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The strength of the relationships of corn (Zea mays L.) yield, plant biomass, and leaf N concentration with early- to mid-growing season combined normalized difference vegetation index (NDVI) and plant height measurements has not been adequately documented. The objective of this study was to compare the strength among the relationships of corn yield, plant biomass, and leaf N with combined and respective NDVI and plant height measurements taken during the early to mid-season under major cropping systems. Two field N rate response studies in non-irrigated corn after soybean [Glycine max (L.) Merr.] (CS), non-irrigated corn after cotton [Gossypium hirsutum (L.)] (CCT), non-irrigated corn after corn (CC), and irrigated corn after soybean (ICS) were conducted at Jackson and Milan, TN, from 2008 through 2010. Regressions of corn yield, plant biomass, and leaf N concentration with NDVI x plant height and NDVI + plant height were slightly to markedly stronger in terms of R² values than those of corn yield, plant biomass, and leaf N with NDVI alone during 6-leaf growth stage (V6) to 12-leaf growth stage (V12) regardless of cropping system. No strength difference was observed between the regressions of corn yield, plant biomass, and leaf N with NDVI x plant height or NDVI + plant height and with plant height alone. Our results suggest that the benefits are variable in using combined NDVI and plant height measurements to assess corn growth and N nutrition and/or predict corn yield relative to the utilization of NDVI measurements alone during the early- to mid-season. [ABSTRACT FROM AUTHOR]

The relationship between corn (Zea mays L.) yield and plant height has been poorly documented in major corn production systems. This study was conducted to assess the relationship of corn yield with plant height under four major corn production systems at Milan, TN from 2008 through 2010. Six N treatments at rates of 0, 62, 123, 185, 247, and 308 kg N ha-1 with four replications were evaluated in a randomized complete block design in the following corn production systems: nonirrigated corn after corn, nonirrigated corn after soybean [Glycine max (L.) Merr.], nonirrigated corn after cotton [Gossypium hirsutum (L.)], and irrigated corn after soybean. The regression of corn yield with plant height was significant and positive at 6-leaf growth stage (V6), 10-leaf growth stage (Yb), and 12-leaf growth stage (V12), and mostly became stronger as plant growth progressed from V6 to Y10 and to V12 under an exponential model in the four corn production systems for all 3 yr. In general, corn yield was strongly related with plant height measurements made at Y10 and V12. Factors affecting the responses of plant height measured at V6, Y10, and V12 or/and yield to the N treatments may have contributed to the variations of determination coeffient (R2) values across years. In conclusion, corn yield may be predicted with plant height measurements collected during Y10 to V12. This prediction provides a physiological basis for the utilization of high resolution plant height measurements to guide variable-rate N applications within the field on corn at around V10 and to more accurately estimate yield for earlier grain marketing purposes. [ABSTRACT FROM AUTHOR]