Tissue Nitrogen Levels For Dryland Hard Red Winter Wheat

Plant tissue analysis could be an effective diagnostic tool for identifying N sufficiency or deficiency at early growth stages for hard red winter wheat (Triticum aestivum L.). This study was conducted to determine critical plant tissue N and NO3‐N concentrations of three plant parts at three growth stages. Nitrogen was applied preplant (fall) at rates of 0, 22, 44, and 66 kg N ha−1 to establish a range of spring plant tissue N levels and grain yields within a location. Critical plant N levels were calculated by the cate‐Nelson procedure. All plant N measurements made at early tiller (Feekes 3) had limited diagnostic value. Late tillering (Feekes 5) and early jointing (Feekes 7) were the best growth stages to sample. Stem and whole‐plant NO3‐N concentrations were highly variable and have limited use for N recommendations. Total N in the whole plant or in the leaves was found to be the best plant part to sample at Feekes 5 and 7 growth stages. Critical N levels recommended for Feekes 5 growth stages are: 32 g kg−1 total N for the whole plant and 38 g kg−1 total N for the leaves. Critical N levels recommended for Feekes 7 growth stage are: 27 g kg−1 total N for the whole plant and 35 g kg−1 total N for the leaves