Abstract Seasonality and lack of organic substrates suitable for the production of citrus rootstocks are the main problems in seedling production, coupled with the fact that these materials have alkaline pH. The objective of this study was to evaluate the effect of substrates composed of Pinus sp. needles and a commercial alkaline substrate at different concentrations on the growth and development of Poncirus trifoliata (L.) Raf rootstock. The development of 'Trifoliata' was assessed in different mixtures (v:v) of a commercial substrate (Vida®) based on eucalyptus bark and Pinus sp. needles (0, 25, 50, 75 and 100 %) with two particle sizes (3.5 and 8.0 mm). A randomized block experimental design with 10 treatments of seven plants each and four replications was used. During rootstock development, we monitored: the pH, electrical conductivity and stability of the substrates; the dry mass of the aerial part, roots and stem; and vegetative growth and development. Increasing the proportion of needles in the mixture with alkaline substrate reduced the pH, electrical conductivity and density. Treatments with 3.5 mm needles showed greater stability than those with 8 mm ones. The use of 25 % needles provided better results compared to 0 % (alkaline substrate only); however, the need for a specific fertilization and irrigation system for each treatment was detected, as each new substrate has its own physical and chemical characteristics.

Resumen La estacionalidad y carencia de sustratos orgánicos adecuados para la producción de portainjertos cítricos son de los principales problemas en la producción de plántulas, aunado al hecho de que estos materiales poseen pH alcalino. El objetivo de este trabajo fue evaluar el efecto de sustratos compuestos de acícula de Pinus sp. y un sustrato comercial alcalino a diferentes concentraciones sobre el crecimiento y desarrollo del portainjerto Poncirus trifoliata (L.) Raf. Se evaluó el desarrollo de ‘Trifoliata’ en distintas mezclas (v:v) de un sustrato comercial (Vida®) a base de corteza de eucalipto y acículas de Pinus sp. (0, 25, 50, 75 y 100 %) con dos granulometrías (3.5 y 8.0 mm). El diseño experimental fue en bloques al azar con 10 tratamientos de siete plantas cada uno y cuatro repeticiones. Durante el desarrollo de los portainjertos se monitoreó el pH, la conductividad eléctrica y la estabilidad de los sustratos, la masa seca de la parte aérea, raíces y tallo, además del crecimiento y desarrollo vegetativo. El aumento de la proporción de acículas en la mezcla con sustrato alcalino redujo el pH, la conductividad eléctrica y la densidad. Los tratamientos con acícula de 3.5 mm mostraron mayor estabilidad que los de 8 mm. El uso de 25 % de acícula proporcionó mejores resultados en comparación con el de 0 % (solo sustrato alcalino); no obstante, se detectó la necesidad de un sistema de fertilización y riego específico para cada tratamiento, ya que cada sustrato nuevo posee características físicas y químicas propias.

Resumo A produção de mudas de citros em ambiente protegido demanda grande quantidade de substrato, o qual deve apresentar características físicas e químicas adequadas. O uso de condicionadores ácidos, como acículas de Pinus, em mistura com substratos alcalinos, possibilita o cultivo de mudas com maior qualidade. O objetivo foi avaliar o desenvolvimento do porta-enxerto “Fepagro C37 Reck” cultivado em diferentes misturas do substrato comercial alcalino (Humosolo ES®) com acículas de Pinus elliottii. O experimento foi realizado testando misturas entre o substrato alcalino e acículas de Pinus com cinco meses de decomposição in situ e em duas granulometrias: 3,5 e 8,0 mm. As misturas foram realizadas em proporções entre as acículas com o Humosolo, (v/v) de 0%; 25%; 50%; 75% e 100%. Utilizaram-se bandejas alveoladas de poliestireno expandido para acomodação das misturas e semeadura do porta-enxerto. Realizaram-se avaliações físicas e químicas das misturas, bem como do desenvolvimento das mudas. A utilização de acícula de Pinus acidificou o substrato Humosolo ES®, reduziu sua condutividade elétrica e tornou as misturas com maior porcentagem de espaço poroso e menor retenção de água. Os tratamentos contendo mistura de 25 e 50% de acícula, indiferentemente da granulometria, proporcionam maior desenvolvimento de plantas do porta-enxerto “Fepagro C37 Reck”.

Abstract The production of citrus seedlings in protected environment requires a large amount of substrate, which must have adequate physical and chemical characteristics. The use of acidic conditioners, such as Pinus needles mixed with alkaline substrates, allows the cultivation of seedlings with better quality. The objective of this work was to evaluate the development of the “Fepagro C37 Reck” rootstock grown in different alkaline commercial substrate mixtures (Humosolo ES®) with Pinus elliottii needles. The experiment was carried out by testing alkaline substrate mixed with 5-month old of decomposition Pinus needles in situ decomposition and two granulometry sizes, 3.5 and 8.0 mm. The mixtures were performed in proportions between the needles with the Humosolo, (v / v) 0%; 25%; 50%; 75% and 100%. Expanded cellular polystyrene trays were used to accommodate the mixtures and seeding of the rootstock. Physical and chemical evaluateons of the mixtures were carried out, as well as the development of the seedlings. The use of Pinus needles acidified the substrate Humosolo ES®, reduced its electrical conductivity and increased the percentage of porous space of the mixtures and reduced water retention. The treatments containing 25 and 50% of the Pinus needles mixture, regardless of the granulometry, provide greater development of rootstock plants “Fepagro C37 Reck”.