HIGHLIGHTS:
Intercropping of maize with ruzigrass increases straw yield, nitrogen cycling, and soybean yield in successive crops.
Nitrogen fertilization of second-crop maize increases the yield of soybean grown in succession.
An increase in plant density of second-crop maize increases straw yield but not soybean yield.
ABSTRACT
Second-crop maize-ruzigrass (Urochloa ruziziensis) intercropping, nitrogen (N) fertilization, and high maize plant densities enhance biomass production and N cycling, which may favor soybean growth and yield in the following season. This study aimed to assess the effects of second-crop maize-ruzigrass intercropping, N top dressing, and maize plant density on straw production in autumn/winter, N cycling, and agronomic performance of soybean crops grown in succession. Field experiments were installed in the 2018/2019 and 2019/2020 seasons using a randomized complete block design with split-split plots and four replications. The following factors were investigated: cropping system (sole maize and maize intercropped with ruzigrass), N top dressing (0 and 80 kg ha-1), and maize plant density (40, 60, 80, and 100 thousand plants ha-1). Maize-ruzigrass intercropping improved straw yield (2,365 kg ha-1) and N cycling (50 kg ha-1), and increased soybean yield in the following season (232 kg ha-1). N fertilization of maize increased soybean grain yield by 180 kg ha-1. Maize plant density did not influence the performance of succeeding soybean crops, regardless of the growing season.
Key words:
Urochloa ruziziensis; nitrogen supply; cover crop; plant population; Glycine max
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S, sowing; R5.1, beginning of grain filling; H, harvest
An asterisk (*) indicates significant differences between intercropping treatments by Tukey’s test (p ≤ 0.05); ns, not significant. Different uppercase letters above bars indicate significant differences between fertilization treatments by Tukey’s test (p ≤ 0.05); (*) and (**) in the equations refer to the significance of coefficients at p ≤ 0.05 and p ≤ 0.01, respectively
FertN, N fertilized; Unfert, unfertilized; an asterisk (*) indicates significant differences between N fertilization treatments by Tukey’s test (p ≤ 0.05); ns, not significant; (*) and (**) in the equations refer to the significance of the coefficients at p ≤ 0.05 and p ≤ 0.01, respectively
Different uppercase letters above bars indicate significant differences between fertilization treatments, and distinct lowercase letters above bars indicate significant differences between intercropping treatments by Tukey’s test (p ≤ 0.05)