Abstract
Behavioural interactions between insect pollinators and host plants increase pollinator efficiency, conservation and crop yield. This study analyzed the diversity and abundance of insect pollinators on sunflower varieties, Jos local and SAM-SUX-1 grown in soils treated with different application rates of NPK 15-15-15, namely 0, 30, 60 and 90 kg/ha. A field experiment was conducted on two sunflower varieties combined with four rates of NPK-15-15-15 fertilizer split applied at 2 and 4 weeks after planting and laid out in a randomized complete block design with three replicates. The nutritional content of the pollen grains, flavonoid, vitamin A and beta-carotenoid contents of the flowers of the two sunflower varieties were analysed to determine treatment effect on nutritional quality. Data were collected on the abundance, diversity of insect pollinators' species and foraging response of honeybees. Descriptive and inferential statistics analysis of variance and the Student Neumans-Keuls test test (alpha=0.05) were used as appropriate for data collected. NPK-15-15-15 fertilizer produced no significant effect (p>0.05) on the flower external morphology of both varieties but increased pollen grain crude protein, fat, flavonoid contents, vitamin A and beta-carotenoid contents of the flowers florets at the application rate of 90 kgha-1. Honeybees demonstrated distinct foraging preference for both sunflower varieties at 90 kgha-1 NPK 15-15-15 (p<=0.05). The two cultivated sunflower varieties attracted different assemblages of evenly distributed insect pollinators (90 – 92 %). The results showed that Jos local had the highest insect visitors (60.31%) while SAM-SUX-1 recorded 39.69% of insect pollinators visit. The study also revealed honeybees as second in abundance (37.75%) and foraging rate (2.17 s) on SAM-SUX-1 variety. The highest insect diversity was observed in Lepidoptera (Shannon's, H' = 2.40), while Hymenoptera (H' = 2.38) was the lowest. However, the highest insect dominance was observed in Hymenoptera (dominance, D = 0.099) and on Jos local variety (D = 0.110).
