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Providing evidence to improve practice

Action: Crop production: Use crop rotations Mediterranean Farmland

Key messages

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Crop yield (8 studies): Four replicated, controlled studies (three randomized) from Italy, Spain, and Turkey found higher crop yields in plots with rotations, compared to monocultures, in some comparisons. Four replicated, randomized, controlled studies from Australia, Portugal, and Spain found similar crop yields in plots with or without rotations.

Crop quality (1 study): One replicated, controlled study from Italy found more protein in wheat that was grown in rotation, compared to continuously-grown wheat.

Implementation options (2 studies): One study from the USA found higher tomato yields in four-year rotations, compared to two-year rotations. One study from Italy found higher wheat yields in rotations with beans, compared to clover.

 

Supporting evidence from individual studies

1 

A replicated, randomized, controlled study in 1983–1996 in a rainfed wheat field in the Henares river valley, Spain, found similar wheat yields in plots with or without crop rotations. Crop yield: Similar wheat yields were found in plots with or without crop rotations (2.5–2.7 vs 2.5–2.8 Mg/ha). Methods: Wheat was grown in continuous monoculture or in rotation with vetch (12 plots each, 20 x 30 m plots). Fertilizer and post–emergence herbicide were used on all plots. Wheat was harvested at maturity (July 1996), and yield was measured in two strips/subplot (1.4 x 30 m strips).

2 

A replicated, randomized, controlled study in 1994–1998 on an irrigated, arable farm near Davis, California, USA, found higher tomato yields in plots with four-year crop rotations, compared to two-year rotations. Implementation options: Higher tomato yields were found in plots with four-year rotations, in one of five years (in 1994: 92 vs 85 mg/kg). Methods: A four-year rotation (tomato, safflower, corn and wheat, beans) was used on 16 plots (four plots for each phase, each year), and a two-year rotation (tomato, wheat) was used on eight plots (four plots for each phase, each year). Each plot was 68 x 18 m. Fertilizer and pesticide were used on all plots.

 

3 

A replicated, randomized, controlled study in 2004–2006 in an occasionally irrigated oat field in Portugal, found similar oat yields in plots with a lupin-oat sequence, compared to an oat-oat sequence. Crop yield: Similar oat yields were found in all plots (4.2 t dry matter/ha). Methods: Oats or white lupins Lupinus albus were grown in six plots each in 2003–2004 (year 1). Oats were grown in all plots in 2004–2005 (year 2). Each plot was 5 x 10 m. Half were tilled (15 cm depth), and half were not (crop residues were retained). All plots were fertilized with phosphorus (60 kg/ha), and oats were also fertilized with nitrogen (100 kg/ha). The seeds were sown in September and the oats were harvested in May.

 

4 

A replicated, randomized, controlled study in 1993–1997 in a rainfed barley field near Madrid, Spain, found higher barley yields in plots with vetch-barley or fallow-barley rotations, compared to plots with continuous barley. Crop yield: Higher barley yields were found in plots with rotations (4,107–4,395 vs 2,465 kg/ha). Methods: Barley was grown continuously (one plot), or in rotation with vetch Vicia sativa or fallow (one plot/phase), in each of three tillage treatments (conventional, reduced, or no tillage), in each of four blocks. Plots were 10 x 25 m. The barley phases were fertilized (8-24-8 NPK: 200 kg/ha; ammonium nitrate: 200 kg/ha). Before the experiment, barley was grown in these plots for over 10 years. Barley was harvested in June.

