Organic mulching, irrigation and fertilization affect soil CO2 emission and C storage in tomato crop in the Mediterranean environment

Published source details Mancinelli R., Marinari S., Brunetti P., Radicetti E. & Campiglia E. (2015) Organic mulching, irrigation and fertilization affect soil CO2 emission and C storage in tomato crop in the Mediterranean environment. Soil and Tillage Research, 152, 39-51.
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This study is summarised as evidence for the following.

	Action	Category
	Water: Grow cover crops in arable fields Action Link
	Crop production: Grow cover crops in arable fields Action Link
	Soil: Grow cover crops in arable fields Action Link

Water: Grow cover crops in arable fields

A replicated, randomized, controlled study in 2011–2013 in two irrigated tomato fields in central Italy found that winter cover crops had inconsistent effects on water availability. Water availability: More water was found in plots with winter cover crops (mulched in the spring), compared to control plots, in some comparisons in July–August (data on soil water content not clearly reported), but inconsistent differences in soil water content were found in May–June (sometimes more, sometimes less). Methods: Three species of winter cover crops (Vicia villosa hairy vetch, Phacelia tanacetifolia lacy phacelia, or Sinapis alba white mustard) were sown on three plots each, in September, and winter weeds were controlled with herbicide on three control plots (18 x 6 m plots). The cover crops were mown and mulched (strips, 80 cm width) in May, and the control plots were tilled (depth not reported). Tomato seedlings were transplanted in May (transplanted into the) and harvested in August. All plots were tilled (30 cm depth) and fertilized (100 kg P₂O₅/ha, harrowed to 10 cm depth) in September. Some plots were also fertilized (100 kg N/ha) in June–July. Plots were irrigated to replace 50–100% of water lost through evapotranspiration. Soil water content (soil moisture meter, 20 cm depth) was measured weekly, or within 48 hours of rainfall, in the tomato-growing season. It was not clear whether these results were a direct effect of cover cropping, mulching, herbicide, or tillage.
Crop production: Grow cover crops in arable fields

A replicated, randomized, controlled study in 2011–2013 in two irrigated tomato fields in central Italy (same study as (23)) found that cover crops had inconsistent effects on tomato yield. Crop yield: Higher tomato yields were found in plots that were cover cropped and mulched with hairy vetch, compared to control plots (5.4–5.9 vs 3.6–5.2 kg fresh weight/m²), but lower yields were found in plots that were cover cropped and mulched with lacy phacelia or white mustard (2.4–4.3 kg). Methods: Three species of winter cover crops (Vicia villosa hairy vetch, Phacelia tanacetifolia lacy phacelia, or Sinapis alba white mustard) were sown on three plots each, in September, and winter weeds were controlled with herbicide on three control plots (18 x 6 m plots). The cover crops were mown and mulched (strips, 80 cm width) in May, and the control plots were tilled (depth not reported). Tomato seedlings were transplanted in May (transplanted into the mulch) and harvested in August. All plots were tilled (30 cm depth) and fertilized (100 kg P₂O₅/ha, harrowed to 10 cm depth) in September. Some plots were also fertilized (100 kg N/ha) in June–July. It was not clear whether these results were a direct effect of cover cropping, mulching, herbicide, or tillage.
Soil: Grow cover crops in arable fields

A replicated, randomized, controlled study in 2011–2013 in two irrigated tomato fields in central Italy found more organic matter and greater carbon accumulation in plots with winter cover crops, compared to plots without cover crops, but cover crops had inconsistent effects on nitrogen. Organic matter: When the tomatoes were harvested, more organic carbon was found in soils with winter cover crops, in 17 of 24 comparisons (1.1–1.8% vs 1–1.6% of soil was organic carbon). Nutrients: When the tomatoes were harvested, more organic nitrogen was found in soils with winter cover crops, in 14 of 24 comparisons (0.12–0.2% vs 0.11–0.15% of soil was organic nitrogen), but less was found in five of 24 comparisons (0.12–0.13% vs 0.14–0.15%). Greenhouse gases: Similar amounts of carbon dioxide were emitted from soils with or without cover crops (3.2–4.2 Mg C/ha), but more carbon accumulated in soils with cover crops, in four of six comparisons (1.1–2.1 vs 0.4–0.7 ratio of C input to output). Implementation options: More carbon accumulated in soils that were cover cropped and mulched with hairy vetch, compared to other species, in three of four comparisons (1.9–2.1 vs 1.1–1.4 ratio of C input to output). Methods: Three species of winter cover crops (Vicia villosa hairy vetch, Phacelia tanacetifolia lacy phacelia, or Sinapis alba white mustard) were sown on three plots each, in September, and winter weeds were controlled with herbicide on three control plots (18 x 6 m plots). The cover crops were mown and mulched (strips, 80 cm width) in May, and the control plots were tilled (depth not reported). Tomato seedlings were transplanted in May (transplanted into the mulch in treatment plots) and harvested in August. All plots were tilled (30 cm depth) and fertilized (100 kg P₂O₅/ha, harrowed to 10 cm depth) in September. Some plots were also fertilized (100 kg N/ha) in June–July. Soil samples were collected after the tomatoes were harvested (0–20 cm depth). Carbon dioxide emissions (closed chambers, 1,334 cm³ volume, 30–180 seconds/sample) were measured weekly, or within 48 hours of rainfall, in the tomato-growing season. It was not clear whether these results were a direct effect of cover cropping, mulching, herbicide, or tillage.