Nitrogen conservation in soil and crop residues as affected by crop rotation and soil disturbance under Mediterranean conditions

Published source details de Varennes A., Torres M.O., Cunha-Queda C., Goss M.J. & Carranca C. (2007) Nitrogen conservation in soil and crop residues as affected by crop rotation and soil disturbance under Mediterranean conditions. Biology and Fertility of Soils, 44, 49-58.
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This study is summarised as evidence for the following.

	Action	Category
	Crop production: Use crop rotations Action Link
	Soil: Use crop rotations Action Link

Crop production: Use crop rotations

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.
Soil: Use crop rotations

A replicated, randomized, controlled study in 2004–2006 in an occasionally irrigated oat field in Portugal found less organic matter, phosphorus, and fungi in soils with a lupin-oat sequence, compared to an oat-oat sequence. Organic matter: Less organic carbon was found in soils with a lupin-oat sequence, in one of two comparisons (tilled plots: 6.2 vs 7.7 g/kg). Nutrients: Less phosphorus was found in soils with a lupin-oat sequence, in one of two comparisons (tilled plots: 51 vs 59 mg/kg). Similar amounts of nitrogen, and similar pH levels, were found in soils with both sequences (35–39 vs 41–44 g mineral N/kg, pH 5.2–5.4). Soil organisms: Fewer fungi were found in soils with a lupin-oat sequence (0.0023–0.0034 vs 0.0036–0.0045 colony forming units/g soil), but similar numbers of bacteria were found in both sequences (data not reported). 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. Soil samples were collected in year 2, in October, November, January, March, May, and July (0–15 cm depth). Bacteria and fungi were cultured from soil samples.