Simultaneous determination of soil bulk density and water content: a heat pulse-based method

The effects of tillage and crop rotation on the soil carbon, the soil bulk density, the porosity and the soil water content were evaluated during the 6<sup>th</sup> season of an on-going field trial at the University of Fort Hare Farm (UFH), South Africa. Two tillage systems; conventional tillage (CT) and no-till and crop rotations; maize (Zea mays L.)-fallow-maize (MFM), maize-fallow-soybean (Glycine max L.) (MFS); maize-wheat (Triticum aestivum L.)-maize (MWM) and maize-wheat-soybean (MWS) were evaluated. The field experiment was a 2 × 4 factorial, laid out in a randomised complete design. The crop residues were retained for the no-till plots and incorporated for the CT plots, after each cropping season. No significant effects (P > 0.05) of the tillage and crop rotation on the bulk density were observed. However, the values ranged from 1.32 to1.37 g/cm<sup>3</sup>. Significant interaction effects of the tillage and crop rotation were observed on the soil porosity (P < 0.01) and the soil water content (P < 0.05). The porosity for the MFM and the MWS, was higher under the CT whereas for the MWM and the MWS, it was higher under the no-till. However, the greatest porosity was under the MWS. Whilst the no-till significantly increased (P < 0.05) the soil water content compared to the CT; the greatest soil water content was observed when the no-till was combined with the MWM rotations. The soil organic carbon (SOC) was increased more (P < 0.05) by the no-till than the CT, and the MFM consistently had the least SOC compared with the rest of the crop rotations, at all the sampling depths (0–5, 5–10 and 10–20 cm). The soil bulk density negatively correlated with the soil porosity and the soil water content, whereas the porosity positively correlated with the soil water content. The study concluded that the crop rotations, the MWM and the MWS under the no-till coupled with the residue retention improved the soil porosity and the soil water content levels the most.

Download Full-text

Effect of Biochar Application and Re-Application on Soil Bulk Density, Porosity, Saturated Hydraulic Conductivity, Water Content and Soil Water Availability in a Silty Loam Haplic Luvisol

Agronomy ◽

10.3390/agronomy10071005 ◽

2020 ◽

Vol 10 (7) ◽

pp. 1005 ◽

Cited By ~ 2

Author(s):

Lucia Toková ◽

Dušan Igaz ◽

Ján Horák ◽

Elena Aydin

Keyword(s):

Hydraulic Conductivity ◽

Water Content ◽

Bulk Density ◽

Soil Water ◽

Soil Water Content ◽

Soil Bulk Density ◽

Relative Increase ◽

Saturated Hydraulic Conductivity ◽

Soil Drought ◽

Silty Loam

Due to climate change the productive agricultural sectors have started to face various challenges, such as soil drought. Biochar is studied as a promising soil amendment. We studied the effect of a former biochar application (in 2014) and re-application (in 2018) on bulk density, porosity, saturated hydraulic conductivity, soil water content and selected soil water constants at the experimental site in Dolná Malanta (Slovakia) in 2019. Biochar was applied and re-applied at the rates of 0, 10 and 20 t ha−1. Nitrogen fertilizer was applied annually at application levels N0, N1 and N2. In 2019, these levels were represented by the doses of 0, 108 and 162 kg N ha−1, respectively. We found that biochar applied at 20 t ha−1 without fertilizer significantly reduced bulk density by 12% and increased porosity by 12%. During the dry period, a relative increase in soil water content was observed at all biochar treatments—the largest after re-application of biochar at a dose of 20 t ha−1 at all fertilization levels. The biochar application also significantly increased plant available water. We suppose that change in the soil structure following a biochar amendment was one of the main reasons of our observations.

Download Full-text

A new method for simultaneous measurement of soil bulk density and water content

International Journal of Radiation Applications and Instrumentation Part A Applied Radiation and Isotopes ◽

10.1016/0883-2889(86)90073-0 ◽

1986 ◽

Vol 37 (7) ◽

pp. 563-565 ◽

Cited By ~ 12

Author(s):

G.S. Mudahar ◽

H.S. Sahota

Keyword(s):

Water Content ◽

Bulk Density ◽

Simultaneous Measurement ◽

Soil Bulk Density ◽

New Method

Download Full-text

Laboratory and field evaluation of five soil water sensors

Canadian Journal of Soil Science ◽

10.4141/s03-097 ◽

2004 ◽

Vol 84 (4) ◽

pp. 431-438 ◽

Cited By ~ 24

Author(s):

Q. Huang ◽

O. O. Akinremi ◽

R. Sri Rajan ◽

P. Bullock

Keyword(s):

