The Evaluation of Yield and Advantage Indices for Agroforestry of Populus euramericana and Medicago sativa in Karaj, Iran

Today, agroforestry production systems as viable strategy for sustainable agriculture, is appreciated by both researchers and farmers, as it increases the efficiency of natural resources uses and may enhance the combined production of wood and crop products and hence income of the rural communities. In order to investigate the benefits of the agroforestry system of Euramerican poplar (Populus euramericana clone of 92/40) and alfalfa fodder plant (Medicago sativa), an experiment was carried out in the form of Randomized Complete Block Design (RCBD) with three replications at the Alborz Research Station in the south of Karaj, Iran. The treatments included poplar pure culture, alfalfa pure culture, and poplar-alfalfa mixed culture. Alfalfa plants were planted between the rows of poplar (Populus euramericana clone of 92/40) which were planted in March 2015 at a distance of 3 × 4 m, in late autumn 2016. The height and diameter at breast height (DBH) of the poplar trees were measured at the end of each growing season for three consecutive years, and then the annual increment in growth of height, diameter and stem volume (m3/ha) were calculated and evaluated using the T-Test. The plant height and dry weight of alfalfa were measured for the three years and its total annual fodder dry mass yield was obtained. Competitive and economic evaluation of each of the pure and agroforestry cultivations was done based on the indices of land equality ratio (LER), relative value total (RVT) and advantage index (IA). In 2019 and 2020, there was a statistically significant difference in the DBH and stem volume in pure and agroforestry cultivations, indicating the highest values for both parameters in pure poplar culture. In 2018, the highest alfalfa fodder dry mass yield was obtained in agroforestry cultivation with 11320 kg ha-1 but the highest alfalfa fodder dry mass in 2019 (with 10928 kg ha-1) belonged to its pure cultivation. In all the studied years, LER was greater than one and ranged from 1.27 to 2.39, with the three-year average being 1.78. The values for RVT in 2018, 2019, and 2020 were 1.6, 0.69 and 0.41 and those for IA were 6.53, 4, and 2.81, respectively. Therefore, adopting agroforestry by cultivation of poplar and alfalfa will enable the farmers to receive 160%, 69%, and 41% increases in income compared to the income from pure cultivation of poplar and alfalfa for the years 2018, 2019 and 2020, respectively.