Assessment of nitrogen status of soils for cereal crops: Use of plant and soil analysis to diagnose nitrogen status of spring barley

The results of field experiments with spring barley at two locations in 1978 and 1979 were used to evaluate early season measurement of soil mineral N, plant N and chlorophyll, and nitrogen stress as indicators of straw and grain yields and N uptake at maturity. A new definition of N stress based upon rates of N uptake is proposed. Plant N and chlorophyll contents early in the season were positively related (P< 0.001) to final N uptake. Early season N stress (based on growth rate) was negatively related (mainly P< 0.001) to grain yield and, less strongly, to N uptake. There appeared to be some advantage in using rate of N uptake rather than growth rate to define N stress for the purpose of predicting crop final N uptake.