Soil sampling intensity and spatial distribution pattern of soils attributes and corn yield in no-tillage system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Spatial relationships between soil attributes and corn yield in no-tillage system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The use of scaled semivariograms to plan soil sampling in sugarcane fields

Spatial sampling designs used to characterize the spatial variability of soil attributes are crucial for science studies. Sample planning for the interpolation of a regionalized variable may use several criteria, which could be best selected from an estimated semivariogram from a previously established grid. The objective of this study was to optimize the procedure for scaled semivariogram use to plan soil sampling in sugarcane fields in the Alfisol and Oxisol regions of Jaboticabal Town in So Paulo State, Brazil. A scaled semivariogram for several soil chemical attributes was estimated from the data obtained from two grids positioned on a sugarcane field area, sampled at a depth of 0.0-0.5 m. The research showed that regular grids with uniform intervals did not express the real spatial variability of the soil attributes of Oxisols and Alfisols in the study area. The calculated final sampling density based on the scaled parameters of the semivariogram was one sample for each 2 ha in Area 1 (convex landscape) and one sample for each 1 ha in Area 2 (linear landscape), as indicated by SANOS 0.1 software. The combined use of the simulation programs and scaled semivariograms can be used to define sampling points. These results may help in soil fertility mapping and thereby improve nutrient management in sugarcane crops.

Variabilidade espacial de atributos do solo antes e após calagem e fosfatagem em doses variadas na cultura de cana-de-açúcar

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Current status, uncertainty and future needs in soil organic carbon monitoring

Increasing human demands on soil-derived ecosystem services requires reliable data on global soil resources for sustainable development. The soil organic carbon (SOC) pool is a key indicator of soil quality as it affects essential biological, chemical and physical soil functions such as nutrient cycling, pesticide and water retention, and soil structure maintenance. However, information on the SOC pool, and its temporal and spatial dynamics is unbalanced. Even in well-studied regions with a pronounced interest in environmental issues information on soil carbon (C) is inconsistent. Several activities for the compilation of global soil C data are under way. However, different approaches for soil sampling and chemical analyses make even regional comparisons highly uncertain. Often, the procedures used so far have not allowed the reliable estimation of the total SOC pool, partly because the available knowledge is focused on not clearly defined upper soil horizons and the contribution of subsoil to SOC stocks has been less considered. Even more difficult is quantifying SOC pool changes over time. SOC consists of variable amounts of labile and recalcitrant molecules of plant, and microbial and animal origin that are often operationally defined. A comprehensively active soil expert community needs to agree on protocols of soil surveying and lab procedures towards reliable SOC pool estimates. Already established long-term ecological research sites, where SOC changes are quantified and the underlying mechanisms are investigated, are potentially the backbones for regional, national, and international SOC monitoring programs. © 2013 Elsevier B.V.

Variabilidade espacial de atributos do solo e da produtividade de milho

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Atributos físicos do solo em áreas de plantio direto com e sem escarificação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Produtividade e compactação do solo em diferentes ciclos anuais da cultura de cana-de-açúcar

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Optimization of the sampling scheme for maps of physical and chemical properties estimated by kriging

The sampling scheme is essential in the investigation of the spatial variability of soil properties in Soil Science studies. The high costs of sampling schemes optimized with additional sampling points for each physical and chemical soil property, prevent their use in precision agriculture. The purpose of this study was to obtain an optimal sampling scheme for physical and chemical property sets and investigate its effect on the quality of soil sampling. Soil was sampled on a 42-ha area, with 206 geo-referenced points arranged in a regular grid spaced 50 m from each other, in a depth range of 0.00-0.20 m. In order to obtain an optimal sampling scheme for every physical and chemical property, a sample grid, a medium-scale variogram and the extended Spatial Simulated Annealing (SSA) method were used to minimize kriging variance. The optimization procedure was validated by constructing maps of relative improvement comparing the sample configuration before and after the process. A greater concentration of recommended points in specific areas (NW-SE direction) was observed, which also reflects a greater estimate variance at these locations. The addition of optimal samples, for specific regions, increased the accuracy up to 2 % for chemical and 1 % for physical properties. The use of a sample grid and medium-scale variogram, as previous information for the conception of additional sampling schemes, was very promising to determine the locations of these additional points for all physical and chemical soil properties, enhancing the accuracy of kriging estimates of the physical-chemical properties.

Sampling density and proportion for the characterization of the variability of Oxisol attributes on different materials

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Organic phosphorus fractions in soil fertilized with cattle manure

Inorganic phosphorus (Pi) usually controls the P availability in tropical soils, but the contribution of organic P (Po) should not be neglected, mainly in systems with low P input or management systems that promote organic matter accumulation. The aims of this study were to evaluate the changes in the Po fractions over time in soil fertilized and not fertilized with cattle manure and to correlate Po forms with available P extracted by anion exchange resin. The experiment was carried out under field conditions, in a sandy-clay loam Haplustox. The experimental design was a 2 x 9 randomized complete block factorial design, in which the first factor was manure application (20 t ha(-1)) or absence, and the second the soil sampling times (3, 7, 14, 21, 28, 49, 70, 91, and 112 days) after manure incorporation. Labile, moderately labile and non-labile Po fractions were determined in the soil material of each sampling. Manure fertilization increased the Po levels in the moderately labile and non-labile fractions and the total organic P, but did not affect the Po fraction proportions in relation to total organic P. On average, 5.1 % of total Po was in the labile, 44.4 % in the moderately labile and 50.5 % in the non-labile fractions. Available P (resin P) was more affected by the manure soluble Pi rather than by the labile Po forms. The labile and non-labile Po fractions varied randomly with no defined trend in relation to the samplings; for this reason, the data did not fit any mathematical model.

