Relationship of nitrogen and crop performance in aerobic rice and continuous flooding irrigation in weathered tropical lowland

Aerobic rice is a promising rice production system which enables rice to grow in water-constrained environments and provides an alternative to continuous flooding irrigation. Although significant water savings are reported in aerobic systems in different lowland regions, a negative impact in crop performance prevents its wide deployment. The main reasons for grain yield decreases are given to be genotype and inappropriate water supply. However, agronomic practices such nitrogen management can interfere in overall crop performance of rice due to the influence of soil moisture on N availability to crop uptake. The goal of this research was to establish a relationship between nitrogen use and crop performance by comparing flooding conditions to aerobic rice in a tropical environmental with adequate water supply. A field experiment was carried out from 2014 to 2016 with an experimental design of split plot with irrigation regime (IR) in the main plot: continuous flooding (CF) and non-flooding aerobic (NF), and in the subplot fertilizer nitrogen rates: (0, 50, 150 and 250 kg ha(-1)). Crop above ground biomass (AGB) and nitrogen uptake (NU) were quantified during crop development only in the 0 and 150 kg ha(-1) subplots, as was the relationship between AGB, NU, grain yield and its components and all nitrogen rates at harvest. The aerobic rice provided higher NU throughout rice development. At harvesting, NU and panicle density (PD) had different relationships to N rates among CF and NF, with NF showing 18% higher NU and 27% PD across years and N rate. The grain yield (GY) relationship to N rates was also distinct in 2014 and 2015, and GY across N rates in NF was 20% and 12% higher than CF for 2014 and 2015, respectively. We conclude that lowland rice managed through aerobic system improves nitrogen uptake by rice crop as long the water filled space remains around 60%.