Nitrogen balance in a stockless organic cropping system with different strategies for internal N cycling via residual biomass

• A major future challenge in agriculture is to reduce the use of new reactive nitrogen (N) while maintaining or increasing productivity without causing a negative N balance in cropping systems. We investigated if strategic management of internal biomass N resources (green manure ley, crop residues and cover crops) within an organic crop rotation of six main crops, could maintain the N balance. Two years of measurements in the field experiment in southern Sweden were used to compare three biomass management strategies: anaerobic digestion of ensiled biomass and application of the digestate to the non-legume crops (AD), biomass redistribution as silage to non-legume crops (BR), and leaving the biomass in situ (IS). Neither aboveground crop N content from soil, nor the proportion of N derived from N2 fixation in legumes were influenced by biomass management treatment. On the other hand, the allocation of N-rich silage and digestate to non-legume crops resulted in higher N2 fixation in AD and BR (57 and 58 kg ha−1 year−1), compared to IS (33 kg ha−1 year−1) in the second study year. The N balance ranged between − 9.9 and 24 kg N ha−1, with more positive budgets in AD and BR than in IS. The storage of biomass for reallocation in spring led to an increasing accumulation of N in the BR and AD systems from one year to another. These strategies also provide an opportunity to supply the crop with the N when most needed, thereby potentially decreasing the risk of N losses during winter. © 2018, The Author(s).

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Jordbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Agricultural Science (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Markvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Soil Science (hsv//eng)

Nyckelord

Anaerobic digestion

Arable and horticultural crops

N balance

N2 fixation

Soil and residue N

Strategic biomass N management

agricultural management

biomass

crop plant

crop production

crop rotation

cropping practice

nitrogen

nitrogen fixation

organic farming

seasonal variation

soil nitrogen

strategic approach

Sweden

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