Transitioning from standard to minimum tillage: trade-offs between soil organic matter stabilization, nitrous oxide emissions, and N availability in irrigated cropping systems

Published source details Kong A.Y.Y., Fonte S.J., van K.C. & Six J. (2009) Transitioning from standard to minimum tillage: trade-offs between soil organic matter stabilization, nitrous oxide emissions, and N availability in irrigated cropping systems. Soil & Tillage Research, 104, 256-262.
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This study is summarised as evidence for the following.

	Action	Category
	Crop production: Use organic fertilizer instead of inorganic Action Link
	Soil: Use organic fertilizer instead of inorganic Action Link
	Crop production: Use reduced tillage in arable fields Action Link
	Soil: Use reduced tillage in arable fields Action Link

Crop production: Use organic fertilizer instead of inorganic

A replicated, randomized, controlled study in 2003–2004 in three maize-tomato fields near Davis, California, USA, found lower crop yields in organically-fertilized plots, compared to inorganically-fertilized plots. Crop yield: Lower maize yields were found in organically-fertilized plots, compared to inorganically-fertilized plots (4.1–6.7 vs 9.3–13.6 Mg grain/ha). Methods: Organic or inorganic fertilizer was used on six plots each (1.5 x 1.0 m plots). Urea was added to inorganically-fertilized plots (April: 60 kg N/ha; May: 200 kg N/ha). On organically-fertilized plots, inorganic fertilizer was replaced, every other year, with the residues of legume cover crops (100 kg N/ha). Maize was sown at different times (organically-fertilized plots: March; inorganically-fertilized plots: May), and different amounts of nitrogen were applied. It was not clear whether these results were direct effects of differences in the type of fertilizer (organic or inorganic), the amount of fertilizer, or the planting date.
Soil: Use organic fertilizer instead of inorganic

A replicated, randomized, controlled study in 2003–2004 in three maize-tomato fields near Davis, California, USA, found lower greenhouse-gas emissions in soils with organic fertilizer, compared to inorganic fertilizer. Organic matter: Similar amounts of organic carbon were found in soils with organic or inorganic fertilizer (18 vs 19 Mg C/ha). Nutrients: Similar amounts of nitrogen were found in soils with organic or inorganic fertilizer (1.8–1.9 vs 2.0 Mg N/ha). Soil erosion and aggregation: Similar amounts of aggregation were found in soils with organic or inorganic fertilizer (1.2 vs 1.4 mm mean weight diameter). Greenhouse gases: Lower nitrous oxide emissions were found in soils with organic fertilizer, compared to inorganic fertilizer, in two of seven comparisons (emissions not reported for all comparisons; the highest emissions were found in plots with conventional tillage: 40 g N₂O–N/ha/day). Methods: Organic or inorganic fertilizer was used on six plots each (1.5 x 1.0 m plots). Urea was added to inorganically-fertilized plots (April: 60 kg N/ha; May: 200 kg N/ha). On organically-fertilized plots, inorganic fertilizer was replaced, every other year, with the residues of legume cover crops (100 kg N/ha). Soil samples were collected with soil cores (two cores/plot, 4 cm diameter, 0–15 cm depth), when the maize was harvested (September). Greenhouse-gas emissions were measured with closed chambers (March–September, every three week). Maize was sown at different times (organically-fertilized plots: March; inorganically-fertilized plots: May), and different amounts of nitrogen were applied. It was not clear whether these results were direct effects of differences in the type of fertilizer (organic or inorganic), the amount of fertilizer, or the planting date.
Crop production: Use reduced tillage in arable fields

A replicated, randomized, controlled study in 2003–2004 in three irrigated maize-tomato fields near Davis, California, USA, found similar crop yields in plots with reduced tillage or conventional tillage. Crop yield: Similar maize yields were found in plots with reduced tillage or conventional tillage (6.7–9.3 vs 4.1–13.6 Mg grain/ha). Methods: Reduced tillage or conventional tillage was used on nine plots each (1.5 x 1.0 m plots). Nine tillage practices, in 12–15 tractor passes, were used for conventional tillage. Five tillage practices, in 5–10 tractor passes, were used for reduced tillage. Maize seeds were sown with a seed drill in early May or mid-March. All plots were irrigated and fertilized with organic and/or inorganic fertilizer. Maize was harvested in September.
Soil: Use reduced tillage in arable fields

A replicated, randomized, controlled study in 2003–2004 in three irrigated maize-tomato fields near Davis, California, USA, found higher greenhouse-gas emissions in soils with reduced tillage, compared to conventional tillage. Nutrients: Similar amounts of nitrogen were found in soils with reduced tillage or conventional tillage (1.8–2.6 vs 1.9–2.7 Mg N/ha). Soil erosion and aggregation: Similar amounts of soil aggregation were found in soils with reduced tillage or conventional tillage (1.2–1.7 vs 1.2–1.8 mm mean weight diameter). Greenhouse gases: Higher nitrous oxide emissions were found in soils with reduced tillage, compared to conventional tillage, in two of seven comparisons (emissions not reported for all of these comparisons, but the highest emissions were found in plots with reduced tillage: 29–40 g N₂O-N/ha/day). Methods: Reduced tillage or conventional tillage was used on nine plots each (1.5 x 1.0 m plots). Nine tillage practices, in 12–15 tractor passes, were used for conventional tillage. Five tillage practices, in 5–10 tractor passes, were used for reduced tillage. Soil samples were collected with soil cores (two cores/plot, 4 cm diameter, 0–15 cm depth), when the maize was harvested (September). Greenhouse-gas emissions were measured with closed chambers (March–September, every three weeks, from each plot).