Nitrogen application in winter wheat grown in Mediterranean conditions: Effects on nitrogen uptake, utilization efficiency, and soil nitrogen deficit
Montemurro, F.; Convertini, G.; Ferri, D.
Journal of Plant Nutrition 30(10-12): 1681-1703
ISSN/ISBN: 0190-4167 DOI: 10.1080/01904160701615541
Nitrogen (N) is one of the most growth restricting nutrients in cereal grain and represents one of the highest input costs in agricultural systems; therefore, environmental and economic considerations require the effective use of N fertilizer in plant production. This study was conducted for three years to better understand wheat plant response to optimize N fertilizer and how to reduce the risk of ground water pollution.Two of the most important durum wheat cultivars in Southern Italy and four N fertilization levels (0, 60, 120, and 180 kg N ha(-1), indicated as NO, N60, N120, and N 180, respectively) were compared in this experiment. During plant growth, fresh and dry matter, plant nutritional state (SPAD readings and stem nitrate content), and N uptake were determined. At harvest, plant N content, N uptake, grain yield, yield components and quality were determined, allowing the calculation of the pre- and postanthesis N uptake and the N utilization efficiency indices. Furthermore, at the beginning and at the end of each year, soil mineral N was measured to calculate mineral N deficit in the soil.The results indicated that the treatment with 120 kg N ha(-1) of fertilizer ensures a good balance between yield and N utilization. In fact, N 180 and N 120 showed similar yield (3.01 and 3.07 t ha(-1), respectively) and protein content (13.7 and 13.5%). Meanwhile, throughout the three-year experiment, N 180 presented the highest final mineral N content in the soil at the end of the cropping cycles, increasing the amount of N available for leaching. The N 120 treatment showed the same values of N utilization indices as compared to N 180, indicating that further doses of N fertilizer did not increase wheat N utilization. Plant N status shows that it is possible to modify the N fertilization to reach its optimum level during plant growth, in accordance with variable weather conditions, and consequently the plants requirements. The mean treatments of the preanthesis N uptake were about 67.5% of the total N uptake, and it was significantly and positively correlated with wheat yield. On the contrary, the postanthesis N uptake showed positive correlation with grain protein content, confirming the importance of late N supply in grains quality. The variation of weather conditions affected winter wheat yield, quality, N utilization and plant N status, but any difference throughout years was found between N 180 and N 120, confirming that higher N rate did not influence wheat growth, yield, and N uptake.