Is magnesium deficiency the major cause of needle chlorosis of Pinus taeda in Brazil?

Authors: MOTTA, ANTONIO - Universidade Tuiti Do Parana; MAEDA, SHIZUO - Brazilian Agricultural Research Corporation (EMBRAPA); RODRIGUES, VALDÉCIO - Universidade Tuiti Do Parana; ERCOLE, TAMIRES - Universidade Tuiti Do Parana; Prior, Stephen - Steve; BRUMAT, ANA ELISA - Universidade Tuiti Do Parana; MOURA, AMANDA - Non ARS Employee; BARBOSA, JULIERME - Federal University Of Minas Gerais; GOMES, JOÃO BOSCO - Brazilian Agricultural Research Corporation (EMBRAPA)

Submitted to: Journal of Forestry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2023
Publication Date: 12/20/2023
Citation: Motta, A.C., Maeda, S., Rodrigues, V.D., Ercole, T.M., Prior, S.A., Brumat, A.L., Moura, A.P., Barbosa, J.Z., Gomes, J.V. 2023. Is magnesium deficiency the major cause of needle chlorosis of Pinus taeda in Brazil?. Journal of Forestry Research. 35:24. https://doi.org/10.1007/s11676-023-01656-9.
DOI: https://doi.org/10.1007/s11676-023-01656-9

Interpretive Summary: In sites forested with loblolly pine (Pinus taeda) in Brazil, detailed evaluation of soil and trees with severe chlorotic symptoms indicated that Mg deficiency was the most likely cause for chlorosis since this nutrient was low in the soil and very low in diagnosed tree material. Variations in tissue Mg levels were reflective of chlorosis level, and symptoms were similar to those described in previous studies. Low levels of Ca, P, Zn, and B and high Al possibly influenced observed chlorotic symptoms. Based on our findings, Ca and Mg from lime addition to pine forests on acidic soils could possibly help mitigate chlorosis and improve overall tree nutrition.

Technical Abstract: Occurrence of yellow needle chloroses (YNC) in Pinus taeda L. systems has become more frequent following second and third harvest rotation cycles in Brazil. To identify factors for YNC occurrence, trees grown in soils originating from contrasting parent materials were evaluated. Foliar tissue from four P. taeda sites exhibiting YNC were sampled based on branches age (one and two years-old) and needles flush release (first and second). Needles with YNC were evaluated whole or divided into chlorotic and green portions. All soils showed very low base levels (Ca, Mg, and K) and P suggesting a possible lack of multiple elements. YNC symptoms started at needle tips and migrated toward the needle base with age. First flush needles had larger length portions exhibiting YNC compared to second flush needles. Needles from lower crown positions also exhibited more symptoms along their length compared to higher canopy positions. Observed symptoms were similar to those reported for Mg. Results indicated that Mg and Ca concentrations were well below critical values; in particular, Mg levels were only one third of the critical value. Needle lengths with yellow chlorosis had large decreases in Mg (i.e., values below 0.3 g kg-1). Collectively, results suggest that Mg deficiency was the primary reason for P. taeda yellow chlorosis in Brazil under various soil parent materials.