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Action: Crop production: Use reduced tillage in arable fields Mediterranean Farmland

Key messages

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Crop yield (25 studies)

  • Cereals (16 studies): Nine replicated, controlled studies from Egypt, France, Spain, and Turkey found higher cereal yields in plots with reduced tillage, compared to conventional tillage, in some or all comparisons. Three of these studies also found lower cereal yields in plots with reduced tillage, compared to conventional tillage, in some comparisons. Three replicated, randomized, controlled studies from Lebanon and Spain found lower cereal yields in plots with reduced tillage, compared to conventional tillage. Four replicated, controlled studies from Italy, Spain, and the USA found similar cereal yields in plots with reduced tillage or conventional tillage, in all comparisons. One replicated, randomized, controlled study from Spain found that crops failed in plots with conventional tillage, but not in plots with reduced tillage, in one of three comparisons.
  • Fruits and vegetables (7 studies): Five replicated, randomized, controlled studies from Italy and the USA found higher fruit or vegetable yields in plots with reduced tillage, compared to conventional tillage, in some comparisons. Two of these studies also found lower fruit or vegetable yields in plots with reduced tillage, compared to conventional tillage, in some comparisons. Two replicated, controlled studies from Italy and the USA found similar fruit yields in plots with reduced tillage or conventional tillage, in all comparisons. All fruit or vegetable plots were irrigated, in contrast to most cereal or legume plots.
  • Legumes (3 studies): One replicated, randomized, controlled study from Spain found lower legume yields in plots with reduced tillage, compared to conventional tillage, in one of four comparisons. Two replicated, controlled studies from Italy and Lebanon found similar legume yields in plots with reduced tillage or conventional tillage, in all comparisons. No studies found higher legume yields in plots with reduced tillage, compared to conventional tillage.
  • Oilseeds (1 study): One replicated, randomized, controlled study from Spain found higher rapeseed yields in plots with reduced tillage, compared to conventional tillage.
  • Crop residues (6 studies): Two replicated, randomized, controlled studies from Lebanon and Spain found lower straw yields in plots with reduced tillage, compared to conventional tillage, in some comparisons. One replicated, randomized, controlled study from Spain found higher straw yields in plots with reduced tillage, compared to conventional tillage, in some comparisons. Two replicated, controlled studies from Italy and Spain found similar straw yields in plots with reduced tillage or conventional tillage, in all comparisons. One replicated, randomized, controlled study from the USA found higher cover crop biomass in plots with reduced tillage, compared to conventional tillage.

Crop quality (7 studies): One replicated, randomized, controlled study from Spain found that sunflower seeds had more oil, more monounsaturated fatty acid, and less polyunsaturated fatty acid in plots with reduced tillage, compared to conventional tillage. One replicated, controlled study from Italy found that wheat had a lower protein content in plots with reduced tillage, compared to conventional tillage. Two replicated, controlled studies from Italy and Turkey found similar seed weights in plots with reduced tillage, compared to conventional tillage. One replicated, randomized, controlled study from the USA found that lettuce or broccoli plants were larger in plots with reduced tillage, compared to conventional tillage, in some comparisons, but they were smaller in other comparisons.

Implementation options (2 studies): One replicated, randomized, controlled study from Egypt found higher wheat yields in plots that were tilled at slower speeds. One replicated, randomized, controlled study from Turkey found higher wheat yields, but lower vetch yields, in plots with one type of reduced tillage (rototilling and disking), compared to another type (double disking).

