Effects of foliar nutrition on the reduction of diseases in extensive crops. Field studies in Argentina
Abstract: With the objective of studying the effect of foliar nutrition as a tool to improve thetolerance to diseases we conducted eight trials on Glycine max, four on Triticum aestivum andtwo on Zea mays, with a total of fourteen evaluation sites and four growing seasons (2005/2009).We monitored epidemics and yield in plots with or without foliar fertilizer application inproduction conditions in Argentina. The fertilizers under study were Nitrofoska® Foliar PS andFetrilon® Combi. The results on soybean show a significant reduction of Septoria glycines levelsand an increase in yield in plots treated with the foliar fertilizers. Median yields were 2600kg/ha,with a variation between 1900 and 3500kg/ha. With foliar nutrient applications, we obtained amedian yield of 3204kg/ha, with the highest production at 4000kg/ha, representing improvementsof 23%. In part, these improvements were due to a reduction in bacterial infections(Pseudomonas syringae pv glycines and Xanthomonas axonopodis pv glycines) because the cropswith nutrient application showed leaves with better foliar structure, which decreasedsusceptibility to injury. The epidemiological monitoring on maize showed a reduction ofsymptoms caused by Exserohilum spp. and Helminthosporium spp. in the nutrient treated plotsThe best results in terms of final crop health were achieved in the treatments at the floweringperiod which, allowed yield improvements by 7-12%, entailing an increase of up to 1000 kg/ha.In the wheat crop the study object was leaf spots caused by Pyrenophora tritici-repentis andSeptoria tritici. We compared nutrient application at stages 2.3-3.1 and 4.0-4.5 of the Zadoksdevelopmental scale. Nutrient treatments resulted in yield improvement in all the evaluation sites.During dry seasons, the most favorable application time was at Zadoks stage 2.3-3.1, withimprovements of 9-43%. In wet years the best application time was during Zadoks 4.0-4.5, withyield improvements up to 46% and reduction in disease severity of up to 60% compared to theuntreated control. The results of these studies confirm the importance of foliar nutrition withmicronutrients as a complementary tool in strategies of disease management to obtain asustainable agro system.