Optimization Of Nitrogen Sources At Winter Nurseries For Better Production Of Corn Inbred Lines.

Hybrid corn typically requires high fertilizer nitrogen (N) levels.  Yet growing conditions for inbred lines at winter nurseries offer unique challenges to produce a successful crop. Inbred lines have lower yields and nutrient uptake levels and efficiencies, which may require modifying rates, forms, timing, and placement of fertilizer-N.  Volatilization, leaching, and de-nitrification are some of the major causes of N loss in winter nurseries. In order to understand the impact of various sources of fertilizer-N on production of corn inbred lines, an experiment was conducted during spring of 2009 and 2010 at Santa Isabel, PR. The study was conducted in a split-split plot where three sources of pre-plant fertilizer-N (ammonium nitrate, ammonium sulphate, urea) were used as main plot, two corn inbred lines (DAS 1102, and DAS 1105) were used as sub plot, and six sources of basal N application (ammonium nitrate, ammonium sulphate, sulphur coated urea, polymer coated urea, urea and control) were used as sub-sub plot for this experiment. The study was planted at two locations, and replicated three times within each location. A total of 168 kg N/ha was applied via pre-plant and fertigation sources. Plant height, plant girth, and chlorophyll content at V6 and V10, pre-flowering foliage N analysis, and grain yield were recorded for both years of study. The data was analyzed by SAS 9.1 using mixed models, where sub plots and sub-sub plots were designated as random variables. None of the variables in this study exhibited significant difference for observed traits, nonetheless, significant cost reduction in N fertilization was observed if ammonium sulphate and polymer Coated Urea were not applied as variables. Studying soil profiling of N up to 60 cms. soil depth is under progress to find indications of N availability at winter nursery conditions for corn inbred lines production.