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 crop yields in plots with reduced tillage or conventional tillage. Crop yield: Similar wheat yields were found in plots with reduced tillage or conventional tillage (2.6 vs 2.5 Mg/ha). Methods: Conventional tillage or reduced tillage was used on four plots each. Each plot had two subplots (20 x 30 m, with or without crop rotations). A mouldboard plough (30 cm depth) was used for conventional tillage, in autumn. A chisel plough (20 cm depth) was used for reduced tillage, in autumn. A tine cultivator (10–15 cm depth, two passes) was used for both conventional and reduced tillage, in spring. 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 1998–2000 in an irrigated vegetable field in the Salinas Valley, California, USA, found that tillage had inconsistent effects on crop yield and quality. Crop yield: Lower broccoli yields were found in plots with reduced tillage, compared to conventional tillage (610–620 vs 630–640 g dry weight/m2). Higher lettuce yields were found in plots with reduced tillage, compared to conventional tillage, in two of six comparisons (310–410 vs 300–390 g dry weight/m2), but lower lettuce yields were found in two of six comparisons (280–390 vs 300–430). Crop quality: Smaller lettuce or broccoli plants were found in plots with reduced tillage, compared to conventional tillage, in five of eight comparisons (lettuce: 750–1,080 vs 830–1,150 g fresh weight/plant; broccoli: 240 vs 270), but larger plants were found in two of eight comparisons (lettuce: 1,090 vs 1,050; broccoli: 230 vs 210). Methods: There were four plots (0.52 ha), for each of four treatments (reduced tillage or conventional tillage, with or without added organic matter). In plots with added organic matter, compost was added two times/year, and a cover crop (Merced rye) was grown every autumn or winter. Lettuce or broccoli crops were grown in raised beds. Sprinklers and drip irrigation were used in all plots. Soils were disturbed to different depths (conventional tillage: disking to 50 cm depth, cultivating, sub-soiling, bed re-making, and bed-shaping; reduced tillage: cultivating to 20 cm depth, rolling, and bed-shaping). Crops were collected in two 2 m2 areas/plot.

 

3 

A replicated, randomized, controlled study in 1996–1999 in three rainfed barley fields in the Ebro river valley, Spain (same study as (12-14,17)), found that tillage had inconsistent effects on crop yields. Crop yield: Higher barley yields were found in plots with reduced tillage, compared to conventional tillage, in one of nine comparisons (2,507 vs 1,557 kg grain/ha), but lower barley yields were found in one of nine comparisons (1,043 vs 1,672 kg grain/ha). Methods: Reduced tillage or conventional tillage was used on 27 plots each (50 x 6 m plots). A mouldboard plough (25–30 cm depth) and a cultivator (15 cm depth, 1–2 passes) were used for conventional tillage, in August–September. A cultivator (10–15 cm depth, 1–2 passes) was used for reduced tillage, in September. Two-thirds of the plots were fertilized (50–75 or 100–150 kg N/ha). Barley was sown, with a seed drill, in October–November.

 

4 

A replicated, randomized, controlled study in 2001–2004 in a rainfed wheat-vetch field in the Marmara region, Turkey (same study as (5)), found higher wheat yields in plots with reduced tillage, compared to conventional tillage. Different types of reduced tillage had different effects on wheat and vetch yields. Crop yield: Higher wheat yields were found in plots with reduced tillage, compared to conventional tillage (4,821–5,057 vs 4,683 kg/ha), but similar vetch yields were found (2,462–3,764 vs 3,593 kg/ha). Crop quality: Similar seed weights were found in plots with reduced tillage or conventional tillage (35.8–38.9 vs 37.8 g/1,000 seeds). Implementation options: Higher wheat yields, but lower vetch yields, were found in plots that were rototilled and disked, compared to plots that were double disked (wheat: 5,057 vs 4,821 kg/ha; vetch: 2,462 vs 3,764), and similar seed weights were found (38.9 vs 35.8 g/1,000 seeds). Methods: Conventional tillage with a mouldboard plough (20–22 cm depth) and a double disc (two passes, 8–10 cm depth), reduced tillage with a rototiller (20–22 cm depth) and a double disc (one pass, 8–10 cm), or reduced tillage with a double disc (two passes, 8–10 cm) was used on three plots each (15 x 75 m plots). Fertilizer and herbicide were used on all plots. Wheat was sown in December 2001, October 2002, and November 2003. Vetch was sown in December 2001, November 2002, and December 2003. Wheat and vetch were harvested in June 2002–2004 (3 m2 samples, three/plot).

 

5 

A replicated, randomized, controlled study in 2001–2003 in a rainfed wheat field in northwest Turkey (same study as (4)) found higher crop yields in plots with reduced tillage, compared to conventional tillage, in one of four comparisons. Crop yield: Higher wheat yields were found in plots with reduced tillage, compared to conventional tillage, in one of four comparisons (rototiller in 2002: 4,055 vs 3,540 kg/ha). Methods: Conventional tillage with a mouldboard plough, reduced tillage with a rototiller, or reduced tillage with a disc was used on three plots each (75 x 15 m plots). Fertilizer and herbicide were used on all plots. Winter wheat was planted in December 2001 and October 2002 and harvested in June 2002 and 2003. Crop yields were measured in three sections/plot (3 m2 sections).

