Hourly, Daily, and Monthly Soil Temperature Fluctuations in a Drought Tolerant Crop

Abstract

Soil temperature is a physical property of great agricultural importance in the soil-plant relationship and in energy exchange with the atmosphere. This study was conducted in a degraded Cambissolo Háplico Ta Eutrófico (Cambisol; Inceptisol) in the Irecê Identity Territory, Bahia, Brazil, aiming to evaluate the hourly, daily, and monthly fluctuations of soil temperature at depth, and soil thermal diffusivity in the castor bean crop. Hourly soil temperature data from February 4, 2014, to September 30, 2015, were obtained by using thermocouple sensors (copper-constantan) horizontally installed at 0.05, 0.10, and 0.20 m depths. Soil thermal diffusivity was estimated by phase and amplitude methods. Results showed that, for most days, the soil temperature was at the level recommended for castor bean. The maximum and minimum hourly and daily soil temperatures were observed in October and July, respectively, and the maximum soil temperature values occurred at 4 p. . Soil temperature variability is low, requiring few measurement points to estimate this factor in an area. The amplitude method led to soil thermal diffusivity values compatible with results in the literature. The absence of a relationship between thermal diffusivity and soil moisture was attributed to the clay-loam soil texture, predominance of micropores, and iron oxides allowing greater approximation to the soil particles, with high thermal diffusivity even under low soil moisture conditions.

Temperatura e umidade do solo em função do uso de cobertura morta no cultivo de milho

“…Desta maneira, em solos com menores quantidades de água, a difusividade térmica diminui e, assim, a transferência de calor entre ar e solo diminui, ocorrendo diminuição na amplitude térmica da temperatura do solo daquele momento (Roxy et al, 2014;Farias et al, 2018). No período em que ocorrem os maiores índices de umidade , estes propiciaram um resfriamento gradativo do solo ocasionando diferentes valores da temperatura do solo para cada profundidade, ao mesmo tempo, diminuindo o fluxo de energia no solo assim diminuindo a temperatura e ocorrendo menores amplitudes da temperatura do solo (Carneiro et al, 2014).…”

Importance of Diurnal Temperature Range (DTR) for predicting the temperature sensitivity of soil respiration

“…The dampening of the DTR with soil depth represents an interesting analogue for the expected pattern in air or surface temperatures forecasted in future climate scenarios. For instance, de Farias et al (31) assessed hourly, daily and monthly soil temperature from 5, 10, and 20 cm depths and found that, Possible mechanism whereby pre-incubating soils at diurnally oscillating temperatures results in similar respiration rates to pre-incubating constantly at the maximum daily temperature when respiration is measured at a given temperature. When soil is pre-incubated constantly at low temperature (Scenario A) extracellular depolymerisation is the rate limiting step for respiration at a given temperature.…”

“…However, the reasons for differential temperature sensitivity with depth also include confounding changes in biotic and abiotic conditions with soil depth. For example, the amplitude of DTR (31), texture, organic carbon (34), abundance and distribution of heterotrophic soil microbial groups (35), and enzyme activities (36) all vary with soil depth. Hicks Pries et al ( 22) measured the carbon flux through the whole soil profile in response to 4°C warming and observed similar temperature sensitivity down the profile.…”