Aime J. Messiga

Soil Phosphorus Fractions Change in Winter in a Corn-Soybean Rotation with Tillage and Phosphorus Fertilization

ABSTRACT Determining how agricultural management practices affect soil phosphorus (P) over the winter may further our understanding of the soil P cycle under specific environmental conditions in eastern Canada. This study assessed changes over winter for soil P fractions and other selected chemical properties as affected by tillage and P fertilization. In 1992, a long-term corn ( Zea mays L.) and soybean ( Glycine max L.) rotational experiment was established in the province of Quebec, Canada. Soil samples (0–15 cm) were collected in fall 2001 and 2007 after a soybean harvest, and in the following spring 2002 and 2008 before corn seeding, in main plots under moldboard plow and no-till managements and selected subplots fertilized with 0, 17.5, or 35 kg P ha −1 and 160 kg N ha −1 . Soil samples were analyzed for P fractions and other chemical properties to assess changes over winter for 2001–2002 and 2007–2008. Changes over winter of all soil P fractions were significant for the two periods, indicating the occurrence of soil P transformation and movement over winter. The Mehlich-3-extractable Fe, Al, Ca, and Mg decreased during the two studied periods. Tillage had no significant effect on all soil P fractions. The resin-extractable P in 2001–2002 and NaHCO 3 -extractable inorganic P and NaOH-extractable organic P during the two winters were significantly increased under P fertilization. This study demonstrated that P in cultivated soils changed during winter as a result of changes in labile P fractions possibly due to the solubilization of residual fertilizer P combined with environmental factors.

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.