Assessing root penetration ability and resource capture from deeper soil layers

Rice crops commonly encounter zones of restricted root access, which can greatly reduce uptake of resources from deeper soil layers. As a result, yield can decrease with greater vulnerability to fluctuating weather conditions, especially under rainfed systems (Samson eta al 2002). Root access can be restricted by hardpan formation during cultivation, smearing during puddling, or sudden changes in soil texture with depth. These zones of higher soil strength and increased impedance to root elongation are not uniform across the field, so repeatable screens involving the placement of a paraffin wax/petroleum jelly layer in a soil column have been sued to identify promising lines (Yu et al 1995, Ray et al 1996, Babu et al 2001, Clark et al 2000, 2002). Field validation is still essential (Samson et al 2002).