Alterações da temperatura em solo coberto de palha de aveia-preta

The objective of this work was to evaluate the effect of different amounts of black oat (Avena strigosa) straw covering soil surface on soil temperature at different depths. The treatments consisted of 0, 3, 6, and 9 Mg ha-1 straw. Soil temperature was measured hourly by a thermocouple inserted at different depths (0, 5, 15, 30, and 50 cm) and was used to adjust an equation correlating the temperature of covered soil with that of bare soil. With the correlations, it was possible to observe a point value of temperature (inversion temperature of straw effect), below which the presence of straw acts positively on the maintenance of soil temperature and above which the presence of straw acts negatively on soil heating.O objetivo deste trabalho foi avaliar o efeito de diferentes quantidades de palha de aveia-preta (Avena strigosa) em cobertura do solo sobre a temperatura do solo em diferentes profundidades. Os tratamentos consistiram de 0, 3, 6 e 9 Mg ha-1 de palha. A temperatura do solo foi medida a cada hora por meio de termopares inseridos em diferentes profundidades (0, 5, 15, 30 e 50 cm) e usada para ajustar uma equação que correlaciona a temperatura do solo coberto com a do solo descoberto. A partir dessas correlações, foi possível observar um valor pontual de temperatura (temperatura de inversão do efeito da palha), abaixo do qual a presença de palha atua positivamente na manutenção da temperatura do solo e acima do qual a presença de palha atua negativamente no aquecimento do solo

Qualidade da água de poços tubulares utilizada no abastecimento: escolas do campo na Região Central do Rio Grande do Sul

O presente estudo visou realizar um diagnóstico da qualidade da água fornecida a comunidade escolar de 22 escolas rurais, localizadas em quatro municípios da Região Central do estado do Rio Grande do Sul. Foram considerados 1.716 registros laboratoriais que integram 13 parâmetros de qualidade da água. Entre eles: potencial hidrogeniônico, condutividade elétrica, cloreto, cobre, fluoreto, nitrato, zinco, dureza total, cor aparente, turbidez, sólidos dissolvidos totais, coliformes totais e coliformes termotolerantes - Escherichia coli. Verificou-se que alguns parâmetros de qualidade da água se encontraram com valores inadequados ao consumo humano, em diferentes poços, assim, necessitando de um conjunto de práticas de melhoria da qualidade da água

Estimating lateral flow in double ring infiltrometer measurements

The steady infiltration rate of soil profiles is commonly determined for irrigation and soil conservation planning, but the divergence of methods reduces the reliability of measurements. In this study, the steady infiltration rate measured with a double ring infiltrometer (i sr‐dri ) in different layers of a soil profile was compared between layers and with the steady vertical saturated flow rate estimated by the Richards equation (i sr‐hy ). The measurements of i sr‐dri at the top of the A, E, and Bt horizons were compared to each other and also compared with the i sr‐hy to detect the occurrence of lateral flow in double ring infiltrometer measurements. The i sr‐dri in the A horizon (236 mm h -1 ) was around 10 times higher than in the Bt horizon (20 mm h -1 ), which implies in a lateral flow of almost 90 % in the surface horizon. The occurrence of lateral flow in double ring infiltrometer measurements was also shown by comparing i sr‐dri with the vertical saturated flow rate estimated with the Richards equation, i sr‐hy . The main conclusion is that i sr‐dri measured at the soil surface overestimates the steady infiltration rate of soil profiles when underlying horizons are less permeable and more restrictive to water flow. In these cases, the use of an effective saturated hydraulic conductivity of the soil profile would imply inaccurate planning of drainage, irrigation, and soil conservation designs

Terracing increases soil available water to plants in no-tillage

Several management practices can increase soil water storage capacity, but their effectiveness to minimize the adverse effects of drought depends on their potential to increase the soil available water to plants. Terracing is an effective option to increase soil water storage, but its effect on available water to plants in no-tillage system is still a knowledge gap. In this study, we monitored soil water content at eight layers down to 1.6 m in two zero-order paired catchments for 16 months. Presence of five broad-based terraces in one of the catchments was the main difference between the two. Water availability to plants over time was expressed as a fraction of available water capacity (FAW). Positive differences of FAW between the terraced and non-terraced catchments were noticed over periods of rainfall shortage, but they were barely perceptible in periods of abundant rainfall. Over the 16 months, the frequency of FAW higher than 0.75 was between 46 and 50 % in the non-terraced catchment, and between 67 and 75 % in the terraced catchment. This benefit of terracing is more noticeable in thicker upper-section of the soil profile evaluated and with greater number of terraces upstream from the point of observation. We concluded that terracing in no-tillage turn excess rainfall into noticeable positive increases in available water to plants in the following periods of rainfall shortage

