Nitrogen Management and Water Productivity of Limited Irrigation Corn

In arid areas around the world, water scarcity threatens agricultural and food sustainability. Water scarcity is driven by increasing competition for a limited water supply, drought and declining groundwater resources. One coping strategy is timing irrigation and N fertilization with plant growth stage. The project uses field and greenhouse studies to evaluate the interaction of N fertility status and limited irrigation for maize. Results of the greenhouse study are reported here.

Remote sensing of crop canopy temperature can assess crop water status for more precise irrigation management. One objective was to evaluate N fertility status and remotely sensed maize leaf temperature under full and limited irrigation. For most observations, 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 and N fertilizer management is a critical factor under drought conditions.

A second objective was to evaluate how N fertility interacts with root and shoot growth under full and limited irrigation. Root and shoot biomass were determined with combinations of full and limited irrigation and three N fertility levels approximately 60 days after sowing. Both irrigation and N level had significant effects on shoot, root and total biomass development. Maximum shoot and total biomass was achieved at the high N rate for the well watered treatment, but at the medium N rate for the limited irrigation treatment. 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 show that 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.