Wheat yields have increased over the decades, more concretely during the second half of the XX century when grain production per unit area doubled. This increase was boosted by genetic improvements in the crop, as well as by better agricultural practices amongst which is the use of nitrogenated fertilizers which has enabled enhancement not only in crop yield but also in the end quality of the wheat. Nevertheless, the use of nitrogenated fertilizers has had negative consequences for the environment, as plants only manage to incorporate about half of this substance, the rest filtering to subterranean waterbeds in the form of nitrates and which can be toxic for human consumption; or otherwise it is freed into the atmosphere in the form nitrogenated gases, such as ammonia.
Within this context, farmers are obliged to combine a number of different objectives: maximise crop yield, limit production costs and do this reducing the negative impact on the environment. Besides, the quality of the wheat obtained has to comply with market demands. In the case of flour wheat, employed in bread making, the quality is determined by its genetic configuration and the extant climatic conditions, although research undertaken to date reveal that a judicious handling/dosage of nitrogenated fertilizers has a positive influence on the quality of the grain.
In her PhD, entitled Physiology of wheat crop and grain quality under different regimes of nitrogenated fertilizers, UPV/EHU researcher, Teresa Fuertes Mendizábal, analysed the behaviour of wheat with different uses of nitrogenated fertiliser, with the goal of establishing suitable guidelines for application – optimum dosage, number of applications and so on. Ms. Fuertes is a graduate in Biological Sciences and has an advanced studies diploma in Environmental Agricultural Biology. She is currently contracted as a researcher at the Department of Plant and Ecological Biology of the Faculty of Science and Technology (UPV/EHU). Her PhD was led by Ms María Begoña González Moro and Mr José María Estavillo and undertaken in collaboration with the Public University of Navarre and the NEIKER-Tecnalia Institute.
Seeking the correct dosage
One of the aims of the UPV/EHU research was to better understand the physiological response of the wheat crop to nitrogen. By means of a field study in the Basque province of Araba, carried out with a wide-ranging variety of flour wheat – known as Soissons -, Dr Fuertes studied the physiological processes involved in the efficient use of nitrogen by the plant. According to her conclusions, applying an insufficient dosage of fertiliser will result in scant yields in terms of volume of production, while excessive dosage will cause environmental problems without achieving appreciable improvement in the quality of the grain. For Dr Fuertes, drawing up the procedures or protocols for the application of nitrogenated fertilisers should take into account the source of the nitrogen, the quantity to be applied and the distribution of the dosage, i.e. in how many stages should this amount be applied.
Less fertiliser, but better dosage
The PhD thesis of Ms Fuertes revealed that the optimum dosage enabling the maximum yield for wheat crop, in the climatic conditions extant in Araba, is about 155 kg of nitrogen per hectare. She also pointed out that dosages of 100 kg or less per hectare produce flours that are insufficient for bread making, while 140 kg per hectare produces mediocre flours, but 180 kg per hectare produces flours with good bread making properties.
Moreover, according to the research, the distributing the fertiliser dosage in three stages (instead of two) not only enables the attenuation of nitrogen losses by filtering to subterranean waterbeds and emission of gas, but also the beneficial effects are such that they confirm that lesser dosage, better distributed over time, can improve the quality of the grain. For example, a dosage of 140 kg of nitrogen per hectare distributed in three applications achieves the same quality of flour as the application of 180 kg per hectare in two stages.
The UPV/EHU researcher has also studied at depth the influence of nitrogenated fertilisation on the proteic composition of the grain, arriving at the conclusion that it has a positive effect on the indices of quality. According to Ms Fuertes, increasing the dosage of fertiliser or distributing it better produces stronger and more balanced flours, i.e. ones that are more suitable for the bread making industry.
Finally, the monitoring of data from crop tests in containers has been initiated and in which, apart from simulating conditions in the field, it has been possible to collect samples of the plant roots, something unviable in the field itself.