Water Content ◽

Bulk Density ◽

Soil Water ◽

Soil Water Content ◽

Soil Depth ◽

Field Evaluation ◽

Soil Bulk Density ◽

Laboratory Evaluation ◽

Engineering Sciences ◽

Probe Calibration

Accurate in situ determination of soil water content is important in many fields of agricultural, environmental, hydrological, and engineering sciences. As numerous soil water content sensors are available on the market today, the knowledge of their performance will aid users in the selection of appropriate sensors. The objectives of this study were to evaluate five soil water sensors in the laboratory and to determine if laboratory calibration is appropriate for the field. In this study, the performances of five sensors, including the Profile Probe™ (PP), ThetaProbe™ , Watermark™, Aqua-Tel™, and Aquaterr™ were compared in the laboratory. The PP and ThetaProbe™ were more accurate than the other soil water sensors, reproducing soil water content using factory recommended parameters. However, when PP was installed on a loamy sand in the field, the same soil that was used for the laboratory evaluation, it overestimated field soil water, especially at depth. Another laboratory experiment showed that soil water content readings from the PP were strongly influenced by soil bulk density. The higher the soil bulk density, the greater was the overestimation of soil water content. Two regression parameters, a0 and a1, which are used to convert the apparent dielectric constant to volumetric water content, were found to increase linearly with the soil bulk density in the range of 1.2 to 1.6 Mg m-3. Finally, the PP was calibrated in the field and a good calibration function was obtained with an r2 of 0.87 and RMSE of 2.7%. The values of a0 and a1 obtained in the field were different from factory recommended parameters (a0 = 2.4 versus 1.6 while a1 = 12.5 versus 8.4) and were independent of soil depth, bulk density, and texture. As such, individual field calibration will be necessary to obtain precise and accurate measurement of soil water content with this instrument. Key words: Soil water content, Profile Probe, calibration, soil water content sensor

Download Full-text

Incorporation of globally available datasets into the roving cosmic-ray neutron probe method for estimating field-scale soil water content

Hydrology and Earth System Sciences ◽

10.5194/hess-20-3859-2016 ◽

2016 ◽

Vol 20 (9) ◽

pp. 3859-3872 ◽

Cited By ~ 27

Author(s):

William Alexander Avery ◽

Catherine Finkenbiner ◽

Trenton E. Franz ◽

Tiejun Wang ◽

Anthony L. Nguy-Robertson ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Water Content ◽

Bulk Density ◽

Soil Water Content ◽

Cosmic Ray ◽

Soil Bulk Density ◽

Local Soil ◽

Calibration Parameters

Abstract. The need for accurate, real-time, reliable, and multi-scale soil water content (SWC) monitoring is critical for a multitude of scientific disciplines trying to understand and predict the Earth's terrestrial energy, water, and nutrient cycles. One promising technique to help meet this demand is fixed and roving cosmic-ray neutron probes (CRNPs). However, the relationship between observed low-energy neutrons and SWC is affected by local soil and vegetation calibration parameters. This effect may be accounted for by a calibration equation based on local soil type and the amount of vegetation. However, determining the calibration parameters for this equation is labor- and time-intensive, thus limiting the full potential of the roving CRNP in large surveys and long transects, or its use in novel environments. In this work, our objective is to develop and test the accuracy of globally available datasets (clay weight percent, soil bulk density, and soil organic carbon) to support the operability of the roving CRNP. Here, we develop a 1 km product of soil lattice water over the continental United States (CONUS) using a database of in situ calibration samples and globally available soil taxonomy and soil texture data. We then test the accuracy of the global dataset in the CONUS using comparisons from 61 in situ samples of clay percent (RMSE  =  5.45 wt %, R2  =  0.68), soil bulk density (RMSE  =  0.173 g cm−3, R2  =  0.203), and soil organic carbon (RMSE  =  1.47 wt %, R2  =  0.175). Next, we conduct an uncertainty analysis of the global soil calibration parameters using a Monte Carlo error propagation analysis (maximum RMSE ∼  0.035 cm3 cm−3 at a SWC  =  0.40 cm3 cm−3). In terms of vegetation, fast-growing crops (i.e., maize and soybeans), grasslands, and forests contribute to the CRNP signal primarily through the water within their biomass and this signal must be accounted for accurate estimation of SWC. We estimated the biomass water signal by using a vegetation index derived from MODIS imagery as a proxy for standing wet biomass (RMSE  <  1 kg m−2). Lastly, we make recommendations on the design and validation of future roving CRNP experiments.

Download Full-text

Effects of tillage on soil physical properties and root growth of maize in loam and clay in central China

Plant Soil and Environment ◽

10.17221/57/2013-pse ◽

2013 ◽

Vol 59 (No. 7) ◽

pp. 295-302 ◽

Cited By ~ 17

Author(s):

B. Ji ◽

Y. Zhao ◽

X. Mu ◽

K. Liu ◽

C. Li

Keyword(s):

Root Growth ◽

Water Content ◽

Bulk Density ◽

Root Length ◽

Root Length Density ◽

Penetration Resistance ◽

Soil Bulk Density ◽

Conventional Tillage ◽

Central China ◽

Deep Tillage

Subsoil compaction can result in unfavourable soil physical conditions and hinder the root growth of maize. The effects of deep tillage and conventional tillage on soil physical properties and root growth of maize were studied during 2010–2011 at two sites (loam at Hebi and clay at Luohe) in central China. The results showed that soil penetration resistance, bulk density, water content and root length density were significantly affected by tillage, soil depth and year. Deep tillage had lower penetration resistance and lower soil bulk density, but higher soil water content than conventional tillage across years and depths. Averaged over the whole soil profile, deep tillage not only significantly decreased penetration resistance and soil bulk density, but significantly increased soil water content and root length density on loam, while deep tillage only significantly increased the root length density on clay. We conclude that deep tillage on the loam is more suitable for the root growth of summer maize.

Download Full-text