Nitrogen fertilization and root growth dynamics of durum wheat for a sustainable production

In an area of the Apulian Tavoliere (southern Italy), the effects of three levels of nitrogen fertilization (0, 50 and 100 kg N ha–1) on root development, growth analysis and yield parameters of durum wheat were evaluated. The research was conducted over a four-year period (1994-97). The non-destructive mini-rhizotron method was used to study the root system at stem extension and at the beginning of heading and ripening stages. At the end of tillering and at boot and flowering stages, samples of wheat biomass were taken and subjected to growth analysis. Yield data and the main biometric parameters were collected at harvest time. The doses of nitrogen (N) fertilizer 50 and 100 kg N ha–1 had a greater effect on root development in the 20-30 cm soil layer and on epigeal biomass than the control test (N0) without nitrogen fertilization. In the test (N0) the growth of root and epigeal biomass was slower during the first vegetative phases, however, afterwards both of them recovered and the root system was mainly developed in the 30-40 cm soil layer. A better development of root system in deeper soil layers, without nitrogen supply, has allowed the plant to overcome more easily the water-deficit and thermal stresses during the ripening stage. The results of this research have shown that the production of grain with 50 kg ha–1 of N is similar to those of 100 kg ha–1 of N doses and higher than the test without nitrogen fertilization. In this kind of environment can be recommended a nitrogen dose of 50 kg ha–1 for obtaining an increase in grain production with low costs and reduced agricultural sources of pollution.