Efeitos de Lithothamnium calcareum no crescimento e na nodulação do feijão-caupi

Abstract

The adoption of sustainable agricultural practices has stimulated the use of bio-inputs capable of improving soil fertility and biological balance. Lithothamnium calcareum, a marine calcareous algae, stands out for its potential in correcting soil acidity and promoting essential biological processes, such as nodulation and biological nitrogen fixation in legumes. In this context, the present work aimed to evaluate the effects of different doses of Lithothamnium calcareum, associated or not with mineral fertilization (NPK), on the agronomic performance of cowpea. The experiment was conducted in a greenhouse at UEMA, between August and November 2025, using cowpea grown in pots with previously characterized soil. A completely randomized design was adopted, in a factorial scheme, with four doses of Lithothamnium calcareum and two levels of mineral fertilization (with and without NPK). Biometric parameters, biomass, nodulation, photochemical efficiency of Photosystem II, and relative chlorophyll index were evaluated. Data were subjected to statistical analysis at a 5% significance level. The treatments resulted from the combination of four doses of Lithothamnium calcareum (0, 266, 533, and 1067 kg/ha) with two levels of conventional mineral fertilization (with and without NPK), applied at doses of 156 kg/ha of triple superphosphate, 24 kg/ha of urea, and 52 kg/ha of potassium chloride, converted to g/pot. The dose of 534 kg ha⁻¹ associated with NPK (T7) stood out for number of leaves, leaf area, stem diameter, and shoot biomass, indicating greater vegetative vigor. In general terms, the most significant results were obtained with the intermediate doses of 534 kg ha⁻¹ without NPK and the dose of 266 kg ha⁻¹ + NPK, which were superior for root length, nodulation, root mass, and relative chlorophyll index, reflecting better physiological balance. High doses (1,067 kg ha⁻¹), especially those associated with NPK, caused morphophysiological imbalances, reducing root growth and nodulation, and are therefore less recommended. These results indicate that Lithothamnium acts as an effective bio-input in the development of cowpea, highlighting the importance of properly managing its application to optimize the physiological and morphological performance of the plants.