Evaluating oat yield and economic profitability in integrated crop-livestock systems with Eucalyptus trees and varying nitrogen levels

Integrating trees into typical crop-livestock systems (ICLS) in South America, which are primarily characterized by the succession of annual pastures in winter and crops in summer, may enhance ecosystems functions. However, during the initial phase of tree introduction in ICLS, livestock may not be introduced due to the negative impact of animals on trees. Therefore, cash crop alternatives during winter are important in subtropical regions during this phase. Our study evaluates white oat (cv. Artemis) grain yield, its components (number of panicles, panicle length, number of spikelets per panicle, number of grains per panicle and 1000-grain weight), and economic profitability during two consecutive winters in systems along with (238 trees ha-1) and without eucalyptus trees, using two N levels (20 vs. 60 kg N ha-1). Oat was sown with 0.17 m line spacing, at seed rates of 70-100 kg ha-1 in winter 2020- 2021. The randomized complete block design included four treatments (2 systems × 2 N levels) and three replicates. We observed a negative impact of immature trees on panicle length (-6%), number of panicles per m² (-13%), and grain yield (-18%). An increase in N level did not guarantee an increase in oat grain yield or profit, regardless of the system. Economic losses were observed in all treatments (-107±16.3 U$ ha-1), due to low yield and market prices. Our results suggest that oat production is unsuitable in association with eucalyptus at a density of 238 trees ha-1, particularly in shallow soils where competition between trees and intercrops is more intense.