and Mg phythoavailability. The higher doses of the corrective-residue, associated to the amount of organic matter, reduced exchangeable Pb in the soil, and it increased the amount of exchangeable Ca and Mg, even thought the amounts of absorbed Pb have been greater for the higher corrective-residue doses. The presence of the organic matter increased the absorption of Ca and Mg and presented the relative elevation of the pH in the soil. For the soil exchangeable AI there was a decrease in its amount caused by the increase of the pH and the increase of the amount organic matter

Multinomial logistic regression and random forest classifiers in digital mapping of soil classes in Western Haiti

Digital soil mapping (DSM) has been increasingly used to provide quick and accurate spatial information to support decision-makers in agricultural and environmental planning programs. In this study, we used a DSM approach to map soils in western Haiti and compare the performance of the Multinomial Logistic Regression (MLR) with Random Forest (RF) to classify the soils. The study area of 4,300 km2 is mostly composed of diverse limestone rocks, alluvial deposits, and, to a lesser extent, basalt. A soil survey was conducted whereby soils were described and classified at 258 sites. Soil samples were collected and subjected to physical and chemical analyses. Recursive Feature Elimination (RFE) was used to select the most important covariates from auxiliary data, such as climate, lithology, and morphometric properties to describe the soil-landscape relationship. Mapping performance was assessed by the Kappa index and overall accuracy derived from a confusion matrix generated using a 5-fold cross validation process. In addition, an external mapping validation was carried out using an independent soil dataset. Accordingly, the soil dataset was split into 80 % and 20 % for training and validation of the models, respectively. No significant statistical difference (Z = 0.56< |1.96|) was found between maps generated with both classifiers (Kappa index 0.45 for MLR and 0.42 for RF). Based on the Kappa values, the classification performance can be characterized as moderate for both algorithms. Surprisingly, the RF classifier outperformed MLR in the validation process (Kappa values of 0.55 and 0.33, respectively). These results suggest a higher generalization ability of RF. However, no significant statistical difference (Z = 1.83< |1.96|) was observed. The soil map derived from RF indicated the occurrence of Leptosols (48.5 %), Gleysols (19.6 %), Chernozems (8 %), and Fluvisols (6.6 %) in most of the study area. The DSM approaches proved suitable for mapping soils in western Haiti and could be used in other parts of the country, thereby closing information gaps with regard to Haitian soils

Multinomial Logistic Regression and Random Forest Classifiers in Digital Mapping of Soil Classes in Western Haiti

ABSTRACT Digital soil mapping (DSM) has been increasingly used to provide quick and accurate spatial information to support decision-makers in agricultural and environmental planning programs. In this study, we used a DSM approach to map soils in western Haiti and compare the performance of the Multinomial Logistic Regression (MLR) with Random Forest (RF) to classify the soils. The study area of 4,300 km2 is mostly composed of diverse limestone rocks, alluvial deposits, and, to a lesser extent, basalt. A soil survey was conducted whereby soils were described and classified at 258 sites. Soil samples were collected and subjected to physical and chemical analyses. Recursive Feature Elimination (RFE) was used to select the most important covariates from auxiliary data, such as climate, lithology, and morphometric properties to describe the soil-landscape relationship. Mapping performance was assessed by the Kappa index and overall accuracy derived from a confusion matrix generated using a 5-fold cross validation process. In addition, an external mapping validation was carried out using an independent soil dataset. Accordingly, the soil dataset was split into 80 % and 20 % for training and validation of the models, respectively. No significant statistical difference (Z = 0.56< |1.96|) was found between maps generated with both classifiers (Kappa index 0.45 for MLR and 0.42 for RF). Based on the Kappa values, the classification performance can be characterized as moderate for both algorithms. Surprisingly, the RF classifier outperformed MLR in the validation process (Kappa values of 0.55 and 0.33, respectively). These results suggest a higher generalization ability of RF. However, no significant statistical difference (Z = 1.83< |1.96|) was observed. The soil map derived from RF indicated the occurrence of Leptosols (48.5 %), Gleysols (19.6 %), Chernozems (8 %), and Fluvisols (6.6 %) in most of the study area. The DSM approaches proved suitable for mapping soils in western Haiti and could be used in other parts of the country, thereby closing information gaps with regard to Haitian soils

Intervalo hídrico ótimo e densidade crítica de um Latossolo Amarelo coeso sob diferentes usos no ecossistema Tabuleiro Costeiro

