N Deprivation in Maize During Grain‐Filling. I. Accumulation of Dry Matter, Nitrate‐N, and Sulfate‐S¹

Abstract

Maize (Zea mays L.) has a noted propensity for accumulating large amounts of nitrate‐N (NO3‐N). However, the availability of such NO3‐N for assimilation during periods of restricted N supply has not been assessed. In addition, the availability of sulfate‐S (SO4‐S) affects the accumulation and assimilation of NO3‐N. Little is known about the effect of NO3‐N supply on SO4‐S accumulation. Such information is vital to efforts to improve the efficiency of nutrient utilization by crops. The objective of this greenhouse experiment was to determine the effect of N deprivation during grain‐filling on the accumulation of dry matter, NO3‐N, and SO4‐S. Maize plants were grown hydroponically in a modified Hoagland's solution. At silking the nutrient solution was replaced with fresh solution, with or without NO3‐N. Plants were harvested and separated into seven fractions at silking and 1, 2, 3, 5, and 7 weeks after silking. Plants that were supplied NO3‐N during grain‐filling contained almost twice (1.8×) as much N at physiological maturity (7 weeks after silking) as did N‐deprived plants. Ear dry weight was not affected by N deprivation. The concentration of NO3‐N in all fractions declined during grain‐filling; however, N deprivation enhanced this decline in the roots, lower stem, and upper stem. Lack of N did not affect NO3‐N concentration in the lower leaves, upper leaves, or ear. The concentration of SO4‐S in the roots nearly doubled between silking and physiological maturity when plants were deprived of NO3‐N, but did not change when N was supplied. The concentration of SO4‐S in all other parts was not markedly affected by N deprivation. Apparently, maize plants can compensate for a restricted N supply during grain‐filling by utilizing NO3‐N stored in the roots and stem.

A simplified test of cornstalk nitrate for better N management

“…3). These findings are consistent with the reports of Friedrich et al (1979) and Wilhelm et al (2005), who found that nitrate concentrations tended to decrease with increasing height in corn plants and is consistent with the knowledge that nutrient translocation after physiological maturity goes from top to bottom within each individual plant. The slopes of the linear regressions shown in Figure 3 indicate that the relative concentrations of nitrate in the upper third of the normal samples tended to be about 55% of those found in the lower third.…”

Corn Responses to Post‐tasseling Nitrogen Deprivation and to Various Ammonium/Nitrate Ratios

“…C ORN takes up 60 to 75% of its total N after the onset of the reproductive stage, tasseling (Friedrich et al, 1979;Mills and McElhannon, 1982). Therefore, the availability of N from tasseling through maturity can affect the plant's vegetative growth and ear development.…”

Invloed van nitraat:ammoniumverhoudings op die ontwikkeling van Zea mays L.

“…Volgens Warnke & Barber (1973) is die optimum verhouding 1: 1. Hierdie navorsers het die droemassas egter op vroee groeistadiums gemeet en volgens Schrader (1978) en Friedrick, Schrader & Nordheim (1979) is maksimum nitraatopname eers 63 dae na plant. Die bepaling van die optimum nitraat:ammoniumverhouding moet daarom tot volwassenheid gedoen word.…”