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Providing evidence to improve practice

Individual study: Cultivar mixtures of processing tomato in an organic agroecosystem

Published source details

Barrios-Masias F.H., Cantwell M.I. & Jackson L.E. (2011) Cultivar mixtures of processing tomato in an organic agroecosystem. Organic Agriculture, 1, 17-30


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Crop production: Grow cover crops in arable fields Mediterranean Farmland

A replicated, randomized, controlled study in 2005–2006 in an irrigated, organic tomato field in Yolo County, California, USA, found lower tomato yields in plots with winter cover crops, compared to winter fallows. Crop yield: Lower tomato yields were found in plots with cover crops, compared to fallows (162 vs 234 g harvestable fruit/m2). Crop quality: Tomatoes were not as red in plots with cover crops, compared to fallows (39.8 vs 38.9 L*a*b colour values), but firmer tomatoes were found in plots with cover crops (77% vs 75%). Tomato weight, soluble solids, pH, and titratable acidity did not differ between plots with cover crops or fallows (data not reported). Methods: The field was levelled and fertilized (17 Mg compost/ha). Eight plots had winter cover crops (mustard Brassica nigra, planted on 3 November 2005) and eight plots had winter fallows. Each plot was 16 x 9 m. Cover crops were mown on 26 April 2006, sprinkler irrigated, and tilled into the soil (10 cm depth) after 19 days, when fallow plots were also tilled. Plots were weeded and sulfur was used against mites and diseases. Tomatoes were furrow irrigated (approximately every 11 days: 88 mm/event). Tomatoes were transplanted on 18–19 May 2006 and harvested on 7–8 September 2006.

 

Soil: Grow cover crops in arable fields Mediterranean Farmland

A replicated, randomized, controlled study in 2005–2006 in an irrigated, organic tomato field in Yolo County, California, USA, found less nitrate, more ammonium and microbial biomass, and higher carbon dioxide emissions in soils with winter cover crops, compared to winter fallows. Nutrients: Less nitrate was found in soils with cover crops, compared to fallows, in two of five comparisons (7 days after planting tomatoes: 3.3 vs 5.3 g N/m2; 32 days before: 0.2 vs 0.5). More ammonium was found in soils with cover crops, compared to fallows, in one of five comparisons (7 days after planting: 2.1 vs 1.7 g N/m2). Similar amounts of potentially mineralizable nitrogen were found in soils with cover crops or fallows (4.1–8.8 g N/m2). Soil organisms: More microbial biomass (measured as carbon) was found in soils with cover crops, compared to fallows, in one of four comparisons (7 days after planting: 95 vs 75 g C/m2). Greenhouse gases: More carbon dioxide was emitted from plots with cover crops, compared to fallows (28 days after planting: 223 vs 140 mg CO2-C/m2/hour). Methods: The field was levelled and fertilized (17 Mg compost/ha). Eight plots had winter cover crops (mustard Brassica nigra, planted on 3 November 2005) and eight plots had winter fallows. Each plot was 16 x 9 m. Cover crops were mown on 26 April 2006, sprinkler irrigated, and tilled into the soil (10 cm depth) after 19 days, when fallow plots were also tilled. Plots were weeded and sulfur was used against mites and diseases. Tomatoes were furrow irrigated (approximately every 11 days: 88 mm/event). Soil samples were collected on a total of five dates, before and after planting tomatoes (nutrients: 0–60 cm depth; microbial biomass: 0–30 cm depth). Greenhouse gas samples were collected after irrigation events, 28, 77, and 100 days after planting (closed chambers, for 30 minutes).