Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 26, 1999
Publication Date: N/A
Interpretive Summary: Scientists worldwide find out about objects and systems by observing their behavior under stress. For a growing corn crop, drought stress provides the same opportunity to discover crop characteristics. Drought stress for corn on a particularly variable field provides opportunity to observe the crop under many different levels of stress, because different soils provide different amounts of water to the crop. The SE drought in 1993 was severe; average yields were 1/3 the prior year's yields. Measurements of crop growth and yield documented the different responses of the corn to different levels of water stress. Plant height 56 days after planting ranged from 0.48 to 1.34 m (19-58 in). Tasselling and maturity were both spread over 3-week periods. Field mean yield was 2480 +/- 916 kg/ha (40 +/- 15 bu/ac) at 15.5% moisture. The two sites with the highest yield achieved it in dramatically different ways. Corn at one site grew tall quickly and had many small kernels per plant, where that at another site was delayed almost a month, resulting in fewer, but larger kernels. Explaining the reasons for these responses would materially assist managers raising corn using site-specific farming.
Technical Abstract: In the Middle Coastal Plain of South Carolina and surrounding states, up to 30% of the land is affected by Carolina Bays. Soils in these shallow depressions contrast markedly from the surroundings and dramatically impact growth and yield, particularly for corn [Zea mays] during drought. In 1993, severe drought in the Southeast dropped average corn yields to 34% of the 1992 yield. The objective is to document the spatial effects of soil variation on corn growth and yield in a severe test case. Corn yields were measured at 209 sites in an 8-ha field. Site-specific effects of soil variation on crop phenology, biomass, and yield components were measured at 11 primary sites that ranged from severe leaf rolling to no visually apparent stress. Plant height on day of year 155 (56 days after planting) ranged from 0.48 to 1.34 m. Mid-silk leaf area index ranged from 1.15 to 2.56. Tasselling and black layer formation occurred over 3 weeks. Grain yield ranged from 104 to 318 g/sqm dry weight at the 11 primary sites, and from 18 to 420 g/sqm in the entire field. Field mean yield was 215 +/- 79 g/sqm dry weight (2481 +/- 916 kg/ha at 15.5% moisture). Variation in yield components was large and in some cases compensatory, with similar final yields obtained in distinctly different ways. Quantitatively accounting for interactions between soil variation and crop response would significantly improve the knowledge base needed for site-specific management of corn.