Crop sequencing

This study consists of field experiments at six sites in western Canada established as matrices of crop x crop stubble to evaluate six to nine crops, depending on land and labor availability at each site using a protocol similar to that of Krupinsky et al. (2006). A core set of five crop species are common to all sites: wheat (either bread or durum), barley, canola, pea and corn; additional crops were added at the discretion of each collaborator (Table 1).

For example, at Saskatoon, the matrix includes nine crops, lentil, canaryseed, oat and flax in addition to the core set of five crops (durum wheat, barley, canola, field pea and corn). All sites were managed under a no-till cropping system. Cultivars of the crops grown are relevant to the region of each site. Soil testing was conducted late each fall or early spring to be sure enough fertilizer (NPKS and micronutrients if required) was added at rates recommended for each crop by the soil test lab. Weeds were managed by application of appropriate herbicides for each crop in western Canada. All sites have weather monitoring equipment and or Environment Canada weather stations on-site or close by. Weather data (precipitation, relative humidity, and temperature) were collected and correlation explored with FHB measurements (FHB index, FDK in the harvest sample and DON concentration in the harvested grain).

Table 1. Crops additional to the core set (wheat, barley, canola, pea and corn) grown at each site.

The experiments at each site were designed as a split-block, also known as a strip plot design (Little and Hills 1978). In Year 1, the crops were seeded in strips of 10 M wide and up to 44 M long (for the 9 crop site), with 2 M alleyways between crop strips (plots) and 10 M alleyways between replicates (actual size of the individual plots and the experiment will depend on land and equipment availability at each site). This test requires a significant amount of land, one experiment with nine crops requires approximately 2.2 ha (~5.5 acres), six crop sites requires approximately 1.2 ha (3 acres) for each experiment.

The same crops were seeded perpendicular into the stubble of each previous crop to establish up to a 6 x 6 (or 9 x 9) matrix of 36 (or 81) treatments in each of three replicates. The plot size in Year 2 was approximately 2 X 10 M. In Year 2, data on FHB index, % FDK, toxin content and chemotype, and Fusarium species identification, as well as other leaf and root diseases, as detected, was collected from cereal crops (wheat, barley, canaryseed).

In Year 3, durum wheat was seeded at two sites (Lethbridge and Saskatoon), bread wheat at one site (Brandon) and barley at three sites (Mefort, Indian Head and Morden) over the entire area of all replicates to evaluate FHB in these crops as affected by the previous crop sequence. Data collection in cereals was focused prioritizing the core set of five crops and it included intensive assessment of FHB (FHB index, %FDK and toxin content), yield and grain quality (test weight, thousand kernel weight and protein) in the durum (or bread wheat) crop, depending on site. For the case of barley sites, FHB assessment using the FHB index scale is not possible.