S. 2007. Nutritional implications of biosolids and paper mulch applications in high density apple orchards. Can. J. Plant Sci. 87: 551-558. A field experiment was designed to assess the effects on tree nutrition of surface application of municipal biosolids and shredded paper mulch, which have previously been reported to improve the performance of high-density apples despite wide differences in nutrient content. The experiment involved four treatments which included two levels (with or without) of two organic amendments, shredded paper mulch and Greater Vancouver Regional District (GVRD) municipal biosolids. Treatments were established over a 2 m wide strip centred on the tree row in a high-density (3700 trees ha -1 ) Golden Delicious (Malus × domestica Borkh.) orchard in the year of planting (1997) and maintained until 2004. GVRD-biosolids was applied at 40 t ha -1 (DW) in 1997 and 20.3 t ha -1 (DW) in 2001 potentially supplying larger amounts of all plant nutrients (N, P, K, Mg, Zn, Cu and Mn) except Ca than the paper mulch. All trees received standard commercial treatments of drip fertigation of 30 g N tree -1 yr -1 and 20 g P tree -1 in the establishment year. Leaf N concentration was unaffected by biosolids application and decreased, but not to inadequate concentrations, in 3 of 6 yr for trees grown in the high C:N ratio shredded paper mulch. This response indicates the effectiveness of drip fertigated N. Leaf K declined to inadequate concentrations by the end of the experiment, regardless of treatment, but trees in the paper mulch treatment were able to sustain higher leaf K, were more vigourous, had higher yield the first three fruiting seasons and cumulatively after 8 yr despite the low N and K content of the paper. Improved K uptake was attributed to better distribution of soil moisture beneath the mulch but for longterm sustainable production, K fertigation would have been desirable. Biosolids application often raised leaf Zn, Cu and Mn concentration but increases were modest, with concentrations of Zn insufficient to change standard commercial recommendations for annual dormant Zn applications.

Use of and interest in organic mulches for both integrated fruit production (IFP) and organic fruit production is increasing given recent efforts to reduce pesticide inputs and improve soil health. A series of four experiments was conducted in the southern interior of British Columbia over 5 years to investigate the use of a spray-on-mulch (SOM) slurry, comprised primarily of recycled waste newsprint fiber, as an effective method to control excessive weed competition and enhance tree establishment and performance. In four experiments, ‘Gala’, ‘Granny Smith’, ‘Ambrosia’, and ‘Honeycrisp’ apple (Malus ×domestica) trees on ‘Malling 9’ (‘M.9’) rootstock were exposed to a series of treatments including a glyphosate check, SOM waste paper, SOM over an organic underlay, SOM incorporated with dichlobenil or tackifier, SOM over black landscape fabric, rowcover cloth, or polyethylene plastic. SOM provided superior weed control in comparison with the glyphosate check treatment, a standard orchard practice in many modern orchards in North America. SOM application over compost, paper, and especially over cloth barriers were found to be more effective weed barriers than SOM alone. In comparison with glyphosate checks, SOM improved tree growth during tree establishment. Although the addition of dichlobenil provided season-long weed control, tree growth was diminished in comparison with SOM alone and remained similar to that of the glyphosate checks. There was little or no benefit of including a 2.5% tacking agent to help improve SOM integrity and long-term surface stability. When applied to bearing 4-year-old trees, SOM provided similar tree vigor as glyphosate checks over four growing seasons. The addition of landscape fabric, plastic, or cloth underlay material in combination with SOM improved tree vigor in formative years, but this benefit diminished over time. SOM-treated trees had greater cumulative yields over glyphosate checks after 3 years of production. SOM provided significant temperature moderation during the summer and winter months and provided moisture conservation during the summer. There were few SOM effects on plant nutrient status.

High NO 3 concentrations in the Abbotsford-Sumas aquifer are linked to raspberry (Rubus idaeus L.) production. Passive capillary wick samplers were used to quantify the impacts of N, irrigation, and alley managements on drainage and NO 3 leaching from raspberry rows and alleys over 4 yr. Conventional management (100 kg N ha −1 surface broadcast on the row as a split application, clean cultivation of alleys, and fixed-duration drip irrigation) was compared with different mineral fertilizer N rates, N applied as manure, alleys seeded to a perennial forage grass or an autumn-seeded spring barley (Hordeum vulgare L.) crop, or evapotranspiration (ET)-scheduled irrigation. The temporal pattern of drainage and NO 3 leaching was driven by seasonal precipitation and growing season irrigation. Growing season drainage and NO 3 leaching were much lower under ETscheduled irrigation compared with fixed irrigation. Nitrate leaching was high (up to 90 kg N ha −1), even with no managed N inputs due to high inherent soil fertility and large quantities of N applied in irrigation water. Nitrate leaching was insensitive to N fertilizer rate. Application of N as poultry manure more than doubled NO 3 leaching compared with fertilizer, emphasizing the need to use organic N inputs judiciously. The perennial grass alley cover crop resulted in the greatest overall reduction in NO 3 leaching. Our data indicate that no single management strategy is sufficient to protect groundwater quality. Rather, an integrated package of improved practices (i.e., application of a reduced rate of mineral N through fertigation, combined with ET-scheduled irrigation and perennial alley crop) is necessary to protect groundwater quality.

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Source nitrogen (N) identification of leachate or groundwater nitrate is complicated by N source mixing and N and oxygen (O) isotope fractionation caused by microbial N transformations. This experiment examined the δN and δO values in leachate collected over 1 yr at 55 cm below raspberry ( L.) plots receiving either synthetic fertilizer (FT) or poultry manure (MT). The large ranges of δN (FT: -2.4 to +8.7‰, MT: +1.6 to +9.6‰) and δO (FT: -9.9 to -0.3‰, MT: -10.9 to +1.7‰) values in leachate collected under crop rows prohibited the reliable identification of the applied N sources on individual sampling dates. However, the mass-weighted average δN (FT: +3.2‰, MT: +7.3‰) values in leachate were significantly different and can be explained by accounting for the estimated contributions of nitrate and δN values of the various N sources, including applied fertilizer (-0.7‰) or manure (+7.9‰), nitrate-rich irrigation water (+9.0‰), and nitrate from soil N mineralization and nitrification (FT: +3.7‰, MT: +4.6‰; the seasonal timing of which is unknown). This study illustrates the importance of characterizing all major N sources and considering the seasonal variation of these sources and of N cycling processes, as they contribute to the δN values of leachate.