Soil microorganisms and crop yields after cattle manure, hog manure, or fertilizer application

Abstract

Soil biological properties can be significantly impacted by land management. Cattle manure, hog manure or inorganic fertilizers were applied annually or triennially to a Gray Wooded soil at Falher, Alberta, over three years. A control treatment without manure or fertilizer was also included. Canola (Brassica napus) was grown in Year 1, hulless barley (Hordeum vulgare) in Year 2, and wheat (Triticum aestivum) in Year 3. Where effects were significant, cattle manure increased soil microbial biomass C (MBC) by 26-86%, hog manure by 31%, and inorganic fertilizers reduced MBC by 20%. Similar effects, except the reduction by inorganic fertilizers, were observed for functional diversity of soil bacteria (Shannon index, H’). Crop N uptake from hog manure was higher than that in other treatments in Year 1, when hog manure increased grain yields by 75%, cattle manure by 49%, and inorganic fertilizers had no significant effect. However, cattle manure out-yielded other treatments in Years 2 and 3 (25-50% increase over the control) even though N uptake from inorganic fertilizers was the highest in Year 2. This implies that factors other than nutrient uptake also influenced crop yields. Frequency of application usually had no effects on MBC or H’, but the triennial application rate of inorganic fertilizers reduced crop yields relative to annual applications in Year 1.