Southwestern Pecan Orchard Soil Standards

The Rio Grande Basin in southern New Mexico and western Texas has become a large source of commercially produced pecans over the past few decades, yet agronomic research specific to soil management and fertilization in this area has not yet been fully developed. This project aims to review the currently published optimal soil analysis ranges as well as to identify significant relationships between soil characteristics and yield which merit further investigation. Over the 2012 growing period, 106 production blocks in Dona Ana County were observed. Soil analysis was conducted on each block prior to budbreak and after harvest to review soil changes over the full growth cycle; yield and tree counts were also collected. Due to alternate bearing in pecans, yield has been analyzed in four population groupings: “ON” blocks only, “OFF” blocks only, all blocks using a two year yield average, and all blocks using a dummy variable to isolate the alternate bearing yield differences. Mixed regression models were used to identify optimal levels and significant relationships within all four groupings. Of the production blocks observed, the soil analysis results fell within only 22% of the published optimal ranges, which are not crop specific. Boron, Bulk Density, Copper, Iron, Magnesium, Manganese, and Zinc were all identified as exhibiting significant, largely negative, relationships with yield, suggesting that these variables may be inhibiting production. The observed relationships merit further investigation and optimal soil analysis ranges must be developed in order to ensure correct interpretation of results and subsequent soil management practices