RELAY INTERCROPPING SYSTEMS OF CORN INTO SUNFLOWER

With the objective of comparing corn (Zea mays L.) grain yield grown i n relay planting into sunflower (Helianthus spp.), in two sowing dates , with that obtained as a sole crop, a two-year study was carried out in the state of Rio Grande do Sul, Brazil. Four treatments were tested in the 1989/90 growing season: relay planting of coni (Zea mays L.) i nto sunflower at 19 and 40 days after sunflower anthesis and com as a sole crop planted in sequence to sunflower in both sowing dates. In 19 90/91, two other treatments were added: coni as sole crop planted in s equence to com sowed in the same date of sunflower. The effect of rela y intercropping on com yield planted 19 days after sunflower anthesis varied with the year. As In the first year corn yield was 33% less in the relay intercropped system into sunflower than in sole cropping sys tem, in the second year com yield was similar in both systems. These d ifferences could be partially attributed to the use of different sunfl ower cultivars. In the second date of relay planting of com into sunfl ower, com grain yields were similar to those obtained as a sole crop i n both trials.