Seasonal variations in water uptake of summer maize under different fertilization treatments: A case study using stable isotopes in Beijing, China

Abstract:

Crop water use from soil horizons may be significantly affected by fertilization management practices. Based on stable water isotopes in crop stem and soil water, we investigated seasonal variations in water uptake patterns for summer maize influenced by amount of fertilization application during 2013 and 2014 in Beijing, China. The Bayesian stable isotope mixing model (MixSIAR) and direct inference method were used to determine water uptake depth and proportional soil water contribution to summer maize. The results showed that the main soil water source for summer maize was 0-20 cm at seeding (67.7%) and jointing stages (60.5%). Water at deep soil depths (50-90 cm and 90-200 cm) was tended to be extracted as crop grew, even up to 45.2% at grain filling stage. About 72.0% of crop water was sourced from soil water at 0-50 cm depth at maturity stage. However, pronounced differences of water uptake for summer maize with different nitrogen application rate were presented at depths of 0-20 and 20-50 cm during tasseling and grain filling stages, ranging from 5.4% to 68.9%. Comparing water uptake patterns in two experimental seasons, it was largely concentrated at 0-50 cm depth in 2013. This might be due to continuous rainfall before tasselling stage promoted crop root development in shallow soil depth. On the other hand, seasonal drought resulted in 27.2% more deep soil water contribution at grain filling stage in 2014 than that in 2013. These findings can provide quantitative implications for further studies on water flow and nitrate transport in agricultural filed.