Applicability of Different Indices to Evaluate Nutrient Status of Winter Wheat in the Organic System

Nitrogen (N), phosphorus (P), and potassium (K) nutrient status of two winter wheat cultivars (Kobra and Juma) in the organic crop production system was compared with integrated and conventional systems. This research was conducted between 1998 and 2000 at the Experimental Station in Osiny (Lublin province, Poland) on a grey-brown podzolic soil. To determine N, P, and K contents shoot samples of wheat were taken at the shooting and earing growth stages. Measurements of chlorophyll content were performed with a chlorophyll meter (SPAD) to estimate N nutrient status. Four different methods Nitrogen Nutrient Index (NNI), Soil Plant Analysis Development (SPAD), Diagnostic Recommendation Integrated System (DRIS), and Sufficiency Range (SR)] of nutrient status evaluation were compared. Nitrogen (N) and potassium (K) nutrient status of wheat cultivated in the organic system was lower compared with the other farming systems. Assuring sufficient supply of nitrogen to cereals under the conditions of organic farming is particularly difficult in early growth stages. In the integrated and conventional systems wheat was sufficiently supplied with NPK. Kobra cv. proved to be more adapted to the organic system. Results indicate that classical nutrient status indices are of lesser use for organic farming.