DOI: 10.5061/dryad.0vt4b8h3d
title: Towards efficient N cycling in intensive maize: role of cover crops and application methods of digestate liquid fraction

description: Digestate, a by-product of biogas production, is widely recognized as a
 promising renewable nitrogen (N) source with high potential to replace
 synthetic fertilizers. Yet, inefficient digestate use can lead to
 pollutant N losses as ammonia (NH3) volatilization, nitrous oxide (N2O)
 emissions and nitrate (NO3-) leaching. Cover crops may reduce some of
 these N losses and recycle the N back into the soil after incorporation,
 but the net effect on the N balance depends on the cover crop species. In
 a one-year field study, we tested the effects of two application methods
 (i.e., surface broadcasting, BDC; and shallow injection, INJ) of the
 liquid fraction of separated co-digested cattle slurry (DLF), combined
 with different winter cover crop options (CCs, i.e., rye, white mustard or
 bare fallow), as starter fertilizer for maize. Later in the season,
 side-dressing with urea was required to fulfill maize N-requirements. We
 tested treatment effects on yield, N-uptake, N-use efficiency parameters,
 and N-losses in the form of N2O emissions and NO3- leaching. Cover crop
 development and biomass production were strongly affected by their
 contrasting frost tolerance, with spring-regrowth for rye, while mustard
 was winter killed. After the cover crops, injection of DLF increased N2O
 emissions significantly compared with BDC (emission factor of 2.69 vs.
 1.66%). Nitrous oxide emissions accounted for a small part (11-13%) of the
 overall yield-scaled N losses (0.46 - 0.97 kg N Mg grain-1). The adoption
 of CCs reduced fall NO3- leaching, being 51% and 64% lower for mustard and
 rye than under bare soil. In addition, rye reduced NO3- leaching during
 spring and summer after termination by promoting N immobilization, thus
 leading to -57% lower annual leaching losses compared to mustard. Our
 study confirms the potential of CCs to reduce NO3- leaching, but it also
 highlights that their residue can increase N losses once terminated and
 that they may cause yield reductions. DLF application method modified
 N-loss pathways, but not the cumulative yield-scaled N losses. Overall,
 these insights contribute to inform an evidence-based design of cropping
 systems in which nutrients are recycled more efficiently.
description: # Towards efficient N cycling in intensive maize: role of application
 method of digestate liquid fraction and cover crops Author/Principal
 Investigator Information Name: Federico Capra ORCID:0000-0001-5034-0781
 Institution: Catholic University of the Sacred Heart
 Email:federico.capra@unicatt.it Author/Associate or Co-investigator
 Information Name: Andrea Fiorini Institution: Catholic University of the
 Sacred Heart Email: andrea.fiorini@unicatt.it SHARING/ACCESS INFORMATION
 Licenses/restrictions placed on the data: None Links to publications that
 cite or use the data: Please see the publication associated with these
 data in GCB Bioenergy (doi: https://doi.org/10.1111/gcbb.13036) DATA
 & FILE OVERVIEW File List: DATASET The worksheets 1 WINTER: data
 from "winter cover crops monitoring period" (from 6 October 2018
 to 9 April 2019) * PLOT the elementar plot (from 1 to 27) * BLOCK the
 block (from 1 to 3) * TH thesis (Bare soil, BS; Mustard, M and Rye, R) *
 WFPS Water Filled Pore Space (weighted average for the monitoring period),
 % * CCS\_BIOM Cover crops DM production, Mg ha-1 * CCS\_N Cover crops N
 content, g kg-1 * CCS\_C Cover crops C content, g kg-1 * CCS\_CN Cover
 crops C/N ratio * CCS\_NYIELD Cover crops N release, Mg ha-1 * CCS\_CYIELD
 Cover crops C release, Mg ha-1 * NO3\_up NO3-N content in the soil in the
 0-10 cm layer (weighted average for the monitoring period), g kg-1 *
 NO3\_down NO3-N content in the soil in the 10-30 cm layer (weighted
 average for the monitoring period), g kg-1 * NH4\_up NH4-N content in the
 soil in the 0-10 cm layer (weighted average for the monitoring period), g
 kg-1 * NH4\_down NH4-N content in the soil in the 10-30 cm layer (weighted
 average for the monitoring period), g kg-1 * N2O N2O-N cumulative
 emissions of winter monitoring period, kg ha-1 * NO3\_leached NO3-N
 cumulative leaching losses of winter monitoring period, kg ha-1 2
 DIGESTATE: data from "digestate monitoring period" (from 9 April
