Pest regulation: Use no tillage in arable fields

Supporting evidence from individual studies

1. A replicated, controlled study in 1996–1998 in an irrigated tomato field in the San Joaquin Valley, California, USA, found more weeds in plots with no tillage (and winter cover crops), compared to plots with tillage (and winter fallows), when herbicide was used on the fallows. When herbicide was not used, differences were inconsistent. Pest numbers: More weeds were found in plots with no tillage, in some comparisons (9 of 12 comparisons with herbicide use on fallows, in 1998: 4–12% vs 0–3% weed cover; two of 12 comparisons without herbicide use on fallows, in 1998: 5–6% vs 2%), but fewer weeds were found in two of 12 comparisons without herbicide use on fallows, in 1998 (4–5% vs 11%). In 1997, similar weed cover was found in plots with or without tillage (1–4%). Methods: There were 12 plots (4.5 x 27.5 m plots) for each of four treatments (two grass-legume mixtures, or two legumes without grasses, as winter cover crops, sown in October 1996–1997, killed and retained as mulch, with no tillage, in March 1997–1998) and each of two controls (bare-soil fallows in winter, with or without herbicide, and conventional tillage in spring). Tomato seedlings were transplanted in April 1997–1998. The tomatoes were irrigated (two inches/week) and fertilized (0, 100, or 200 lb N/acre). All plots were hand weeded in May, June, and July, and control plots were also cultivated in May and June. Weed cover was estimated before cultivation (July 1997 and May, June, and July 1998) or after cultivation (May and June 1997), in three quadrats/plot (1.8 m² quadrats). It was not clear whether these results were a direct effect of cover crops or tillage.

   Study and other actions tested

   Referenced paper

   Herrero E.V., Mitchell J.P., Lanini W.T., Temple S.R., Miyao E.M., Morse R.D. & Campiglia E. (2001) Use of cover crop mulches in a no-till furrow-irrigated processing tomato production system. HortTechnology, 11, 43-48.

2. A replicated, randomized, controlled study in 1997–2001 in a rainfed pea-wheat-barley field near Barcelona, Spain, found more weeds in plots with no tillage, compared to conventional tillage. Pest numbers: More weed biomass was found in plots with no tillage, compared to conventional tillage, in one of two comparisons (grasses: 12 vs 0 g/m²). Methods: No tillage or conventional tillage was used on two plots each (30 x 45 m plots). A mouldboard plough was used for conventional tillage (25 cm depth). Pre-emergence herbicide was used for no tillage. A seed drill, fertilizer, and post-emergence herbicide were used on all plots. Weeds were sampled each year, when crops were harvested (June–July 1998–2001, 10 quadrats/plot, 0.25 m² quadrats).

   Study and other actions tested

   Referenced paper

   Mas M.T. & Verdú A.M.C. (2003) Tillage system effects on weed communities in a 4-year crop rotation under Mediterranean dryland conditions. Soil and Tillage Research, 74, 15-24.

3. A replicated, randomized, controlled study in 1993–2001 in a rainfed cereal field in central Italy (partly the same study as (7)) found more weed species in plots with no tillage, compared to conventional tillage, but tillage had inconsistent effects on weed abundance. Pest numbers: More weed species were found in plots with no tillage, compared to conventional tillage (19 vs 14 species). More weeds were found in plots with no tillage, compared to conventional tillage, for five of seven weed species (959–8,069 vs 13–454 weed seedlings/m²), but fewer weeds were found, for two of seven weed species (71–97 vs 849–884). Methods: Conventional tillage or no tillage was used on 48 plots each (21 x 11 m sub-sub-plots, in a split-split-plot experimental design), from 1994–2000. A mouldboard plough (30 cm depth, in spring) and a standard precision seed drill were used for conventional tillage. A direct seed drill was used for no tillage. Herbicide and fertilizer were used on all plots. Winter cover crops were grown on three of four plots, and cereal crop residues were retained over winter on one of four plots. Weed seeds were sampled in soil cores in February 2001 (27 cores/plot, 0–15 cm depth, 3.5 cm diameter) and identified after germination in a greenhouse.

   Study and other actions tested

   Referenced paper

   Moonen A.C. & Bàrberi P. (2004) Size and composition of the weed seedbank after 7 years of different cover-crop-maize management systems. Weed Research, 44, 163-177.

4. A replicated, controlled study in 1993–2006 in an irrigated tomato-corn field in Davis, California, USA, found similar numbers of natural enemies in soils with no tillage or conventional tillage. Natural enemy numbers: Similar numbers of predatory mites were found in soils with no tillage or conventional tillage (14 vs 7 individuals/100 g fresh soil). Methods: No tillage or conventional tillage was used on three plots each (conventional: 0.4 ha plots; no tillage: 3 m² microplots). Plots with conventional tillage were tilled about five times/year (depth not reported). Plots with no tillage were hand weeded. All plots were irrigated. Half of the plots were fertilized, and compost was added to the other half. Soil samples were collected eight times in March 2005–November 2006 (three samples/plot). Mites were sampled with soil cores (5 cm diameter, 10 cm depth).

