Background. Blueberries are ornamental plants grown in pots in many yards in the
Mekong Delta (MD) region. In this region, the recent alluvial (RA) soil is fertile and
ancient alluvial (AA) soil is considered degraded because it only has around a quarter
of the nutrient content of the RA soil. Both soils have a high clay content, so organic
matter is needed to improve their physical condition. This study aimed to identify the
nutrients that limit the yield of blueberries in RA and AA soils of the MD.
Methods. The pot experiment was performed using a factorial randomized block design
(RBD) with two factors: (a) two soil types (RA and AA) and (b) four omission or
treatment conditions (NPK, PK, NK, and NP). The same fertilizer formula was used
for all treatments, including 45N–20P2O5–20K2O and mixing CHC (10 tha-1) into the
potting soil.
Results. The blueberry yield in AA soil was only 81% of that in RA soil. In both RA
and AA soils, N omission caused foliar N content deficiency (10.42 g kg-1), resulting
in the content of foliar P (0.84 g kg-1) and K (3.78 g kg-1) to fall below the Trevett
threshold. In both RA and AA, N omission resulted in reduced fruit yield (47% and
39%, respectively) as well as reduced weight of the stem (70% and 42%, respectively)
and leaf (59% and 46%, respectively). Increased crop yields in soils were mainly related
to nitrogen fertilizer. The indigenous nutrient supply (INS) of RA, which is fertile, was
high but its apparent nutrient recovery efficiency (ARE) index was low, whereas the
INS of AA, or the level of degraded soil, was low but its ARE index was high. In alluvial
soils, the higher the INS level, the less positive the impact on the ARE index. In AA
soil, the indigenous N and K supplies can be improved through fertilizer investment;
however, a balance must be achieved considering economic efficiency.