 

6 

A replicated, randomized, controlled study in 1993-2000 in a rainfed field near Madrid, Spain, found lower crop yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Lower barley yields were found in plots with reduced tillage, compared to conventional tillage (3,061 vs 4,312 kg/ha). Methods: Conventional tillage or reduced tillage was used on 20 subplots each (10 x 25 m subplots). Barley-barley, barley-vetch, or barley-fallow rotations were used on the subplots. A mouldboard plough (30 cm depth) was used for conventional tillage. A chisel plough (20 cm depth) was used for reduced tillage. Barley was fertilized, but vetch and fallows were not. Herbicide was used when needed. Barley was sown in October and harvested in June. Soil samples were collected after harvest (0–90 cm depth; nitrogen was measured at 0–30 cm depth; phosphorus and potassium at 0–80 cm depth).

 

7 

A replicated, randomized, controlled study in 2002–2005 on three rainfed farms in the Ebro river valley, Spain, found that tillage had inconsistent effects on crop yield. Crop yield: Lower crop yields were found in plots with reduced tillage, compared to conventional tillage, in three of 10 comparisons (barley: 2,273–3,071 vs 2,493–3,514 kg/ha; wheat: 1,830 vs 2,703), but higher yields were found in two of 10 comparisons (rapeseed: 1,783 vs 1,261 kg/ha; wheat: 911 vs 798). Methods: Reduced tillage or conventional tillage was used on ten plots each (Peñaflor: three plots each, 33 x 10 m plots; Agramunt: four plots each, 9 x 50 m plots; Selvanera: three plots each, 7 x 50 m plots). In Peñaflor, a mouldboard plough (30–40 cm depth) and a cultivator (10–15 cm depth) were used for conventional tillage. In Agramunt, a mouldboard plough (25–30 cm depth) and a cultivator (15 cm depth) were used for conventional tillage. In Selvanera, a subsoil plough (40 cm depth) and a cultivator (15 cm depth) were used for conventional tillage. A cultivator (Agramunt and Selvanera: 15 cm depth) or chisel plough (Peñaflor: 25–30 cm depth) was used for reduced tillage.

 

8 

A replicated, randomized, controlled study in 1999–2003 in an irrigated tomato-cotton field in the San Joaquin Valley, California, USA (same study as (24)), found higher tomato yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Higher tomato yields were found in plots with reduced tillage, compared to conventional tillage, in one of two comparisons (without winter cover crops: 58 vs 50 t/ha). Methods: Reduced tillage or conventional tillage was used on eight tomato plots each, in 1999–2003. The plots (9 x 82 m) had six raised beds each. Winter cover crops (triticale, rye, and vetch) were planted on half of the plots, in October 1999–2002, and crop residues were chopped in March. Different numbers of tillage practices were used for conventional tillage (19–23 tractor passes, including disc and chisel ploughing) and reduced tillage (11–12 tractor passes, not including disc and chisel ploughing). Tomato seedlings were transplanted in April 2000–2003. Fertilizer and herbicide were used in all plots. Tomatoes were grown in rotation with cotton.

 

9 

A replicated, randomized, controlled study in 2003–2004 in three irrigated maize-tomato fields near Davis, California, USA, found similar crop yields in plots with reduced tillage or conventional tillage. Crop yield: Similar maize yields were found in plots with reduced tillage or conventional tillage (6.7–9.3 vs 4.1–13.6 Mg grain/ha). Methods: Reduced tillage or conventional tillage was used on nine plots each (1.5 x 1.0 m plots). Nine tillage practices, in 12–15 tractor passes, were used for conventional tillage. Five tillage practices, in 5–10 tractor passes, were used for reduced tillage. Maize seeds were sown with a seed drill in early May or mid-March. All plots were irrigated and fertilized with organic and/or inorganic fertilizer. Maize was harvested in September.

