The rates of nitrogen, phosphorus, and potassium fertilizers used in the cultivation of potatoes are often considered excessive, as they can cause imbalance among the essential elements present in the soil. Using leaf nutrient analysis, this study aimed to evaluate the productivity of potato tubers subjected to different rates of nitrogen (N), phosphorus (P), and potassium (K) to establish the diagnosis and recommendation integrated system indices. Three experiments were conducted, one for each nutrient (N, P, and K), with Agata and Atlantic cultivars in Unaí (Minas Gerais state) and the Agata cultivar in Mucugê (Bahia state). The nutrient rates were 0, 30, 70, 120, and 280 kg ha⁻¹ of N; 0, 150, 300, 600, and 900 kg ha⁻¹ of P₂O₅; and 0, 70, 110, 220, and 450 kg ha⁻¹ of K₂O. Agata and Atlantic had adequate nutritional balance under K application. Agata had a more adequate nutritional balance under P application in Mucugê, whereas K fertilization was more decisive for the nutritional balance in Unaí. The differences in the results can be explained by the different soil textures and nutrients in the soil between the regions. The results show the need to consider the soil conditions and the nutrient uptake/translocation capacity of cultivars before establishing rates to increase production revenue and avoid the waste of fertilizers.

Filter cake has been one of the most widely used waste products as a source of organic matter in the production of biofertilizers. However, sanitized sewage sludge is a recommended alternative for agricultural use because of environmental issues. Studies that examine the use of this particular class of fertilizer are needed. The objective of this work was to evaluate the efficiency of sewage sludge and filter cake as sources of organic matter in the composition of pelletized biofertilizers for soybean production. The experimental design was a randomized block design in a 2 x 4 + 2 factorial, which includes two sources of organic matter (sanitized sewage sludge and filter cake) and four levels of nitrogen (50, 75, 100, and 125%) relative to the recommended dose of phosphorus pentoxide compared with the mineral fertilizer. The use of organomineral fertilizer with the formulation of 75% sewage sludge showed greater growth for aerial plant parts. Biofertilizers formulated with sewage sludge and filter cake can replace mineral fertilizer and increase soybean growth. Quantitative changes in peroxidase, catalase and urease activity, as well as lipid peroxidation, were observed following the use of biofertilizers.

The combined application of organic fertilizer with mineral fertilizer increases the yield of sugarcane. It promotes greater residual beneficial effect in relation to the use of each fertilizer in isolation. The organo-mineral fertilizer presents gradual solubilization during the period of development of the crop. Thus, when compared to soluble mineral sources, its agronomic efficiency may be higher. Various types of organic material can be used, such as pig manure, poultry litter, filter cake and sewage sludge, among others. Organic matter is responsible for maintaining and increasing soil porosity to improve water retention and to ensure soil microbial balance. The efficiency in nourishing the sugarcane crops or availing the available nutrients is maximized. The use of biostimulants in world agriculture has achieved significant growth rates in the last decades. Hormone compounds ensure the sustainability of crops. It can be an alternative to improve plant nutrition, support of abiotic and biotic stresses. They act in the activation and potentiation of the metabolism of the cells, give more vigor to the immune system and help to enable the physiological processes in the different stages of development. The emergence and use of new technologies is the way to achieve greater productivity, sustainability and profitability.

The objective of this study was to evaluate the residual concentration from the application of levels of phosphorus contained in an organomineral fertilizer (OMF) in two soils cultivated with cabbage and lettuce in succession. In randomized blocks, five doses of OMF were used as a source of P in Oxisol (0, 50, 100, 200, and 300% of the P dose was recommended for cabbage crop using OMF), plus an additional treatment (100% mineral). The doses applied to the Entisol were as follows: 0, 50, 100, 200, and 300% of the recommended P dose with OMF for cabbage crop, plus an additional treatment (100% mineral), with four repetitions. The production of fresh matter (FM) and dry matter (DM), the nutritional status of the cabbage and lettuce, and the residual effect of nutrients in the soil were also evaluated. The P concentration in the soil increased (p ≤ 0.05) with higher doses of OMF in the Oxisol in the two cycles evaluated. However, this occurred only in the first cycle in the Entisol. Using the 50% dose of OMF in the cabbage in both soils provided FM and DM production values that were at least 11% higher than those attained with mineral fertilizer.

