ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 68 Number 4
Direct and interactive effect of boron and nitrogen on selected agronomic parameters and nutrient uptake by cowpea [Vigna unguiculata (L.) Walp.] under glasshouse conditions
The effect of N and B applications on plant growth and tissue B concentration in cowpea in relation to dry matter yield was investigated in the glass house using three representative savanna soils: an Alfisol, Ultisol and Inceptisol. Treatment applications consisted of factorial combinations of four levels of N (none, 60, 120 and 240 ?g g-1) and three levels of B ( none, 1.0 and 2.0 ?g g-1) in a randomized complete block design. The above-ground proportions of the plants were cut 35 days after planting, over-dried, weight, milled and analysed for boron. Applied N at 60 and 120 ?g g-1 significantly increased growth components, dry matter yield and nutrient uptake over the control, but increasing N to 240 ?g g-1 had no effect on the growth parameters of interest in the study. Applied B decreased growth and dry matter yield in all but one soil and increased B concentration in plant tissue, but N had no significance effect on the B content of plant tissue. A critical level of B toxicity in the plant tissue was approximated to be 30 ppm. There was no significant N and B interaction effect on the parameters assessed in the trial.
Keywords: Boron concentration; Cowpea; Critical level; Dry matter; Growth components; Toxicity