Can Late‐Split Nitrogen Application Increase Ear Nitrogen Accumulation Rate During the Critical Period in Maize?

Abstract

Ear and plant growth rates during the critical period (CP) in maize (Zea mays L.) are known to affect grain yield, but little is known about how CP ear N accumulation and vegetative N dynamics respond to N fertilizer timing. In a 2‐yr study, the influences of in‐season split N applications on ear N accumulation rate (ENAR), ear growth rate (EGR), and stem and leaf dry matter and N accumulation were determined from 14 d before to 14 d after silking (R1). Up to eight N rate and timing treatments (0, 110, 155, 200, and 245 kg N ha−1, either applied in a single application or with the last 45 kg ha−1 delayed until V12) were imposed on four hybrids: two modern (P1498HR and P1360HR) and two released 20 yr ago (3335 and 3394). Both EGR and ENAR during the CP were very stable among N treatments and were only uniquely influenced by the zero N after R1. Both leaf N and ear N contents during the CP were highly conserved and were not affected by the timing of N application. Late‐split N application resulted in less stem N remobilization in the 14 d after R1 than a single N application at moderate and high N rates. Despite sporadic hybrid group differences in EGR as the CP period progressed, the lower yielding older hybrids realized consistently lower presilking ENAR and higher postsilking ENAR. These data suggest that late‐split N applications near the CP onset benefits stem N content, which may enhance N source capacity for developing ears but does not increase either ear or leaf N content during the CP.

Differential Regulation of Kernel Set and Potential Kernel Weight by Nitrogen Supply and Carbohydrate Availability in Maize Genotypes Contrasting in Nitrogen Use Efficiency

“…Previous research has generally found that late N application near the critical stage had neither negative nor positive impacts on yield when compared with early season application (Mueller et al, 2017;Mueller and Vyn, 2018b). Interestingly, comparison of modern and 20-year-old genotypes did not show any differences between these two groups in terms of their efficiency at using late applied N fertilizer or with respect to other physiological differences, such as N allocation or DM distribution, among the different organs during the critical period of kernel set establishment (Mueller and Vyn, 2018a). Thus, the differences found here between our two genotypes might be specifically related to the focus of the breeding program, which aimed at breeding genotypes capable of high yield under low N supply conditions.…”

Traits and trade-offs: dissecting nitrogen use efficiency in maize using plant modeling

“…In maize, N for grain filling does not only come from new N assimilation during reproductive growth (∼50%) but also incorporates N remobilization from N assimilated in vegetative organs before silking (∼50%) (Mueller & Vyn, 2016;Hirel et al, 2007;Ning et al, 2017). Leaves are the major photosynthetic organs and maintaining photosynthesis requires N. Rather than leaves, the stem is the most important temporary sink for N accumulation before grain filling and also an important source when remobilizing N during pollination, fertilization, and kernel set (Yang et al, 2017;Mueller & Vyn, 2018). Maize leaves and stems contribute approximately 45% each to the total nitrogen remobilization towards the ear, while remobilization from roots contributes only 10% (Ta & Weiland, 1992).…”