Low-N stress tolerant maize hybrids have higher fertilizer N recovery efficiency and reduced N-dilution in the grain compared to susceptible hybrids under low N conditions

Developing high yielding maize (Zea mays L.) varieties that have relatively high grain protein content under low nitrogen stress is critical to ensure food and nutrition security in sub-Saharan Africa. This study evaluated the efficiency for fertilizer N recovery, grain yield and grain protein content of 10 maize hybrids selected for their contrasting yield performance under low-N stress conditions in the field. The hybrids were grown under 6 N rates (0-10-20-40-80 and 160 kg Ammonium Nitrate ha−1) at 2 sites that differ for residual soil nitrogen (N-NO3). Fertilizer N recovery, estimated using the difference method, decreased with increasing N rates or residual soil N and was significantly higher for the low-N tolerant (LNT) hybrids than low-N sensitive (LNS) hybrids, especially at low N rates. Although there was yield increase with increased N rate, the yield of tolerant hybrids responded more strongly than that of sensitive ones. Under low residual soil N, higher grain yield was associated with lower grain protein content in both low-N tolerant and susceptible hybrids but tolerant ones exhibited a significantly lower decrease in grain protein content compared to susceptible hybrids. In addition, LNT hybrids were able to maintain relatively higher grain protein content at high yield level under depleted soil N conditions as well as under high N level. We concluded that LNT hybrids could contribute to optimizing the use of small N fertilizer rates by resource-poor smallholder farmers to increase the nutritional value and profitability of producing maize.