Soil nitrogen and moisture as influenced by composts and inorganic fertilizer rate

Abstract

The addition of compost may mitigate soil degradation and contribute to the soil nutrient supply in spring cereal monoculture. A field study was carried out in eastern Quebec, Canada, to assess the impact of composts from four sources and ammonium nitrate (AN) applied at different rates in spring on soil moisture and inorganic N in spring wheat production (Triticum aestivum L. 'Messier'). The experiment was conducted in 1994 and 1995 on two different soils: a Kamouraska clay (Orthic Humic Gleysol) and a Saint-André sandy loam (Fragic Humo-Ferric Podzol). Composts were applied at rates of 0, 90, 180 and 360 kg total N ha−1. Ammonium nitrate was applied at 0, 45, 90 and 180 kg N ha–1. Treatments in which AN was added to composts were also included. Thirty days after N application, profile soil inorganic N increased linearly with rates of commercial composts and AN but not with farm composts, whereas at harvest, residual soil N was not affected by composts but was increased by AN. The relative contribution of the compost organic fraction was negligible in the first year of application. Soil inorganic N at 30 d after fertilizer applications was significantly related to plant N uptake at harvest (r2 = 0.74), suggesting useful index of compost N availability. Large amounts of compost raised soil moisture content of the sandy loam by 3–5%, particularly under dry climatic conditions. Commercial composts have a small N fertilizer value, whereas composted dairy manure should be considered preferable as a soil amendment. Key words: Dairy manure compost, shrimp wastes, peat moss, wheat