Presented by: Kasia Caputa, PAg, SYLVIS Environmental

Solonetzic soils contain high concentrations of soluble sodium relative to magnesium and calcium, which results in a high sodium adsorption ratio (SAR). In fine-textured soils, a high SAR disrupts the structure of the soil, and when cultivated often leads to erosion of topsoil and the development of an impermeable hardpan near the surface that restricts root penetration. These soils tend to have low organic matter, poor drainage, and marginal crop productivity. Soils with high SAR can be rehabilitated with the addition of soluble calcium and magnesium, which can displace excess sodium in the soil, and organic matter, which can improve soil aggregation. As beneficial sources of these constituents, the use of biosolids as an amendment was identified as a tool to ameliorate solonetzic soil conditions.

In 2013, SYLVIS Environmental established a demonstration near Ryley, Alberta to test the effect of biosolids applications on soil SAR status and crop yield. Two fields that were previously used for long-term pasture were selected for this demonstration. Biosolids were applied in each of the fields at four different soil-amending rates (11 tons per acre (t/ac), 11 t/ac with lime added at
2 t/ac, 20 t/ac and 29 t/ac). Soil samples were collected before and after application from each of the applied areas, as well as from a control area where no biosolids were applied.

Comparing soil data before biosolids applications and two growing seasons after applications, decreases in SAR of approximately 50% were observed in the top 6 inches of soil in all of the treatments compared to the control (Figure 1). Dry yield and protein yield of wheat increased with biosolids additions by up to 50% and 60%, respectively (Table 1). The demonstration provides strong evidence that biosolids, applied at soil amending rates, can reduce soil solonetzic status, and subsequently improve crop yield.  With over one million acres of solonetzic soils in Alberta, biosolids could become a valuable tool for improving soil quality and yields province-wide in these challenging soils.

Table 1: The effect of biosolids applications on wheat crop yield, planted the first year following biosolids applications.

Treatment

Dry Yield (t/ac)

Protein (%)

Protein Yield (t/ac)

Control

1.46

18.4%

0.27

11 t/ac + Lime

1.95

19.4%

0.38

11 t/ac

2.04

19.7%

0.40

20 t/ac

2.13

20.1%

0.43

29 t/ac

2.23

19.5%

0.43

 
 
 

Figure 1: Sodium adsorption ratio (SAR) in the top 6 inches of soil before (2013) and two years following biosolids applications.