Abstract
We studied cover crops in maize-based cropping systems in the agricultural plain areas of Northern Italy (Lombardia region), to: quantify the growth of winter cover crops, nitrogen uptake, weed control capacity, and nitrogen credits for maize; to test the possibility of sensing cover crop biomass and nitrogen (N) concentration using aerial images, and to estimate N concentration using near-infrared spectroscopy (NIRS); and to quantify cover crop cultivation costs. We set up six experiments to compare different cover crop species in rotation with maize. The experiments started in September 2017 and ended in August 2019. Cover crop growth in autumn was rapid for white mustard, tillage radish and black oat (which accumulated 1.5–3.0 t DM/ha until November), while legume cover crops (Egyptian clover, hairy vetch and purple vetch) had a lower crop growth rate (reaching 0.5–1.5 t DM/ha). Therefore, non-legume cover crops controlled weeds better compared to legume cover crops. Nitrogen uptake in autumn was highest for white mustard, tillage radish and hairy vetch (77-125 kg N/ha). Rye and black oat were intermediate, while Egyptian clover and purple vetch were lowest (35 kg N/ha). Rye and hairy vetch survived winter, while white mustard was always destroyed by winter frosts. We did not observe relevant effects of cover crops on maize yield and N uptake. In one experiment, we also established relationships between vegetation indices (NDVI, Normalised Difference Vegetation Index; and CIg, Chlorophyll Index) obtained with a multispectral digital camera carried by an Unmanned Aerial Vehicle and cover crop biomass and nitrogen concentration. Increasing biomass above about 1 and 2 t DM/ha for NDVI and CIg, respectively, did not correspond to increasing values of the indices, thus reducing their predictive capacity. A new index (calculated using measured crop height) improved the predictions of cover crop biomass substantially (R2 = 0.64–0.86). Cover crop nitrogen concentration was poorly predicted by the vegetation indices. We finally scanned cover crops with two NIR instruments, and used the spectra for chemometric elaborations (Partial Least Squares regression). Predictions of N concentrations on spectra of fresh materials were rather poor, while dried and ground samples provided better results (R2 = 0.86 for the bench instrument, and 0.70 for the portable instrument). Locally Weighted Regression further improved the R2 (0.90 and 0.84, respectively). Cultivation costs ranged between 112 €/ha for white mustard (a winter killed species that does not require termination and has a low seed cost) and 208 €/ha for rye (winter-hardy, with more expensive seed).
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Claims 20
Claim · model-written summary
White mustard, tillage radish and black oat accumulated 1.5–3.0 t DM/ha by November.
Verbatim
e0“Cover crop growth in autumn was rapid for white mustard, tillage radish and black oat (which accumulated 1.5–3.0 t DM/ha until November)”
Claim · model-written summary
Egyptian clover, hairy vetch and purple vetch reached 0.5–1.5 t DM/ha with lower growth rate.
Verbatim
e0“legume cover crops (Egyptian clover, hairy vetch and purple vetch) had a lower crop growth rate (reaching 0.5–1.5 t DM/ha)”
Claim · model-written summary
Non-legume cover crops controlled weeds better than legume cover crops.
Verbatim
e0“non-legume cover crops controlled weeds better compared to legume cover crops”
Claim · model-written summary
White mustard, tillage radish and hairy vetch had the highest autumn nitrogen uptake at 77-125 kg N/ha.
Verbatim
e0“Nitrogen uptake in autumn was highest for white mustard, tillage radish and hairy vetch (77-125 kg N/ha)”
Claim · model-written summary
Rye and black oat had intermediate nitrogen uptake.
- Taxon
- Rye and black oat
Secale cereale
Avena strigosae0 - Outcome
- intermediatee0
- Direction
- intermediatee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rye and black oat were intermediate”
Claim · model-written summary
Egyptian clover and purple vetch had the lowest nitrogen uptake at 35 kg N/ha.
Verbatim
e0“Egyptian clover and purple vetch were lowest (35 kg N/ha)”
Claim · model-written summary
Rye and hairy vetch survived winter.
- Taxon
- Rye and hairy vetch
Vicia villosaSecale cerealee0 - Outcome
- survived wintere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rye and hairy vetch survived winter”
Claim · model-written summary
White mustard was always killed by winter frost.
- Taxon
- white mustard
Sinapis albae0 - Outcome
- destroyed by winter frostse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“white mustard was always destroyed by winter frosts”
Claim · model-written summary
Cover crops had no relevant effect on maize yield.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We did not observe relevant effects of cover crops on maize yield and N uptake”
Claim · model-written summary
Cover crops had no relevant effect on maize nitrogen uptake.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We did not observe relevant effects of cover crops on maize yield and N uptake”
Claim · model-written summary
NDVI saturation above about 1 t DM/ha reduced its biomass prediction capacity.
Verbatim
e0“Increasing biomass above about 1 and 2 t DM/ha for NDVI and CIg, respectively, did not correspond to increasing values of the indices, thus reducing their predictive capacity”
t0“cover crop growth”
Claim · model-written summary
CIg saturation above about 2 t DM/ha reduced its biomass prediction capacity.
Verbatim
e0“Increasing biomass above about 1 and 2 t DM/ha for NDVI and CIg, respectively, did not correspond to increasing values of the indices, thus reducing their predictive capacity”
t0“cover crop growth”
Claim · model-written summary
An index using measured crop height improved biomass predictions with R2 0.64–0.86.
Verbatim
e0“A new index (calculated using measured crop height) improved the predictions of cover crop biomass substantially (R2 = 0.64–0.86)”
Claim · model-written summary
Vegetation indices poorly predicted cover crop nitrogen concentration.
Verbatim
e0“Cover crop nitrogen concentration was poorly predicted by the vegetation indices”
Claim · model-written summary
Spectral predictions of nitrogen concentration from fresh samples were poor.
Verbatim
e0“Predictions of N concentrations on spectra of fresh materials were rather poor”
t0“cover crop growth”
Claim · model-written summary
Dried, ground samples yielded better NIRS nitrogen predictions, with R2 0.86 for the bench instrument.
Verbatim
e0“dried and ground samples provided better results (R2 = 0.86 for the bench instrument, and 0.70 for the portable instrument)”
t0“cover crop growth”
Claim · model-written summary
Dried, ground samples yielded R2 0.70 with the portable instrument.
Verbatim
e0“dried and ground samples provided better results (R2 = 0.86 for the bench instrument, and 0.70 for the portable instrument)”
t0“cover crop growth”
Claim · model-written summary
Locally Weighted Regression improved bench instrument R2 to 0.90.
Verbatim
e0“Locally Weighted Regression further improved the R2 (0.90 and 0.84, respectively)”
t0“cover crop growth”
Claim · model-written summary
Locally Weighted Regression improved portable instrument R2 to 0.84.
Verbatim
e0“Locally Weighted Regression further improved the R2 (0.90 and 0.84, respectively)”
t0“cover crop growth”
Claim · model-written summary
Cultivation cost ranged from 112 €/ha for white mustard to 208 €/ha for rye.
- Taxon
- white mustardSinapis albae0
- Outcome
- Cultivation costse0
- Value
- 112 €/hae0
- Qualifier
- 208 €/hae0
- Comparator
- ryee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cultivation costs ranged between 112 €/ha for white mustard (a winter killed species that does not require termination and has a low seed cost) and 208 €/ha for rye (winter-hardy, with more expensive seed)”
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