Management of Nitrogen Fertilizer for Performance Optimization of Maize Inbred Lines (Zea mays L.).

Nitrogen (N) is the most important nutrient for maximizing crop yield and profitability. An evaluation of the effects of cover crops and the determination of the optimum fertilizer-N rate that will maximize crop yield, will help to improve on-farm N management.  This study evaluated the effects of covercrop (Vigna unguiculata) and six fertilizer-N levels (0, 33, 68, 102, 135 y 203 kg N/ha) on maize (Zea mays L.) yields in the southern semiarid coast of Puerto Rico with drip irrigation system in a Fluventic Haplustolls. Each of the plots had a known fertilizer-N management history that ranged from 68 to 180 kg N/ha since summer 2011.  The covercrop was planted in summer 2013 followed by maize planting in winter 2013-2014 and harvested in March 2014. Agronomic measurements (such as plant height, leaf area, and sensing tools such as GreenSeeker and SPAD-502) during the maize growth cycle [33, 42, 52 and 62 days after planting] were gathered.  Obtained seed yields (15.5% moisture) ranged from702 to 2670 kg/ha under fertilizers rates levels of inbred lines under studied conditions. Maximum seed yield was obtained with fertilizer-N between 68 and 102 kg N/ha with covercrop and fallow treatments. Covercrop did not affect seed yields.