Shaking settings to reduce the breakdown of Entisol fragile particles in texture analysis

Finding the proper shaking setting to ensure total particle dispersion without altering the content of sand, silt and clay in soils composed of fragile particles such as saprolite fragments is still a research gap. This study aimed to identify the best shaking setting to optimize particle dispersion and minimize particle change in samples of Entisol (Neossolos). Samples were dispersed using an electric mixer at 12,000 rpm for 5, 15, 30 and 60 min, a horizontal shaker at 150 cycles min -1 for 1, 2, 4, 8 and 16 h with and without the use of nylon spheres, and an ultrasonic shaker at 70 and 110 J mL -1 for approximately 20 and 30 min, respectively. All the treatments affected particle distribution. Coarse sand reduced up to 14 % and clay content increased up to 18 % with the horizontal shaker with nylon spheres and the electric mixer. These changes were attributed to the breakdown of saprolite fragments, which represented around 1/3 of the coarse sand. Our results showed that the best setting was the horizontal shaker at 150 cycles min -1 for 1 to 2 h without using nylon spheres. This option allowed optimizing particle dispersion and minimizing changes in particle size distribution

Transpiration Reduction Factor and Soybean Yield in Low Land Soil with Ridge and Chiseling

<div><p>ABSTRACT Water and oxygen deficiencies in the soybean crop cultivated on lowland soils are an important topic of research. The objective of this study was to investigate changes in water and oxygen supply and soybean yield caused by soil management in lowland soils. A soybean crop was grown under four soil conditions: no-tillage (NT), chiseling (CH), ridge tillage on no-tillage (NTR), and ridge tillage on chiseling (CHR). Soil bulk density, total porosity, macro- and microporosity, air permeability, and saturated hydraulic conductivity were measured at 0.05, 0.15, 0.25, and 0.35 m depths. Soil volumetric water content was monitored at the same depths every 30 min during the soybean cycle. The transpiration coefficient was calculated from volumetric water content to express both water and oxygen deficiency. The groundwater level was monitored throughout the soybean cycle. Plant performance was evaluated by measuring plant population, shoot dry matter, yield, and taproot depth. Soil porosity, air permeability, and saturated hydraulic conductivity were most improved in CH and CHR, and less in NTR. Nonetheless, expected improvement in soil aeration in CH, CHR, and NTR was eliminated when the water table raised to near the soil surface. The transpiration coefficient indicated that CH decreased oxygen deficiency, but caused little water deficit. The CH also provided the highest yield (4,610 kg ha-1), which was not surpassed by the addition of ridge tillage on chiseled soil (CHR) (4,001 kg ha-1). The lowest yields were observed in NT (2,842 kg ha-1), and NTR (3,565 kg ha-1), in which oxygen deficiency was more severe. Lower oxygen deficiency for soybean in chiseled lowland soil is regulated by the water table. As the transpiration coefficient is dependent on all the processes determining soil water dynamics, it is more informative than soil structural properties regarding water and oxygen deficiency in soybean in lowland soil.</p></div

Temperature changes in soil covered by black oat straw

<div><p>Abstract: The objective of this work was to evaluate the effect of different amounts of black oat (Avena strigosa) straw covering soil surface on soil temperature at different depths. The treatments consisted of 0, 3, 6, and 9 Mg ha-1 straw. Soil temperature was measured hourly by a thermocouple inserted at different depths (0, 5, 15, 30, and 50 cm) and was used to adjust an equation correlating the temperature of covered soil with that of bare soil. With the correlations, it was possible to observe a point value of temperature (inversion temperature of straw effect), below which the presence of straw acts positively on the maintenance of soil temperature and above which the presence of straw acts negatively on soil heating.</p></div