Earthworm populations in relation to soil organic matter dynamics and management in California tomato cropping systems

Published source details Fonte S.J., Winsome T. & Six J. (2009) Earthworm populations in relation to soil organic matter dynamics and management in California tomato cropping systems. Applied Soil Ecology, 41, 206-214.
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This study is summarised as evidence for the following.

	Action	Category
	Soil: Use no tillage in arable fields Action Link
	Soil: Grow cover crops in arable fields Action Link
	Soil: Use reduced tillage in arable fields Action Link

Soil: Use no tillage in arable fields

A replicated site comparison in 2004–2005 in 11 irrigated tomato fields in the Sacramento Valley, California, USA, found more earthworms, more carbon and nitrogen, and greater soil aggregation in soils with no tillage, compared to tillage. Organic matter: More carbon was found in soils with no tillage, compared to tilled fallows (1.6 times as much total carbon). Nutrients: More nitrogen was found in soils with no tillage, compared to tilled fallows (1.5 times as much total nitrogen). Soil organisms: More earthworms, and larger earthworms, were found in soils with no tillage, compared to tilled fallows (85 vs 19 g earthworms/m²; 2.9 times larger). Soil erosion and aggregation: Greater aggregation was found in soils with no tillage, compared to tilled fallows (larger mean weight diameter; data presented as model results). Methods: Earthworms were collected from 11 tomato fields (four fields that were tilled, incorporating the tomato residues into the soil, and seven fields that were not tilled, retaining the tomato residues as mulch), in three 30 cm³ soil pits/field, in February–April 2005. Organic matter and nutrients were measured in horizontal soil cores, collected from the walls of the soil pits (0–15 cm length). All fields were tilled in 2004, after the tomatoes were harvested. All fields were fertilized and irrigated.
Soil: Grow cover crops in arable fields

A replicated site comparison in 2004–2005 in nine irrigated tomato fields in the Sacramento Valley, California, USA, found similar numbers of earthworms in fields with winter cover crops or bare fallows. Soil organisms: Similar numbers of earthworms were found in fields with cover crops or fallows (26 vs 19 g earthworms/m²). Methods: Earthworms were collected from nine tomato fields (five fields with cover crops, four with bare fallows; three 30 cm³ soil pits/field), in February–April 2005. Organic matter and nutrients were measured in horizontal soil cores, collected from the walls of the soil pits (0–15 cm length). All fields were tilled in 2004, after the tomatoes were harvested, and before the cover crops were planted. The cover crops were legumes. All fields were fertilized and irrigated.
Soil: Use reduced tillage in arable fields

A replicated site comparison in 2004–2005 in 16 irrigated tomato fields in the Sacramento Valley, California, USA, found more earthworms in fields with fewer passes of the plough. Organic matter: More carbon was found in fields with fewer passes of the plough in the year before they were sampled (total carbon; data reported as model results). Nutrients: More nitrogen was found in fields with fewer passes of the plough in the year before they were sampled (total nitrogen; data reported as model results). Soil organisms: More earthworms were found in fields with fewer passes of the plough in the year before they were sampled, in one of three comparisons (individual earthworm biomass; data reported as model results). Methods: Earthworms were collected from 16 tomato fields, in February–April 2005. In 2004, these fields had different numbers of tillage operations (3–10 passes of the plough). Five fields were cover cropped, and seven were mulched with crop residues. All fields were fertilized and irrigated.