Jean Lafond

Field evaluation of anion exchange membranes as a N soil testing method for grasslands

The in situ use of anion exchange membranes (AEMs) as a soil-testing procedure may provide a more precise evaluation of N availability to forages than standard methods. The main objective of this study was to evaluate the potential of AEMs to predict soil NO3–N availability for forage production in the western part of the province of Quebec, Canada. In 1995 and 1996, AEMs were buried (0–15 cm) in soils at four sites. The fertilizer treatments consisted of five NH4NO3 rates (0, 60, 120, 180, and 240 kg N ha–1). At all sites, NO3−sorbed on the AEMs (NO3AEMs) increased with increasing N fertilizer rates. The NO3AEMs fluxes were significantly related to water soluble NO3–N (NO3w) concentration in soil (R2 varied from 0.35 to 0.98) in the two growing seasons. Forage N uptake was better related with NO3AEMs fluxes (R2 = 0.88 and 0.92 in spring 1996 and 1995, respectively) than with NO3w concentration (R2 = 0.39 and 0.97 in spring 1996 and 1995, respectively). Based on their simplicity, rapidity, and low cost, A...

Impact de l’hernie des crucifères [Plasmodiophora brassicae] sur la productivité et la qualité du canola

Clubroot, a disease caused by Plasmodiophora brassicae, first appeared in canola fields in Quebec in 1997. The objective of this project was to assess the impact of a soil infested with P. brassicae on the productivity and grain quality of canola. In 1998 and 1999, 31 cultivars in total (23 of Brassica napus in 1998 or 25 of B. napus in 1999 and 6 of Brassica rapa) were evaluated. In 2000, 25 cultivars and two lines (70584 et 70585) of B. napus and 6 cultivars of B. rapa were tested. These cultivars or lines were sown on a soil where P. brassicae had been prevalent for a few years and on another soil which had never been sown with a cruciferous crop before. The soil infested with P. brassicae reduced canola productivity. Grain yield losses were 80%, 91%, and 85% in 1998, 1999, and 2000, respectively, for the Argentine cultivars (B. napus). In the Polish cultivars (B. rapa), yield losses were 69%, 96%, and 89%, respectively, for the same years. Clubroot also reduced straw yield, oil content of the grain, and the grain mass. As opposed to overall B. napus cultivars, the two lines of B. napus appeared to be resistant to clubroot in 2000. Grain yields of these two lines were not affected by the disease. Since there is no registered canola cultivar tolerant or resistant to clubroot in Quebec, agronomic practices used to prevent or reduce the incidence of the disease should be encouraged.

Changes in phosphorus fractions of a Humic Gleysol as influenced by cropping systems and nutrient sources

Information about the dynamics of soil P fractions is useful to predict their bioavailability and risk of P transfer from soils to surface waters. The objective of this study was to assess the effects of cropping systems and nutrient sources on P fractions in a Labarre silty clay (Humic Gleysol). Soil samples (0-15 cm) were collected in 1989, 1994 and 1997 from a field with four cropping systems, combining two crop rotations, barley (Hordeum vulgare L.) monoculture and 3-yr barley-forage rotation, with two tillage operations (chisel and moldboard plowing) as main plots, and two nutrient sources (mineral fertilizer and liquid dairy manure) as subplots. A modified Hedley sequential fractionation scheme was used. The inorganic P (Pi) fractions (resin-P, NaHCO3-Pi, and NaOH-Pi) increase with time in all cropping system and nutrient source combinations. Organic (Po) fraction (NaHCO3-Po and NaOH-Po) changes were related to C inputs and total soil C contents. The barley monoculture combined with mineral fertiliz...