 

10 

A replicated, randomized, controlled study in 2005–2007 in a rainfed field in the central Bekaa Valley, Lebanon, found lower seed and straw yields in plots with reduced tillage, compared to conventional tillage, in some crops. Crop yield: Lower seed yields were found in plots with reduced tillage, compared to conventional tillage, in two of three crops (barley: 3,250 vs 4,550 kg/ha; safflower: 1,900 vs 2,400), and lower straw yields were found in one of three crops (safflower: 7,450 vs 9,050). Methods: Reduced tillage or conventional tillage was used in four plots each (14 x 6 m), in October. Conventional plots were ploughed (25–30 cm depth) and then shallowly disc cultivated. Reduced plots were shallowly disc cultivated (10 cm depth). Barley, chickpeas, and safflower were planted in November. Barley and safflower were fertilized (60–100 kg N/ha). Mature crops were collected in three quadrats/plot (0.25 m2 quadrats).

 

11 

A replicated, controlled study in 2004–2008 in an irrigated maize field in the Garonne River corridor, southern France, found higher crop yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Higher maize yields were found in plots with reduced tillage, compared to conventional tillage, in three of eight comparisons (11–12 vs 10–11 t/ha). Methods: Conventional tillage or reduced tillage was used on six plots each (20 x 50 m plots). Three of these plots had winter cover crops (white mustard or oats), and three had bare soil. A mouldboard plough (28–30 cm depth) and a cultivator (8 cm depth, 1–2 passes) were used for conventional tillage, in April–May. A cultivator (7–9 cm depth) and a disc harrow (8–12 cm depth) were used for reduced tillage, in March–April. Maize was sown in April–May 2005–2008 and harvested in October 2005–2008. A centre-pivot sprinkler was used for irrigation (857–943 mm water/year, irrigation plus rainfall).

 

12 

A replicated, randomized, controlled study in 1996–2009 in a rainfed barley field in the Ebro river valley, Spain (same study as (3,12-14,17)), found higher crop yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Higher barley yields were found in plots with reduced tillage, compared to conventional tillage, in six of nine comparisons (1,050–1,950 vs 300–700 kg/ha). Methods: Reduced tillage or conventional tillage was used on nine plots each (50 x 6 m plots) in October or November. A mouldboard plough was used for conventional tillage (25–30 cm depth, 100% incorporation of crop residues). A cultivator was used for reduced tillage (10–15 cm depth, 50% incorporation of crop residues). Two-thirds of the plots were fertilized (60 or 120 kg N/ha). Mature barley was harvested in June 2006–2009.

 

13 

A replicated, randomized, controlled study in 1996–2009 in a rainfed barley field in the Ebro river valley, Spain (same study as (3,12,14,17)), found more barley straw in plots with reduced tillage, compared to conventional tillage. Crop yield: More barley straw was found in plots with reduced tillage, compared to conventional tillage, in two of six comparisons (456–484 vs 210–242 g/m2). In one of three years, the barley crop failed with conventional tillage, but not with reduced tillage. Methods: Reduced tillage or conventional tillage was used on nine plots each (50 x 6 m plots). A mouldboard plough was used for conventional tillage (25–30 cm depth, 100% incorporation of crop residues). A cultivator was used for reduced tillage (10–15 cm depth, 50% incorporation of crop residues). Two-thirds of the plots were fertilized (60 or 120 kg N/ha). Mature barley was harvested in June 2006–2009 (three samples/plot, 50 cm of one row/sample).

 

14 

A replicated, randomized, controlled study in 1996–2009 in a rainfed barley field in the Ebro river valley, Spain (same study as (3,12,13,17)), found higher crop yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Higher barley yields were found in plots with reduced tillage, compared to conventional tillage (1,792 vs 1,155 kg/ha). Methods: Reduced tillage or conventional tillage was used on nine plots each (50 x 6 m plots) in October or November. A mouldboard plough was used for conventional tillage (25–30 cm depth, 100% incorporation of crop residues). A cultivator was used for reduced tillage (10–15 cm depth, 50% incorporation of crop residues). Two-thirds of the plots were fertilized (60 or 120 kg N/ha). Mature barley was harvested in June 2006–2009.

