Nitrogen Management and Water Productivity of Limited Irrigation Corn

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

Background: Water scarcity is one of the most pressing contemporary challenges for agricultural and food sustainability. In many arid and semi-arid regions of the world, irrigation has been developed to allow stable, high yield agriculture and avoid the effects of drought. But water scarcity in many of these regions is now a pressing issue due to declining groundwater levels, increasing competition for water by municipal and industrial users, increasing frequency and severity of drought, and declining water quality due to pollution and salinity (Gleeson et al., 2012; Vorosmarty et al., 2000). For example, increasing demand for water by a growing urban population in Colorado is expected to drive a loss of 175,000 ha of irrigated farmland by 2030 (Colorado Water Conservation Board, 2004). Severe yield losses have also occurred throughout much of the U.S. Great Plains during recent droughts due to low capacity irrigation wells failing to meet crop water demand. Similar concerns are observed in arid and semi-arid regions worldwide, including key food production regions in China, India, and Africa (Alghariani, 2007; Basch et al., 2012; Kahlon et al., 2012).

Innovative cropping systems that increase resilience to drought and improve crop water productivity are needed. Some crops have been developed with enhanced drought tolerance, most notably drought tolerant corn hybrids. For example, DuPont Pioneer developed drought tolerant corn hybrids (trait branded as Optimum AQUAmax) using a complex of native genes from a wide background of maize genetics. These hybrids have shown yield advantages under drought stress (Joel Schneekloth, Colorado State University, personal communication). However, increasing water-limited crop yield must go beyond drought tolerance toward increasing crop water productivity in water scarce environments. Water productivity is the amount of crop yield per amount of water used, often referred to as the amount of “crop per drop.” Improving crop water productivity depends not only on new genetics, but also on a comprehensive set of environmental and management factors. For example, DuPont Pioneer’s new Optimum AQUAMax maize hybrids reach their water-saving potential only when grown under recommended management practices (Jeff Schussler, DuPont Pioneer, personal communication). This proposal is part of a broader effort to evaluate water-stressed drought tolerant corn hybrids in a system of innovative crop, soil, and irrigation practices designed to improve crop water productivity. Specifically, this proposal will evaluate the interaction of limited irrigation and plant nitrogen fertility status on crop water productivity for corn.

Limited irrigation is a management approach that targets application of a limited supply of irrigation water to key crop growth stages. While the potential benefits of limited irrigation have been documented (DeJonge et al., 2011; Saseenndran et al., 2008), less is known about how limited irrigation practices interact with the nitrogen fertility status of crop plants. Rates and timing of nitrogen fertilizer application need to be optimized for improved crop water productivity, but a better understanding of the interaction of limited irrigation and plant nitrogen status on crop water productivity is needed. In this study, a combination of field, greenhouse, and crop modelling efforts will be used to evaluate this interaction in maize.

Approach:
Field study. A field plot study of the interaction of limited irrigation and crop nitrogen status will be conducted on a 10 m x 30 m outdoor research plot at the Brigham Young University greenhouse. At this site, a 0.45 m deep, homogeneous topsoil layer was artificially created as a mixture of mineral and organic materials and spread over the native soil. The topsoil mixture has a clay loam texture 41.4% sand, 29.6% silt, and 29% clay, 1.5% organic matter, and a pH of 7.8. The experimental treatments will be combinations of full or limited irrigation and nitrogen fertility rate and timing. Treatments will be replicated three times in a randomized, complete block design. Irrigation will be applied with an automated drip irrigation system and controlled separately for full and limited irrigation.
Crop measurements will include crop phenological development and growth staging, crop height, leaf number and leaf area index (Kang et al., 1992), normalized differential vegetation index, crop canopy temperature, biomass accumulation measured by destructive sampling at maturity, and grain yield.

Greenhouse and Modelling Studies. The results of the initial field study will be used to develop follow-up studies in the greenhouse as well as modelling studies. The greenhouse studies will allow for closer evaluation of the physiological responses of maize to combinations of nitrogen status and water stress and will include measurement of evapotranspiration rates, leaf growth, and stomatal resistance. Results of the greenhouse and field studies will be used to parameterize and validate a cropping systems model, which will then be used to optimize the interaction of limited irrigation and crop nitrogen status for improving crop water productivity under corn production environments typical for the US Great Plains (model locations will include Akron and Fort Collins, Colorado). The crop model will be the Root Zone Water Quality Model (RZWQM2, Saseendran et al., 2008). The model allows extrapolation of the research results from the specific environmental conditions of the field and greenhouse research to other environments.

Citations:
Alghariani S.A. 2007. Reducing agricultural water demand in Libya through the improvement of water use efficiency and crop water productivity. In: N. Lamaddalena, C. Bogliotti, M. Todorovic, and A. Scardigno, editors, Water saving in Mediterranean agriculture and future research needs. Bari: CIHEAM, 2 007. p. 99-107.

Basch, G. A. Kassam, T. Friedrich, F.L. Santos, P.I. Gubiani, A. Calegari, J.M. Reichert, and D.R. dos Santos. 2012. Sustainable soil water systesms. In: R. Lal and B.A. Stewart, editors, Soil water and agronomic productivity. CRC Press, New York, NY, p. 229-288.
Colorado Water Conservation Board. 2004. Statewide Water Supply Initiative. Denver, CO. http://cwcb.state.co.us/IWMD/General.htm

DeJonge, K.C., Andales, A.A., Ascough II, J.C., and Hansen, N.C. 2011. Modeling of full and limited irrigation scenarios for corn in a semiarid environment. Transactions of the American Society of Agricultural and Biological Engineers 54(2):481-492.
Gleeson, T, Y. Wada, M.F.P. Bierkens, and L. P.H. van Beek. 2012. Water balance of global aquifers revealed by groundwater footprint. Nature 488:197-200.

Havlin, J.L., J.D. Beaton, S.L. Tisdale, and W.L. Nelson. 2005. Soil Fertility and Fertilizers, 7^th Ed. Pearson-Prentice Hall. New Jersey.

Kahlon, M.S., R. Lal, and P.S. Lubana. 2012. Sustaining groundwater use in South Asia. In: R. Lal and B.A. Stewart, editors, Soil water and agronomic productivity. CRC Press, New York, NY, p. 131-161.

Saseendran, S. A., L.R. Ahuja, D.C. Nielsen, T.J. Trout, and L. Ma. 2008. Use of crop simulation models to evaluate limited irrigation management options for corn in a semiarid environment. Water Resources Research 44:6181.

Vorosmarty, C. J., P. Green, J. Salisbury, and R.B. Lammers. 2000. Global water resources: vulnerability from climate change and population growth. Science 289:284–288.