Long-term effect of tillage, nitrogen fertilization and cover crops on soil organic carbon and total nitrogen content

Published source details Mazzoncini M., Sapkota T.B., Bàrberi P., Antichi D. & Risaliti R. (2011) Long-term effect of tillage, nitrogen fertilization and cover crops on soil organic carbon and total nitrogen content. Soil and Tillage Research, 114, 165-174.
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This study is summarised as evidence for the following.

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

Pest regulation: Use no tillage in arable fields

A replicated, randomized, controlled study in 1993–2008 in a rainfed wheat-maize-wheat-sunflower field in central Italy (partly the same study as (3)) found more weeds in plots with no tillage, compared to conventional tillage. Pest numbers: More weeds were found in plots with no tillage, compared to conventional tillage (21 vs 12 Mg/ha). Methods: No tillage or conventional tillage was used on 64 plots each (21 x 11 m sub-sub-plots). A mouldboard plough was used for conventional tillage (30–35 cm depth), and crop residues were incorporated into the soil. Pre-emergence herbicide was used for no tillage, and crop residues were mulched onto the surface. Post-emergence herbicide and fertilizer were used on all plots. Some plots had winter cover crops. Weeds were collected when the crops were harvested or the cover crops were suppressed (2–4 m² quadrats), in 1994–2008.
Pest regulation: Grow cover crops in arable fields

A replicated, randomized, controlled study in 1993–2008 in a rainfed wheat-maize-wheat-sunflower field in central Italy found fewer weeds in plots with winter cover crops, compared to plots without cover crops. Pest numbers: Fewer weeds were found in plots with cover crops (7–18 vs 28 Mg/ha). Implementation options: Fewer weeds were found in plots with non-legume cover crops, compared to legumes (14–18 Mg/ha). Fewer weeds were found in plots with high-nitrogen-supply legumes, compared to low-nitrogen supply legumes (14 vs 18 Mg/ha). Methods: There were 32 plots (21 x 11 m sub-sub-plots) for each of three treatments (non-legumes, low-nitrogen-supply legumes, or high-nitrogen-supply legumes as winter cover crops) and there were 32 control plots (no cover crops: crop residues and weeds over winter). Different species of cover crops were used in different years. Half of the plots were tilled, and half were not tilled (but pre-emergence herbicide was used). Post-emergence herbicide and fertilizer were used on all plots. Weeds were collected when the crops were harvested or the cover crops were suppressed (2–4 m² quadrats), in 1994–2008.
Soil: Grow cover crops in arable fields

A replicated, randomized, controlled before-and-after study in 1993–2008 in a rainfed wheat-maize-wheat-sunflower field in central Italy found more organic matter and nitrogen in soils with winter cover crops, compared to soils without cover crops. Organic matter: After 15 years, more carbon was found in soils with cover crops, compared to soils without cover crops, in four of six comparisons (legume cover crops, organic carbon concentration, 0–30 cm depth, in 2008: 11–14 vs 10–12 g/kg soil), and carbon increased more over time, in two of three comparisons (legume cover crops: 6–6.5% vs 1.5% increase in Mg organic C/ha, 0–30 cm depth). Nutrients: After 15 years, more nitrogen was found in soils with cover crops, compared to soils without cover crops, in five of six comparisons (total nitrogen concentration, 0–30 cm depth, in 2008: 1.2–1.5 vs 1.1–1.3 g/kg soil), and nitrogen increased over time, rather than decreased, in two of three comparisons (0.14–0.3% increase vs 0.7% decrease in Mg total N/ha, 0–30 cm depth). Implementation options: More carbon was found in soils that were cover cropped with high-nitrogen-supply legumes, compared to non-legumes (organic carbon concentration, 0–30 cm depth: 11–14 vs 10–13 g/kg soil), and more nitrogen was found at one of two depths (total nitrogen, 0–10 cm depth: 1.5 vs 1.4 g/kg soil). Methods: There were 32 plots (21 x 11 m sub-sub-plots) for each of three treatments (non-legumes, low-nitrogen-supply legumes, or high-nitrogen-supply legumes as winter cover crops) and one control (no cover crops: crop residues and weeds). Different species of cover crops were used in different years. Half of the plots were tilled, and half were not tilled (but pre-emergence herbicide was used). Post-emergence herbicide and fertilizer were used on all plots. Soil cores were collected in 1993, 1998, and 2008 (0–30 cm depth; two samples/plot in September).
Soil: Use no tillage in arable fields

A replicated, randomized, controlled before-and-after study in 1993–2008 in a rainfed wheat-maize-wheat-sunflower field in central Italy found more organic matter and nitrogen in soils with no tillage, compared to conventional tillage. Organic matter: After 15 years, more carbon was found in soils with no tillage, compared to conventional tillage, at one of two depths (0–10 cm depth, in 2008: 16 vs 11 g C/kg soil), and carbon increased over time (0–30 cm depth, from 1993 to 2008: 9% increase vs 1% decrease in C/ha). Nutrients: More nitrogen was found in soils with no tillage, compared to conventional tillage, at one of two depths (0–10 cm depth, in 2008: 1.7 vs 1.2 g total N/kg soil), and nitrogen increased over time (0–30 cm depth, from 1993 to 2008: 0.6% increase vs 0.5% decrease in N/ha). Methods: No tillage or conventional tillage was used on 64 plots each (21 x 11 m sub-sub-plots). A mouldboard plough was used for conventional tillage (30–35 cm depth), and crop residues were incorporated into the soil. Pre-emergence herbicide was used for no tillage, and crop residues were mulched onto the surface. Post-emergence herbicide and fertilizer were used on all plots. Some plots had winter cover crops. Soil cores were collected in 1993, 1998, and 2008 for nutrients and organic matter (0–30 cm depth; two samples/plot in September).