*2.1. Study Site*

The case studies are four agroforestry systems in Italy and two systems, specifically one agroforestry and one conventional wheat production system, in Denmark. The four agroforestry systems are olive trees under (i) silvopastoral agroforestry, (ii) organic agroforestry, (iii) traditional agroforestry, and (iv) conventional olive system, located in Orvieto in the Umbria region in Italy. The two production systems in Denmark are (v) a combined food and energy agroforestry system and (vi) a conventional wheat production system in Denmark.

The four production systems in Italy have olive trees as one of the components, while managemen<sup>t</sup> and inputs di ffer among the systems depending on the production system as described below:

(i) Silvopastoral agroforestry system consists of 135 trees in 1.0 ha. Olive production is 3.6 t ha−1, and natural grass pasture is present between the olive trees. A total of 177 sheep graze the pasture for 150 days a year, producing 0.33 kg dung in dry matter and 2.9 kg urine per day per sheep, with fertilization e ffects on the grass pasture. The trees were planted in 1956. While no synthetic fertilizer was used, biological copper was applied at 1.7 kg ha−<sup>1</sup> [16].

(ii) Organic agroforestry system covered an area of 4.5 ha. The system has 200 trees ha−<sup>1</sup> and olive yield is 2.2 t ha−1. Naturally growing grass are present in between the trees, fertilizer application is 4.0 t ha−<sup>1</sup> cow manure in dry matter, and no pesticides were used [16].

(iii) In traditional agroforestry, olive trees were planted in 1982. The yield is 7.05 t ha−<sup>1</sup> olives with tree density of 529 trees ha−1. The cultivation area was drip-irrigated and fertilized with olive prunings and olive pomace. Glyphosate was applied to control weeds [16].

(iv) Conventional olive system has planting density of 250–400 olive trees ha−<sup>1</sup> with irrigation facility and practice mechanized harvesting of olives. The olive trees are fertilized with nitrogen (90–150 kg ha−1), phosphorus (20–30 kg ha−1), and potassium (70–120 kg ha−1). Olive yield is estimated to be 4.5 t ha−<sup>1</sup> with 300 trees ha−<sup>1</sup> [17,18].

In Denmark, two production systems, namely a combined food and energy production agroforestry system and a conventional wheat production system, were investigated and the descriptions of the system are provided below:

(v) The combined food and energy system covers an area of 11.1 ha, of which 10.1 ha is cropped with barley, wheat, and clover in a four-year crop rotation and 1.0 ha of biofuel crops (mix of willow, hazelnut, and alder). The biofuel crops consist of four shelterbelts of short rotation woody crops, spatially placed at 50, 100, 150, and 200 m, forming alleys for the food and fodder crop production. The production yields were 5430 kg wheat ha−1, 3750 barley kg ha−1, 6700 kg clover ha−1, and 4078 kg woodchips ha−<sup>1</sup> annually [19,20].

(vi) Conventional wheat production systems relate to winter wheat production, which is sown in September or October and harvested the following year in August. A total of 50% of nitrogen (95 kg ha−1), potassium (20 kg ha−1), and phosphorus (60 kg ha−1) is applied at the time of sowing and the remaining 50% of the nitrogen (95 kg ha−1) is applied in the spring. Fungicides and herbicides are applied as per the standard practice at the experimental farm in Taastrup in Denmark. The details of the managemen<sup>t</sup> and crop production are available from another study at the same experimental farm [19].
