Silk Development and Kernel Set in Maize As Related to Nitrogen Stress

Nitrogen deficiency limits yield in maize (Zea mays L.) through reduced kernel number. A day‐by‐day investigation of silk emergence and kernel establishment has not been conducted to determine when the reduction occurs. A field study was established near Adair, IL, in 2013 and Sciota, IL, during 2014 to investigate the effect of N deficiency on silk number per ear (SPE) and kernel number per ear (KPE). Three N treatments (0 [0N], 56 [56N], and 201 kg N ha−1 [201N]) and two DuPont Pioneer hybrids (P1395HR and P1498HR) were tested. The 0N treatment reduced specific leaf N by 33%, grain biomass by 35%, and KPE by 21% in 2013 and specific leaf N by 49%, grain biomass by 58%, and KPE by 50% in 2014, compared with 201N. Reduced N status had no effect on spikelet number in 2013 but reduced spikelet number by 7% in 2014. Nitrogen stress had no influence on the rate of silk emergence in 2013 but reduced silk emergence by 142 SPE d−1 in 2014. Compared with 0N, 201N increased the rate of KPE establishment by 67 KPE d−1 in 2014. Over 2 yr and three N rates, >76% of the silks emerged within 1.6 d and 97% of the kernels were established in 1.9 d. Kernel number was reduced under N deficiency by (i) kernel establishment from emerged silks, (ii) emerged silk number, and (iii) spikelet number. Alleviation of N stress by the R1 growth stage would effectively maintain optimum SPE, KPE, and yield potential.