Spring Oat Yields in Crop Rotation and Continuous Cropping: Reexamining the Need for Crop Protection When Growing Modern Varieties

Oats are regaining interest because of their nutritional and agro-environmental benefits. Hence, research into increasing oat productivity through sustainable agronomic practices has become increasingly important, especially as new varieties are developed and weather patterns become more unpredictable. The paper presents the effects of the cropping system (six-field crop rotation, continuous cropping since 1968), variety (two per six-year period), chemical crop protection (control, herbicide, herbicide plus fungicide), and study year, on spring oat grain yields for two six-year crop rotation cycles (2011–2016, 2017–2022) of a long-term experiment in Poland. The cropping system was the most influential factor. Studies confirmed that growing oats in crop rotation ensures higher productivity than continuous cropping and sustains satisfactory yields in Polish conditions despite yearly weather variability. The cultivated varieties differed in yield levels and degree of yield reduction in response to continuous oat cropping. Only during the 2011–2016 cycle was a decreasing trend in yields observed as continuous cropping was prolonged. Oats grown in crop rotation rarely benefited from chemical protection against weeds and pathogens. In continuous cropping, herbicide and fungicide treatments typically did not mitigate oat yield losses associated with the system, exacerbating them in the 2017–2022 cycle. Among the evaluated agronomic practices, the six-field crop rotation system proved the most reliable yield-enhancing strategy, whereas chemical protection rarely improved oat performance. In individual years, contradictory reactions of the two cultivated varieties to cropping systems and crop protection levels were often noted.