Comparison of soil N availability and leaching potential, crop yields and weeds in organic, low-input and conventional farming systems in northern California

Published source details Poudel D.D., Horwath W.R., Lanini W.T., Temple S.R. & van B.A.H.C. (2002) Comparison of soil N availability and leaching potential, crop yields and weeds in organic, low-input and conventional farming systems in northern California. Agriculture, Ecosystems & Environment, 90, 125-137.
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This study is summarised as evidence for the following.

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

Pest regulation: Use crop rotations

A replicated, randomized, controlled study in 1994–1998 on an irrigated, arable farm near Davis, California, USA, found similar amounts of weed biomass in plots with four-year or two-year crop rotations. Implementation options: Similar amounts of weed biomass were found in plots with four-year or two-year crop rotations (4–273 vs 140–467 kg dry weight/ha). Methods: A four-year rotation (tomato, safflower, corn and wheat, beans) was used on 16 plots (four plots for each phase, each year), and a two-year rotation (tomato, wheat) was used on eight plots (four plots for each phase, each year). Each plot was 68 x 18 m. Fertilizer and pesticide were used on all plots. Weeds were sampled in the tomato plots, at harvest, in 1994–1998.
Soil: Use crop rotations

A replicated, randomized, controlled study in 1994–1998 in arable farmland in California, USA, found similar amounts of nitrogen in plots with four-year or two-year crop rotations. Implementation options: Similar amounts of nitrogen were found in plots with four-year or two-year crop rotations (29–42 vs 26–40 mg ammonium and nitate/kg soil, 0–15 cm depth). Methods: A four-year rotation (tomato, safflower, corn and wheat, beans) was used on 16 plots (four plots for each phase, each year), and a two-year rotation (tomato, wheat) was used on eight plots (four plots for each phase, each year). Each plot was 68 x 18 m. Fertilizer and pesticide were used on all plots. Soil samples were collected from tomato plots (every 2–3 weeks in the cropping season in 1994–1998, 0–15 cm depth).
Crop production: Use crop rotations

A replicated, randomized, controlled study in 1994–1998 on an irrigated, arable farm near Davis, California, USA, found higher tomato yields in plots with four-year crop rotations, compared to two-year rotations. Implementation options: Higher tomato yields were found in plots with four-year rotations, in one of five years (in 1994: 92 vs 85 mg/kg). Methods: A four-year rotation (tomato, safflower, corn and wheat, beans) was used on 16 plots (four plots for each phase, each year), and a two-year rotation (tomato, wheat) was used on eight plots (four plots for each phase, each year). Each plot was 68 x 18 m. Fertilizer and pesticide were used on all plots.