Contrasting Responses of Corn Ecophysiological Performance and Yield to Agricultural Practices in Two Years with Different Rainfalls

The United States (US) is the largest corn producer in the world. It is very important to understand how agricultural practices would influence corn ecophysiological performance and yield under different climatic conditions. We conducted a field experiment in two years (2012 and 2013) with different precipitation patterns to study the responses of corn ecophysiological performance and yield to various management practices. We considered six treatments, including convenient tillage (CT) and no tillage (NT), with different nitrogen types and application methods: CT-urea (CT, normal applications of liquid urea), NT-urea (NT, normal applications of liquid urea), NT-inhibitor (NT-urea+denification inhibitor), NT-biochar (NT-urea+biochar), NT-litter (NT, chicken litter), and NT-split (NT, multiple applications of liquid urea). A complete randomized block design was applied with six replications. We measured leaf photosynthesis rate, soil respiration, plant height and yield. Results showed that no-tillage treatments significantly increased corn leaf photosynthesis —by 7%—over the conventional tillage. Soil respiration, corn crop height and yield were significantly and positively related to leaf photosynthesis. As a result, CT-urea also had the lowest corn height and yield, and the relative low soil respiration. However, all the leaf photosynthesis, soil respiration, soil moisture, plant height and yield in 2013 were significantly higher than those in 2012, probably due to a drought event in 2012. We further found that leaf photosynthesis, soil respiration, corn height and yield tend to be positively related to soil moisture in 2012, but no significant relationship was found in 2013. The water use efficiency of corn leaf was also significantly lower in the 2013 than those in 2012. Our results suggest that with increasing extreme climate conditions forecasted in the future, stability of crop performance and yield could be a serious problem in sustainable agriculture.