Field trials were conducted during 2004 and 2005 to determine the effect of sowing seeds from plants with multiple heads and seeds from single headed plants of sunflower on seed yield, head characteristics and oil content of three widely grown open pollinated varieties (Funtua, Record and Isaanka) in the humid forest -savanna transition zone which is outside the current growing areas with a view to improving stability and sunflower productivity in this region. Seeds from multiple headed plants produced plants that flowered and matured 2-3 days later than plants from single headed plants. Apart from days to flowering in 2004, number of days to maturity and plant height were affected independently by variety and seed source factors. However, the seeds from single headed plants produced plants that recorded significantly (P < 0.01) higher head weight, head diameter, achene weight and number per head than plants from seeds of plants with multiple heads. Seed source had little effect on sunflower seed yield and oil content. However, Funtua produced significantly (P < 0.05) high seed yield (1956.0 kg ha −1 ± 76.06) when seeds from plants with multiple heads were sown, while Isaanka recorded comparatively high seed yield from seeds of plants from either multiple (1221.0 kg ha −1 ± 165.90) or single heads (1388.0 kg ha −1 ± 135.84) and Record (1201.0 kg ha −1 ± 96.97) when seeds from single headed plants were sown. Therefore, it is recommended that prospective sunflower growers who wish to cultivate Isaanka, can sow seeds from either the multiple or single head and preferably the multiple head for Funtua, and single head for Record.

The two field trials evaluated the performance of sesame (var. PBTil) and sunflower (var. Isaanka) intercropped with cassava (var. TMS 30572 and TME 1) in a cassava‐based cropping system with a view to studying the phenology of the component crops and establishing mixture productivity in terms of biological efficiency (land equivalent ratio [LER] and area time equivalency ratio [ATER]), intercrop compatibility land equivalent coefficient (LEC) and economic efficiency (monetary advantage index [MAI] and cassava yield equivalent [CYE]) of the systems under humid tropical conditions during the early and late cropping seasons of 2003/2004. Intercropping highly significantly (P < 0.01) delayed number of days to flowering, physiological maturity and height at both stages, seed yield and yield attributes of sesame and sunflower relative to their monocrops. Similarly, intercropping highly significantly (P < 0.01) reduced number of leaves and plant height at 2, 3, 4 and 12 months after planting (MAP), number and weight of tubers per plant, mean tuber weight and tuber yield of cassava relative to their monocrops. The six intercropping systems recorded significantly (P < 0.05) higher biological efficiency (LER > 1.00 in both plantings and ATER > 1.00 in the late planting) than their respective monocrops and relatively high intercrop compatibility (LEC > 0.037 and 0.25). Based on MAI and CYE, TME 1/Ses/Sun, TMS 30572/Ses/Sun and TMS 30572/Sun were the three most economically efficient cropping systems, especially in the late and more preferred planting season and are hereby recommended to prospective growers for cultivation, economic empowerment, and reduction of household food insecurity.

The impact of hydrothermal variability on organic sunflower seed yield in the humid tropical region of Nigeria was studied between 2001 and 2008 using rainfall and temperature as proxies for climate variability. The test variety was "Funtua", a local adapted, open pollinated, and late maturing sunflower variety. Rainfall amount during the period of study compared favorably with the long-term mean (25 years). September recorded adequate amount of rain throughout the period of study, except in 2002. Sum of effective temperature and growing degree days (GDD) ranged between 1,907.1 and 2,440.3°C and 2,435.2 and 3,634.3°C and appeared adequate for the production of organic sunflower in the region. Sunflower seed yield obtained between 2001 and 2005 ranged between 1.03 and 1.26 t/ha and were superior to the Nigerian average of 1.00 t/ha, African average of 0.81 t/ha, and a little below the world average of 1.52 t/ha. Grain yield, however, declined in 2006 and thereafter remained below 1.0 t/ha till 2008. Nevertheless, it could be concluded that despite the global increase in climatic variability a good yield of sunflower is still possible in the humid tropical region.