Estimating the curve number for conventional and soil conservation technologies using a rainfall simulator

The aim of the article was to verify the curve number (CN) values given in the National Engineering Handbook (NEH) methodology, whether they really correspond to all wide-row crops. The tested crops were maize, hops and potatoes grown using conventional and soil conservation technologies. All these crops are classified as wide-row crops, but they are very different in terms of the cultivation process. The basis for the calculation of our CN values were field measurements carried out using a rainfall simulator within the time span from 2014 to 2020 on the soil corresponding to hydrological group B in two repetitions: naturally dry soil corresponding to an ARC II curve and saturated soil corresponding to an ARC III curve. The results show that our calculated CN values for the conventional cultivation of wide-row crops are, in principle, the same as the CN values given in the NEH methodology. On the contrary, a certain difference was recorded in the soil conservation technologies with plant residues on the surface, in the case of naturally dry soil. Lower CN values are clearly seen in the technologies of no-till maize, strip-till maize and hops with catch crops, which was confirmed by the statistical tests, probably due to the interception and surface roughness.