In Brazil, several silicic rocks can be used as powder-based K sources, which can reduce production costs in agriculture. The optimized supply of K not only increases yield but also contributes to soil fertility preservation and long-term sustainability by curtailing nutrient losses and reducing the risk of nutrient imbalances. Therefore, this study aimed to investigate the effects of K application timing, source, and doses on nodulation, productive components, and productivity of soybeans in a not-tillage system in the Savannah. The experiment was carried out in the field, for two years, in an Oxisol, with a clayey texture. The experimental design was in random blocks, in a 2 × 4 × 3 factorial scheme, as follows: two application timings (early and sowing), four K₂O rates (0, 40, 80, and 120 kg ha⁻¹), and three sources (KCl, Potasil, and Ekosil), with four replicates. Potassium fertilizer was broadcasted on the soil without incorporation into the soil. Due to the interactions between doses and K₂O sources, there was a linear adjustment for KCl sources, the higher the dose, the lower the nodule mass. Also, for nodule mass, the interaction between dose and application time was significant for the early application of the Ecosil and Potasil sources for 80 kg ha⁻¹. The highest estimated soybean grain productivity was 3262 kg ha⁻¹ with 78 kg ha⁻¹ of K₂O, being the most suitable for growing soybeans under a no-tillage system.

This research analyzed the effects of inoculation with Rhizobium tropici, combined with beneficial microorganisms, on the reduction of NPK fertilization and its impacts on common beans. Conducted in two types of soil (clayey Oxisol and sandy Ultisol), the experimental design was a randomized block design under a factorial scheme 4 × 4, with different combinations of inoculation (Rhizobium tropici alone or in combination with Azospirillum brasilense, Bacillus subtilis, and Trichoderma harzianum) and fertilization doses (0%, 33%, 66%, and 100% of the recommended dose). The results showed that inoculation with R. tropici, especially in combination with Trichoderma harzianum, increased nodule formation and improved agronomic parameters such as leaf chlorophyll, dry matter of the plant, number of pods, and grains. Co-inoculation with Azospirillum brasilense resulted in a significant increase in grain yield, particularly in clayey soil with 33% NPK. Inoculation with lower doses of NPK was sufficient for good yield, suggesting the feasibility of reducing the use of mineral fertilizers. This study indicates that soils with corrected fertility, in a no-tillage system, can contribute to the reduction of fertilizer use due to the cycling of organic matter and improvement of soil health. Additionally, the use of microorganisms is an effective ally for the sustainability of agroecosystems.

Mechanical soil intervention with a chisel in cover crops (CCs) is a promising strategy for minimizing the superficial compaction of soil in a no-tillage system (NTS). The objective of this study was to evaluate the effect of mechanical chiseling associated with successive crops and preceding cover crops to assess grain yield and changes in soil chemical properties after rice cultivation for two consecutive years. The experimental design comprised randomized blocks in a 5 × 2 factorial scheme with four replications. The treatments consisted of five cover crops (Cajanus cajan, Crotalaria juncea, Urochloa ruziziensis, Pennisetum glaucum, and fallow), with or without soil mechanical chiseling. Soil samples from the 0–5, 5–10, 10–20, and 20–40 cm layers were collected, and the chemical properties were analyzed after rice cultivation. Under U. ruziziensis, the chemical properties were improved by mechanical scarification; however, the initial acidity increased in the 5–40 cm layer. The cultivation of P. glaucum and C. juncea prior to rice, regardless of scarification, improved the soil chemical properties in the 0–40 cm layer. Mechanical soil scarification and the use of C. cajan as a cover crop increased the grain yield of upland rice by approximately 552 and 1454 and 1330 kg ha⁻¹ compared to the P. glaucum and U. ruziziensis, respectively.

Golden mussel is an invasive species in South America that causes environmental and economic damage due to the formation of large colonies without natural predators. This study aimed to test the agricultural use of golden mussel shell as a limestone substitute, as the shell is rich in calcium carbonate. The experiment was carried out in pots, with eight treatments (sandy soil; clay soil; sandy soil + 1.0 Mg ha⁻¹ of limestone; clay soil + 1.0 Mg ha⁻¹ of limestone; sandy soil + 1.0 Mg ha⁻¹ of fresh shell; clay soil + 1.0 Mg ha⁻¹ of fresh shell; sandy soil + 1.0 Mg ha⁻¹ of calcined shell; clay soil + 1.0 Mg ha⁻¹ of calcined shell), in addition to the application of the following fresh and calcined shell doses: 0, 1.0, 1.5 and 2.0 Mg ha⁻¹. Rice was cultivated in all treatments, and the soil fertility and rice shoot and root dry masses were evaluated. The shell provided good chemical conditions to the soils and raised their pH and phosphorus and calcium contents. The agricultural use of golden mussel shell showed to be efficient for soil correction and can be considered an alternative to limestone.

Silicate rocks represent alternative K sources when finely ground, reducing production costs and dependence on imported fertilizers. Therefore, this study aimed to evaluate the effects of potassium (K) dose, application timing, and fertilizer sources on the concentrations and accumulation of K, silicon (Si), and sodium (Na) in maize diagnostic leaves, straw, and grains under a no-tillage system in Savanna. The soil was classified as Typic Haplustox (Oxisol). The experiment followed a randomized block design in a 2 × 4 × 3 factorial scheme, with two application times (30 days before sowing soybean and at sowing soybean), four K₂O rates (0, 40, 80, and 120 kg ha⁻¹), and three sources (KCl, Potasil, and Ekosil). K fertilization was applied by broadcasting without incorporation, before the preceding crop. Potasil provided a higher foliar Si concentration, and Si accumulation in grain and straw increased with the increment of K fertilization using the Potasil. Early fertilization promoted greater K accumulation in maize straw. For grain K accumulation, moderate K₂O doses favor greater accumulation, with Ekosil and Potasil showing superior results compared to KCl. There was less sodium accumulation in the grains with Ekosil compared to KCl. Agronomic efficiency is maximized at 40 kg ha⁻¹ of K₂O, with Ekosil showing the best performance for maize crop. These findings indicate that alternative K sources, applied at optimized rates, improve crop nutrition and promote sustainability in soybean–maize crop rotation.