Influence of fertilization and soil tillage on nitrogen uptake and utilization efficiency of quinoa crop (Chenopodium quinoa Willd.)

In recent years, quinoa (Chenopodium quinoa Willd.) has attached the interest as a multi-purpose crop. A 3-year field experiment was conducted to determine the effects of tillage systems and fertilization on nitrogen uptake and use efficiency of quinoa crop. The experiment was laid out in a split-plot design with two replicates, two main plots [conventional and minimum tillage] and four sub-plots (fertilization treatments: untreated (control), inorganic fertilization of 100 (N1) and 200 kg N ha(-1) (N2) and sheep manure). The results indicated that nitrogen uptake and utilization efficiency were only influenced by fertilization. The higher biomass nitrogen content (4.08-4.33%), biomass nitrogen yield (371-386 kg N ha(-1)), seed nitrogen content (2.59-2.78%), sued nitrogen yield (62.58-65.42 kg N ha(-1)) and total plant nitrogen uptake (437.20-454.93 kg N ha(-1)) were found in N2. Nitrogen harvest index and nitrogen utilization efficiency were up to 60% lower and 40% lower, respectively, in inorganic treatments than in the control. Rates of nitrogen higher than 100 kg N ha(-1) (N1) did not increase the nitrogen agronomic efficiency. Regarding apparent nitrogen recovery efficiency, the higher values observed under inorganic fertilization and being greater than 100%. The highest rates of change of nitrate reduction in soil (-0.108 to -0.188 N% day(-1)) and nitrogen increase in plant (0.025 to 0.027 N% day(-1)) were observed under N2 treatment. As a conclusion, quinoa has a high capacity to take up nitrate from the soil, but presents lower nitrogen remobilization from the vegetative parts into the seeds under high nitrogen supply.