   Study and other actions tested

   Referenced paper

   Sanchez-Moreno S., Nicola N.L., Ferris H. & Zalom F.G. (2009) Effects of agricultural management on nematode-mite assemblages: soil food web indices as predictors of mite community composition. Applied Soil Ecology, 41, 107-117.

5. A replicated, randomized, controlled study in 2005–2007 in a rainfed field in the central Bekaa Valley, Lebanon, found similar amounts of weeds in plots with no tillage or conventional tillage. Pest numbers: Similar amounts of weeds were found in plots with no tillage or conventional tillage (density: 43 vs 44 weeds/m²; dry weight: 34 g/m²). Methods: No tillage or conventional tillage was used on four plots each (14 x 6 m), in October. Conventional plots were ploughed (25–30 cm depth) and then shallowly disk-cultivated. Barley, chickpeas, and safflower were planted in November. Barley and safflower were fertilized (60–100 kg N/ha). Weed density and dry weight were measured on 30 March. Herbicide was used on all plots after sowing the seeds in November 2005. Herbicide was also used, and all plots were hand weeded, after the weed measurements in 2006.

   Study and other actions tested

   Referenced paper

   Yau S.K., Sidahmed M. & Haidar M. (2010) Conservation versus conventional tillage on performance of three different crops. Agronomy Journal, 102, 269-276.

6. A replicated, randomized, controlled study in 2002–2004 in a rainfed olive grove in Córdoba, Spain, found fewer weeds in plots with no tillage, compared to tillage. Pest numbers: Fewer weeds were found in plots with no tillage, compared to tillage, in one of two years (69 days after mowing, in 2004: 80 vs 130 weeds/m²). Methods: Cover crops were grown on 16 plots, from mid-October to mid-April, when the cover crops were mown and chopped (3 x 3 m plots). Weed seeds were broadcast over all plots, in January. Half of the plots were then rototilled (depth not reported), to incorporate the cover crop residues into the soil, and half were not tilled (but the residues were retained as mulch). All plots were superficially tilled in autumn (10 cm depth). Common mustard Sinapis alba subsp. mairei was used as a cover crop. Weeds were sampled in five quadrats/plot (31 x 62 cm, every week, 20–69 days after mowing).

   Study and other actions tested

   Referenced paper

   Alcántara C., Pujadas A. & Saavedra M. (2011) Management of Sinapis alba subsp. mairei winter cover crop residues for summer weed control in southern Spain. Crop Protection, 30, 1239-1244.

7. 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.

   Study and other actions tested

   Referenced paper

   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.

8. A replicated, randomized, controlled study in 1985–2008 in a rainfed wheat-vetch field near Madrid, Spain, found similar numbers of weed species in plots with no tillage or conventional tillage. Pest numbers: Similar numbers of weed species were found in plots with or without tillage (6.7 vs 7.3 species), and no differences in the evenness or diversity of weed communities were found (reported as Pielou’s index and Shannon’s index). Methods: Wheat and vetch were grown in rotation. Conventional tillage or no tillage was used on four plots each (20 x 40 m). A mouldboard plough and a cultivator were used for conventional tillage (depths not reported). Pre-emergence herbicide was used for no tillage (and the wheat stubble was chopped, before the vetch was planted). Post-emergence herbicide was used on all plots, when the wheat was tillering. Fertilizer and a seed drill were used on all plots. Weeds were sampled when the wheat was tillering or the vetch stems were elongating (February–April 1986–2008, 5–20 samples/plot, 30 x 33 cm sampling areas).

   Study and other actions tested

   Referenced paper

   Plaza E.H., Kozak M., Navarrete L. & Gonzalez-Andujar J.L. (2011) Tillage system did not affect weed diversity in a 23-year experiment in Mediterranean dryland. Agriculture, Ecosystems & Environment, 140, 102-105.

