By Gary Kruger, PAg, Irrigation Agrologist, Outlook
Before we begin, we would like to thank the Rudy Agro pulse processing facility of Broderick Saskatchewan for sharing this learning experience with us. A faba bean field under supervision of Rudy Agro had stunted plants as shown on the right in Figure 1. The plant on the right reflects "normal growth" of faba bean from a portion of the field that was recently broken after development of irrigation at the site. The field, adjacent to Diefenbaker Lake, was exposed to wind off the lake and had suffered significant erosion events over the course of its cultivated history. Both plant and soil samples were collected from the two areas to gather data for understanding the situation. Obviously superior growth was supported on the newly cultivated area but what was the exact cause of the stunted growth of the mature site? Nodulation of the faba bean roots was normal both sites (Figure 2).
Table 1: Plant tissue analysis of faba bean
|Stunted faba bean
The plant tissue analysis of the stunted plants showed reduced phosphorus, potassium and sulphur levels relative to normally expected levels in faba bean plant tissue. Copper, zinc and boron micronutrients were also deficient.
The soil analysis from the two areas helped identify the cause of the differences. The newly cultivated soil had nearly double the organic matter content of the long term cultivated soil. Organic matter contributes nutrients, tilth and moisture holding capacity to the soil. The level of available potassium from the "new breaking" soil sample was also much higher than the quantity found in the mature cultivated soil while the extracted phosphorus (often called Olsen-P) was about the same in the two soils.
The key observation from the soil data is that lower organic matter caused by erosion was associated with lower nutrient supply of potassium (K). This is especially true of sandy soil which tends to be deficient in potassium. Soil management to prevent erosion and maintain soil organic matter levels on new breaking will help sustain its productivity.
Table 2: Soil analysis of compared growth areas: Long term cultivation versus new breaking
||CEC meq/100 g
|Long term cultivation
*Extractable with 1.0 mole ammonium acetate (NH4OAc).