Investigating the effect of chemical and organic fertilizer system on the quality and quantity of Amaranthus (cv. Cim) forage under the influence of different irrigation levels

Amaranth forage plants, due to their nutritional properties and ability to adapt to drought conditions, can be a good option to deal with water deficiency and increased productivity under different fertilizer systems. This experiment spans for 2 years in form of a complete random block design based on a factorial with three replications, three levels of irrigation (irrigation after depleting 40%, 60%, and 75% of available water) as the first factor and organic (cow manure and phosphate-2), chemical (phosphorus and nitrogen), integrated, and control (no fertilizer) fertilizer systems as the second one. Results of this study show that crude protein, digestibility of dry matter, water-soluble carbohydrates, digestible nutrients, relative nutritional value, and specific energy of lactation, due to the application of different fertilizer systems in each irrigation level have been improved, compared to non-consumption of the fertilizer. The performance of biomass and forage protein are increased by 38.89% and 54.37%, 30.60% and 41.23%, and 22.20% and 34.92% in optimal, moderate, and severe stress conditions, respectively in integrated fertilizer system than the control. Also, this study shows that the use of organic fertilizers alone or combined with chemical fertilizers improve quantitative and qualitative traits of amaranthus forage irrigation after depleting 40% and 60% of available water. So, optimal use of biological inputs for sustainable agriculture and reduction of pollution, caused by the use of chemical fertilizers, is recommended.