Comparative Growth Stages and Plant Parts for Critical Nitrate-N Concentration of Squirreltail

Abstract

The critical nitrate-N concentration for growth of squirreltail, Sitanion hystrix (Nutt.) J. G. Smith, was not appreciably affected by plant maturity when recently-matured blades rather than entire shoots were analyzed for nitrate-N. The critical nitrate-N concentrations for recently-matured blades were, respectively, 400, 500, and 500 ppm nitrate-N, dry basis, for the early vegetative, late vegetative, and late-boot growth stages. In contrast, the critical nitrate-N concentrations for shoots were 400, 600, and 1300 ppm, respectively, for the same growth stages. Recently-matured blades should, therefore, be collected to determine the N status of squirreltail in the field at any active growth stage. A high N status increased top growth preferentially to root growth. Hence, the ratio of tops to roots increased from 1.0 to 3.0, for N deficient and N sufficient plants, respectively.