 

5 

A replicated, randomized, controlled study in 1999–2005 in a rainfed cereal field in northeast Spain found higher barley yields in plots with rotations, compared to continuous barley. Crop yield: Higher barley yields were found in plots with rotations, compared to continuous barley, in one of two comparisons (2,716 vs 2,192 kg/ha). Similar wheat yields were found in plots with or without rotations (1,981–2,125 vs 2,272 kg/ha). Similar aboveground biomass was found in cereal plots with or without rotations (6–9 vs 7–8 t/ha). Methods: Continuous wheat (one plot), continuous barley (one plot), a wheat-barley-rapeseed Brassica napus rotation (one plot/phase), or a wheat-barley-vetch Vicia sativa rotation (one plot/phase) were grown in each of three blocks. Each plot was 50 x 8 m. Wheat and barley were sown in early November (450 seeds/m2). Vetch and rapeseed were sown in late September to early October (150 and 80 seeds seeds/m2, respectively). Fertilizer was used on all plots (except vetch phases) in January and February. Herbicide was used in all plots.

 

6 

A replicated, randomized, controlled study in 2003–2005 in a rainfed winter wheat field in Central Anatolia, Turkey, found higher wheat yields in plots with rotations, compared to continuous wheat. Crop yield: Wheat yields were higher in plots with rotations (1,320–2,243 vs 543 kg grain/ha). Methods: Wheat was grown continuously (three plots) or in rotation with one of five other phases (three plots each: winter lentil, chickpea, sunflower, spring lentil, or fallow). Each plot was 5 x 15 m. All plots were fertilized. Before the experiment, these rotations had been used for 21 years in this field. The wheat was harvested in July.

 

7 

A replicated, controlled study in 1991–2009 in a rainfed durum wheat field in Sicily, Italy, found higher wheat yields, and higher protein content in wheat, in plots with rotations, compared to continuous wheat. Crop yield: Wheat yields were higher in plots with rotations (4.2–4.7 vs 3.2 mg grain/ha). Crop quality: Wheat protein content was higher in plots with rotations (141–143 vs 136 g protein/kg grain). Implementation options: Wheat yields were higher in rotations with faba beans, compared to rotations with berseem clover (4.7 vs 4.2 mg/ha). Methods: Continuous durum wheat Triticum durum, or durum wheat in rotation with faba bean Vicia faba or berseem clover Trifolium alexandrinum, was grown in three subplots each (in plots with conventional, reduced, or no tillage), in each of two blocks (one phase of each rotation in each block, each year). Each subplot was 18.5 x 20 m. The seeds were sown in December, and the wheat was harvested in May. All plots were fertilized (wheat: 69 kg/ha P2O5 before planting and 120 kg N/ha after; beans or clover: 46 kg/ha P2O5 before planting and 80 kg N/ha after). Herbicide was used in all plots. Wheat straw was removed from all plots, but bean and clover straw was not. Yield was measured in three samples areas/plot/year (8.6 x 8.6 m areas).

 

8 

A replicated, randomized, controlled study in 2009–2010 in a rainfed wheat field in the Wongan Hills, Western Australia, found similar wheat yields in plots preceded by lupins or wheat. Crop yield: In 2010, wheat yields were similar in plots preceded by lupins or wheat (1.4 t/ha). Methods: Wheat or lupin Lupinus angustifolius was planted on six 150 m2 plots each, in June 2009. In June 2010, wheat was planted on all plots. Lime was added to half of the plots (3.5 t/ha). Different fertilizers were used on each crop (e.g., no nitrogen was used on lupin). No plots were tilled.

 

9 

A replicated, randomized, controlled study in 2010–2011 in a rainfed field in Western Australia, found similar wheat yields in plots preceded by canola or wheat. Crop yield: Similar wheat yields were found in plots preceded by canola or wheat (2,500 vs 2,600 kg/ha). Methods: Wheat or canola was grown on three plots each, in 2010, and wheat was grown on all plots in 2011. Each plot was 1.4 x 40 m. Fertilizer (150 kg/ha/year) and herbicide were used on all plots. Yield was measured in 2011.

 

Referenced papers

Please cite as:

Shackelford, G. E., Kelsey, R., Robertson, R. J., Williams, D. R. & Dicks, L. V. (2017) Sustainable Agriculture in California and Mediterranean Climates: Evidence for the effects of selected interventions. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.