The plant ionome revisited by the nutrient balance concept

Tissue analysis is commonly used in ecology and agronomy to portray plant nutrient signatures. Nutrient concentration data, or ionomes, belong to the compositional data class, i.e., multivariate data that are proportions of some whole, hence carrying important numerical properties. Statistics computed across raw or ordinary log-transformed nutrient data are intrinsically biased, hence possibly leading to wrong inferences. Our objective was to present a sound and robust approach based on a novel nutrient balance concept to classify plant ionomes. We analyzed leaf N, P, K, Ca, and Mg of two wild and six domesticated fruit species from Canada, Brazil, and New Zealand sampled during reproductive stages. Nutrient concentrations were (1) analyzed without transformation, (2) ordinary log-transformed as commonly but incorrectly applied in practice, (3) additive log-ratio (alr) transformed as surrogate to stoichiometric rules, and (4) converted to isometric log-ratios (ilr) arranged as sound nutrient balance variables. Raw concentration and ordinary log transformation both led to biased multivariate analysis due to redundancy between interacting nutrients. The alr- and ilr-transformed data provided unbiased discriminant analyses of plant ionomes, where wild and domesticated species formed distinct groups and the ionomes of species and cultivars were differentiated without numerical bias. The ilr nutrient balance concept is preferable to alr, because the ilr technique projects the most important interactions between nutrients into a convenient Euclidean space. This novel numerical approach allows rectifying historical biases and supervising phenotypic plasticity in plant nutrition studies.

Interactive effects of management practices on water-stable aggregation and organic matter of a Humic Gleysol

In many soils, the content and quality of organic matter (OM) control water-stable aggregation, which in turn preserves soil surface integrity. The effects of management practices on soil OM and aggregation remain to be determined for certain soils and climatic conditions. We assessed the effects of eight management systems involving two crop sequences: [barley ( Hordeum vulgare L.) monoculture (M) and barley in rotation (R) with a forage mix of red clover ( Trifolium pratense L.) and timothy ( Phleum pratense L. ‘Champ’)], two fall tillage [moldboard plowing (MP) and chisel plowing (CP)] and two nutrient sources [liquid dairy manure (LDM) and mineral fertilizers (MIN)] on soil aggregation and OM fractions of a silty clay Humic Gleysol. Soil samples from the 0–7.5 cm layer were taken periodically during 7 yr, and the total C and N, microbial biomass C (MBC) and carbohydrate (AHC) contents, alkaline phosphatase activity (APA), and water-stable aggregation were determined. By the 7th yr, initial total C and...

Soil phosphorus dynamics after ten annual applications of mineral fertilizers and liquid dairy manure: Fractionation and path analyses

Knowledge of phosphorus (P) dynamics in soil is essential for predicting its bioavailability and the risk of P transfer from soil to bodies of water. A comparative study was conducted to assess the changes in P fractions and pathways of P transformation in soil measured after 10 annual applications of mineral fertilizers (MIN) and liquid dairy manure (LDM). Fractionation and path analyses were performed to quantify inorganic P (Pi) and organic P (Po) forms and the relationships between P pools in the 0 to 15-cm layer of a Labarre silty clay (fine, mixed, frigid, Humic Cryaquept) under barley monoculture. The MIN additions resulted in larger increases in Pi fractions and smaller increases in the NaOH-Po compared with the LDM applications. The LDM, however, produced 1.9 times more total soil labile P than the MIN plot. Path analysis indicated that path coefficients between the source and recipient P pools were P-source dependent. The NaOH-Pi was a primary sink of added Pi and a source of NaHCO3-Pi. The roles of Po pools were more important than the Pi pools for P transformations. The NaHCO3-Po was sensitive to P sources and likely acted as a transitory pool rather than as a sink or source of soil P. The NaOH-Po constituted a sink for added Po and immobilized labile Pi in the MIN plot; it was conversely mineralized and contributed to labile Pi in the LDM plot. The results of this study stress that the pathways of P transformation in this Cryaquept can be revealed by the descriptive path analysis.

