Salinity is a significant challenge for agriculture in semi-arid regions, affecting the growth and productivity of plants like Tropaeolum majus (nasturtium), which is valued for its ornamental, medicinal, and food uses. Salt stress disrupts the plant’s biochemical, physiological, and anatomical processes, limiting its development. This study investigates the potential of proline as an osmoprotectant to mitigate the effects of salt stress on nasturtium’s growth and physiology. A completely randomized factorial design was employed, testing five levels of electrical conductivity (0.0, 1.50, 3.00, 4.5, 6.5 dS m⁻¹) and four proline concentrations (0.0, 5.00, 10.0, 15.0 mM) with six replicates. The results showed that proline application, particularly at 15.0 mM, enhanced growth parameters such as leaf number, stem diameter, and root length. At moderate salinity (3.0 dS m⁻¹), proline significantly improved gas exchange, increasing net photosynthesis, transpiration, and stomatal conductance. Additionally, proline reduced the negative impact of salt stress on the fresh mass of leaves, stems, and roots, and increased both the mass and number of flowers. Proline also elevated the levels of total phenolic compounds and vitamin C while reducing soluble sugars, particularly under moderate salt stress (4.75 dS m⁻¹). Overall, applying 15.0 mM proline shows promise for enhancing the biomass accumulation, flower production, and overall quality of nasturtium under saline conditions.

Species of the genus Capsicum, especially peppers, are economically important and widely consumed worldwide. The application of animal waste as organic fertilizer is a simple and cost-effective technique for applying nutrients to the soil. Combining cattle manure with humic substances can stimulate plant metabolism, resulting in increased nutrient absorption and assimilation. Therefore, the objective in this study was to evaluate doses of cattle manure combined with humic substances for stimulating plant metabolism and morphophysiological and nutritional processes in pepper plants. A randomized block design with four replicates was used, in a 4×3 factorial arrangement consisting of four cattle manure doses (8, 18, 28, and 38 Mg ha^-1) and three humic substance doses (0, 8, and 12 kg ha^-1). Humic substances (12 kg ha^-1) enhanced gas exchange, increasing net photosynthesis (34.2%), stomatal conductance (12.7%), instantaneous water use efficiency (15.87%), instantaneous carboxylation efficiency (37.37%), and absorbed energy conversion efficiency (23.53%). Cattle manure adequately met the crop’s nutritional requirements, while humic substances increased the number and thickness of plant root hairs. The most effective combination to increase photosynthetic activity in pepper plants was 38 Mg ha^-1 of cattle manure combined with 8 kg ha^-1 of humic substances. Humic substances stimulated positive morphophysiological responses in organic pepper crops, which resulted in increased production.

Salt stress hampers the growth and physiology of nasturtium (Tropaeolum majus), due to biochemical, physiological, and anatomical disruptions. The application of salicylic acid stands as an alternative to alleviate the detrimental effects of salt stress, but studies on nasturtium are scarce. Thus, the aim of present study was to assess the effects of foliar application of salicylic acid on nasturtium cultivated under salt stress. The experiment followed a completely randomized design in a 3 x 3 factorial scheme, with 0 (no stress), 50 (moderate salt stress), and 100 (severe salt stress) mM of NaCl, and application of 0, 0.5, and 1 mM of salicylic acid, each with six replications. Growth (plant height, stem diameter, and number of leaves), gas exchange (stomatal conductance, photosynthesis, transpiration, internal CO₂ concentration, intrinsic water use efficiency, instantaneous water use efficiency, and intrinsic carboxylation efficiency), as well as chlorophyll indices and chlorophyll a fluorescence were evaluated. Salt stress affected the variables analyzed in this study. The application of salicylic acid had a positive effect on mitigating the effects of severe salt stress, resulting in a significant increase in the number of leaves. The most effective dose was 1 mM, also leading to notable improvements in water use efficiency and photochemical efficiency. However, other combinations of salinity and salicylic acid reduced growth and gas exchange in nasturtium plants.