A major challenge in sorghum intercropping systems is maintaining their yields compared to the yields of the solo crops, especially in arid and semi-arid regions. This study aimed to test the hypothesis that intercropping systems using sorghum (Sorghum bicolor (L.) Moench.) and Brachiaria sp. are viable means to increase sorghum production and soil carbon in the conservation systems. Field trials were conducted in the semi-arid region of Minas Gerais, Brazil, during two crop cycles of sorghum associated with different grasses (Andropogon gayanus—AG; Cenchrus ciliaris cv. Aridus—CCA; Cenchrus ciliaris cv. 131—CC; Brachiaria decumbents—BD; Brachiaria brizantha—BB; Brachiaria ruziziensis—BR; Panicum maximum—PM), using row spacings of 0.4 and 0.8 m. Panicles of sorghum (yield) and grass dry matter were collected to determine yields. Results showed that the addition of grasses in systems decreased the grain yield in all systems, except in the systems using sorghum with CCA in 0.4 m, AG in 0.8 m, or BR in 0.8 m. In the 0.4 m row spacing, the sorghum associations with CC, BB, or PM are greater alternatives to increase soil carbon. However, when the row spacing was increased, the sole sorghum was the best alternative to increase the carbon. In machine learning, sorghum systems with CCA and AG are better alternatives to increase the yields, while sorghum with CC, PM, BR, and BB increases the grass dry matter in soil.

Organomineral fertilizers (OFs) can provide the macro- and micronutrients contained in organic matter slowly and gradually throughout the crop cycle. However, the residual effect of this slow release is still unclear and needs to be better evaluated. In this context, the objective of this study was to evaluate the use of different doses of OF in the cultivation of vegetables and to quantify the residual effects of P, B, and Zn in the soil. A randomized block design was applied, using different doses of fertilizer as a P source, with four replications. In the randomized block design, different doses of OF were evaluated as a source of P (all with four repetitions): T1 = no P supplied (zero dose); T2 = 200 mg dm⁻³ of P₂O₅; T3 = 400 mg dm⁻³ of P₂O₅; T4 = 800 mg dm⁻³ of P₂O₅; and T5 = 1200 mg dm⁻³ of P₂O₅ plus an additional treatment with mineral fertilizer (MF) (200 mg dm⁻³ of P₂O₅). The fresh weight (FW) and dry weight (DW) and the nutritional status of the lettuce and cabbage were determined through leaf analysis at harvest. Soil analysis was also conducted before planting and immediately after harvest in order to assess soil P, B, and Zn content. The FW and DW cabbage production was higher when fertilization was used for the crop (either OF or MF). No differences were observed in the effects of the OF and MF doses in cabbage production, which ranged from 281.2 g plant⁻¹ to 341.8 g plant⁻¹, while lettuce production was highest in MF (45.1 g plant⁻¹), followed by OF doses of 800 mg dm⁻³ (37.1 g plant⁻¹) and 1200 mg dm⁻³ (36.8 g plant⁻¹) of P₂O₅. OF fertilization had a beneficial residual effect on lettuce production, the FW and DW production of which increased as the OF doses increased (from 18.8 g plant⁻¹ to 36.8 g plant⁻¹ for FW and from 2.4 g plant⁻¹ to 4.0 g plant⁻¹ for DW). The highest doses of OF increased the availability of P and Zn in the soil and facilitated the absorption of nutrients by the cabbage and lettuce crops. In the cultivation of cabbage and lettuce, the residual effects of the P, B and Zn in the soil were higher under the highest doses of OF. An antagonistic effect between the P and Zn in the soil was evidenced in this study, and this needs to be confirmed in other subsequent studies.