Limits to maize productivity in Western Corn-Belt: A simulation analysis
for fully irrigated and rainfed conditions
Patricio Grassini, Haishun Yang, Kenneth G. Cassman
*
Department of Agronomy and Horticulture, University of Nebraska-Lincoln, P.O. Box 830915, Lincoln, NE 68583-0915, USA
1. Introduction
Yield potential is defined as the yield of a crop cultivar when
grown in an environment to which it is adapted, with nutrient and
water non-limiting and pests and diseases effectively controlled
(Evans, 1993). Hence, yield potential for a given genotype is
determined by the particular combination of solar radiation,
temperature and plant population at a specific location (van
Ittersum and Rabbinge, 1997). Yield potential can be diminished as
a consequence of insufficient water supply to meet crop water
demand. Thus, water-limited yield is determined by the genotype,
solar radiation, temperature, plant population and the degree of
water limitation (Loomis and Connor, 1992). Insufficient water
supply can result from sub-optimal seasonal water supply (stored
soil water plus growing-season rainfall) in rainfed systems or sub-
optimal irrigation in irrigated systems. Accurate quantification of
yield potential and water-limited limited yield is essential to
estimate the magnitude of the exploitable gap between actual (i.e.,
those achieved by farmers) and attainable yields, to predict global
change scenarios, and to help formulate policies to ensure local and
global food security (Cassman et al., 2003). The lack of data from
experiments in which yield-limiting factors have been effectively
Agricultural and Forest Meteorology 149 (2009) 1254–1265
ARTICLE INFO
Article history:
Received 7 November 2008
Received in revised form 11 February 2009
Accepted 16 February 2009
Keywords:
Maize
Zea mays L.
Yield potential
Water-limited yield
Simulation model
Rainfall shortage
Water productivity
Water-use efficiency
ABSTRACT
Unlike the Central and Eastern U.S. Corn-Belt where maize is grown almost entirely under rainfed
conditions, maize in the Western Corn-Belt is produced under both irrigated (3.2 million ha) and rainfed
(4.1 million ha) conditions. Simulation modeling, regression, and boundary-function analysis were used
to assess constraints to maize productivity in the Western Corn-Belt. Aboveground biomass, grain yield,
and water balance were simulated for fully irrigated and rainfed crops, using 20-year weather records
from 18 locations in combination with actual soil, planting date, plant population, and hybrid-maturity
data. Mean values of meteorological variables were estimated for three growth periods (pre- and post-
silking, and the entire growing season) and used to identify major geospatial gradients. Linear and
stepwise multiple regressions were performed to evaluate variation of potential productivity in relation
to meteorological factors. Boundary functions for water productivity and water-use efficiency were
derived and compared against observed data reported in the literature. Geospatial gradients of seasonal
radiation, temperature, rainfall, and evaporative demand along the Western Corn-Belt were identified.
Yield potential with irrigation did not exhibit any geospatial pattern, depending instead on the specific
radiation/temperature regime at each location and its interaction with crop phenology. A linear and
parabolic response to post-silking cumulative solar radiation and mean temperature, respectively,
explained variations on yield potential. Water-limited productivity followed the longitudinal gradient in
seasonal rainfall and evaporative demand. Rainfed crops grown in the Western Corn-Belt are frequently
subjected to episodes of transient and unavoidable water stress, especially around and after silking. Soil
water at sowing ameliorates, but does not eliminate water stress episodes. Boundary functions for water
productivity had slopes of 46 and 28 kg ha
À1
mm
À1
, for aboveground biomass and grain yield,
respectively. At high seasonal water supply, productivity was weakly correlated with water supply
because many crops did not fully utilize seasonally available water due to percolation below the root
zone or water left in the ground at physiological maturity. Fitted boundary functions for water-use
efficiency had slopes (%seasonal transpiration-efficiency) of 54 and 37 kg ha
À1
mm
À1
for aboveground
biomass and grain yield, respectively, and an x-intercept around 25–75 mm (%seasonal soil
evaporation). Data collected from experiments conducted in low-rainfall environments indicated that
the boundary functions for water-use efficiency, derived from this study, are broadly applicable.
ß 2009 Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: +1 402 472 5554; fax: +1 402 472 7904.
E-mail address: kcassman1@unl.edu (K.G. Cassman).
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journal homepage: www.elsevier.com/locate/agrformet
0168-1923/$ – see front matter ß 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.agrformet.2009.02.012