Calcareous soil had sufficient phosphorus and potassium (PK) in different forms due to the high contents of PK-bearing minerals; however, the available PK state was reduced due to its PK-fixation capacity. Compost, coupled with high PK solubilization capacity microbes, is a sustainable solution for bioorganic fertilization of plants grown in calcareous soil. A 2-year field experiment was conducted to investigate the effect of compost (20 t ha⁻¹) with Aspergillus niger through soil drenching (C-AN) along with partial substitution of PK fertilization on quinoa performance in normal and calcareous soils. Treatments included PK_100% (72 kg P₂O₅ ha⁻¹ + 60 kg K₂O ha⁻¹ as conventional rate), PK_100%+C-AN, PK_75%+C-AN, PK_50%+C-AN, PK_25%+C-AN, and only C-AN in normal and calcareous soils. Results showed that C-AN and reduced PK fertilization (up to 75 or 50%) increased photosynthetic pigments and promoted nutrient acquisition in quinoa grown in calcareous soil. Reduced PK fertilization to 75 or 50% plus C-AN in calcareous soil increased osmoprotectants, nonenzymatic antioxidants, and DPPH scavenging activity of quinoa’s leaves compared to the PK_0%+C-AN treatment. The integrative application of high PK levels and C-AN enhanced the quinoa’s seed nutritional quality (i.e., lipids, carbohydrates, mineral contents, total phenolics, total flavonoids, half maximal inhibitory concentration, and antiradical power) in calcareous soil. At reduced PK fertilization (up to 75 or 50%), application of compost with Aspergillus niger through soil drenching increased plant dry weight by 38.7 or 53.2%, hectoliter weight by 3.0 or 2.4%, seed yield by 49.1 or 39.5%, and biological yield by 43.4 or 33.6%, respectively, compared to PK_0%+C-AN in calcareous soil. The highest P-solubilizing microorganism’s population was found at PK_0%+C-AN in calcareous soil, while the highest Azotobacter sp. population was observed under high PK levels + C-AN in normal soil. Our study recommends that compost with Aspergillus niger as a bioorganic fertilization treatment can partially substitute PK fertilization and boost quinoa’s tolerance to salt calcareous-affected soil.

This study aims to evaluate the effect of organic amendments and soil mulching on soil properties and soybean productivity grown under a drip irrigation system. The experiment was conducted at the Faculty of Agriculture farm (Demo) at Fayoum University, Egypt, located at 29°17′006″N and 30°54′055″E in the SI 2023 and SII 2024 seasons. Four soil amendment treatments were assessed, i.e., zero (control), 20 t ha-1 of compost (C), 10 t ha-1 of vermicompost (V) and a mixture of both 10 t ha-1 of compost + 5 t ha-1 of vermicompost (CV), and two organic soil mulching (SM) rates of rice straw (M0 and M1; zero and 8 t ha-1). The treatments were conducted using a randomized complete block arrangement (split-plot design) with three replicates. The results showed that the values of soil bulk density and hydraulic conductivity were significantly decreased by 5.56 and 10.98%, 12.35 and 31.44%, and 16.67 and 46.97% when applied to C, V, and CV, respectively, as compared with the control. On the other hand, there are significant increases in values of total porosity, water-holding pores, and useful pores by 0.43, 17.32, and 1.44%; 5.10, 26.45, and 5.66%; and 7.39, 33.19, and 8.28% when C, V, and CV are applied, respectively, as compared with the control. Soybean growth parameters and physiological attributes were significantly affected by the applied treatments. The application of CV+ SM8 significantly increased the values of weight 100 of seeds and seed and straw yield by 21.17, 6.11, and 24.29%, respectively, as compared with the control. It could be concluded that the combination of CV and SM8 led to an improvement in soil properties and the productivity of soybean plants.