Iron and zinc fortification in amaranthus (Amaranthus tricolor) through bioaugmentation

Abstract

An investigation entitled “Iron and Zinc fortification in amaranthus (Amaranthus tricolor) through bioaugmentation” has been carried out at the College of Agriculture, Vellayani during May to August 2012. The main objective was to study the effect of Fe and Zn application and bioaugmentation of soil with microbial additives on yield and nutrient composition of amaranthus, particularly with that of Fe and Zn. This was accomplished through a pot culture experiment using laterite soil.The design was Factorial Completely Randomized Design (4 x 4 x 4). The treatments include four methods of bioaugmentation (POP + AMF; POP + P solubilizer; POP + K solubilizer and POP alone), Four levels of iron (Zero; 5 mg kg-1 of soil, 10 mg kg-1 of soil and Foliar application of 1.0 mg kg-1 FeSO4) and Four levels of zinc ( Zero; 5 mg kg-1 of soil; 10 mg kg-1 of soil and Foliar application of 0.5 mg kg-1 ZnSO4).The experiment results revealed that the treatment combination M4F0Z2 (POP x Fe0 x Zn @ 10 mg kg-1 ) recorded the highest shoot biomass and B:C ratio. The above treatment was on par with several treatment combinations of M2 (P solubilizer) and M4 (POP) and with M3F0Z3. Root biomass was also highest for M4F0Z2. The biometric characters like plant height, number of branches per plant, number of leaves per plant, leaf weight, stem weight, leaf: stem ratio, root length and root volume were significantly influenced by the treatments while girth of stem was not significant. Interaction effects of treatment on most of the variable were also significant. Considering the individual effects, among the bioaugmentation methods, M4 (POP) showed highest values for all the above observations except root length and the lowest by M1 (AMF). Levels of iron had shown a negative effect on most of the plant characteristics while zinc maintained a positive significant effect.Treatment effect was significant on concentration of nutrients viz., N, P, K, Ca, Mg, S, Fe, Mn, Zn, and Cu in shoot and root at each harvest. Evaluating the individual effects, it was observed that the microbial additives in general significantly increased N, Ca, Mg, Fe and Zn compared to POP. P solubilizer had significantly increased P and Zn content of the shoot and K solubilizer the K content. Fe @ 5 mg kg-1 alone recorded an increase in Fe content of shoot. Zn maintained a significant positive relation with shoot Zn content and foliar application recorded the significantly highest value. Nutritional parameters like crude protein, β-carotene, nitrate, vitamin C, oxalate and phenol contents were significantly influenced by the treatments. Bioconcentration factor and translocation index were significant only for Zn.Soil characteristics like pH, EC, organic carbon, available N, P, K, Ca, Mg, S, Fe, Mn, Zn and Cu at the time of each harvest were significantly influenced by the treatments. Levels of Zn showed a positive influence on available Zn content. Treatment with microbial additives had favorably influenced the biological parameters like AMF colonization and rhizosphere microbial count.From the above experiment, it can be concluded that the treatment combination POP x Fe @ zero x Zn @ 10 mg kg-1 (M4F0Z2) recorded the highest economic yield and B:C ratio. Considering the nutritional quality and iron and zinc content of economic plant part, the treatment combination K solubilizer x Fe @ zero x Zn as foliar, (M3F0Z3) is the best treatment since it is on par with the above treatment in yield and B:C ratio and at the same time recorded better nutritional quality and iron and zinc content.