RESUMO Os impactos do uso e do manejo na qualidade física do solo têm sido quantificados, utilizando-se o intervalo hídrico ótimo e a densidade crítica do solo. O objetivo deste trabalho foi determinar o intervalo hídrico ótimo (IHO) e a densidade crítica de um Latossolo Amarelo coeso, dos Tabuleiros Costeiros do Recôncavo da Bahia, submetido a diferentes usos e manejo do solo. Foram selecionadas três áreas, sobre solo coeso típico, submetidas aos seguintes usos e manejos: mata nativa (Mata Atlântica); pastagem de Brachiaria decumbens Stapf, em estado de degradação, e cana-de-açúcar, com subsolagem no sulco de plantio. Foram retiradas em cada área 40 amostras com estrutura indeformada, na porção central de cada horizonte (A e AB). Foram determinados nessas amostras, após serem submetidas a dez valores de tensão e pressão, a umidade, a resistência à penetração e a densidade do solo. Na área cultivada com cana, a coleta das amostras foi feita nas linhas de plantio, onde foi realizada a subsolagem. O intervalo hídrico ótimo do horizonte A, da mata, e do Ap, da cana-de-açúcar foram semelhantes e, ambos, maiores que na pastagem. Já no horizonte AB, o IHO da cana-de-açúcar foi maior que o da mata e, o desta, maior que o da pastagem. Os horizontes A e Ap apresentaram valores de densidade crítica maiores que os de AB para todos os usos avaliados. O uso que apresentou maior frequência de valores de densidade do solo acima da densidade crítica foi a pastagem

Intervalo hídrico ótimo e densidade crítica de um Latossolo Amarelo coeso sob diferentes usos no ecossistema Tabuleiro Costeiro

Os impactos do uso e do manejo na qualidade física do solo têm sido quantificados, utilizando-se o intervalo hídrico ótimo e a densidade crítica do solo. O objetivo deste trabalho foi determinar o intervalo hídrico ótimo (IHO) e a densidade crítica de um Latossolo Amarelo coeso, dos Tabuleiros Costeiros do Recôncavo da Bahia, submetido a diferentes usos e manejo do solo. Foram selecionadas três áreas, sobre solo coeso típico, submetidas aos seguintes usos e manejos: mata nativa (Mata Atlântica); pastagem de Brachiaria decumbens Stapf, em estado de degradação, e cana-de-açúcar, com subsolagem no sulco de plantio. Foram retiradas em cada área 40 amostras com estrutura indeformada, na porção central de cada horizonte (A e AB). Foram determinados nessas amostras, após serem submetidas a dez valores de tensão e pressão, a umidade, a resistência à penetração e a densidade do solo. Na área cultivada com cana, a coleta das amostras foi feita nas linhas de plantio, onde foi realizada a subsolagem. O intervalo hídrico ótimo do horizonte A, da mata, e do Ap, da cana-de-açúcar foram semelhantes e, ambos, maiores que na pastagem. Já no horizonte AB, o IHO da cana-de-açúcar foi maior que o da mata e, o desta, maior que o da pastagem. Os horizontes A e Ap apresentaram valores de densidade crítica maiores que os de AB para todos os usos avaliados. O uso que apresentou maior frequência de valores de densidade do solo acima da densidade crítica foi a pastagem.The impacts of the use and management on soil physical quality have been quantified using the least limiting water range and the critical density of the soil. The critical soil bulk density obtained by the least limiting water range (LL WR) assists in making decisions on the management conditions adopted or to be adopted in certain soil. This study aimed to determine the LL WR and the critical soil bulk density of a cohesive Oxisoil from Tabuleiros Costeiros of Reconcavo da Bahia subjected to different uses and soil management. We selected three areas on typical cohesive soil, subjected to the following uses and management: native forest (Mata Atlântica), Brachiaria decumbens Stapf, in a state of degradation, and sugar cane, with subsoiling at planting. In each area, 40 samples were taken with undisturbed structure in the central portion of each horizon (A and AB). In the area cultivated with sugarcane, the sample collection was done in the rows. The LL WR in the A horizon of the forest and the sugar cane were similar and both were greater than the pasture on the horizon AB. The LL WR for cane sugar was higher than the forest and this was higher than the pasture. Horizons A and Ap presented higher critical density values than AB for all evaluated uses. The use thatshowed values of bulk density greater than the critical density was pasture