Balance sheet method assessment for nitrogen fertilization in winter wheat: II. alternative strategies using the CropSyst simulation model

It is important, both for farmer profit and for the environment, to correctly dose fertilizer nitrogen (N) for winter wheat growth. Balance-sheet methods are often used to calculate the recommended dose of N fertilizer. Other methods are based on the dynamic simulation of cropping systems. Aim of the work was to evaluate the balance-sheet method set up by the Region Emilia-Romagna (DPI), by comparing it with the cropping systems simulation model CropSyst (CS), and with an approach based on fixed supplies of N (T). A 3-year trial was structured as a series of N fertility regimes at 3 sites (Papiano di Marsciano, Ravenna, San Pancrazio). The N-regimes were generated at each site-year as separate trials in which 3 N rates were applied: N1 (DPI), N2 (DPI+50 kg ha-1 N at spike initiation), N3 (DPI + 50 kg ha-1 N at early booting). Above ground biomass and soil data (NO3-N and water) were sampled and used to calibrate CS. Doses of fertilizer N were calculated by both DPI and CS for winter wheat included in three typical rotations for Central and Northern Italy. Both these methods and method T were simulated at each site over 50 years, by using daily generated weather data. The long-term simulation allowed evaluating such alternative fertilization strategies. DPI and CS estimated comparable crop yields and N leached amounts, and both resulted better than T. Minor risk of leaching emerged for all N doses. The N2 and N3 rates allowed slightly higher crop yields than N1

Balance sheet method assessment for nitrogen fertilization in bread wheat: I. yield and quality

In the European Union the production of high quality wheat is mainly located in the Mediterranean regions where the climatic conditions positively affect protein concentration in the grain. High quality wheat calls for proper management of nitrogen fertilization, thus there is a need to verify whether the limitations imposed by local governments on maximum rate of nitrogen fertilization admitted may affect bread making quality. Trials were conducted in fourteen environments (E) to study the effects of different nitrogen fertilizations on eight cultivars (C), belonging to four quality grades (Q). Nitrogen (N) was applied to crops according to three rates/modalities: N1 corresponding to the maximum rate admitted calculated according to a balance sheet method and distributed at the stage of spike initiation; N2 with 50 kg ha-1 of nitrogen more than N1, also distributed at the stage of spike initiation; N3 with 50 kg ha-1 of nitrogen more than N1 but distributed at the stage of flag leaf appearance. The effects of environment, nitrogen and cultivar were significant for grain yield, test weight, 1000 kernel weight, heading time, plant height and for quality traits (protein content and alveograph indices). The existence of variability among cultivars and quality grades in the response to rate and timing of nitrogen fertilization was demonstrated by the significance of NxC and NxQ interactions. Dry matter and nitrogen contents of plant at anthesis and at harvest were significantly affected by the main sources of variation. High quality cultivars yielded more grain of better quality with higher N rates (N2 and N3) as compared to the maximum rate of nitrogen admitted by the local government (N1). These results demonstrated that the adopted balance sheet method for the calculation of N requirements of wheat crop adversely affects the full potential expression of the cultivars belonging to superior bread making quality grades