Measurement of Volumetric Water Content by Gravimetric and Time Domain Reflectometry Methods at Field Experiment with Biochar and N Fertilizer

Abstract

There are many methods used for soil water content measurement which we can divide into direct gravimetric methods from using soil samples or indirect methods that are based on the measurement of another soil property which is dependent on soil moisture. The paper presents the findings of volumetric water content measurements with gravimetric and time domain reflectometry (TDR) methods. We focused on four variants in the field experiment in Dolná Malanta (Slovakia): control variant (B0+N0), variant with biochar at dose 20 t.ha−1 without N fertilizer (B20+N0), variant with biochar 20 t.ha−1 and N fertilizer 160 kg.ha−1 (B20+N160) and variant with biochar 20 t.ha−1 and N fertilizer 240 kg.ha−1 (B20+N240). TDR is nowadays a well-established dielectric technique to measure volumetric water content; however, its accuracy is influenced by high concentration of salts in soil. In this paper, we evaluated the effect of added N fertilizer on the measuring accuracy of HydroSense II device that is operating under the TDR principle.

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

“…The research was conducted at the experimental site of the Slovak University of Agriculture in Nitra located in Dolná Malanta approximately 5 km north-east from the city of Nitra (Slovakia) (48 • 19 00" N; 18 • 09 00" E) (Figure 1). The continuous biochar field experiment was established in 2014 to examine the effect of biochar application on greenhouse gas emissions [13,36], soil quality [14,[37][38][39][40][41][42][43][44] and crop yields [34,45,46]. The soil was classified as Haplic Luvisol according to World Reference Base [47] with the initial soil organic carbon content of 9.13 g kg −1 , pH of 5.71 (slightly acidic) and silty loam soil texture.…”

“…In total, 1755 soil water content measurements were obtained for 13 sampling days in 2019. Calibration of measurements was performed according to our previously published findings [44]. Past calibration equations were derived for some treatments of the field experiment using the gravimetric method.…”

“…This method generally serves as a standard method [57,58] for the calibration of soil moisture sensors. Using the calibration equations according to Toková et al [44], further equations were calculated for remaining treatments of the field experiment. These equations are summarized in Table 4.…”

The importance of initial application and reapplication of biochar in the context of soil structure improvement

“…Biochar is a solid, carbon-rich product and is formed during the thermochemical decomposition of various types of organic materials (Shackley et al, 2016). Application of biochar is reported to improve soil chemical (Juriga and Šimanský, 2019;Liang et al 2006), physical (Balashov et al, 2019;Igaz et al, 2018;Toková et al, 2019;Vítková et al, 2017) and biological properties (Lehmann et al, 2011). Biochar also can increase crop yields (Kondrlová et al, 2017), reduce GHG emissions and increase soil carbon sequestration (Lehmann et al, 2006;Šimanský et al, 2018b).…”