Capacidade de suporte de carga e densidade do solo em áreas de plantio direto com e sem escarificação

No-till has been used in many different regions of Brazil. However, depending on the location and intensity of machinery traffic, this has caused the problem of soil compaction and many producers are scarification the land as a solution to break through the layer that is restricting plant growth. The objective of this study was to evaluate the influence of scarification (0.30 m) in the physical properties of a dystrophic Alfisol comparing the results with a non-scarified contiguous area; both were previously conducted using no-till. The density and pressure of pre-consolidation were sampled in two areas of non-tillage, one with chiseling (PDCE) and one without (PDSE) by using the UMAS -Mobile Soil Sampling Unit built by NEMPA – Agroforestry Machinery and Tire Testing Center/FCA / UNESP, Botucatu ,SP. The UMAS is equipped with GPS which allows the samples to be georeferenced. The samples were evaluated in the laboratory through the collection of standardized rings. Sampling was performed at a dimension of 15 x 50 m, with 160 rings being collected. The samples containing rings which were used in determining the density and also for testing the consolidometer, were collected from the layers of 0 to 0.10 m, 0.10 to 0.20 m, 0.20 to 0.30 0.30 to I 0.40 m. For the odometer test the undisturbed sample rings were used in obtaining the load bearing capacity of the soil. The soil management adopted provided a decrease in soil density using no-tillage with scarification depths from 0.0 to 0.10 0.10 to 0.20 m while the other depths did not show any decrease. The pre-consolidation pressure in combination with soil aggregate resistance identified that the management process PDCE within all layers was subjected to water content reliability regarding a greater load bearing capacity of the soil. For the PDSE that only was possible in the 0 to 0.10 m, showing greater consolidation of this layer.

Forma da paisagem como critério para otimização amostral de latossolos sob cultivo de cana-de-açúcar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estimativa da erodibilidade do solo para fins conservacionistas na microbacia córrego do Tijuco, SP

The soil erodibility factor is represented by the integrated effect of processes that regulate the water infiltration, soil resistance and the transport of soil particles. Therefore, this study had as objective to estimate the soil erodibility in the Corrego do Tijuco watershed, São Paulo State, Brazil, for guiding farmers in decision making for application of techniques for soil conservation. The soil samples were collected in a regular spacing of 500 m, resulting in a total of 310 points in a 0-20.0 m depth in an area of approximately 8,000 ha. For the estimation of soil erodibility (K) was applied a mathematical model which takes into account the soil organic matter content, the sand and silt size fractions, the soil permeability, and the particle mean diameter for each point of soil sampling. Estimated values greater than 0.040 Mg ha h ha(-1) MJ(-1) mm(-1) were considered very high for this factor. In areas with greater degree of erodibility occurs the Argisols order predominance, that shows high susceptibility to the development of interrill erosion due to its remarkable performance in relation to textural gradient, thereby, the interrill erosion rates can be very intensive due to rapid saturation of upper horizon, increasing the erosion process. At the Latosols (Oxisols) areas were also observed high soil erodibility values that under inappropriate conditions of soil occupation, concentrating runoff of rain water, leading to appear deep gullies.

Lodo de esgoto como fonte de nitrogênio: concentração no perfil do solo e em plantas de milho

O objetivo deste trabalho foi avaliar a concentração de nitrogênio em plantas de milho e ao longo do perfil de um Latossolo Vermelho eutroférrico submetido a doses de lodo de esgoto e fertilizante mineral. O experimento foi instalado em delineamento experimental em blocos casualizados com 4 tratamentos (0,0; 55,0; 110,0 e 167,5 Mg.ha-1 de lodo de esgoto em doses acumuladas) e 5 repetições para um período de avaliação de 1 ano. A amostragem de solo foi realizada aos 60 dias após a emergência (d.a.e.) das plantas nas profundidades 0,0-0,1, 0,1-0,2, 0,2-0,4, 0,4-0,6, 0,6-0,8 e 0,8-1,0 m. Também aos 60, 80 e 128 d.a.e. foram coletadas, respectivamente, folha diagnose, planta inteira e grão. As maiores doses de lodo de esgoto proporcionaram maiores quantidades de nitrogênio no solo. O nitrogênio do solo, após a profundidade de 0,6 m, não diferiu entre as camadas avaliadas. Quanto maior a dose de lodo de esgoto, menor a proporção de nitrogênio em profundidade.