 

15 

A replicated, controlled study in 1991–2009 in a rainfed faba bean field in Sicily, Italy, found no differences in crop yield or crop quality in plots with reduced tillage, compared to conventional tillage. Crop yield: No differences in faba bean yields were found in plots with reduced tillage, compared to conventional tillage (1.91 vs 1.80 Mg grain/ha; 3.80 vs 3.86 Mg straw/ha). Crop quality: No differences in faba bean seed weight (99 vs 98 g/100 seeds), or numbers of seeds/pod (2.6 seeds/pod), were found in plots with reduced tillage, compared to conventional tillage. Methods: Reduced tillage or conventional tillage was used on two plots each (18.5 x 20 m plots). A mouldboard plough (30 cm depth; in summer) and a harrow (depth not reported; before sowing) were used for conventional tillage. A chisel plough (40 cm depth), a mouldboard plough (15 cm depth, in 1991–1998), and a harrow (depth not reported; before sowing) were used for reduced tillage. In all plots, a hoe was used to control weeds (depth not reported; 1–2 times/year). Faba beans were grown in rotation with durum wheat. During durum wheat growth, herbicide was used in all plots. All plots were fertilized (46 kg P2O5/ha). Faba beans were sown in December and harvested at maturity (month not reported). Yield and quality were measured in three samples/plot (four rows/sample, 3 m rows).

 

16 

A replicated, controlled study in 2007–2009 in an irrigated tomato field in Davis, California, USA, found similar crop yields in plots with reduced tillage or conventional tillage. Crop yield: Similar tomato yields were found in plots with reduced tillage or conventional tillage (24–34 vs 26–33 marketable t/acre). Methods: Conventional tillage or reduced tillage was used on four plots each (90 x 220 feet). Broadcast disking, subsoiling, land planing, and rebedding were used for conventional tillage. A Wilcox Performer was used for reduced tillage (two passes; beds were conserved). Sprinklers, furrow irrigation, and drip-tape (in furrows) were used to irrigate the tomatoes. Winter cover crops (triticale) were grown on half of each plot, and the other half was fallow in winter. All plots were fertilized.

 

17 

A replicated, randomized, controlled study in 1996–2008 in a rainfed barley field in the Ebro river valley, Spain (same study as (3,12-14)), found similar crop yields in plots with reduced tillage or conventional tillage. Crop yield: Similar amounts of barley straw were found in plots with reduced tillage or conventional tillage (1,190–1,679 vs 1,351–1,748 kg/ha). Methods: There were nine plots (50 x 6 m) for each of two tillage treatments (reduced tillage: cultivator, 10–15 cm depth; conventional tillage: mouldboard plough, 25–30 cm depth). Plots were tilled in October or November. Two-thirds of the plots were fertilized (60 or 120 kg N/ha/year). Barley was harvested in June.

 

18 

A replicated, controlled study in 1991–2009 in a rainfed wheat field in Sicily, Italy, found similar crop yields, but lower crop quality, in plots with reduced tillage, compared to conventional tillage. Crop yield: Similar wheat yields were found in plots with reduced tillage or conventional tillage (4 Mg/ha). Crop quality: Wheat grains had less protein in plots with reduced tillage, compared to conventional tillage (141 vs 144 g/kg). Methods: Reduced tillage or conventional tillage was used on six plots each (18.5 x 20 m plots). Mouldboard ploughing (30 cm depth, in summer) and harrowing (1–2 passes) were used for conventional tillage. Chisel ploughing (40 cm depth, in summer) and mouldboard ploughing (15 cm, in autumn) were used for reduced tillage. A seed drill and pre-emergence herbicide were used for no tillage. All plots were fertilized (before planting wheat: 69 kg/ha P2O5; before planting bean and berseem: 46 kg/ha P2O5; wheat mono crop: 120 kg N/ha; rotational crops: 80 kg N/ha). Weeds were controlled with post-emergence herbicide. Yield was measured in three areas (8.6 x 8.6 m) in each plot, in each year.

 

19 

A replicated, randomized, controlled study in 2009–2011 in two irrigated pepper fields in central Italy found no difference in crop yields between plots with reduced tillage or conventional tillage. Crop yield: No difference in pepper yields was found between plots with reduced tillage or conventional tillage (3.7–41.4 vs 2.2–40.2 t/ha, fresh weight). Methods: A mouldboard plough (30 cm depth) was used on all plots in autumn, before winter cover crops were planted. Cover crops were mown or chopped in spring, before tillage. Conventional tillage or reduced tillage was used on 12 plots each (6 x 12 m plots), in May 2010–2011. A mouldboard plough and a disc (two passes) were used for conventional tillage (which incorporated the cover crop residues into the soil to a depth of 30 cm). A rotary hoe was used for reduced tillage (which incorporated the cover crop residues into the soil to a depth of 10 cm). Pepper seedlings were transplanted into the plots in May, and fruits were harvested twice/year in August–October 2010–2011. All plots were fertilized before the cover crops, but not after. All plots were irrigated.

