Onion (Allium cepa L.) yield and Phosphorus use efficiency as affected by plant extracted Humic acid application

To study the effect of plant derived Humic acid (HA) on the nutrient use efficiency and yield of onion a pot experiment was conducted in a greenhouse of Land Resources Research Institute, National Agricultural Research Centre Islamabad, during year 2013. The experiment was laid out in Complete randomized design with two factor i.e. HA (150 mL 5 kg-1 and 300 mL 5 kg-1) and Phosphorus (P) levels (60 kg ha-1 P2O5 (75 %) and 80 kg ha-1 P2O5 (100 %). Soil application of plant derived HA @ 300 mL 5 kg-1 along with 80 kg ha-1 P2O5 as Di-ammonium Phosphate (DAP) recorded the highest onion yield of 13.47 t ha-1. However it was statistically at par with the treatment receiving 75% (60 kg ha-1) P application along with plant derived HA @ 150 mL 5 kg-1 soil. Secondly soil application of plant derived HA @ 300 mL 5 kg-1 along with 80 kg ha-1 P2O5 showed highest content of P (0.22%) in onion plant at maturity whereby HA @ 150 mL 5 kg-1 along with 60 kg ha-1 P2O5 (75% RDF) registered highest content of N (4.1%). It may concluded from the result of the experiments that HA applied @ 300 mL 5 kg-1 integrated with Phosphatic fertilizers gave promising result and may be recommended for enhancing the onion yield and P and N concentration of soil.