Post-fallow tillage and crop effects on soil enzymes and other indicators

Published source details de Varennes A. & Torres M.O. (2011) Post-fallow tillage and crop effects on soil enzymes and other indicators. Soil Use and Management, 27, 18-27.
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This study is summarised as evidence for the following.

	Action	Category
	Crop production: Use no tillage in arable fields Action Link
	Use crop rotation Action Link
	Soil: Use no tillage in arable fields Action Link
	Change tillage practices Action Link

Crop production: Use no tillage in arable fields

A replicated, randomized, controlled study in 2003–2005 in an occasionally irrigated oat field in Portugal found similar crop yields in plots with or without tillage. Crop yield: Similar oat yields were found in plots with or without tillage (4.2 t/ha). Methods: Tillage or no tillage was used on four plots each (400 m² plots). A disk plough was used for tillage (two passes, 15 cm depth). The plots were intercropped with oats and Lupinus albus lupins in 2003–2004 (residues were retained, and incorporated into the soil in the plots with tillage) and oats were grown in monoculture in 2004–2005. The plots were fertilized in 2003–2004 (60 kg P/ha; 100 kg N/ha), but not in 2004–2005.
Use crop rotation

A randomized, replicated experiment in 2004-2005 on sandy soil in Portugal (de Varennes & Torres, 2011) found greater enzyme activity after the lupin Lupinus spp. (2.2μmol nitrophenol/g/h) than oat Avena sativa crop (1.7 μmol nitrophenol/g/h). A higher number of fungal colonies (0.004 colonies/g soil), higher soil organic carbon levels (6.75 g C/kg) and extractable phosphorus (63.25 mg P/kg) were found following oat compared to lupin (0.003 colonies/g soil, 6.15 g C/kg, and 60.25 mg P/kg respectively). There were two treatments in 400 m² plots: conventional tillage (two passes with a disc plough to 15cm), and no-till (left undisturbed). Each tillage treatment was divided into six 5 x 10 m plots. Three were sown with lupin and three with oat. Soils were sampled to 15 cm depth six times each year during the experiment.
Soil: Use no tillage in arable fields

A replicated, randomized, controlled study in 2003–2005 in an occasionally irrigated oat field in Portugal found less organic matter and phosphorus, lower pH, and fewer fungal colonies in plots with no tillage, compared to tillage. Organic matter: Less organic carbon was found in soils with no tillage, compared to tillage, in three of four comparisons (5.6–6.2 vs 6.0–7.7 g organic C/kg soil). Nutrients: Similar amounts of nitrogen were found in plots with or without tillage (30–45 mg mineral N/kg soil). Less phosphorus was found in soils with no tillage, compared to tillage, in three of four comparisons (47–70 vs 75–81 mg extractable P/kg soil). Lower pH levels were found in soils with no tillage, compared to tillage, in two of four comparisons (pH 5.5 vs 5.7–5.8). Soil organisms: More fungal colonies were found in plots with no tillage, compared to tillage (2004–2005: 3.6 vs 4.5 colonies/mg soil). Methods: Tillage or no tillage was used on four plots each (400 m² plots). A disk plough was used for tillage (two passes, 15 cm depth). The plots were intercropped with oats and Lupinus albus lupins in 2003–2004 (residues were retained, and incorporated into the soil in the plots with tillage) and oats were grown in monoculture in 2004–2005. The plots were fertilized in 2003–2004 (60 kg P/ha; 100 kg N/ha), but not in 2004–2005. Soils samples were collected in October, November, January, March, May, and July each year (15 cm depth, 15 samples/plot).
Change tillage practices

A randomized, replicated experiment in 2004-2005 on sandy soil in Portugal (de Varennes & Torres, 2011) found higher soil organic carbon (5.75 g C/kg), extractable phosphorus (57.75 mg P/kg) and number of fungal colonies (0.003 colonies/g soil) under no-tillage compared to conventional tillage (6.45 g C/kg, 65.5 mg P/kg and 0.004 colonies/g soil respectively). Mineral nitrogen remained the same over the two years of the experiment. Tillage treatment had no effect on overall grain yield for lupin (1.2 t/ha dry weight) or oat (4.2 t/ha dry weight). There were two treatments in 400 m² plots: conventional tillage (two passes with a disc plough to 15cm), and no-till (left undisturbed). Each tillage treatment was divided into six 5 x 10 m plots. Three were sown with lupin and three with oat. Soils were sampled to 15 cm depth six times each year during the experiment.