 

20 

A replicated, randomized, controlled study in 2009–2012 in two irrigated vegetable fields in central Italy found higher crop yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Higher crop yields were found in plots with reduced tillage, compared to conventional tillage, in one of six comparisons (in plots with hairy vetch as the winter cover crop: 21 vs 17 t/ha endive, fresh weight). Methods: Reduced tillage or conventional tillage was used on nine plots each (6 x 4 m plots). Each plot had a winter cover crop (hairy vetch, oats, or oilseed rape). Cover crops were sown in September 2009–2010 and suppressed in May 2010–2011. A mouldboard plough and a disk harrow (two passes) were used for conventional tillage (incorporating the cover crop residues to 30 cm depth). A rotary hoe was used for reduced tillage (incorporating the cover crop residues to 10 cm depth). Pepper seedlings were transplanted into these plots in May 2010–2011 and were last harvested in October 2010 and September 2011. After the pepper harvest, endive and savoy cabbage seedlings were transplanted into these plots, and they were harvested in December 2010 and November 2011 (endive) or March 2011 and February 2012 (cabbage). No fertilizer was added while the crops were growing, but the plots were irrigated.

 

21 

A replicated, randomized, controlled study in 2008–2013 in a rainfed wheat-sunflower-pea field near Seville, Spain, found similar crop yields, but differences in crop quality, in plots with reduced tillage, compared to conventional tillage. Crop yield: Similar crop yields were found in plots with reduced tillage or conventional tillage (data reported for multiple crops and years). Crop quality: More oil, more of five nutrients, more monounsaturated fatty acid, and less polyunsaturated fatty acid were found in sunflower seeds in plots with reduced tillage, compared to conventional tillage (49.6 vs 48.0% oil). Methods: Reduced tillage or conventional tillage was used on three plots each (6 x 33.5 m plots). A mouldboard plough (25–30 cm depth), a chisel plough (25 cm depth, twice/year), and a disc harrow (12 cm depth) were used for conventional tillage. A chisel plough (25 cm depth, once/year), a disc harrow (5 cm depth), and herbicide were used for reduced tillage. Wheat, sunflowers, and peas were grown in rotation. Wheat was fertilized, but sunflowers and peas were not. Sunflowers were sown in May 2013 (three months later than usual) and harvested in September. Yield and quality were measured in 16 sunflower heads/plot.

 

22 

A replicated, randomized, controlled study in 1987–2010 in rainfed cereal fields in the Ebro river valley, Spain, found lower crop yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Lower grain yields were found in plots with reduced tillage, compared to conventional tillage (3,923 vs 4,210 kg/ha). Crop quality: No difference in grain weight was found between plots with reduced tillage or conventional tillage (34 vs 32 mg/grain). Methods: Reduced tillage or conventional tillage was used on ten plot each (Peñalba: three plots each, 34 x 175 m plots, established in 2005; Agramunt: four plots each, 9 x 50 m plots, established in 1990; Selvanera: three plots each, 7 x 50 m plots, established in 1987). In Peñalba, a disk plough (20 cm depth) and a cultivator (10 cm depth) were used for conventional tillage. In Agramunt, a mouldboard plough (25 cm depth) and a cultivator (15 cm depth) were used for conventional tillage. In Selvanera, a subsoil plough (40 cm depth) and a chisel plough (15 cm depth) were used for conventional tillage. A cultivator (Peñalba: 10 cm depth; Agramunt: 15 cm) or a chisel plough (Selvanera: 15 cm) was used for reduced tillage. Barley (Peñalba) or wheat (Agramunt and Selvanera) was planted in November 2009 with a seed drill (2–4 cm depth) and harvested in June–July 2010.

