Salinity, Boron, and Irrigated Pecan Productivity along New Mexico's Rio Grande Basin

Abstract

AbstractWe surveyed 15 commercial irrigated orchards of ‘Western’ pecan [Carya illinoinensis (Wangenh.) K. Koch] along a 120‐km stretch of the middle Rio Grande basin in southern New Mexico. Our intent was to determine if high salinity and boron (B) broadly threaten pecan cultivation in this region. Ten of the fifteen sites were found to be on soils considered too saline for pecan trees (>2–3 dS m−1 in the soil saturation extract of the upper 0–60 cm of soil depth). Of these 10 sites, 4 had saturation extract Na concentration exceeding 20 mM, which is at or about the concentration corresponding to pecan seedling rootstock growth suppression. A laboratory study showed that cell membranes of excised, subapical seedling root segments from ‘Riverside’ pecan were damaged by about twice the salinity of the saturation extract at the highest salinity sites (9 dS m−1). At all sites, midsummer leaflet B concentration surpassed the published accepted range for pecan of about 50 to 100 mg B kg−1 dry weight, especially at the sites with higher soil salinity. Evaluation of two nearby sites (low salinity and B and high salinity and B orchards) showed that the higher salinity and B were associated with 25% lower yield efficiency, 3% lower percentage kernel, 13% lower mass per nut, and a 9 to 16% reduction in the tree's capacity to recycle N and P into perennial storage organs. The findings bring attention to the sustainability of current irrigation and soil management practices in much of this concentrated pecan producing region.