Effect of plant density and nitrogen fertilizer rate on forage yield and quality of cultivated amaranth (Amaranthus cruentus L.)

To study the effect of plant density and nitrogen rate on forage quantity and quality of cultivated amaranth (Amaranthus cruentus L.), a field experiment was conducted at Tarbiat Modares University, Iran, on 2012 growing season. Three nitrogen rate (60, 120 and 180 kg N. ha-1) and three plant density (70000, 105000 and 140000 plant. ha-1) were studied as factorial arrangement in randomized complete block design with three replications of. Sampling was performed for morphological characters in early flowering stage. Forage quality (crude protein, soluble carbohydrates, cell wall, acid detergent fiber (ADF) and digestible dry matter) were studied in flowering stage. Results showed that the effect of nitrogen fertilizer rate was significant on morphological traits, forage quantity and some quality traits, however, had no significant effect on some forage quality traits (NDF and ADF). The effect of plant density was not significant on forage quality traits but significantly influenced the morphological traits. The highest forage yield (8776 kg. ha-1) was obtained in plant density of 140000 plant.ha-1 with 180 kg N.ha-1. Also the highest crude protein 21.8%), digestible dry matter (54.4%) and total ash (13.4%) were obtained from 180 kg N.ha-1 treatment. Generally, response of forage quality and quantity of cultivated amaranth to nitrogen fertilizer was positive and linear.