The application of fertilizers as a topdressing in maize raises serious concerns because too much fertilizer is retained in the upper leaves, causing burning to the tissues. In this study, the use of a controlled-release and a stabilized fertilizer (with 3, 4-dimethylpyrazole phosphate) was compared with the application of a conventional fertilizer split into two equivalent applications in a forage maize-oats cropping system. In maize, 100 and 200 kg N ha−1 of different fertilizers were used in addition to an unfertilized control. The oat crop was not fertilized, since it served only as a winter catch crop. Maize dry matter (DM) yield increased significantly with N rate only in 2019, being the second growing season, with the control showing the lowest average value (7.1 t ha−1). The most fertilized treatments (200 kg N ha−1) gave the highest DM yields, ranging between 14.2 and 16.7 t ha−1, but with no significant differences between them. Oats had a relevant role as a catch crop recovering residual N that could have potentially been lost from the soil. Stalk nitrate concentration proved to be very sensitive to N fertilization (varying from 150.4 to 1945.6 mg kg−1 in 2018 and 494.9 to 1574.9 mg kg−1 in 2019), showing great potential as a tool of N management. These three fertilization strategies seem to be valid options that farmers can consider, after incorporating technical-economic information related to equipment suitability and the price of fertilizers.
The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and European Regional
Development Fund (ERDF) under Programme PT2020 for financial support to CIMO (UIDB/00690/2020).