 2019 to 12 June 2019) * PLOT the elementar plot (from 1 to 27) * BLOCK the
 block (from 1 to 3) * TH thesis (Bare soill, Mustard and Rye). Those are
 the main-plots * STH subthesis: DLF application method (Surface broadcast,
 BDC or shallow injection, INJ) plus unfertilized control (C). Those are
 the subplots * SUBJECT a unique code to identify the main plots which
 represent the randomization factor in the mixed model analysis * WFPS
 Water Filled Pore Space (weighted average for the monitoring period), % *
 NO3\_up NO3-N content in the soil in the 0-10 cm layer (weighted average
 for the monitoring period), g kg-1 * NO3\_down NO3-N content in the soil
 in the 10-30 cm layer (weighted average for the monitoring period), g kg-1
 * NH4\_up NH4-N content in the soil in the 0-10 cm layer (weighted average
 for the monitoring period), g kg-1 * NH4\_down NH4-N content in the soil
 in the 10-30 cm layer (weighted average for the monitoring period), g kg-1
 * N2O N2O-N cumulative emissions of DLF monitoring period, kg ha-1 *
 NO3\_leached NO3-N cumulative leaching losses of DLF monitoring period, kg
 ha-1 * NH3 cumulative NH3-N losses after digestate application, kg ha-1 3
 UREA: data from "urea monitoring period" (from 12 June 2019 to 4
 October 2019) * PLOT the elementar plot (from 1 to 27) * BLOCK the block
 (from 1 to 3) * TH thesis (Bare soill, Mustard and Rye). Those are the
 main-plots * STH subthesis: DLF application method (Surface broadcast, BDC
 or shallow injection, INJ) plus unfertilized control (C). Those are the
 subplots * SUBJECT a unique code to identify the main plots which
 represent the randomization factor in the mixed model analysis * WFPS
 Water Filled Pore Space (wheighted average for the monitoring period), % *
 NO3\_up NO3-N content in the soil in the 0-10 cm layer (weighted average
 for the monitoring period), g kg-1 * NO3\_down NO3-N content in the soil
 in the 10-30 cm layer (weighted average for the monitoring period), g kg-1
 * NH4\_up NH4-N content in the soil in the 0-10 cm layer (weighted average
 for the monitoring period), g kg-1 * NH4\_down NH4-N content in the soil
 in the 10-30 cm layer (weighted average for the monitoring period), g kg-1
 * N2O N2O-N cumulative emissions of Urea monitoring period, kg ha-1 *
 NO3\_leached NO3-N cumulative leaching losses of Urea monitoring periog,
 kg ha-1 * NH3 cumulative NH3-N losses after urea application, kg ha-1 4
 YEAR: data from year-round monitoring (from 6 October 2018 to 4 October
 2019) * PLOT the elementar plot (from 1 to 27) * BLOCK the block (from 1
 to 3) * TH thesis (Bare soill, Mustard and Rye). Those are the main-plots
 * STH subthesis: DLF application method (Surface broadcast, BDC or shallow
 injection, INJ) plus unfertilized control (C). Those are the subplots *
 SUBJECT a unique code to identify the main plots which represent the
 randomization factor in the mixed model analysis * GRAINYIELD maize grain
 DM yield, Mg ha-1 * PLANTYIELD maiz biomass DM production, Mg ha-1 *
 NPLANT N uptake by maize plant, kg ha-1 * NGRAIN N uptake by maize grain,
 kg ha-1 * NTOT N uptake by maize plant plus grain, kg ha-1 * NUE Nitrgen
 Use Efficiency of maize crop, kg grain kg-1 N supply * NUPE Nitrogen
 Uptake Efficiency, kg of total N uptake kg-1 N supply * NUTE Nitrogen
 Utilization Efficiency, kg grain kg-1 total N uptake * WFPS Water Filled
 Pore Space (wheighted average for the monitoring period), % * NO3\_up
 NO3-N content in the soil in the 0-10 cm layer (weighted average for
 year-round monitoring period), g kg-1 * NO3\_down NO3-N content in the
 soil in the 10-30 cm layer (weighted average for year-round monitoring
 period), g kg-1 * NH4\_up NH4-N content in the soil in the 0-10 cm layer
 (weighted average for year-round monitoring period), g kg-1 * NH4\_down
 NH4-N content in the soil in the 10-30 cm layer (weighted average for
 year-round monitoring period), g kg-1 * N2O annual cumulative N2O-N
 emissions, kg ha-1 * EF\_ANNUAL emission factor for N2O-N: annual N2O-N
 losses as % of applied N * NO3\_leached year-round cumulative NO3-N
 leaching losses, kg ha-1 * NH3 cumulative annual NH3-N losses, kg ha-1 *
 N\_LOSSES annual cumulative N losses as sum of N2O-N + NH3-N + NO3-N *
 YSC\_NH3 yield-scaled NH3-N losses, kg N kg-1 grain * YSC\_N2O
 yield-scaled N2O-N losses, kg N kg-1 grain * YSC\_NO3 yield-scaled NO3-N
 losses, kg N kg-1 grain * YSC\_NTOT cumulative yield-scaled N-losses, kg N
 kg-1 grain