Electronic Supplementary Material

Supplement to: Do organic inputs matter – A meta-analysis of additional yield effects for arable crops in Europe

Journal: Plant and Soil

Authors: R. Hijbeek1, M.K. van Ittersum1*, H.F.M. ten Berge2, G. Gort3, H. Spiegel4, and A.P. Whitmore5

Affiliations: 1Plant Production Systems, Wageningen University and Research, Wageningen, The Netherlands. 2Plant Research International, Wageningen University and Research, Wageningen, The Netherlands. 3Biometris, Wageningen University and Research, Wageningen, The Netherlands. 4Institute for Sustainable Plant Production, Austrian Agency for Health and Food Safety, Vienna, Austria. 5Sustainable Soils and Grassland Systems, Rothamsted Research, Harpenden, UK

Corresponding author: Renske Hijbeek, , tel: 0031-317482141, fax: 0031-317484892

Content:

Individual response curves for root and tuber crops 2

Individual response curves for spring sown cereals 3

Individual response curves for winter sown cereals 4

Forest plot: additional yield effect and 95% confidence interval for each data set. 5

Sensitivity analysis 6

Model selection 1: including all experiments with data available on both percentage of clay and SOM content. 7

Model selection 2: including all experiments with data available on on soil organic matter change. 8

Differences in mineral fertiliser N application rates to reach equal yields with and without organic inputs 9

Individual response curves for root and tuber crops

Supplementary Fig. 1: Yield response curves of root and tuber crops to mineral fertiliser with and without organic inputs. X-axes are mineral fertiliser applied in kg N/ha. Y-axes are crop yield in ton/ha. Colours indicate types of organic input. Black lines are treatments without organic input (only mineral fertiliser). Squares indicate the maximum of each curve. Shaded areas lie outside the experimental set-up.

Individual response curves for spring sown cereals

Supplementary Fig. 2: Yield response curves of spring sown cereals to mineral fertiliser with and without organic inputs. X-axes are mineral fertiliser applied in kg N/ha. Y-axes are crop yield in ton/ha. Colours indicate types of organic input. Black lines are treatments without organic input (only mineral fertiliser). Squares indicate the maximum of each curve. Shaded areas lie outside the experimental set-up.

Individual response curves for winter sown cereals

Supplementary Fig. 3: Yield response curves of winter sown cereals to mineral fertiliser with and without organic inputs. X-axes are mineral fertiliser applied in kg N/ha. Y-axes are crop yield in ton/ha. Colours indicate types of organic input. Black lines are treatments without organic input (only mineral fertiliser). Squares indicate the maximum of each curve. Shaded areas lie outside the experimental set-up.

Forest plot: additional yield effect and 95% confidence interval for each data set.

Supplementary Fig. 4: Yield effect of organic matter across experiments, crops and types of organic input. For each data set, the additional yield effect of organic inputs is shown with the 95% confidence interval. Circles indicate the relative difference in maximum yield when organic inputs are added. Lines indicate the 95% confidence interval. Colours show crop type. A star at the right side of a line means maximum yield was estimated outside the experimental set-up (these often come with a larger uncertainty and therefore larger confidence interval).

Sensitivity analysis

Supplementary Fig. 5: Sensitivity analysis for including or excluding estimations of maximum yield outside the experimental set-up. Including maxima estimated outside the experimental set-up increases the data size of the meta-analysis, but increases uncertainty of individual points. This figure shows the effect on group means when including or excluding estimations of maximum yield outside experimental set-ups. Circles are mean effect size, lines show the 95% confidence interval. The number in brackets is the number of data sets in each group. GM = green manure or cover crop. FYM = farmyard manure.

Model selection 1: including all experiments with data available on both percentage of clay and SOM content.

Supplementary Table 1: Model selection including all experiments with data available on percentage of clay and SOM at start. Response variable is additional yield effect of organic input, given in percentage increase as a number between 0 and 100. A plus sign means a factor is included. A number gives the value of the coefficient for a variable when included. Factor levels for crop type are: root or tuber crops, winter sown cereals, spring sown cereals. Factor levels for type of organic input are: farmyard manure, green residues, slurry, straw, straw and green residues, straw and green residues and slurry, straw, slurry. An empty cell means the co-variate is not included. No interactions were selected within the first 20 models. df means degrees of freedom of the model. AICc is the corrected Aikake’s Infomation Criterion for each model, indicating the fit. Lower values of AICc means the model fits better to the data, having adjusted for the degrees of freedom used.

# / Inter-cept / Factors / Coefficients for continuous variables / Model evaluation
Crop / Type of organic input / percentage clay particles (<2 µm) / percentage SOM at start experiment (% SOM) / aridity / input amount (ton C
/ha/year) / Duration (years) / total C added over the years
(ton C
/ha) / df / AICc
1 / -1.84 / + / 6.10 / 0.06 / 8 / 513.86
2 / 3.51 / + / 0.05 / 7 / 514.22
3 / 3.71 / + / 0.60 / 7 / 514.90
4 / 4.48 / + / 6 / 515.39
5 / 4.31 / + / -0.06 / 0.07 / 8 / 515.69
6 / 5.75 / + / + / 12 / 515.70
7 / 0.14 / + / 4.24 / 0.57 / 8 / 516.06
8 / 0.48 / + / 4.70 / 7 / 516.18
9 / -1.00 / + / 5.51 / -0.03 / 0.07 / 9 / 516.24
10 / -1.33 / + / -0.26 / 6.27 / 0.06 / 9 / 516.31
11 / 4.36 / + / -0.06 / 0.05 / 8 / 516.31
12 / -1.55 / + / -0.01 / 5.97 / 0.06 / 9 / 516.37
13 / -1.82 / + / 6.07 / 0.02 / 0.06 / 9 / 516.38
14 / 3.45 / + / 0.26 / 0.04 / 8 / 516.40
15 / 3.44 / + / 0.03 / 0.05 / 8 / 516.68
16 / 4.81 / + / -0.08 / 0.59 / 8 / 516.68
17 / 5.64 / + / -0.08 / 7 / 517.03
18 / 2.13 / + / + / 4.28 / 13 / 517.28
19 / 3.53 / + / 0.61 / 0.01 / 8 / 517.33
20 / 3.78 / + / -0.03 / 0.60 / 8 / 517.36

Model selection 2: including all experiments with data available on on soil organic matter change.

