Biofertilizers and Silicon Fertilization as a Sustainable Option for Maize Production

Due to the rapid growth of human population and increasing living standards, there is a continuous increase in the gap between food productivity and demand. At the same time there is a global reduction in freshwater availability for agriculture. Several options have been proposed along the way to increase water use efficiency in the field. One promising possibility is the adoption of fertilization with silicon (Si) combined with biofertilizers (microorganisms). Si is estimated to impact on the root volume and distribution, while microorganisms added to the soil in the rhizosphere also impact directly on root growth. In this work we have tested the influence of Si fertilization (magnesium silicate + diatomaceous earth) combined with biofertilizers and 20% reduction in NPK fertilization in the growth of maize and the soil water balance on a field trial located in Companhia das Lezirias (Portugal). Data on soil water content was collected regularly and root analysis was performed at harvest. The water balance was calculated through the model HYDRUS, using root growth model calibrated for maize in the present conditions. Results showed that using an alternative source of fertilization (Si+microbes) while reducing NPK fertilization impacted on root growth development, with roots growing more horizontally, while conventional NPK fertilization resulted in deeper roots. As a consequence,, root water uptake increased and evaporation losses were lower in the treatment supplemented compared to the conventional, without compromising the yield obtained. Using biofertilizers combined with Si sources resulted in higher water use efficiency (2.64 kg m-3) than the NPK fertilization, normally applied for maize growth (2.56 kg m-3). The results imply that the supplementation+biofertilization allows a potential saving of 206 m3 ha-1 water and 157 kg NPK ha-1 fertilization in a growing season assuring the same yield as obtained with the conventional NPK fertilization (18.64 ton ha-1). Implications are important for Portuguese agriculture, where maize is one of the most important cereals cultivated, especially in Centre and Southern part of the country where water is a scarce resource.