Characterizing compaction variability with an electromagnetic induction sensor in a puddled paddy rice field

Paddy rice (Oryza sativa L.) fields are repeatedly puddled at water saturation to loosen the top soil and to form a uniformly compacted plow pan required to reduce losses of water and nutrients. In paddy growing conditions however, the non-invasive detection of compaction variation within the plow pan layer is challenging. This paper evaluates a proximal soil sensing based methodology to identify areas compacted by different intensities of puddling to support precise land preparation of paddy rice fields. Therefore, a 1.6-ha alluvial paddy field of silt loam texture (Aeric Haplaquepts) located in the Brahmaputra floodplain of Bangladesh was selected. Three areas within the field were variably puddled and characterized by soil properties and soil apparent electrical conductivity (ECa). The Floating Soil Sensing System (FLoSSY) employing the EM38 electromagnetic induction sensor was used to record the ECa of the soil for each of the puddling intensities. The effects of plow pan compaction on water percolation losses and paddy yield were assessed. The results show that the variably puddled areas had significant differences in soil bulk density which was linked to the soil penetration resistance. Spatial comparison of ECa data sets showed that the ECa values increased systematically under increased puddling. Sufficient soil compaction could be identified when percolation losses were significantly the lowest and paddy yield was significantly the highest. It was concluded that a non-invasive ECa survey using electromagnetic induction based soil sensing allowed the detection of soil heterogeneity linked to soil compaction caused by puddling, which offers an interesting potential for precision puddling and land preparation in paddy rice fields