The Effect of Chemical and Biological Fertilizers on some Physiological and Yield Traits of Quinoa (Chenopodium quinoa Willd.) under Drought Stress in Saline Soil

Introduction

Considering prolonged drought condition in the country, water shortage, and water and soil salinity, some crop and current horticulture productions in the arid zone of the country face many constraints in terms of water supply for growth and yield loss. In this way, introducing new plants with high production yield is at the top of the agenda of the Iran Ministry of Agriculture to obtain high-quality production. Quinoa (Chenopodium quinoa Willd.) is an annual plant originated from Latin America. In addition to high nutrition value, this crop shows considerable resistance against a broad range of abiotic stresses such as drought, salinity and cold; and can be cultivated in marginal lands. Considering inability of most agricultural soils in the country to thoroughly supply nutrients for plants, chemical fertilizer consumption in Iran is much higher than the global average. Thus, in order to increase nutrient use efficiency, fertilizer utilization should change to render essential nutritious available for plants during a long time. Using bio-fertilizer dissolving phosphorus and nitrogen stabilizer is an optimal cultivation method, which improves adsorption of nutrition by plants and decreases soil salinity, and environmental contamination caused by indiscriminate use of chemical fertilizers.

In order to evaluate the chemical and bio-fertilizer effects on yield, yield component and some physiological properties of Quinoa under water deficit in saline soil, an experiment was conducted as split plot factorial layout based on the randomized complete block design with three replications in 2018-2019 crop season at Dastgerd area in Isfahan province. In this experiment four levels of irrigation (25, 50, 75 and 100 % of field capacity) as the main factor, and the combination of biofertilizer including control (without bio-fertilizer), Nitroxin, Biophosphorus and combination of Nitroxin, Biophosphorus and chemical fertilizer in two levels of no application and integrated application of nitrogen and phosphorus fertilizers as sub-factor were considered. The average amount of water used in treatments of 100, 75, 50 and 25% of field capacity was 4204.1, 3427.2, 2665.6 and 2828.8 m3, respectively. Chemical fertilizer treatments (250 kg urea and 75 kg triple super phosphate fertilizer per hectare) were based on the results of soil test and fertilizer recommendation by the laboratory.

Results showed that in all fertilizer treatments with drought stress increment, measured physiological traits (total chlorophyll and leaf area index), and seed yield component including the number of clusters per square meter, seed number in cluster and seed thousand weight decreased, and consequently seed yield and Quinoa harvest index decreased. Under severe drought stress (25% field capacity irrigation treatment), grain yield and harvest index decreased by about 76 and 22%, respectively, compared to non-stress conditions (100% field capacity irrigation treatment). However, in all stress levels and both application and non-application of chemical fertilizers, simultaneous inoculation with both Nitroxin, Biophosphorus bio-fertilizers made the largest contribution to decreased stress influences and significantly increased all traits studied. The nitrogen fertilizer resources had the most effect on decreasing osmotic stress consequence in chlorophyll content, leaf area index and spike number per square meter. Therefore, since spike number is the main part of seed yield, it could be stated that nitrogen fertilizer applied in this experiment had the largest contribution to increase of seed yield. Phosphorus fertilizer resources available in this study also showed the highest influence to decrease in stress effects of 1000-seed weight. This could be attributed to nitrogen influence on vegetative growth and physiological role of phosphorus to generate flower and seed production.

Our results revealed that despite soil salinity of surveyed area, Quinoa can complete growth period even in a 25% level of field capacity (severe drought stress) and produce seeds. This highlights the high resistance of Quinoa to severe environmental stress conditions.