Yields of maize and sunflower in relation to sowing time and rainfall distribution under three cropping systems in a semi-arid region of Zimbabwe

A five-year study to assess and relate the performance of maize (Zea mays L .) and sunflower (Helianthus annus L.) in sole-, inter-, and relay-cropping systems to sowing time and rainfall distribution was done at Chiredzi Rese arch Station in the south-east lowveld of Zimbabwe from 1986-87 to 1990-91. Sowing after the average sowing date of the area reduced maize seed yields in sole, inter, and relay cropping by 65.6, 37.6, and 74.9 ks day(-1), res pectively. Maize seed yields in 1989-90 were respectively, 3.6, 2.1, and 2. 3 t ha(-1) in sole, inter, and relay cropping due to above-average rainfall at sowing (October to November) and flowering (January) times. Similar val ues for sunflower in the same year were 0.9, 0.4, and 0.1 t ha(-1) respecti vely. Relay cropping maize and sunflower at 11 000 plants ha(-1) of each cr op was the best cropping system in terms of combined seed yields, land equi valent ratios, and total cash income of both crops over the five years of t he study.