Pest regulation: Use no tillage instead of reduced tillage

Supporting evidence from individual studies

1. A replicated, randomized, controlled study in 1997–2001 in a rainfed pea-wheat-barley field near Barcelona, Spain, found similar numbers of weeds in plots with no tillage or reduced tillage. Pest numbers: Similar amounts of weed biomass were found in plots with no tillage or reduced tillage (36 g/m²). Methods: No tillage or reduced tillage was used on two plots each (30 x 45 m plots). A chisel plough was used for reduced tillage (15 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.

2. A replicated, controlled study in 1993–2006 in an irrigated tomato-maize field in Davis, California, USA, found similar numbers of natural enemies in soils with no tillage or reduced tillage. Natural enemy numbers: Similar numbers of predatory mites were found in soils with no tillage or reduced tillage (14 vs 12 individuals/100 g fresh soil). Methods: No tillage or reduced tillage was used on three plots each (reduced: 0.4 ha plots; no tillage: 3 m² microplots). Plots with reduced tillage were tilled about two 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.

3. A replicated, randomized, controlled study in 2005–2007 in a rainfed field in the central Bekaa Valley, Lebanon, found fewer weeds in plots with no tillage, compared to reduced tillage. Pest numbers: Fewer weeds were found in plots with no tillage, compared to reduced tillage (density: 43 vs 113 weeds/m²; dry weight: 34 vs 61 g/m²). Methods: No tillage or reduced tillage (shallow disc cultivation, 10 cm depth) was used in four plots each (14 x 6 m), in October. 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.

4. A replicated, randomized, controlled study in 1985–2008 in a rainfed wheat-vetch field near Madrid, Spain, found fewer weed species in plots with no tillage, compared to reduced tillage. Pest numbers: Fewer weed species were found in plots with no tillage, compared to reduced tillage (6.7 vs 8.3 species), but no differences in the evenness or diversity of weed communities were found (reported as Pielou’s index and Shannon’s index). Methods: Reduced tillage or no tillage was used on four plots each (20 x 40 m). A cultivator and/or a chisel plough were used for reduced tillage (depths not reported). Pre-emergence herbicide was used for no tillage (and the wheat stubble was chopped, before the vetch was planted). Wheat and vetch were grown in rotation. 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 wheat was tillering or 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.

5. 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 reduced tillage. Pest numbers: Fewer Orobanche crenata root parasites were found in plots with no tillage, compared to reduced tillage (7 vs 10 broomrapes/m²), but there were no differences in the weights of root parasites (1.44 vs 1.50 g). More weeds were found in plots with no tillage, compared to reduced tillage (1.84 vs 1.32 Mg/ha), but there were similar numbers of weed species (16–19 species). Methods: No tillage or reduced tillage was used on two plots each (18.5 x 20 m plots). 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. 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.

6. 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 reduced tillage, but tillage had inconsistent effects on weed biomass. Pest numbers: Fewer weeds were found in plots with no tillage, compared to reduced tillage, in five of eight comparisons (14–50 vs 53–152 plants/m²). Less weed biomass was found in plots with no tillage, compared to reduced tillage, in two of eight comparisons (inside pepper rows: 7–37 vs 47–58 g dry matter/m²), but more was found in one of eight comparisons (outside pepper rows: 54 vs 31). 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. No tillage or reduced tillage was used on 12 plots each (6 x 12 m plots), in May 2010–2011. A rotary hoe (10 cm depth) was used for reduced tillage (which incorporated the cover crop residues into the soil). 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.

7. A replicated, randomized, controlled study in 2010–2011 in a rainfed wheat field in Australia found more weeds in plots with no tillage, compared to reduced tillage. Pest numbers: More weed biomass was found in plots with no tillage, compared to reduced tillage (36 vs 20 g/m²). Methods: No tillage or reduced tillage was used on three plots each (1.4 x 40 m plots) in 2010, when the plots were fallow. A rotary hoe (12 cm depth) was used for reduced tillage. Herbicide was used for no tillage. Wheat was grown on all plots in 2011. Fertilizer (150 kg/ha) and herbicides were used on all plots in 2011. Weeds were sampled in 2011, when the wheat was mature.

   Study and other actions tested

   Referenced paper

   Manalil S. & Flower K. (2014) Soil water conservation and nitrous oxide emissions from different crop sequences and fallow under Mediterranean conditions. Soil and Tillage Research, 143, 123-129.

8. A replicated, randomized, controlled study in 1994–2009 in a rainfed pea-cereal field near Madrid, Spain, found fewer weeds in plots with no tillage, compared to reduced tillage. Pest numbers: Fewer weeds were found in plots with no tillage, compared to reduced tillage, in two of four comparisons (5.1–11.9 vs 11.5–15.4 plants/m²). Similar numbers of weed species were found in plots with no tillage or reduced tillage (data reported as an index of species richness). Methods: No tillage or reduced 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 chisel plough was used for reduced tillage (10 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.