Comparison of water consumption estimates for tropical and winter forages by FDR probes and weighing lysimeters

Abstract

Soil moisture determination is essential for a good use of available water resources. In this regard, the use of frequency domain reflectometry (FDR) probes has as advantages mobility and practicality in relation to lysimeters. The experiment was carried out between April and June 2016 at the Luiz de Queiroz College of Agriculture (ESALQ/USP), located in Piracicaba, SP at the geographical coordinates 22°42?14.6? S and 47°37?24.1? W and altitude of 546 m. This study aimed to assess these FDR probes to estimate water consumption in comparison to measurements by weighing lysimeters (ETcLys) and reference evapotranspiration (ETo) in Mombaça and Bermuda grass pastures under single cultivation and overseeded with oat and ryegrass. Soil moisture was assessed daily by FDR probes by estimating crop evapotranspiration (ETcFDR probe) from soil water balance calculation, which was correlated with ETcLys and ETo (Penman-Monteith, FAO 56). For all treatments, FDR probes presented the highest water consumptions when compared to the other two evapotranspiration methods, with accumulations of 126.5 and 125.6 mm for single and overseeded Mombaça grass, respectively. For Bermuda grass, water consumption was 123.4 mm in the single cultivation and 128.5 mm when overseeded. The method of estimating evapotranspiration by FDR probes showed good correlations with ETo and ETcLys.

Thermal time in nitrogen and boron application on irrigated Mombaça grass “Guinea grass”

“…A previous study from [15] reported a high correlation between the height of the plant and the thermal time. The authors observed that growing degree-day accumulation was slightly lower in a cut cycle during autumn/winter with 12 days more than spring/summer cut cycles.…”

“…In the Brazilian context, meat and leather became essential export goods around the end of century XVIII. Nowadays, the country is one of the main global players exporting to destinations like Russia and China [15].…”

A New Non-Inserted and Portable FDR Instrument for Measuring Surface Soil Water Content

“…Among them, monitoring SWC at a point scale (less than 0.01 cm 2 ) has advanced with various in-situ sensors, and the FDR method has been widely used [16]. The FDR method can measure the soil apparent dielectric constant using Water 2021, 13, 2712 2 of 8 the electromagnetic pulse principle, according to the frequency of the electromagnetic waves propagating in the soil [17][18][19][20]. Because soil dielectric content is related to the SWC, the dynamic SWC can be calculated using the relationship curve generated by the FDR method.…”