Evaluation of Biomass, Physiological Traits, and Advantages of Maize (Zea mays L.)-Amaranth (Amaranthus hypochondriacus) Intercropping in the Cultivation of Barley Residues and Nitrogen Fertilizer

To evaluate the biomass, physiological traits, and advantages of maize-amaranth intercropping in the cultivation in barley residues and different levels of nitrogen in 2020-2021, an experiment was implemented in the research farm of Tarbiat Modares University. This study was conducted as a split-split plot experiment in a randomized complete block design with three replications. The studied factors included: 1- Cultivation in two levels (cultivation in barley residues and cultivation without barley residues) as the main plots, 2- the type of cultivation in two levels (monoculture and intercropping) as subplots, 3- different levels of nitrogen (N) in four levels (0, 100, 200, and 300 kg N ha-1 for maize and 0, 40, 80, and 120 kg N ha-1 for amaranth) as sub-subplots. The results showed that the highest total dry weight of amaranth was observed in the treatment of 80 kg N ha-1 of nitrogen application in the conditions of amaranth monoculture and without the use of barley residues with a production of 8031 kg ha-1. The highest dry weight of maize (11187 kg ha-1) was obtained from the treatment of maize monoculture in barley residues with the application of 300 kg N ha-1. The highest photosynthesis rate of amaranth was observed in the treatments of 40 kg N ha-1 application in the conditions of monoculture without barley residues and N fertilizer, and application of 40 kg N ha-1 in the conditions of intercropping with maize and without barley residues. In addition, the results showed that the highest maize photosynthesis rate was achieved with the application of 300 kg N ha-1, and the photosynthesis rate also significantly decreased with the reduction of nitrogen application. Land equivalent ratio (LER) showed an increase of 30% in the intercropping of maize and amaranth in the cultivation of barley residues with the application of 100 kg N ha-1 for maize and 40 kg N ha-1 for amaranth, which indicated the advantage of intercropping. According to the results of this research, if the goal was to produce amaranth, barley residues should not be used, but in maize cultivation, the use of barley residues is recommended. Also, the use of 40 and 300 kg N ha-1 is recommended to increase biomass of amaranth and maize, respectively.