A field experiment on the effect of crude oil levels: 0.0 (control), 5.2, 10.4, 20.8 and 41.6 ml applied at different stages of growth on maize yield and yield attributes, with a view to making appropriate recommendation to maize growers in the oil producing areas of the Niger Delta, was conducted in Ozoro, Delta State during the 2003 and 2004 cropping seasons. Seven maize varieties: Composite (suwan 1), Hybrid 3x-yx, AMATZER w, TZBRSYN w, AMATZBR y, TZBRSYN y and Ozoro local were evaluated. The current study has objective of evaluating the yield and yield components of seven varieties of maize grown in soil contaminated with crude oil with a view to identifying and selecting the tolerant ones and recommending the same to farmers in the Niger Delta region where oil industrial activities are predominant. The experiment was laid out in a randomized complete block design with five treatments replicated four times. Crude oil application (ring application) was carried out at three weeks after planting (3 WAP), 5 WAP and 7 WAP. Plants were harvested at 112 days after planting and assessed for grain yield, 1000-grain weight, cob girth and shelling percentage. The results showed that crude oil treatment significantly reduced (P > 0.05) grain yield, grain weight and cob girth but increased shelling percentage at P < 0.05. Significant differences at the 5% probably level in the responses of maize varieties to crude oils were also recorded at 5 and 7 WAP with Hybrid 3x-yx recording highest grain yield and weight whereas Ozoro local produced the highest cob girth and shelling percentage. Based on the results obtained from this investigation, Hybrid 3x-yx appeared to be susceptible to soils affected with crude oil as death was eminent at higher oil doses. The open pollinated varieties (AMATZER w, TZBRSYN w, AMATZBR y, TZBRSYN y) are better in terms of relative tolerance hence should be recommended to farmers and maize growers in the oil producing areas of Nigeria. There is therefore the need to test the open pollinated varieties on farmers’ field to determine their adaptability to oil pollution. Furthermore, the need for further studies to determine the level of pollution at which maize growth and yield are adversely affected cannot be overemphasized. The study established varietal differences with respect to maize response to crude oil level and this provides a basis for future breeding work by plant breeders.
Key words: Crude oil, grain yield, yield components, Zea mays.
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