Role of phosphoric acid and potassium humate on nutrient availability in saline-sodic soil

Abstract

Phosphorus is the 2nd nutrient that is scarce (< 10 mg P kg−1 soil) after nitrogen (N) in 90%> of soils in Pakistan. The phosphorus contents decreased in calcareous salt affected soils. Salinity decreases the progress of plants and availability of macro and micronutrients due to high soil pH. Liquid fertilizers are more efficient than granular fertilizers due their rapid availability to the plants and less fixation in the soil. Phosphoric acid is the phosphorus containing liquid fertilizer which not only improves the availability of phosphorus to the plants, as well as it improves the availability of other nutrients like potassium, iron and copper. Potassium humate (PH) is the potassium salt of humic acid (HA) contains 5.2% K2O and 32% carbon. A successive trials were undertaken at different locations of University of Agriculture Faisalabad including field and pot experiments. Nitrogen (N), Phosphorus(P) and potassium(K) were applied by using Urea, SSP and SOP in case of control. Phosphorus was applied through phosphoric acid (10% and 50%) while PH was applied 50 and 100 kg ha-1. NPK rate of 200-150-200 kg ha-1 was followed for maize hybrid Pioneer 30Y87. Similarly for wheat recommended NPK dose 120-90-60 kg ha-1 was followed. Pot and field trial were harvested at maturity while lysimeter trial was harvested at flowering stage (65 days) and leachate was collected three time during growth period with an interval of 20 days. Plants were picked and all the samples were analyzed for growth, ionic and quality parameters. The results showed that in pot experiments growth was more with the use of 50 kg ha-1 PH and phosphoric acid (10 and 50%). All the nutrients were available in the next crop up to 25% as compared to the previous crop growth. While in case of lysimeter growth was more in mutual use of phosphoric acid and PH. Phosphorus concentration was more where phosphoric acid was applied alone however leaching of nutrients was more due to light texture of theused soil especially macro nutrients (N, P and K). Micronutrients were not detected in all the leachate samples. Results of field experiment showed the mutual use of phosphoric acid and PH considerably improved the grain ash contents, soil microbial biomass and soil respiration whereas the grain gluten contents were reduced as related to control. There was noteworthy +ve correlation among soil and crop quality parameters. Grain yield was positively associated with dry weight of shoot (r2 = 0.7592). However grain ash contents had significant negative correlation. Post-harvest analysis showed the destructive correlation among grain yield and ECe or with SAR. In field experiment higher level of both the amendments perform best as compared to other treatment including the quality parameters as well. All the data were analyzed statistically under CRD design in pot and lysimeter experiment whereas data of field experiment were analysed under RCBD design with Tukey multiple comparison test using STATISTICS 8.1 (R) software package.