Poultry layer manure use in raspberry production : soil nitrogen processes and crop nitrogen uptake

Poultry manure application in excess of red raspberry (Rubus idaeus L.) nitrogen (N) requirement has been suggested as a significant contributor to elevated groundwater nitrate concentrations in the Abbotsford Aquifer. The purpose of this study was to examine the effect of poultry layer manure application on N processes in raspberry fields. An experiment was conducted at a site with no history of manure application in 1992 (C92) and 1993 (C93) and a site with a history of manure application in 1992 (H92) to determine the influence of rate of poultry layer manure application on the temporal and spatial variation in soil moisture, ammonium and nitrate concentrations, and on N uptake in raspberries. A comparison of soil inorganic N content over the growing season showed that inorganic fertilizer applied at a rate of 55 kg N ha⁻¹ had similar crop N availability as poultry layer manure applied at a rate of 100 kg N ha⁻¹, although small differences were observed at C93. Using manure as the sole source of N resulted in no adverse impact on estimated berry yield, primocane vigour, and crop N uptake, as compared to the inorganic fertilizer treatment. Greater depletion of soil inorganic N was measured near the crop row suggesting that manure and/or fertilizer should be placed there. Raspberry N uptake by the above-ground portion of the crop was relatively low (90-100 kg N ha⁻¹), averaged across treatments, while N removal from the field was only in the form of berries (up to 20 kg N ha⁻¹) since raspberry canes remain in the field where the plant N is recycled. Soil nitrate in August in the control treatment at H92 was 51 and 83% higher than that at C92 and C93, respectively. A second experiment conducted at C92 and C93 found that manure N recovery as soil inorganic N was approximately 50% within 30 days of manure application in late February to early March. Mineralization and nitrification of manure N was rapid at C93 despite the fact that soil temperatures were 4°C cooler than at C92. Additional experiments showed that the above-ground portion of a spring oats (Avena sativa L.) cover crop can be as high as 100 kg N ha⁻¹ when seeded by early August with no adverse effect on primocanes, however when seeded two weeks later N uptake was only half that amount.Land and Food Systems, Faculty ofGraduat