Effect of Rate and Time of Phosphorous Application and Planting Density on Yield and Net Benefit of Groundnut (Arachis hypogaea)

Groundnut yields are relatively very low in Kenya compared to other countries due to the use of poor agronomic practices and low soil fertility, with phosphorous (P) being the most limiting factor. This study aimed at determining the effect of the rate and time of phosphorous application and planting densities on yield and net benefit of groundnut production. The study was conducted in two locations, Chuka University Horticultural Demonstration Farm and Kenya Agricultural and Livestock Organisation, Embu, Kenya between April and August 2018. The study used a 2 x 3 x 3 factorial experiment laid out in a Randomized Complete Block Design with three replications. There were three factors; P application rates (0, 30, and 60 Kg/ha), time of P application (at sowing, and 14 days after sowing), and planting densities (148,149; 213,331 and 333,334 plants per ha). Data on the number of kernels per pod, number of empty pods and yield of groundnuts were collected and net benefit determined by subtracting the cost of production from the gross product sale price per unit area. Data collected were subjected to analysis of variance using Statistical Analysis Software version 9.4. Significant means were separated using the Least Significance Difference at a 5% probability level. The results of the study showed that the rate and time of phosphorous application and planting densities had a significant effect (p < 0.05) on the yield of groundnuts. The highest kernel yield and net benefit obtained was 1,659.90 and 963.60 Kg/ha while the highest net benefit was KSh 8312 and 12403 which was obtained by applying 30 Kg/ha of P applied at sowing with a plant density of 333,334 plants per hectare at Chuka and Embu, respectively. The study showed that the use of appropriate agronomic practices can lead to sustainable groundnut production, thus ensuring food security and improved farmers’ income. The study recommends spacing of 30 x 10 cm and application of 30 Kg/ha of Phosphorous at sowing for sustainable groundnut production in the study area and within similar agroecological zones.