The effect of adding compound fertilizer of NPK and Humic acid on the availability of NPK soil and cabbage yield

A field experiment was conducted in Jdeidet Al-Shatt in Diyala Governorate during the fall season of 2021. According to modern American classification, silt loam soil is classified at a level lower than Typic Torrifluvent. To study the effect of NPK and humic acid addition on soil NPK availability and total cabbage yield according to RCBD randomized complete block design with three replications. The balanced 20:20:20 NPK compound fertilizer was added at three levels, 0,150,300 kg ha-1 and humic acid at three levels, 0, 15 and 30 kg ha-1. The fertilizers were added to the soil in two batches, the first during the planting process and the second 43 days after the date of the first batch. The concentrations of elements were measured in two stages, and the total yield of cabbage. The results of the study showed the superiority of the compound fertilizer NPK at the level of 300 kg ha-1 of NPK elements and in the first stage 46days (before the emergence of the head), where the concentration of NPK elements reached 36.59 mg kg-1, 35.55 mg kg-1, 224.90 mg kg-1, respectively. While the superiority of the humic acid at the level of 30 kg ha-1 to 30.44 mg kg-1, 25.13 mg kg-1, and 209.39 mg kg-1, respectively. As for the compound fertilizer at the second stage106 days (when the head is fully mature), the concentration of NPK elements and cabbage yield reached 27.17 mg kg-1, 36.92 mg kg-1, 208.69 mg kg-1, 68.23kg Mg ha-1, while the humic acid was 22.86 mg kg-1, 27.91 mg kg-1, 197.11 mg kg-1, 57.53 Mg ha-1, respectively.
 
Keywords: NPK compound fertilizer, Humic acid, NPK readiness, cabbage