9:00 am - 10:00 am
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree. This is an ALES MSc Final Exam Seminar by Keshav Bhattarai. This seminar is open to the general public to attend.
Zoom Link: https://ualbertaca.zoom.us/j/99436857333?pwd=JcyIahSqNUabjKTydjE8tIBLn048Qu.1
MSc with Drs. Malinda Thilakarathna and Nityananda Khanal
Thesis Topic: Diversification of annual cropping sequences with perennial forage seed crops
Abstract:
Identifying profitable cropping systems from a sustainable perspective is crucial for addressing the challenges faced in modern farming. A truly sustainable cropping system can ensure farm profitability, promote environmental stewardship, and advance social equity. In this study, we explored the potential of cropping system diversification as a strategy to achieve the sustainability goals. We hypothesized that integrating perennial forage seed crops into cropping systems would increase productivity and profitability while enhancing soil and environmental health. To test this, a field study was initiated in 2013 at Beaverlodge Research Farm, Agriculture and Agri-Food Canada, Alberta to identify beneficial cropping systems. The experiment was laid out in a split plot design with four replicates. Eight different cropping sequences were considered main-factor treatments and three nitrogen levels (0, 45, 90 kg ha-1) were assigned in sub-plots. The cropping sequences included four annual crops (wheat, canola, pea, barley), three perennial grasses (meadow brome grass, timothy, and creeping red fescue), and two perennial legumes (alsike clover and red clover). Among the eight cropping sequences treatments, six were diversified with both perennial forage legumes and grasses to compare with annual-based traditional sequences.
The first study focused on system productivity, measured as Canola Equivalent Yield (CEY), along with economic performance indicators such as gross revenue and gross margin. It also examined nitrogen use efficiency (NUE) through matrices like agronomic NUE, crop nitrogen uptake, and apparent nitrogen fertilizer recovery in diversified cropping systems. The CEY, gross revenue, gross margin, and corresponding nitrogen use efficiency parameters were notably higher in the legume to vernalizing grass rotation, regardless of nitrogen fertility level. The higher seed price of the perennial legume (red clover) and the higher seed yield and price of the vernalizing grass (meadow bromegrass) during their production phases provided an opportunity to capitalize on favorable seasonal weather and local market demands. The aerial biomass yield was significantly higher in annual cropping sequences and improved with increasing nitrogen rates as compared to perennial forage-based sequences. The nitrogen fertilization improved yield and profitability up to 45 kg N ha-1, but further increases to 90 kg N ha-1 did not result in significant economic benefits in most of diversified cropping systems. Our results provide evidence that forage seed crop-based cropping systems have the potential to reduce reliance on external nitrogen inputs and enhance the economic efficiency of production systems.
The second study assessed soil health properties (physical, chemical, and biological) that are sensitive to change in diversified cropping systems. Soil health indicators such as soil organic carbon, microbial biomass carbon, active carbon, and the activities of carbon and nitrogen cycling enzymes were significantly improved with the inclusion of perennial forages in annual cropping systems. Specifically, the creeping red fescue dominated cropping sequence exhibited higher soil aggregate stability and structural resilience as compared to other sequences. Soil enzymatic activities, particularly β-glucosidase and β-N-acetyl-glucosaminidase which are essential for nutrient cycling were also higher in the surface soils under fescue-and legume-integrated sequences. However, the bulk density and water characteristics remained stable with a similar degree of soil penetration resistance across cropping sequences. Similarly, soil pH remained consistent across cropping sequences, while plant-available nitrogen (NH₄⁺ and NO₃⁻) and total nitrogen levels varied with crop-specific influences. Overall, the inclusion of perennial forage seed crops in conventional annual crop-based cropping systems is an effective way to promote soil health.
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