On Sandy, Boron-Poor Soils, Liming Induced Severe Boron Deficiency and Drastically Reduced the Dry Matter Yield of Young Olive Trees

Abstract

In the northeast of Portugal, like in many parts of the world, most soils are acidic, which may hamper crop productivity. This study presents the findings of a factorial experiment on olive (Olea europaea L.) involving three factors: (i) soil type [schist (Sch) and granite (Gra)]; (ii) cultivars [Cobrançosa (Cob) and Arbequina (Arb)]; and (iii) fertilizer treatments [liming (CaCO₃) plus magnesium (Mg) (LMg), phosphorus (P) application (+P), boron (B) application (+B), all fertilizing materials combined (Con+), and an untreated control (Con-)]. Dry matter yield (DMY) did not show significant differences between cultivars, but plants grown in schist soil exhibited significantly higher biomass compared to those in granite soil. Among the treatments, +B and Con+ resulted in the highest DMY (50.8 and 47.2 g pot^-1, respectively), followed by +P (34.3 g pot^-1) and Con- (28.6 g pot^-1). Treatment LMg yielded significantly lower values (15.6 g pot^-1) than Con-. LMg raised the pH above 7 (7.36), leading to a severe B deficiency. Although Con+ also raised the pH above 7 (7.48), it ranked among the most productive treatments for providing B. Therefore, when applying lime to B-poor sandy soils, moderate rates are advised to avoid inducing a B deficiency. Additionally, it seems prudent to apply B after lime application.

Keywords: Olea europaea; granite soil; olive cultivars; phosphorus fertilization; schist soil; soil acidity.

Figure 1

Dry matter yield (DMY) of olive plants of the cultivars Cobrançosa (Cob) and Arbequina (Arb), grown in schist (Sch) and granite (Gra) derived soils under five fertilizer treatments [untreated control (Con-), boron (+B) and phosphorus (+P) application, calcium carbonate plus magnesium application (LMg), and positive control receiving all these fertilizers (Con+)]. Within cultivar, soil or treatment, means followed by the same letter are not significantly different by the Tukey HSD test (α = 0.05). Lowercase letters compare the different plant parts (leaves, stems or roots) and capital letters total DM yield. Error bars are the standard error.