Water Budget Approach to Quantify Corn Grain Yields Under Variable Rooting Depths

1991). These properties include soil bulk density and chemical properties. This study investigated the relationships between corn (Zea mays An objective of site specific management is to apply L.) grain yield and weather over a range of soil rooting depths with appropriate levels of agricultural inputs to localized areas. and without irrigation. The purpose was to test if variability of corn Since areas with deeper soils that facilitate extensive grain yield over a range of soil rooting depths could be reduced if water is supplied via irrigation. An additional goal was to test a simple root growth tend to be more productive, it would be water balance simulation model which calculates a seasonal moisture useful to have a tool to estimate or quantify the potential stress index based on relative evapotranspiration deficits. Such a water productivity due to water availability related to soil budget model could be used to estimate variations in corn grain yields depth. An estimate of the spatial distribution of potenas a function of spatial differences in soil depth and available water tial soil productivity can be obtained from knowledge holding capacity in site specific agriculture. Corn grain yields were of the spatial variability of soil depth. The relationship measured over a 3-yr period from 70 plots at the Cornell University between soil properties and fertilizer requirements Robert Musgrave Research Farm at Aurora, NY, USA. Soil depths should be considered for site specific management ranged from 0.2 to 1 m. During one year of the study, paired irrigated (Cahn et al., 1994). Fertilizer or seed applications could and non irrigated plots were placed at locations that had varying soil therefore be tailored for the potential response of the rooting depths. Irrigation resulted in significant increases in grain crop as a function of soil depth and water availability yield with the greatest response occurring on the soils with less than (Mathews et al., 1997; Barnhisel et al., 1996). 0.5 m of rooting depth. Yields under irrigation were similar at all soil depths suggesting that, as soil depth decreased on these soils, water was Crop simulation models have become a useful tool the major limiting factor. The water budget model gave satisfactory to characterize and quantify yield and available water. estimates of grain yields as a function of soil depth and available Paz et al. (1998), using a soybean model, showed that water capacity and appears to be a useful tool to estimate corn grain yield variability correlated with variability of simulated yield as a function of soil depth and available water. The estimated water stress. Rooting depth and soil water holding capotential yields can be used as a guide for site specific soil management pacity were important variables. Soil depth was an imgiven variations in available water holding capacity that affect potenportant parameter in a productivity index model used tial soil productivity. by Khakural et al. (1996) to estimate the spatial variability of crop yields. Moore and Tyndale-Brisco (1999) using crop models showed that much of the variability M of the variability of crop response is related of wheat response to nitrogen could be explained by to soil properties that affect water availability differing soil water holding capacities. Mathews and (Boyer et al., 1990). Effective soil rooting depth is one Crosser (1997) used CERES-wheat to study variable such property. Frye et al. (1983) reported higher correlarate nitrogen application. They reported that the optitions between corn grain yields and soil depths during mal nitrogen distribution was to apply more fertilizer years of low rainfall than years with greater rainfall to deeper soils and less to shallow soils. where plant rooting depth was limited by a fragipan. Many of the models currently applied in precision Swan et al. (1987) observed that corn grain yield–soil agriculture have complex input requirements and may depth relationships were significantly influenced by clibe more detailed than necessary for certain applications. mate; during dry years the relationships were more proThey also require some form of calibration. Timlin et nounced. Gantzer and McCarty (1987) reported that al. (1986) described a simple water budget model that topsoil depth (assumed to be A horizon material) was calculated corn grain yields in shallow soils. The model highly correlated to corn yield and the regressions were was based on the assumption that a major portion of stronger in a dry year which indicated a contribution of the yield variability in an otherwise uniformly managed water holding capacity. Changes in soil properties other field, is due to variability in soil available water. This than water holding capacity, however, also influence in turn would be a function of depth to some root reyields as topsoil depth decreases (Thompson et al., stricting layer, pore size distribution, and weather. The model only requires knowledge of soil water holding capacity, rooting depth, crop growth stages, and weather Dennis Timlin, USDA-ARS, Alternate Crops and Systems Lab., Bldg. data. 007, Rm. 116, BARC-West, 10300 Baltimore Ave., Beltsville, MD, The purpose of this study was to gain further under20705, and Yakov A. Pachepsky, USDA-ARS Hydrology and Remote standing of yield and available water relationships under Sensing Lab., Bldg. 007, Rm. 106, BARC-W, 10300 Baltimore Ave., varying seasonal weather conditions and soil rooting Beltsville, MD 20705, Victor A. Snyder, College of Agricultural Sciences, P.O. Box 21360, Rio Piedras, PR 00928; and Ray B. Bryant, depths. The objectives were (i) to determine if the effect Dept. of Soil, Crop, and Atmospheric Sciences, Bradfield Hall, Cornell of soil depth on yield is mainly due to reduced water Univ., Ithaca, NY 14853. Received 17 Aug. 1999. *Corresponding auavailability and (ii) to evaluate the use a simple water thor ([email protected]). budget to describe corn grain yield variability due to variation in soil depth. Published in Soil Sci. Soc. Am. J. 65:1219–1226 (2001).