Optimum leaf nutrient concentrations of wild lowbush blueberry in Quebec

To evaluate the nutritional status of wild lowbush blueberry (Vaccinium angustifolium Ait.), optimum leaf nutrient concentrations were developed in earlier studies conducted in Canadas Maritime Provinces and in Maine. However, these concentrations have not been validated under the climatic and edaphic conditions of the Saguenay-Lac-Saint-Jean region of Quebec (Canada). These concentrations may not be necessarily correlated with the high productivity levels recorded in this region in recent years. The objective of the study was therefore to determine the minimum and maximum blueberry leaf nutrient concentrations under the conditions characterizing this region. These concentrations were derived using the boundary-line approach, which involves estimating the relationship between maximum fruit yield and leaf concentrations of N, P, K, Ca and Mg. The data were obtained from N and P fertilization trials carried out between 2001 and 2006 in eight blueberry fields in the Saguenay-Lac-Saint-Jean region. On averag...

Fractionnement de la fertilisation azotée dans la production du bleuet nain sauvage et suivi de l’azote du sol

In wild lowbush blueberry production, fertilizers are applied in the spring of the vegetative year. To increase fertilizers efficiency and to reduce environmental losses, fertilizer split applications between vegetative and production year have been proposed. The objectives of this project were to determine the effect of split application of the nitrogen (N) in the vegetative and production year on the wild blueberry production and on soil mineral N in six blueberry fields located in Saguenay-Lac-Saint Jean (Quebec, Canada). Four rates of ammonium sulfate were applied in the spring of the vegetative year (0, 30, 60 and 90 kg ha-1). These same rates were applied in the spring of the vegetative (50%) and production (50%) years. The 30 kg N ha-1 rate was also applied only in the production year. For all sites, maximum fruit yields (3800 kg ha-1) were obtained with 62 kg N ha-1. However, the maximum rate ranged from 25 to 90 kg N ha-1 according to the sites. Applying N in the vegetative and production years h...

Impact du précédent cultural et de la fertilisation azotée sur la teneur en désoxynivalénol chez l’orge

Many diseases affect cereals, but fusarium head blight associated with the presence of the fungus Fusarium graminearum is probably one of the most feared diseases in barley (Hordeum vulgare) production in Quebec. In addition to reducing grain yields, the fungus produces the toxin deoxynivalenol (DON), which can affect the health of livestock. An experimental study was conducted over 4 years (2002–2005) at the Research farm of Agriculture and Agri-Food Canada in Normandin to determine the impact of four previous crops (barley, dry pea, soybean, and red clover) and four nitrogen fertilization levels (0, 40, 80, and 120 kg·ha−1) on DON content of barley. The effect of the preceding crop on DON content of barley was significant for 3 years out of 4. Thus, in 2002, 2003, and 2005, the toxin contents were significantly higher when the previous crop was barley compared with dry pea, soybean, or red clover. In 2003, the DON contents were particularly high. For example, when barley was grown the previous year, the average toxin content was 22.5 mg·kg−1. The lowest DON contents were obtained when barley was seeded on a previous dry pea crop with an average content of 10.3 mg·kg−1. The DON contents of barley grown on a previous soybean or red clover crop were 15.2 and 13.4 mg·kg−1, respectively. In 2004, the effect of previous crops had no significant effect on DON content. Similarly, during the 4-year test, nitrogen fertilization had no significant effect on DON content of barley.

Dose optimale économique d’azote et nitrates du sol après la récolte du canola

Centre de recherche et de developpement sur les sols et les grandes cultures, Ferme de recherche, Agriculture et Agroalimentaire Canada, 1468 rue Saint-Cyrille, Normandin, Quebec, Canada G8M 4K3 (courriel: lafondj@agr.gc.ca). Contribution no. 836 du Centre de recherche et de developpement sur les sols et les grandes cultures, Ferme de recherche, Agriculture et Agroalimentaire. Recu 8 janvier 2008, accepte 29 juillet 2008.