A comparative study of the effect of chemical and biological fertilizers on some physiological traits, biochemical traits and yield of quinoa (Chenopodium quinoa L.) in saline and non-saline soils

Quinoa (Chenopodium quinoa Willd) is an annual Latin American plant that, despite its high nutritional value, is able to withstand a wide range of non-biological stresses and can be cultivated in agriculturally marginal lands.Few studies have been conducted on the effect of simultaneous application of biofertilizers on the yield and physiological traits of Quinoa under salt stress conditions. Thus, the present study was an attempt to compare the effect of biological and chemical fertilizers application on yield and some physiological traits of Quinoa in saline and non-saline soils.

In order to compare and evaluate the effect of non-saline and saline soils on yield as well as physiological and biochemical traits of Quinoa under simple and integrated (chemical and biological ) fertilizer treatments, a split plot with randomized complete block design and three replicates was used in two separate farms in the northeast of Isfahan. Two levels of salinity including non-saline soils (EC = 2.91 dS / m) and saline soils (EC = 6.2 dS / m) were regarded as main factor and composition of biofertilizers at four levels of control (no biofertilizer), nitroxin, biophosphorus and nitroxin + biophosphorus and applications of chemical fertilizers at two levels including no fertilizer and factorial application of nitrogen+ phosphorus were considered as sub-factors. Total values of chlorophyll, carotenoids, carbohydrate, soluble protein, leaf area index, grain yield, and biological yields of quinoa were studied under the afore-mentioned treatments.

The results showed that although soil salinity led to significant declines in the biochemical traits such as total chlorophyll level, total carbohydrate level, soluble proteins and leaf area index in the separate biofertilizer application treatments, maximum values of the afore-mentioned traits were obtained in saline soil under combined application of chemical fertilizer and bio-fertilizers (nitroxin + biophosphorus). This suggests that combined application of chemical fertilizers and bio-fertilizers fertilizers (nitroxin + biophosphorus) will not only mitigate the adverse effects of soil salinity on quinoa but will significantly improve the afore-mentioned traits by improving the physiological capacity and biological activities in quinoa. On the other hand, carotenoids, which act as a defense mechanism in response to osmotic stress, through high optical energy dissipation and active oxygen removal, and enhance the ability to cope with stress condition, were found to be 3 times higher in saline soils. Maximum biological yield in non-saline soils was only about 10% higher than that in saline soils. The results indicate high resistance of quinoa to severe osmotic stress conditions.

The results showed that despite the salinity of soil, quinoa managed to complete its growth period and produce seed. Moreover, according to the results, under chemical fertilizer + bio- fertilizer application conditions, maximum yield of quinoa in non-saline soils was only about 12% higher than that in saline soils. This indicates the high resistance of quinoa to salinity stress conditions. Thus, Quinoa as a plant characterized by high yield potential and high quality crop in saline conditions is a perfect choice in areas with low fertility and stress conditions. Moreover, bio-fertilizers as materials that facilitate and contribute to supplying of plant nutrients, can also be introduced as a practical solution to mitigate the effects of environmental stresses and contribute to optimized application of chemical fertilizers in an attempt to achieve sustainable agricultural goals.