Impact of Rock Phosphate Levels, Placement Methods, And Cowpea Varieties on Growth Parameters in Sokoto

Cowpea (Vigna unguiculata) is an essential legume crop widely cultivated in arid and semi-arid regions due to its adaptability to low soil fertility. However, phosphorus deficiency remains a major constraint to its optimal growth. This study investigates the impact of rock phosphate (RP) application levels, placement methods, and cowpea variety selection on growth parameters in Sokoto during the 2024 cropping season. A randomized complete block design (RCBD) was used with two cowpea varieties (Sampea-7 and Baadare), three RP levels (25, 50, and 75 kg ha⁻¹), and three placement methods (plough-sole, broadcast, and side-band). Results showed that increasing RP levels improved canopy height, leaf number, and canopy spread, with 75 kg RP ha⁻¹ yielding the highest vegetative growth. The plough-sole placement method enhanced nutrient uptake, resulting in superior growth parameters compared to broadcast and side-band methods. Additionally, Baadare exhibited better canopy height, while Sampea-7 displayed wider canopy spread and earlier maturity. These findings highlight the importance of optimizing phosphorus application strategies to improve cowpea productivity in phosphorus-deficient soils.