Effects of input level and crop diversity on soil nitrate-N, extractable P, aggregation, organic C and N, and nutrient balance in the Canadian Prairie

Published source details Malhi S.S., Brandt S.A., Lemke R., Moulin A.P. & Zentner R.P. (2009) Effects of input level and crop diversity on soil nitrate-N, extractable P, aggregation, organic C and N, and nutrient balance in the Canadian Prairie. Nutrient Cycling in Agroecosystems, 84, 1-22.
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This study is summarised as evidence for the following.

	Action	Category
	Reduce fertilizer, pesticide or herbicide use generally Action Link
	Convert to organic farming Action Link
	Use crop rotation Action Link
	Change tillage practices Action Link

Reduce fertilizer, pesticide or herbicide use generally

A replicated experiment in 2001-2006 on loamy soil in Saskatchewan, Canada (Malhi et al. 2009) found less nitrate (74 kg N/ha) and phosphorus (19 kg P/ha) in soil under organic inputs than under high or reduced inputs (85 kg N/ha, 24 kg P/ha respectively). Nitrate was usually higher in treatments with fewer crop types. Lower yields were recorded in organic compared to high or reduced input treatments (amounts not specified). Three input (tillage/management) levels (organic, reduced, high) were replicated four times. Within these input levels were three crop diversities: low (fallow/wheat Triticum aestivum/oilseed Brassica juncea); cereal (wheat / mustard Brassica juncea or canola Brassica napus/ lentil Len culinaris rotations; or grain (perennial forage crop (sweet clover Melilotus officinalis, pea Pisum sativum, flax Linum usitatissimum or alfalfa Medicago sativa)/ barley Hordeum vulgare) rotations. Within these were six crop phases, rotating the above species with green manure and fallow phases, which were tested in 40 x 12.8 m plots. Fertilizers and pesticides were not applied to the organic treatment. Crop rotations were six years long. Each year, two soil samples were taken from each crop phase (with a third also taken in 2006) to measure nitrate-N, carbon, nitrogen, and phosphorus.
Convert to organic farming

A replicated experiment in 2001-2006 on loamy soil in Saskatchewan, Canada (Malhi et al. 2009) found less nitrate (74 kg N/ha) and phosphorus (19 kg P/ha) in soil under organic inputs than under high or reduced inputs (85 kg N/ha, 24 kg P/ha respectively). Nitrate was usually higher in treatments with fewer crop types. Lower yields were recorded in organic compared to high or reduced input treatments (amounts not specified). Three input (tillage/management) levels (organic, reduced, high) were replicated four times. Within these input levels were three crop diversities: low (fallow/wheat Triticum aestivum/oilseed Brassica juncea); cereal (wheat / mustard Brassica juncea or canola Brassica napus/ lentil Len culinaris rotations; or grain (perennial forage crop (sweet clover Melilotus officinalis, pea Pisum sativum, flax Linum usitatissimum or alfalfa Medicago sativa)/ barley Hordeum vulgare) rotations. Within these were six crop phases, rotating the above species with green manure and fallow phases, which were tested in 40 x 12.8 m plots. Fertilizers and pesticides were not applied to the organic treatment. Crop rotations were six years long. Each year, two soil samples were taken from each crop phase (with a third also taken in 2006) to measure nitrate-N, carbon, nitrogen, and phosphorus.
Use crop rotation

A replicated experiment in 2001-2006 on loam soil in Saskatchewan, Canada (Malhi et al. 2009) found that nitrate-N was lower in arable rotations (82 kg N/ha) and grain and forage crop rotations (60 kg N/ha) than in in low diversity crop rotation (92.3 kg N/ha). Three treatments were replicated four times: an arable rotation comprising wheat Triticum aestivum-oilseed (mustard Brassica juncea or canola Brassica napus), a grain-forage rotation comprising barley Hordeum vulgare-perennial forage crop (sweet clover Melilotus officinalis, pea Pisum sativum, flax Linum usitatissimum or alfalfa Medicago sativa), and a grain-perennial forage crop comprising mustard-wheat-barley-alfalfa-hay. Fallowing (and green manuring) followed each crop stage for one season, creating six cropping phases over each six-year rotation period. Each treatment plot measured 40 x 12.8 m. Each year, two soil samples were taken during each crop phase, and a third taken in 2006. Nitrate-N, carbon, nitrogen, phosphorus, and yield were measured.
Change tillage practices

A replicated experiment in 2001-2006 on loam soil in Saskatchewan, Canada (Malhi et al. 2009), found that reducing tillage intensity increased soil stability, due to increased crop residue cover (50% cover in the reduced input treatment, compared to 24% in organic and 30% in high input treatments). Excess soil nitrogen was stored as soil organic matter in dry weather, largely due to reduced tillage. Three input levels were replicated four times: organic (organic management under conventional tillage), reduced (combined pest and nutrient management under no tillage) and high (recommended fertilizer and pesticide application under conventional tillage) inputs (treatment size not specified). At the end of each growing season 36 soil samples were taken from each input treatment, with an additional 18 taken in 2006. Soil stability, organic carbon and crop residue cover were measured.