Effect of Harvest in Different Growth Stages on Quantity and Quality of Forage of Amaranth (Amaranthus sp.) Varieties and Its Economic Assessment

To study the effect of harvest in different growth stages on quantity and quality of forage of amaranth varieties a field experiment was carried-out as factorial arrangement in randomized complete block design with three replication in two successive growing seasons (2006 and 2007) in Karaj, Iran. Experimental factors included: four amaranth varieties Ultra, Kharkof, Kharkofsky and Unknown, and two harvest stages flowering and after seed set. For forage yield of amaranth varieties, samples were taken from determined area in each plot. For quality assessment of treatments, standard samples were prepared. Results showed that amaranths variaties significantly (P < 0.01) differed for fresh and forage yields. The highest fresh (86400 kg ha-1) and dry (13320 kg ha-1) forage yields belonged to Ultra. Combined analysis of variance revealed that effects of year and interaction of variety × harvest stage were significant (P < 0.01) on fresh and dry forage yields. Amaranth varieties significantly (P < 0.01) differed for crude protein content which varied from 7.75% to 22.2%. There were highly significant negative relationship between dry matter digestibility (DMD) and acid detergent fiber (ADF) (r = -0.874**) and organic matter digestibility (OMD) (r = -0.911**). The estimated means of DMD, OMD and DOMD (Dry organic matter digestibility) were 71.1%, 67.6% and 58.8%, respectively. Ultra harvested in flowering stage had the highest profit (12880000 IRR). The estimated marginal rate of return of substitution of this treatment with other tretments was 96%. Therefore, Ultra with harvest in flowering stage was identified as suitable treatment.