No abstract

No abstract

The Abbotsford‐Sumas Aquifer is arguably the most studied case in Canada of groundwater nitrate contamination associated with agricultural production. Underlying some of the most productive agricultural land in Canada, this highly vulnerable trans‐boundary aquifer provides a unique case study on the opportunities and challenges of addressing water quality issues. A groundwater monitoring program initiated in the early 1990s has been important in tracking spatial and temporal variation in groundwater nitrate concentration. However, small land parcels with spatially and temporally variable land use and management practices and sub‐horizontal flow in this highly permeable sand and gravel aquifer make it difficult to relate groundwater monitoring results to specific agricultural practices. Other approaches pointed to the historical over‐application of N relative to crop requirement (primarily as manure used to increase soil organic matter during replanting but also as a nutrient source during production). Despite changes in agricultural practices, and programs aimed at raising grower awareness, no appreciable change in average groundwater nitrate concentration has occurred over the monitoring period. On individual land parcels, nitrate contamination may be reduced through development and adoption of an integrated suite of beneficial management practices (BMPs) to improve N fertilization, irrigation and alley vegetation management, and in particular to eliminate application of any organic soil amendment such as untreated manure in which the N has not been stabilized (e.g., by composting). However, the substantial N imbalance on a regional scale, and the lack of an effective on‐going consultative process among stakeholders, remain major barriers to the development, demonstration and adoption of BMPs.

No abstract

Additional index words. Malus ×domestica, drip-fertigation, ground cover, soil man age ment Abstract. 'Spartanʼ apple (Malus ×domestica Borkh.) trees on M.9 (T337) root stock were planted in April 1994 at 1.25 m × 3.5 m spac ing. Seven soil management treat ments were applied within a 2-m-wide strip cen tered on the tree row and arranged in a randomized complete-block experimental de sign. Treat ments included a weed-free strip (check) maintained with four annual ap pli ca tions of glyphosate; surface ap pli ca tion of 45 t·ha -1 of Greater Vancouver Re gion al District (GVRD) biosolids applied in 1994 and again in 1997; mulches of shred ded offi ce paper; alfalfa (Medicago sativa L.) hay; black wo ven polypro py lene; and shredded paper applied over 45 t·ha -1 GVRD-and Kelowna-biosolids applied in 1994 and 1997. All ex per i men tal trees were fertigated with phos pho rus (P) in the fi rst year and with ni tro gen (N) annually. Cu mu la tive yield for the fi rst fi ve harvests was higher for trees sub ject ed to any soil man age ment treatment relative to check trees. Max i mum cu mu la tive yield, exceeding check trees by 80%, was measured for trees grown with a shred ded paper mulch with or without biosolids application. Trees from the three shredded paper treatments were the only ones sig nifi cant ly larger than check trees after six grow ing seasons. No in creas es in leaf nutrient concentration were con sis tent ly as so ci at ed with improved tree per for mance. Notable effects included in creased leaf P con cen tra tion associated with biosolids application, increased leaf K con cen tra tion after alfalfa mulch application and temporary in creas es in leaf Zn and Cu concentration associated with application of biosolids high in Zn and Cu. Use of both mulches and biosolids amendments ben e fi ts growth of trees in high density plantings de spite daily drip irrigation and annual fertigation. Nonsignifi cant or signifi cant at P ≤ 0.05, 0.01, 0.001, or 0.0001, re spec tive ly.