Modifying of calcareous soil with some acidifying materials and its effect on Helianthus annuus (L.) growth

Calcareous soils contain a high concentration of calcium carbonate (CaCO₃), which influences soil properties related to plant growth. Humic acid (HA) and ammonium molybdate (AM) were added as treatments for calcareous soils at concentrations of 0.1, 0.5 and 1 g/l respectively. The pots were divided into three groups. The first set of groups were irrigated with AM, while the second set of groups were irrigated with HA. As a control, the third group was irrigated using only tap water. Many soil properties and plant characteristics were measured during the experiment. The results showed that most of the studied treatments aided to increase organic carbon of calcareous soil and improved sunflower height, leaf area and shoot and root biomass. All investigated treatments significantly enhanced carbohydrates content in the sunflower shoots, except the treatment with 0.1 g/l AM, while only the with AM (under all studied concentrations) significantly enhanced carbohydrates content in roots higher than untreated. Proteins content in the shoots and roots of sunflower significantly increased when treated only with 1 g/l HA higher than control. The amino acid content of sunflower roots enhanced when treated with 0.1 and 1 m/l HA and 0.5 g/l AM Evidently, acidifying materials enhanced the calcareous soil and increased productivity.