A field experiment was carried out at Siwa Research Station, Desert Research Center, Khimisa Farm, Matrouh Governorate, during two successive winter seasons, i.e., 2014/2015 and 2015/2016 to study the effect of the fertigation with four combinations of both humic (H) and Amino acids (A) as (control, 2 L H , 2 L A and 2 L H + 2 L A /fed) as well as the foliar application of three rates of potassium silicate (KS), i.e. , (O, 5 and 10 g) KS / L on the growth, yield parameters, quality content, uptake of N and K of bulb onion plants and soil available N and K after harvesting. The design of the experiment was split plot technique, where the main factor was the foliar spray of KS, while the sub main were fertigation with H, A and combination. Foliar and soil fertigation treatments were applied at three times, i.e., after 30, 60 and 90 days from planting.
Results indicated that the spray rate of 10 g KS foliar spray/l with (H) and (A) either individually or combination was very effective in improving growth, yield, yield component and quality parameters than applied the spray with of 5g KS/L during the studied two seasons compared to control treatment. Both rates of KS (5 and 10 g/l) gave higher increases with (H) application than with (A) application for all the studied parameters. In addition, the best treatment was observed with the integration treatment of (H + A + 10g KS/l) which gave the highest mean values of growth, yield, yield component and quality parameters (TSS %, Protein % and carbohydrates %) during the studied two seasons. Where highest mean values reached to, 2.21, 2.10 ton /fed for dry weight of bulb; 15.33, 14.39 ton /fed for fresh yield of bulb; 6.70, 6.41 for bulb diameter, 1.56, 1.46 for neck diameter, 54.90, 48.17 for plant height and 8.40, 8.0 for leaves numbers in 1st and 2nd seasons, respectively. And the increases of bulb TSS, carbohydrates and protein % reached to 27.67, 27.54 % for TSS; 15.69, 16.73 % for Carbohydrates and 55.05 & 53.41 % for protein relative to control treatment at 1st and 2nd seasons, respectively. Also the best treatment recorded highest values of N, K as concentration and uptake of onion bulb in tow studied seasons. The available amount of N and K in soil after harvesting onion plants increased with increasing acids fertigation and foliar application of KS.