Earthworms Increase Nitrogen Leaching to Greater Soil Depths in Row Crop Agroecosystems

• Published in: Ecosystems (New York) Vol. 7; no. 6; pp. 672 - 685
• Main Authors: Domínguez, Jorge, Bohlen, Patrick J., Parmelee, Robert W.
• Format: Journal Article
• Language: English
• Published: New York, NY Springer-Verlag 01-10-2004; Springer; Springer Nature B.V
• Subjects: Agricultural ecosystems; Agricultural soils; Agrochemicals; Agroecosystems; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Cattle manure; Earthworms; Experimental design; Farming systems; Fundamental and applied biological sciences. Psychology; General aspects; Intensive farming; Leachates; Leaching; Lysimeters; Mineral fertilizers; Nitrogen; Nutrient cycles; Organic nitrogen; Population density; Population growth; Soil depth; Soil invertebrates; Soil microorganisms; Soil nutrients; Soil water; Soils; Synecology; Tillage; Zea mays; USA, Ohio; Earthworm; Soils; Ecosystem; Environmental factor; Invertebrata; Nitrogen; Leaching; Annelida; Oligochaeta; Depth; Agroecosystem
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-004-0150-7

Many biological functions of soil organisms are replaced in intensive agricultural systems, but earthworms and other soil invertebrates may continue to have significant effects on nutrient cycling in these disturbed systems. We investigated the influence of earthworms on leaching of water and nitrogen in corn (Zea mays L.) agroecosystems in a long-term (6-year) field experiment in Wooster, Ohio, USA. We employed a split-plot experimental design in which main plots received one of three nutrient treatments (cow manure, legume-grass mixture, inorganic fertilizer) and contained three 4.5 × 4.5-m field enclosures in which earthworm populations were increased, decreased, or unmodified. We installed zero-tension lysimeters beneath enclosures with increased or decreased populations and collected leachates regularly in 1996, analyzing them for water volume and concentrations of NH4
+, NO3
-, and dissolved organic nitrogen (DON). Earthworms did not influence concentrations of inorganic N or DON but greatly increased leachate volume. The total flux of N in soil leachates was 2.5-fold greater in plots with increased earthworm populations than in those with decreased populations. Earthworm population density was positively correlated with total N leaching flux$(r^{2}=0.49)$. Leaching losses of N to a depth of 45 cm were greater in the inorganically fertilized than in the organically fertilized plots, possibly due to greater inorganic N concentrations and lower immobilization potential in inorganically fertilized systems. Our results indicate that earthworms can increase the leaching of water and nitrogen to greater soil depths, potentially increasing N leaching from the system.