 

23 

A replicated, randomized, controlled study in 1994–2009 in a rainfed pea-cereal field near Madrid, Spain, found lower pea yields and differences in crop quality in plots with reduced tillage, compared to conventional tillage. Crop yield: Lower grain yields were found in plots with reduced tillage, compared to conventional tillage, in one of four comparisons (peas: 0.08 vs 0.3 t/ha), and lower straw yields were found in two of four comparisons (1.5–2.4 vs 2.3–2.8 t/ha). Crop quality: Smaller peas, shorter pods, and fewer peas/pod were found in plots with reduced tillage, compared to conventional tillage, in one of four comparisons (80 vs 156 g/1,000 seeds; 5.7 vs 6.6 cm/pod; 4.8 vs 6.4 seeds/pod), but longer pods were found in one of four comparisons (7.0 vs 6.5 cm/pod). Methods: Reduced tillage or conventional tillage was used on four plots each (with three 10 x 25 m sub-plots each, with different pea-cereal rotations), in October or November. A mouldboard plough was used for conventional tillage (30 cm depth). A chisel plough was used for reduced tillage (10 cm depth). Peas were planted in November 2005–2008 and harvested in June 2006–2009. The peas were not fertilized.

 

24 

A replicated, randomized, controlled study in 1999–2009 in an irrigated tomato-cotton field in the San Joaquin Valley, California, USA (same study as (8)), found higher tomato yields in plots with reduced tillage, compared to conventional tillage. Crop yield: Higher tomato yields were found in plots with reduced tillage, compared to conventional tillage, in four of 10 years (102–120 vs 62–100 t/ha). Higher cover crop biomass was found in plots with reduced tillage, compared to conventional tillage (4,098 vs 3,609 t/ha). Methods: Reduced tillage or conventional tillage was used on eight tomato plots each, in 1999–2009. The plots (9 x 82 m) had six raised beds each. Winter cover crops (triticale, rye, and vetch) were planted on half of the plots, in October 1999–2008, and crop residues were chopped in March. Different numbers of tillage practices were used for conventional tillage (19–23 tractor passes, including disc and chisel ploughing) and reduced tillage (11–12 tractor passes, not including disc and chisel ploughing). Tomato seedlings were transplanted in April 2000–2009. Fertilizer and herbicide were used in all plots. Tomatoes were grown in rotation with cotton.

 

25 

A replicated, randomized, controlled study in 2012–2013 in a rainfed wheat field in Wadi Madwar, northwestern Egypt, found higher crop yields in plots with less frequent tillage, compared to more frequent, lower crop yields in plots with shallower tillage, compared to deeper, and higher crop yields in plots that were tilled at slower speeds, compared to faster. Crop yield: Higher wheat yields were found in plots with reduced tillage, compared to conventional tillage (1,324 vs 1,238 kg grain/ha). Lower wheat yields were found in plots that were tilled to 15 cm depth, compared to 20–25 cm depth (1,392 vs 1,516–1,518 kg/ha). Implementation options: Higher wheat yields were found in plots that were tilled at slower tractor speeds (0.69–1.25 m/s: 1,454–1,528 kg/ha), compared to the fastest speed (1.53 m/s: 1,397 kg/ha). Methods: Reduced tillage or conventional tillage was used on three plots each (0.45 ha plots). A chisel plough was used for both reduced tillage (one pass) and conventional tillage (two passes). Each plot had three subplots (0.15 ha subplots, tilled to 15, 20, or 25 cm depth). Each subplot had four sub-subplots (size not reported; tilled at 0.69, 1, 1.25, or 1.53 m/s). Wheat was planted in December 2012, fertilized, and harvested in May 2013.

 

26 

A replicated, randomized, controlled study in 2009–2011 in an irrigated eggplant field in central Italy found that tillage had inconsistent effects on crop yield. Crop yield: Higher eggplant yields were found in plots with reduced tillage, compared to conventional tillage, in three of four comparisons (21–36 vs 18–32 Mg/ha fresh weight), but lower yields were found in one of four comparisons (7 vs 14). Methods: A mouldboard plough (30 cm depth) was used on all plots in autumn, before winter cover crops were planted. Cover crops were mown or chopped in spring, before tillage. Reduced tillage or conventional tillage was used on 12 plots each (6 x 4 m plots). A mouldboard plough (30 cm depth) and a disc (two passes) were used for conventional tillage (which incorporated the cover crop residues into the soil). A rotary hoe (10 cm depth) was used for reduced tillage (which incorporated some of the cover crop residues into the soil). Eggplant seedlings were transplanted into the plots in May, and fruits were harvested four times/year in July–September 2010–2011. All plots were fertilized before the cover crops were grown, but not after. All plots were irrigated.

 

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.