Mehdi Sharifi

Nitrogen Management in Organic Potato Production

There is increasing interest in organic potato production in Canada, within a context of continuing strong growth rates for organic products globally. Using data from on-farm and station based trials, key characteristics of organic potato production in the Atlantic Canada region, notably the use of extended rotations involving leguminous crop green manures combined with organic amendments, low intensity of nitrogen and residual soil mineral N (RSMN) post harvest, and enhanced soil quality and health, are shown as sustainable outcomes of these systems. Data presented confirm nitrogen as the primary factor limiting total and marketable yields. Without additional N supplementation but following legume green manures (GMr) of red clover, or hairy vetch, potato yields and N uptake are shown to range from 30 to 35 Mg ha−1 and 100–125 kg N ha−1, respectively, while RSMN remains low. Combining N supplementation (with composts or dehydrated manures) with GMr consistently increased total and marketable yield. The effect of N supply and GMr type on pest (wireworm, Colorado potato beetle) population dynamics is also examined. Finally, synchronizing N supply in these systems with crop demand remains challenging and the potential to use novel soil tests and plant bioassays to improve N management in organic production systems is also discussed.

Evaluation of liming properties and potassium bioavailability of three Atlantic Canada wood ash sources

Sharifi, M., Cheema, M., Mahoney, K., LeBlanc, L. and Fillmore, S. 2013. Evaluation of liming properties and potassium bioavailability of three Atlantic Canada wood ash sources. Can. J. Plant Sci. 93: 1209-1216. Wood ash has the potential to enhance productivity in agricultural systems by influencing soil pH and nutrient availability. The liming properties and fertility values of wood ash from three Atlantic wood ash sources were evaluated in this study. The liming properties were tested using three wood ash sources [JD Irving (IR), New Page (NP), and Brooklyn Power (BP)] and two local lime sources in an 8-mo incubation experiment at 25°C. Soil pH was measured 14 times during the incubation. Availability of potassium (K) in wood ash was evaluated in a greenhouse setting with a K-deficient soil using annual ryegrass as the test plant. Total plant K and P uptake and Mehlich-3 extractable K and P were used as predictors of nutrient bioavailability. Wood ash application increased soil pH to the maximum level within the first 50 d after application and stabilized soil pH for 8 mo. The measured effective calcium carbonate equivalent of ashes relative to Mosher lime average among two soils were in order of BP (32)>IR (25)>NP (16). About 96, 38, and 71% of total K in IR, NP and BP ash sources, respectively, were bioavailable for ryegrass in 115 d. Although soil was not P deficient, soil P bioavailability (Mehlich III extractable P) was enhanced by 14 and 48% in NP and BP wood ash treatments, respectively, whereas P bioavailability decreased by 24% in the IR ash treatment. The results clearly demonstrate that these sources of wood ash can be considered as an effective liming agent and source of K in agricultural production systems.

The effect of green manure and organic amendments on potato yield, nitrogen uptake and soil mineral nitrogen

Abstract Fertility management is challenging for organic crops with intensive nutrient demands such as potatoes (Solanum tuberosum L.). Four crop sequences varying in pre-potato green manures as main plots and four fertility treatments applied in the potato phase only [control, inorganic fertilizer (FERT), municipal solid food waste compost (MSW) and paper mill biosolid compost (PMB)] as subplots were compared in five-year organic potato rotations in Eastern Canada. Potato yields did not differ significantly between crop rotations; however, soil amendments had significant impacts on potato yields. Averaged across years, total tuber yields were in the order; FERT (34.2 Mg ha−1) > MSW (29.6 Mg ha−1) > control (26.5 Mg ha−1). Total potato N uptake (TNU) levels were 89, 115, 107 and 147 kg N ha−1, respectively, for control, MSW, PMB and FERT, and were greater when potato followed red clover (119–124 kg N ha−1) compared with oat/pea/vetch mixture (107–108 kg N ha−1). Plant N use efficiency (NUE) was 299, 263, 263 and 235, respectively, for control, MSW, PMB and FERT. Pre-plant soil mineral N (SMN) ranged between 39 and 112 kg N ha−1 among different crop rotations. During the tuber initiation stage, SMN ranged between 40 and 66 kg N ha−1 while during tuber bulking it ranged between 10 and 14 kg N ha−1 among different crop rotations and soil amendments. Post-harvest SMN ranged between 8 and 30 kg N ha−1 for all rotations and amendment treatments.

Crop Productivity and Nutrient Bioavailability in a Potato-Based Three-Year Rotation as Affected by Composted Pulp Fiber Residue Application and Supplemental Irrigation

The possibility of using composted pulp fiber residues (CPFR) in a potato rotation in eastern Canada was tested. Three rates of CPFR (0, 45, and 90 Mg C ha−1) with or without supplementary irrigation were applied. Pea (Pisum sativum L.), corn (Zea mays L.), and potato (Solanum tuberosum L.) were cultivated in 2002, 2003, and 2004, respectively. Soil total carbon (C) and nitrogen (N), bulk density, and water-holding capacity were improved by CPFR. Pea and corn yields and total dry matter were increased using CPFR. Supplemental irrigation increased pea yield compared with the rain-fed system. Total tuber yield was increased by CPFR in the irrigated but not in the rain-fed system. The CPFR application increased plant-available phosphorus (P) and potassium (K) in all rotation crops. Nitrogen accumulation in all rotation crops except potato was increased by CPFR. The CPFR application successfully enhanced soil fertility and crop productivity without any adverse effects.

Grape Yield and Quality Response to Cover Crops and Amendments in a Vineyard in Nova Scotia, Canada

The increasing cost of synthetic fertilizers, combined with their associated environmental impacts and yield instability, has promoted the use of local waste products and cover crops in vineyards. We assessed the effects of cover crop mixtures combined with organic and industrial wastes on grape yield and quality over two full growing seasons in a vineyard (Vitis vinifera) in Eastern Canada. The experimental treatments were arranged in a nested design with three replicates. Four cover crop mixtures: (i) oats + pea + hairy vetch (OPV), (ii) oats mixed with red clover (ORCl), (iii) timothy + alsike + red clover (TM), and (iv) control with no cover crop (CONT) were applied to main plots and five fertility treatments (fertilizer without N [NDEF], full synthetic fertilizer [FERT], wood ash [WA], municipal solid food waste [MSFW], and mussel sediment [MS]) were applied to subplots. During the second growing season, only half of the subplots received fertility treatments. Grape yield for the most productive cover crop and amendment combinations were ORCl × MS (9.52 mg/ha) > OPV × MSFW (9.49 mg/ha) > TM × WA (8.81 mg/ha) > ORCl × MSFW (8.28 mg/ha). The lowest grape yields were obtained with combinations of CONT with either NDEF (3.86 mg/ha) or WA (3.61 mg/ha). The highest berry sugar concentrations among the cover crops were obtained under TM floor management combined with NDEF (16.43 Brix), MS (16.03 Brix), and MSFW (15.98 Brix). Grape yield was affected by cover crop only during the second growing season, but berry sugar was not. Cover crop floor management strategies and organic or industrial wastes can be used as sources of nutrients or soil conditioners for vineyards in the cool humid climate of Eastern Canada.