EVALUATING QUINOA LODGING RISK AND YIELD UNDER DIFFERENT IRRIGATION THRESHOLDS,NITROGEN RATES AND PLANTING DENSITIES IN NORTH-WESTERN CHINA

Lodging is a major yield-limiting factor of quinoa production.In 2018 and 2019,the orthogonal field experiments were conducted to investigate the responses of quinoa lodging risk and yield to irrigation threshold(soil matric potential of-15,-25 and-55 kPa),nitrogen rate(80,160 and 240 kg·ha-1) and planting density(20,30 and 40 plants m-2).Results showed that high irrigation thresholds and nitrogen rates significantly(P<0.05) increased plant height and fresh weight per plant,and high planting densities reduced stem diameter and strength,all of those led to significantly(P <0.05) high lodging risks.The-15and-55 kPa treatments gave the lowest actual yield(P <0.05) in 2018 and2019,respectively.Higher lodging rate with a nitrogen rate of 240 kg·ha-1resulted in a lower actual yield than 80 and 160 kg·ha-1in both years.Planting density of 30 plants m-2gave a significantly(P <0.05) greater estimated yield than 20 plants m-2and had a lower lodging rate than 40 plants m-2,resulting in the maximum actual yield among planting densities.In conclusion,a moderate irrigation threshold of-25 kPa,a nitrogen rate of 80-160 kg·ha-1and an intermediate planting density of 30 plants m-2were determined to be best for quinoa cultivation in North-western China.In addition,the lower-stem lodging index(quarter plant height) could evaluate lodging risk more accurately than middle-stem(half plant height) or upper-stem(three quarters plant height) lodging indexes.