Optimasi Waktu Pemberian Beberapa Sumber P terhadap Serapan Fosfor Tanaman Jagung (Zea mays L.) di Tanah Ultisol

Abstract

Phosphorus is an essential nutrient for plants, but its availability is limited in Ultisols due to phosphorus fixation by aluminum and iron. The efficiency of P fertilizer decreases due to an increase in incubation time, which causes phosphorus transformation. This study aims to know the source of phosphorus fertilizer and the time of phosphorus fertilizer application, as well as the interaction of these two factors, which are suitable for the growth and phosphorus uptake in corn (Zea mays L.) in Ultisols. This research was conducted in a greenhouse and analyzed at the Soil Chemistry and Biology Laboratory, Faculty of Agriculture, Univesitas Sumatera Utara and the Agricultural Instrument Standardization Agency Laboratory in Medan, from March to August 2025. This study used a Randomized Block Design with 2 treatment factors and 2 replications. The first factor was the source of P fertilizer, consisting of 4 treatments: no fertilizer, SP-36 (100 ppm P), TSP (100 ppm P), and NPK 16-16-16 (100 ppm P). The second factor was the time of P fertilizer application, consisting of 5 times: 4 weeks before transplanting (W1), 3 weeks before transplanting (W2), 2 weeks before transplanting (W3), 1 week before transplanting (W4), and transplanting (W5). The results showed that the application of 16-16-16 NPK fertilizer increased plant height, number of leaves, stem diameter, root dry weight, plant P content, and plant P uptake. Application 1 week before transplanting can improve plant height, stem diameter, root dry weight, and plant P uptake. There was no significant interaction between the source of P fertilizer and the time of P fertilizer application on plant growth or P uptake. However, the application of NPK 16-16-16 one week before transplanting increased plant P uptake by 90.41% compared to the control.