Forage quality in a neotropical savanna based on different types of fertilization

Research article https://revistas.unal.edu.co/index.php/refame Forage quality in a neotropical savanna based on different types of fertilization Calidad del forraje en una sabana neotropical basada en diferentes tipos de fertilización https://doi.org/10.15446/rfnam.v75n2.96791 Ramírez-Iglesias Elizabeth1*, Lozano-Pérez Zenaida2, Hernández-Hernández Rosa Mary3 and Ramírez-Iglesias José Rubén4 ABSTRACT Keywords: Agroecosystems Biomass Cover crop Nitrogen fixation The application of different sources of nutrients to the soil with varying degrees of solubility, as well as the use of organic and inorganic fertilizers, can generate different responses in agroecosystems. The objective of this study was to evaluate the effect of different fertilization options on the quality of forage in the conservation-based agroecosystems of neotropical savannas. Both perennial species Brachiaria dictyoneura and the legume Centrosema macrocarpum are associated with corn cultivation. Four fertilization treatments were evaluated within each cover crop, applying 150 kg ha-1 of nitrogen, 150 kg ha-1 of P2O5, 100 kg ha-1 of K2O, and varying the source of phosphorus, being the treatments distributed as follows: i) phosphoric rock, high dose of phosphorus (100% of P2O5 as phosphoric rock), ii) diammonium phosphate, high dose of P (50% of P2O5 as phosphoric rock and 50% as diammonium phosphate), iii) biological fertilization, low dose of P (25% of P2O5 as phosphoric rock and inoculation with biofertilizer based on native arbuscular mycorrhizal fungi, such as Gigaspora, Scutellospora, Acaulospora, and Glomus), and finally, iv) the unfertilized treatment. The results show that under direct sowing and the use of biological fertilization sources using phosphoric rock as a source of P, similar and even higher levels of raw protein can be reached than when using fertilization with soluble sources such as the diammonium phosphate, which induce greater sustainability of the cover biomass, being an alternative in the management of this types of agroecosystems. RESUMEN Palabras clave: Agroecosistemas Biomasa Cultivos de coberturas Fijación de nitrógeno La aplicación de distintas fuentes de nutrientes al suelo, con variados grados de solubilidad, así como el uso de fertilizantes de tipo orgánico e inorgánico, pueden generar diferentes respuestas en los agroecosistemas. El objetivo de este estudio fue evaluar el efecto de diferentes opciones de fertilización sobre la calidad del forraje en el manejo conservacionista de sabanas neotropicales. Las especies introducidas fueron Brachiaria dictyoneura y la leguminosa Centrosema macrocarpum, ambas perennes, asociadas al cultivo de maíz. Dentro de cada cobertura se evaluaron cuatro tratamientos de fertilización, aplicando 150 kg ha-1 de nitrógeno, 150 kg ha-1 de P2O5, 100 kg ha-1 de K2O, y variando la fuente de fósforo, quedando los tratamientos distribuidos de la siguiente forma: i) roca fosfórica, dosis alta de fósforo (100% del P2O5 como roca fosfórica), ii) fosfato diamónico, dosis alta de P (50% del P2O5 como roca fosfórica y 50% como fosfato diamónico , iii) fertilización biológica, dosis baja de P (25% del P2O5 como roca fosfórica e inoculación con biofertilizante a base de hongos micorrízicos arbusculares nativos, como Gigaspora, Scutellospora, Acaulospora y Glomus) y por último, iv) el tratamiento sin fertilizar. Los resultados permiten concluir que bajo siembra directa y uso de fuentes de fertilización biológica empleando roca fosfórica como fuente de P, se pueden alcanzar niveles de proteína cruda similares e incluso mayores, que al utilizar fertilización con fuentes solubles como el fosfato diamonio, por lo cual se induce a una mayor sostenibilidad de la biomasa de las coberturas, siendo una alternativa en el manejo de este tipo de agroecosistemas. Universidad Estatal Amazónica, Ecuador. Universidad Central de Venezuela (UCV), Venezuela. 3 Universidad Nacional Experimental Simón Rodríguez, Venezuela. 4 Universidad Internacional SEK (UISEK), Ecuador. * Corresponding author 1 2 Received: October 29, 2021; Accepted: January 30, 2022 Rev. Fac. Nac. Agron. Medellín 75(2): 9929-9940. 2022 ISSN 0304-2847 / e-ISSN 2248-7026 Ramírez-Iglesias E, Lozano-Pérez Z, Hernández-Hernández RM, Ramírez-Iglesias JR 9930 W ell-drained savanna production systems in Venezuela are acidic, coarse-textured, with a low capacity to retain water and nutrients, especially phosphorus and calcium. The characteristic production systems of the zone are based on extensive cattle raising on low-quality natural pastures (Ramírez-Iglesias et al., 2021). Agroecological technologies, such as cover crops have been tested to provide alternative soil uses for low-income farmers (Gwenzi, 2021). Such alternatives aim at augmenting the biomass of micro-and macrobiota in soils and its application in agroecosystems (Nascimento et al., 2021). The inclusion of cover crops in agricultural or pastoral rotation systems is a very effective tool for the integrated management of weeds, being a key factor in the minimization of agrochemical applications (Campos et al., 2021; Watters, 2021). This occurs mainly because of the effect they have in lowering the weed pressure for the following crop. Besides, they have a leading role in soil conservation, since they get cover crops throughout the year, significantly reducing soil losses due to erosion. These benefits derived from the inclusion of cover crops favor the sustainability of productive systems and can be considered part of a gradual transition to agroecological production systems (Campos et al., 2021). The wide use of cover crop mixes still requires many adjustments both in technical parameters and in agronomic management, in order to achieve a high balanced biomass mix (Ramírez-Iglesias et al., 2020). In general, this technique succeeds in increasing the fertility of the surface soil in the short term, due to the beneficial contribution of the roots, reducing erosion to a minimum, in conservation agriculture systems with total coverage, compared to studies in non-coverage and tillage systems (Albarracín-Zaidiza et al., 2019; Correa et al., 2020). This practice significantly reduces the use of industrial chemical synthesis fertilizers. Thus, in addition to the direct benefits on the soil, others of an economic, social, and environmental nature point towards a more sustainable agriculture (Albarracín-Zaidiza et al., 2019; Francisquini et al., 2020). The use of phosphoric rock (RF) in acid soils has also been widely reported as a beneficial option. The principle of this benefit lies in the variable dissolution rate of RF, which depends on the concentration of protons (H+) and the reaction products, Ca2+ and H2PO4- in solution, around the RF granules (Beura et al., 2021). Thus, the rate of RF dissolution increases as the acidity increases and the concentrations of P and Ca+2 in the soil decreases (Niswati et al., 2021). In this sense, Al (...truncated)