Soybean-Maize Off-season Double Cropping System as Affected by Maize Intercropping with Ruzigrass and Nitrogen Rate

The soybean-maize off-season double cropping is the main grain production system in Brazil. Maize off-season is most commonly grown sole and without topdressing nitrogen (N) fertilization. When used, N fertilizer is commonly applied at rates lower than 100 kg ha- 1. This study aimed to assess the effects of N topdressing rates (0, 60, 120, and 180 kg ha- 1) applied to maize off-season grown sole or intercropped with Urochloa ruziziensis (Ruzigrass) on maize and soybean grain yields, straw production, partial N balance, and soybean oil and protein contents. The experiment was conducted in Londrina, Parana, Brazil, in the 2020/2021 and 2021/2022 growing seasons. At N rates above 120 kg ha- 1, intercropping with ruzigrass did not affect maize yield. Despite the low N use efficiency of maize off-season, a neutral N balance (i.e. equal to 0) was achieved with 130 kg N ha- 1 in 2020/2021. Considering the average of the two seasons and doses of N, intercropping of maize increased by 14.4% the straw production and by 8.34% the subsequent soybean yield. The N topdressing of sole maize led to an increase in the yield of soybean grown in succession (1.63 and 3.52 kg ha- 1 of grains for every 1 kg ha- 1 of N in 2020/2021 and 2021/2022, respectively). An increase in the N rate applied to maize increased soybean oil content (0.039 g kg-1 in 2020/2021 and 0.044 g kg-1 in 2021/2022 for each 1 kg N ha- 1) and decreased protein content (-0.085 g kg-1 in 2020/2021 and -0.088 g kg-1 in 2021/2022 for each 1 kg N ha- 1) in soybean grains.