9. A replicated, randomized, controlled study in 2005–2011 in a rainfed lentil field and wheat-chickpea-barley-lentil field in Syria found similar amounts of most diseases in plots with no tillage or conventional tillage. Crop damage: A higher incidence of Didymella rabiei Ascochyta blight was found in plots with no tillage, compared to conventional tillage (13–23% vs 4–8%), but there was no difference in disease severity (3.75–5.5 vs 3.25–3.75 on a scale from 0 to 9, where 9 is the most severe). Similar incidences of three other diseases were found in plots with no tillage or conventional tillage (Heteredora cicero cyst nematode disease: 8% vs 9–16% incidence; Fusarium oxysporum lentil Fusarium wilt: 3%; Peronospora lentis downy mildew: 2%). Methods: In one experiment, wheat, chickpeas, barley, and lentils were grown in rotation. In another, lentils were grown in monoculture. In the rotation, no tillage or conventional tillage was used on three plots each, in 2008–2010, and four plots each, in 2009–2011. In the monoculture, there were four plots each (plot size not reported, but sub-subplots were 780 m²). Plots received no tillage (direct drilling) or conventional tillage (cultivation and mouldboard ploughing; depth not reported).

   Study and other actions tested

   Referenced paper

   Ahmed S., Piggin C., Haddad A., Kumar S., Khalil Y. & Geletu B. (2012) Nematode and fungal diseases of food legumes under conservation cropping systems in northern Syria. Soil and Tillage Research, 121, 68-73.

10. A replicated, controlled study in 1991–2009 in a rainfed faba bean field in Sicily, Italy, found fewer root parasites, but more weeds, in plots with no tillage, compared to conventional tillage. Pest numbers: Fewer Orobanche crenata root parasites were found in plots with no tillage, compared to conventional tillage (7 vs 10 broomrapes/m²), but there was no difference in the weights of root parasites (1.44 vs 1.59 g). More weeds were found in plots with no tillage, compared to conventional tillage (1.84 vs 1.26 Mg/ha), but there were similar numbers of weed species (16–18 species). Methods: No 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. Herbicide (before sowing) and a seed drill were used for no 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). Root parasites and weeds were measured in three samples/faba bean plot (four rows/sample, 3 m rows).

    Study and other actions tested

    Referenced paper

    Giambalvo D., Ruisi P., Saia S., Di M.G., Frenda A.S. & Amato G. (2012) Faba bean grain yield, N2 fixation, and weed infestation in a long-term tillage experiment under rainfed Mediterranean conditions. Plant and Soil, 360, 215-227.

11. A replicated, randomized, controlled study in 2009–2011 in two irrigated pepper fields in central Italy found fewer weeds in plots with no tillage, compared to conventional tillage, but tillage had inconsistent effects on weed biomass. Pest numbers: Fewer weeds were found in plots with no tillage, compared conventional tillage, in five of eight comparisons (14–50 vs 43–122 plants/m²). Lower weed biomass was found in plots with no tillage, compared to conventional tillage, in one of eight comparisons (inside pepper rows: 7 vs 36 g dry matter/m²), but higher weed biomass was found in two of eight comparisons (outside pepper rows: 41–54 vs 25–31). Methods: A mouldboard plough (30 cm depth) was used on all plots in autumn, before the winter cover crops were planted. Cover crops were mown or chopped in spring, before tillage. No tillage or conventional tillage was used on 12 plots each (6 x 12 m plots), in May 2010–2011. A mouldboard plough (30 cm depth) and a disk (two passes) were used for conventional tillage, incorporating the cover crop residues. Cover crop residues were mulched and herbicide was used for no tillage. Pepper seedlings were transplanted into the plots in May, and fruits were harvested twice/year in August–October 2010–2011. Weeds were sampled 30 days after transplanting (six samples/plot). All plots were fertilized before the cover crops, but not after. All plots were irrigated.

    Study and other actions tested

    Referenced paper

    Radicetti E., Mancinelli R. & Campiglia E. (2013) Influence of winter cover crop residue management on weeds and yield in pepper (Capsicum annuum L.) in a Mediterranean environment. Crop Protection, 52, 64-71.

12. A replicated, randomized, controlled study in 1994–2009 in a rainfed pea-cereal field near Madrid, Spain, found that tillage had inconsistent effects on weeds. Pest numbers: Fewer weeds were found in plots with no tillage, compared to conventional tillage, in one of four comparisons (5.1 vs 9.3 plants/m²), but more weeds were found in one of four comparisons (6.7 vs 3.4). Similar numbers of weed species were found in plots with no tillage or conventional tillage (data reported as an index of species richness). Methods: No tillage or conventional tillage was used on four plots each (each with three 10 x 25 m sub-plots, with different pea-cereal rotations), in October or November. A mouldboard plough was used for conventional tillage (30 cm depth). A seed drill and herbicide were used for no tillage. The peas were not fertilized. Weeds were identified and counted in four quadrats/sub-plot (0.125 m² quadrats).

    Study and other actions tested

    Referenced paper

    Santín-Montanyá M.I., Zambrana E., Fernández-Getino A.P. & Tenorio J.L. (2014) Dry pea (Pisum sativum L.) yielding and weed infestation response, under different tillage conditions. Crop Protection, 65, 122-128.