Abstract
Timing of micronutrient demand and acquisition by maize (Zea mays L.) is nutrient specific and associated with key vegetative and reproductive growth stages. The objective of this study was to determine the fate of foliar-applied B, Fe, Mn, Zn, and Fe/Zn together, evaluate the effect of foliar micronutrients applied at multiple rates and growth stages on maize grain yield, and determine their apparent nutrient recovery efficiency (ANR). Five Randomized Complete Block Design (RCBD) experiments were conducted in 2014 and 2015 at five locations across Nebraska. Total dry matter was collected at 5–6 stages, and separated into leaves, stalk, and reproductive tissue as appropriate to determine micronutrient uptake, partitioning, and translocation. Foliar B, Mn, Zn, and Fe/Zn had no effect on grain yield for most application time by rate levels, though, at the foliar Mn site, there was a 19% yield increase due to a V18 application of 0.73 kg Mn ha−1 which corresponded with reduced Mn uptake in maize grown in control plots. At the foliar Zn site, there was 4.5% decrease in yield due to a split foliar application of 0.84 kg Zn ha−1 total, applied at V11 and V15 stage, which increased leaf Zn concentrations greater than the established toxic level. Only the Fe site had consistent grain yield response and was the only experiment that had visual signs of micronutrient deficiency. Regardless of application time from V6 to R2, there was a 13.5–14.6% increase in grain yield due to 0.22 kg Fe ha−1 foliar application. Most micronutrients had limited or no translocation, however, early season applications of B, prior to V10, had significant mobilization to reproductive tissues at or after VT. Foliar Mn, Zn, and B application had ANR LSmeans of 9.5, 16.9, and 2.5%, respectively, whereas the Fe/Zn mix had negative ANR LSmeans of −9.1% Fe and −1.3% Zn which indicate suppression. These data highlight the importance of confirming a micronutrient deficiency prior to foliar application, guide specific growth stages to target with specific micronutrients, track the fate of foliar-applied micronutrients, and describe the variable effect of foliar-applied micronutrients on grain yield.
Highlights
Best nutrient management practices require synchronous nutrient application with plant demand and nutrient uptake
The objective of this study was to determine the fate of micronutrients applied to the leaf surface, the recovery efficiency of the foliar-applied micronutrients, and evaluate the effect of foliar-applied micronutrients on maize grain yield when applied at key growth stages at high yielding locations
The maize vegetative stages for foliar application are explained by Abendroth et al (Figure S1) [25]
Summary
Best nutrient management practices require synchronous nutrient application with plant demand and nutrient uptake. Bender et al [1] highlighted the need to develop recommendations of timebound nutrient applications to sync up nutrient’s uptake and mobilization during periods of high plant uptake for modern maize hybrids. This is especially critical for micronutrient applications, as micronutrients are needed in relatively small but critical amounts by maize at specific growth stages during the growing season [3]. Fe uptake has two periods of critical accumulation: between V10 and V14, and after R4, whereas Mn uptake is more gradual with a majority of Mn uptake occurring from V10 to R4 [1] Each of these periods of high micronutrient uptake and demand should be targeted for micronutrient specific application
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