Too much fertilizer? An observational association between inputs at planting and crop yield on a Saskatchewan farming operation

Grain yield and its variability is a major driver of seeding rate and inorganic fertilizer use at planting among grain growers. Recommended rates for fertilizer application with regard to crop utilization and soil management are discretionary and vary between producer and agronomist. This observational case study with Bayesian inference examines the association between application rates of inorganic nitrogen, phosphorus, potassium chloride and sulphur at planting, and yield of durum wheat (Triticum turgidum L.), large green lentils (Lens culinaris Medik.), canola (Brassica napus L.), canaryseed (Phalaris canariensis L.), and spring barley (Hordeum vulgare L.). Using precision agriculture, input and crop yield information for each parcel of cultivated land was collected over a 4 yr period from 2015 to 2018 on a continuous no-till farming operation in the semiarid region of Saskatchewan, Canada. Hierarchical models were derived that accounted for yield variability in crop types due to the random effects of field, cultivar, crop planted in previous year, planting year, combine machine, observation location within field, and elevation. Evidence from this longitudinal study suggests that seed-placed fertilizer above the recommended safe rate can be associated with yield decline on farming operations in the semiarid environment of Saskatchewan, Canada.