1. Utilizing Indicator crop N-rich strips for anticipating pre plant and side dress Nitrogen rates for maize.
Rationale
Nitrogen use efficiency (NUE) in cereal grain production of 33% (Raun and Johnson, 1999) can be improved with active optical reflectance sensors. Improvement in NUE has been recorded > 60% for winter wheat (Li et al., 2009) and by 65% for maize (Tubana et al., 2008) with the use of sensor based N rates. However, adoption of this technology has been slow in maize for different reasons. Nitrogen deficiencies are not noticeable in maize until the V6-V7 growth stages in Oklahoma (Martin et al., 2007) and V11 in Nebraska (Solari et al., 2008). After growth stage V7 (maize height, 0.5m), machinery required for midseason applications are expensive and not affordable by most producers. Thus it is important to investigate strategies to widen the window for N fertilizer application in maize with the use of active optical reflectance sensors.
Objective
The objective of this study is to use indicator crops, winter wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) for anticipating pre plant and side dress N rates for an ensuing maize crop.
Methods
The response of wheat and barely indicator crops to 0-N and sufficient rates (168 kg N /ha) will be investigated to estimate optimal early season and first side dress N fertilizer rates for a subsequent maize crop.
Conclusions
In a previous study based on indicator crops for predicting pre plant N rates, strong correlation was found between N fertilizer recommendations generated using a generalized algorithm and optimum N rate for maize crop (R2 = 0.44 and 0.80) and RIHarvest for wheat and barley and RIHarvest for maize (R2 = 0.62 and 0.98) (Miller unpublished , 2014) . The concept of using indicator crops for anticipating N fertilizer for maize is new and modifications in current fertilizer recommendations could modernize N management strategies for all producers.