Chemically degraded soils are found all over the world. Fertilization is an essential agronomic technique for recovering fertility and productivity in these areas. In this context, the objective was to recover the productive capacity of a degraded Red Yellow Argisol, grown with Brachiaria decumbens Stapf, in the presence of mineral fertilization with increasing amounts of nitrogen, evaluating the production of plant mass, plant height, tillering and water consumption. The experiment was conducted in a screened shelter and humidity control, according to a completely randomized experimental design. The treatments were organized in a factorial scheme, 6 treatments (without fertilization, 0, 30, 60, 90, 120 of nitrogen; 80 and 50, phosphorus and potassium for all treatments in g vase^-1, respectively) corresponding to the amount of fertilizer applied in Kg ha-¹, 4 cuts (performed every 30 days, starting 45 days after planting) and 5 repetitions. When fertilizing with 120 Kg ha^-1 of nitrogen, it was obtained increase in fresh (655%) and dry (685%) mass when compared to the phytomasses of the treatment without fertilization, there was also an increase in the number of effective tillers and plant height, as the amounts of nitrogen applied increased in the soil. The maximum amount of nitrogen to be applied to the soil, in order to produce phytomass of B. decumbens in the condition of chemical degradation of the soil, obtained in the work was 120 Kg ha^-1. In addition, the work allowed us to conclude that fertilization is an inexpensive and very important technique to recover the productive capacity of forage in the micro region of Brejo Paraibano, Northeast Brazil.

Fulvic acid-rich biostimulants have gained attention for their ability to enhance plant growth, nutrient uptake, and stress tolerance in sustainable agricultural systems. This study investigated the effects of different application rates and timing strategies of a fulvic acid-rich biostimulant on cauliflower (Brassica oleracea var. botrytis) growth, physiology, nutrient accumulation, and yield. A factorial experiment was conducted, assessing key parameters such as growth parameters, chlorophyll content, fluorescence traits, gas exchange parameters, plant macronutrient content. Multivariate analysis revealed that the application strategy significantly influenced plant responses, with PC1 and PC2 explaining 55.78 and 17.86% of the variance, respectively. Structural Equation Modeling (SEM) confirmed that the biostimulant had a direct impact on plant nutrition (β = 0.93), which further influenced growth (β = 0.20) and physiology (β = 0.38), ultimately affecting yield (β = 0.46). The results indicated that a 20 L/ha fulvic acid application at 100% during early growth (T100) led to the highest leaf P content, whereas split applications (T20/20/60) at 40 L/ha significantly increased inflorescence K content. Correlation analysis highlighted key trade-offs, with leaf P content and chlorophyll a negatively associated with dry biomass, suggesting nutrient allocation trade-offs between physiological efficiency and biomass accumulation. These findings provide insights into optimizing fulvic acid-rich biostimulant applications for maximizing nutrient uptake and productivity in short-cycle crops. While the observed responses were most pronounced in plastic traits such as chlorophyll a content and F₀, the potential long-term effects on perennial crops warrant further investigation. The study underscores the importance of tailoring biostimulant application strategies to enhance nutrient use efficiency and sustainable production in tropical agriculture.

Salinity poses a significant challenge in modern agriculture, often inhibiting growth and yield, especially in sensitive crops like onions (Allium cepa L.). This study evaluated the effectiveness of a freshwater-algae-based biostimulant on two onion cultivars, Franciscana IPA-10 and Vale Ouro IPA-11, to mitigate saline irrigation’s adverse effects. Five biostimulant concentrations (0, 1, 2, 3, and 4 mL L⁻¹, applied to the soil) were tested, along with two foliar treatments at 2 mL L⁻¹ as controls. Our findings showed that applying 4 mL L⁻¹ to the soil boosted growth rates to 1.0 cm per day (1), increased the potassium-to-sodium ratio in bulbs, and improved both average bulb weight by 25.11% and overall productivity by 24.28%, relative to untreated conditions. These results suggest that the biostimulant at 4 mL L⁻¹ is an effective method to enhance resilience to saline stress and increase productivity in the IPA-10 and IPA-11 cultivars. However, while the biostimulant improved plant performance, it did not counteract the accumulation of salts in the soil. Therefore, additional management practices such as leaching and drainage are recommended to ensure sustainable onion production under saline water irrigation.