Asian Journal of Biology

This study evaluated the responses of two buckwheat varieties, K+ and Kz, to diurnal variation in vapour pressure deficit (VPD), water deficit, and mineral fertilisation under pot and field conditions in Niger. Transpiration was monitored during two days with contrasting atmospheric conditions, and a one-week water-deficit treatment was imposed in pots. Mineral fertilisation treatments included control, NPK, phosphorus, and urea. On the day with lower atmospheric demand, VPD ranged from 1 to 2.3 kPa, whereas values reached approximately 4.5 kPa during the early afternoon on the more variable day. Transpiration increased with VPD and approached 85 mg plant⁻¹ in both varieties during the late morning of day 2 before declining later in the day. Water deficit reduced biomass in both varieties, with a stronger reduction in K+, from 0.68 to 0.25 g plant⁻¹, than in Kz, from 0.23 to 0.18 g plant⁻¹. Fertilisation responses differed between varieties and between pot and field conditions. In pots, Kz showed increased biomass with NPK and phosphorus, whereas K+ showed little response to fertilisation. The field-grown varieties flowered but did not produce seed. Overall, the results indicate that buckwheat growth under these conditions is influenced by atmospheric water demand, soil water availability, and mineral nutrition, with measurable differences between the two varieties.