Using Rainfall Simulators to Assess New Soil Protection Technologies

Our aim is to compile a methodology for verifying the soil protection effect of various crop cultivation technologies directly in operating conditions and to design and verify such methods of anti erosion protection together with farmers. The methods should be effective, environmentally friendly, and should not endanger the competitiveness of Czech agriculture. The CTU in Prague, together with the Research Institute for Soil and Water Conservation, has been using a rainfall simulator of 8m plot length (16 m2) for soil loss ratio and C-factor estimation since 2015, putting together a database of several hundreds of representative measurements (Stasek et al., 2023). To be able to test different technologies directly at fields in different field conditions, the simulator construction was modified to portable construction of 1m2 plot size. During 2023 both simulators were compared in the field, especially in cultivated fallow conditions, but also for initial crop stages. Technically to be able to operate in field and use limited amount of water while reaching high enough kinetic energy and rainfall uniformity, the construction uses overflow box capturing and recycling water that would be sprayed outside of the measured plot (Kavka et al., 2018). One of the advantages of the 8m plot length was that several nozzles with overlapping spraying cones still reach higher kinetic energies than a single-nozzle construction. What we investigated is that rill evolution is visible in 8 m long plot in fallow conditions, while for 1 m plot length, mostly only interril erosion is prevailing.  For 1 mm.minute-1 rainfall intensity both constructions reach similar runoff rates after ca 10 minutes of the simulation when starting with fully saturated conditions (0.9 litre per minute for large simulator, 0.85 litre per minute for small simulator using the same nozzle type). On the other hand, the sediment transport values at smaller plot size reach only 63% on average (0.0110 versus 0.0175 kg.minute-1). As expected, the variability of sediment transport is higher in between replications on the smaller plot size, due to the greater influence of small surface irregularities, or due to the greater influence of preferential pathways in both surface runoff and infiltration. The contribution presents ways of standardising smaller rainfall simulator data using previous datasets obtained by larger-scale simulations. Data were obtained from the NAZV QK22010261, Mobility 8J23DE006, H2020Tudi No 101000224, and by the CTU Grant Agency in Prague No. SGS23/155/OHK1/3T/11.