Irrigation Water Management and Quality in Two Rocha Pear Orchards

Abstract

Tackling human malnutrition resulting from mineral deficits in foods is currently an agro-industrial problem. To address this problem, an agronomic workflow to enrich Rocha pears with calcium (Ca) was considered in two orchards in Portugal. This study aims to assess quality differences in the irrigation water of two orchards (of Rocha pear) where an agronomic Ca enrichment workflow would be performed and identify possible conditioning to Ca increases in fruits. Thus, electrical conductivity (EC), pH, pHs, cations (Na+, K+, Ca2+, and Mg2+), and anions (HCO3−, Cl−, and SO42−) were attained to calculate the Sodium Adsorption Ratio (SAR) index and the Langelier Saturation Index (LSI) and assess the agricultural use. The values of EC, pH, pHs, SAR index and LSI of both orchards varied between 1198 and 1211 µS/cm, 7.4 and 7.5, 7.7 and 8.1, 3.5 and 7.4, and −0.69 and −0.21, respectively. Regarding Piper classification, irrigation waters were classified as sodium bicarbonate (orchard 1) and sodium chloride bicarbonate (orchard 2). Both orchards presented different classifications regarding agricultural use, namely C3S1 (orchard 2) and C3S2 (orchard 1). The water of both orchards presented the same salinity hazard (C3), but the use of these irrigation waters is enabled since these trees can be considered salt-tolerant. However, regarding the alkalinization hazard to soils, the irrigation water from orchard 2 offers less danger (S1) in comparison to orchard 1 (S2). Meanwhile, a slightly inferior LSI (orchard 1) can favor a higher tendency to dissolve calcium carbonate. In conclusion, although slightly different, analysis indicated that the waters of both orchards did not induce toxicity in Rocha pear trees.

Keywords

• irrigation water quality
• LSI
• Piper diagram
• <i>Pyrus communis</i> L.
• SAR index
• water hydrochemistry facies