10:00 am - 11:00 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 Jingyu Zhang. This seminar is open to the general public to attend.
Thesis Topic: The long term effects of crop rotation and fertilizer applications on soil health and crop productivity in Alberta
Long-term agricultural management practices affect soil health. Five long-term rotations at the University of Alberta Breton Plots were sampled as part of the Soil Heath Institute (SHI) North American Project to Evaluate Soil Health Measurements (NAPESHM) in 2019: (1) check, NPKS and manure fertility treatments of a wheat–fallow (WF) rotation; (2) check, NPKS and manure fertility treatments of a 5 yr cereal–forage rotation (with and without lime); (3) continuous forage (CF) receiving NPKS fertilizer; (4) continuous grain (CG) receiving NPKS fertilizer; and (5) an 8-yr “agro-ecological” rotation of barley, faba beans and forages receiving manure. In addition to the >25 soil health indicators measured as part of NAPESHM, soil moisture retention curves (SMRC), phospholipid fatty acid (PLFAs) profile, size distribution of water-stable aggregates and total C, N, 13C and 15N within each class of water-stable aggregates were measured on additional samples taken in 2020. These soil health indicators were used to calculate a site-specific soil health index (SPSHI) using methods similar to those used to develop the Cornell comprehensive assessment of soil health (CASH). Multivariate permutational multivariate analysis of variance (PERMANOVA) and non-metric multidimensional scaling (NMDS) were used to assess the significance of long-term crop rotation, fertilization and their interactions on the soil health indicators used to develop the SPSHI. The indicators included in the SPSHI included autoclave-citrate-extractable (ACE) protein, pH, available P, Na, available water holding capacity (AWHC), the proportion of total carbon in aggregates (PTCA) and Phosphomonoesterase. The SPSHI values of each rotation-fertilizer treatment from high to low are 8-yr with manure (0.802), 5-yr cereal-forage with manure and lime (0.79), WF manure (0.686), 5-yr with manure (0.674), 5-yr NPKS with lime (0.633), CG NPKS (0.507), 5-yr check with lime (0.477), 5-yr NPKS (0.432), 5-yr check (0.418), WF with NPKS (0.403), CF with NPKS (0.389), and WF with check (0.38). PERANOVA results indicated significant effects of fertilizer treatments (p-value =0.0064), rotation treatments (p-value =0.0482) and their interaction (p-value =0.0095) on the soil health indicators. The primary difference in SPSHI values was caused by the difference of C and N input in soils, PTCA and pH in response to fertilizer, manure and rotations. The positive correlation between SPSHI values and crop yield is only weak to moderate, mainly because manure has a greater improvement on soil health than crop yield, whereas NPKS fertilizers had the opposite effect.