Nitrogen Management and Water Productivity of Limited Irrigation Corn

This project seeks to improve crop water productivity of irrigated maize by better understanding the interaction of nitrogen fertility management and limited irrigation.


26 May 2016

2015 Annual Interpretive Summary

Many maize-growing regions are chronically plagued with limited soil moisture as a result of erratic rainfall or inconsistent access to irrigation water. The available soil moisture influences how nutrients are taken up by plants and how they are utilized for metabolism. In this two-part research, the water status of greenhouse-grown maize was measured using remote sensing of the crop canopy temperature. The daily measured remotely sensed leaf temperatures were affected by irrigation, but not by N application rate. With limited irrigation, leaf temperature averaged 32 C, compared to 30 C for full irrigation. These differences were related to water stress, but not to leaf color. Plants with sufficient or excess N experience more drought stress in water-limited scenarios, showing that N fertilizer management is a critical factor under drought conditions.

The field portion of this research is evaluating the interaction of water and N fertilization on root and shoot growth. Root and shoot biomass were determined with combinations of full and limited irrigation and three N application rates approximately 60 days after planting. Both irrigation and N application rate had significant effects on shoot, root, and total biomass development. Maximum production of shoot and total biomass was achieved at the high N rate for the well watered treatment, but at the medium N rate when irrigation water was limited. Maximum root biomass was achieved at the low N rate for the well-watered treatment and at the medium N rate for the limited irrigation treatment. Reducing rates of either irrigation or N resulted in a greater root to shoot ratio.

These results reinforce the concept that the soil N supply is an important factor for managing drought stress. Limited root growth with excess N will reduce the volume of soil from which roots can access water during drought conditions. Options for changing the N application rate based on rainfall or the availability of irrigation water should be considered.