Supplementary Table 2: Model selection when including data on soil organic matter change over the years. First 20 models selected are shown. Only experiments are included in the model selection for which data on soil organic matter change is available (8 out of 20). Response variable is additional yield effect of organic input, given in percentage increase as a number between 0 and 100. A plus sign means a factor or interaction is included. A number gives the value of the coefficient for a variable when included. When an interaction is present for a given variable, the coefficient given will differ between factor levels. Factor levels for crop type are: root or tuber crops, winter sown cereals, spring sown cereals. Factor levels for type of organic input are: farmyard manure, green residues, slurry, straw, straw and green residues, straw and green residues and slurry, straw, slurry. An empty cell means the co-variate is not included. Besides the interaction between crop type and increase in soil organic matter, no other interactions were selected within the first 20 models. df means degrees of freedom of the model. AICc is the corrected Aikake’s Infomation Criterion for each model, indicating the fit. Lower values of AICc means the model fits better to the data, having adjusted for the degrees of freedom used.

# / Inter-
cept / Factors / Coefficients for continuous variables / Inter-
actions / Model evaluation
Crop / Type
of organic input / SOM at start experiment (%) / aridity / SOM without organic input (%) / total C added over the years
(ton C
/ha) / increase SOM (percent point) / increase SOM (%) / crop: increase SOM / df / AICc
1 / -1.75 / + / 0.64 / + / 9 / 262.52
2 / -0.01 / + / -0.05 / 0.63 / + / 10 / 262.90
3 / -7.97 / + / 7.44 / 0.64 / + / 10 / 265.00
4 / -3.69 / + / 1.21 / 0.65 / + / 10 / 265.50
5 / -1.82 / + / 5.57 / 0.58 / + / 10 / 265.86
6 / -5.19 / + / 6.10 / -0.05 / 0.64 / + / 11 / 265.92
7 / -1.32 / + / -0.19 / 0.64 / + / 10 / 265.97
8 / 0.57 / + / -0.07 / -12.01 / 0.77 / + / 11 / 266.13
9 / -1.61 / + / 0.97 / -0.05 / 0.64 / + / 11 / 266.28
10 / 0.59 / + / -0.27 / -0.05 / 0.63 / + / 11 / 266.56
11 / -2.77 / + / -2.15 / 3.57 / 0.65 / + / 11 / 267.91
12 / -8.13 / + / 6.38 / 0.66 / 0.65 / + / 11 / 268.58
13 / -7.40 / + / -0.39 / 7.78 / 0.64 / + / 11 / 268.60
14 / -7.81 / + / 7.22 / 1.97 / 0.62 / + / 11 / 268.69
15 / -2.43 / + / 2.17 / -0.08 / -24.01 / 0.93 / + / 12 / 268.88
16 / -0.76 / + / -1.99 / 3.15 / -0.05 / 0.64 / + / 12 / 269.07
17 / -5.57 / + / 7.45 / -0.07 / -15.80 / 0.82 / + / 12 / 269.09
18 / -3.65 / + / 1.19 / 0.43 / 0.64 / + / 11 / 269.21
19 / -0.86 / + / -0.46 / 7.95 / 0.54 / + / 11 / 269.45
20 / -4.54 / + / -0.43 / 6.46 / -0.05 / 0.63 / + / 12 / 269.75

Differences in mineral fertiliser N application rates needed to reach equal yields with and without organic inputs

Supplementary Fig. 6: Illustration of difference in mineral fertiliser N application rate needed to reach equal crop yield with and without organic inputs. Black line is the response curve without organic inputs. Green line is the response curve with organic inputs. Squares indicate the maximum of each curve. The black dotted arrow shows the difference in mineral fertiliser N needed to achieve a similar level of high yield. Data is from maize grown in Novi Sad between 1996 and 2003, with and without farmyard manure.

Supplementary Table 3: Comparing mineral fertiliser N needed to achieve equal yields with and without organic inputs (as illustrated in supplementary figure 6). Mineral fertiliser N requirements are compared at highest yield which is achieved both with and without organic inputs. Analysis and results only for data sets with N contents in inputs measured/reported (38 data sets across 8 experiments).

Organic input / # data sets / Mean difference in mineral fertiliser N needed to reach same level of high yield with organic inputs
(kg N/ha/year) / Mean of added mineral fertiliser N to straw or green manures
(kg N/ha/year) / Mean of total N in organic inputs
(kg N/ha/year) / Δ mineral fertiliser N + added N + total N organic inputs
(kg N/ha/year)
FYM / 17 / -76.92 / 0.00 / 120.22 / 43.30
slurry / 1 / -109.25 / 0.00 / 189.68 / 80.42
straw / 15 / -7.42 / 0.00 / 22.18 / 14.76
straw & beet leaves / 2 / -81.16 / 16.67 / 79.42 / 14.93
straw & GM & beet leaves / 3 / -64.44 / 16.67 / 49.30 / 1.53

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