Grain yield, nitrogen-use efficiency and baking quality of old and modern Italian bread-wheat cultivars grown at different nitrogen levels

The high yields of today's modern wheat cultivars require high input which leads to both higher production costs and a greater risk of environmental pollution. Increasing public awareness of the latter, along with growing consumer demand for healthier products, has led on one hand to greater criticism being leveled at this type of production model and on the other to heightened emphasis on crops grown under integrated-management and organic systems. This applies also to wheat. By contrast, the yield increments registered by the new wheat cultivars during this period have been bolstered by the progressively higher N-inputs. All that has led to the idea that modem cultivars selected under conditions of high N-input are little suited to low-input conditions with respect to old wheat populations and cultivars. The present study investigated the responses of grain yield and quality and N-use efficiency at three input rates (N-0, N-80, N-160, kg ha(-1)) in a set of 16 of the most representative bread-wheat cultivars from 1900 to 1994. The average yield rise throughout the time was 33.5 kg ha(-1) per year, due to an increase of 124 kernel number per square meter per year and of 0.22% per year for harvest index (HI). At the same time, grain N-accumulation increased from 0.21 kg ha(-1) per year at No rate to 0.67 and 0.82 kg ha(-1) per year for N-80 and N-160, respectively. This increase was matched by average yield increments of 44, 50 and 47 kg per kg of N-accumulated. The cultivars exhibited a progressive rise in demand for N-supply over time of release so as to maximize yields accompanied by the upgraded capacity of N-use and enhanced quality traits: alveograph's W-index and P/L dough-gluten index rose from values between 65-170 and 0.25-0.39 for cultivars from 1900 to 1970 to 174-241 and 0.48-0.52 for those released after 1970. All the data show that over the last century the target of upgrading both yield amounts and grain quality for bread-making was successfully achieved. This success also indirectly led to an improved plant nitrogen uptake and use, clearly indicates that even under conditions of limited inputs or under organic-farming practices the best results are to be achieved by employing not old populations or varieties but modem cultivars, the latter being the only ones with the intrinsic traits capable of ensuring yield and quality at low N-supply even though they maximize their traits at high nitrogen inputs. (C) 2003 Elsevier B.V. All rights reserved.