Geostatistical analysis for soil moisture content under the no tillage cropping system

Abstract

Experiments in agriculture usually consider the topsoil properties to be uniform in space and, for this reason, often make inadequate use of the results. The objective of this study was to assess the variability for soil moisture content using geostatistical techniques. The experiment was carried out on a Rhodic Ferralsol (typic Haplorthox) in Campinas, SP, Brazil, in an area of 3.42 ha cultivated under the no tillage system, and the sampling was made in a grid of 102 points spaced 10 m × 20 m. Access tubes were inserted down to one meter at each evaluation point in order to measure soil moisture contents (cm 3 cm -3 ) at depths of 30, 60 and 90 cm with a neutron moisture gauge. Samplings were made between the months of August and September of 2003 and in January 2004. The soil moisture content for each sampling date was analyzed using classical statistics in order to appropriately describe the central tendency and dispersion on the data and then using geostatistics to describe the spatial variability. The comparison between the spatial variability for different samplings was made examining scaled semivariograms. Water content was mapped using interpolated values with punctual kriging. The semivariograms showed that, at the 60 cm depth, soil water content had moderate spatial dependence with ranges between 90 and 110 m. However, no spatial dependence was found for 30 and 90 cm depths in 2003. Sampling density was insufficient for an adequate characterization of the spatial variability of soil moisture contents at the 30 and 90 cm depths.

Spatial variability of soil moisture at typical alpine meadow and steppe sites in the Qinghai-Tibetan Plateau permafrost region

“…2). This result was consistent with several investigations which have noted that the coefficients of variation were low when the soil had higher water content (Robinson and Dean 1993;Grego et al 2006). Considering also the fact that soil moisture content in topsoil decreased gradually with permafrost degradation on the Qinghai-Tibetan Plateau, the CV of soil moisture content increased with permafrost degradation.…”

Soil resistance to penetration in cotton rows and interrows

“…Thus, the soil moisture characterization in the sampling points is important in the compaction mapping because, by itself, it is already a factor that interferes with the measured RP values and, therefore, with their spatial variability. This finding was predicted by Grego et al (2006), who reported that agricultural experiments usually consider soil moisture as uniform in space and, consequently, because of that, the results are frequently misinterpreted. This fact renders inadequate the simple comparison through a correlation analysis of the different RP maps in the same area; thus, comparative control points become essential in studies on this topic.…”

Padrão espaço-temporal da umidade volumétrica do solo em uma bacia hidrográfica com predominância de latossolos

“…Segundo Grego et al (2006), a maior variabilidade da estrutura de dependência espacial no período seco ocorre provavelmente devido ao processo de secagem do solo, e ocasionalmente podem aparecer algumas fissuras no solo, aumentando a aleatoriedade da variação espacial. Outro fato que deve ser destacado é que, quando a umidade do solo for baixa, outros fatores passam a influenciá-la, com maior participação na aleatoriedade da variação espacial.…”