Coordinating maize source and sink relationship to achieve yield potential of 22.5 Mg ha-1

Coordination between source and sink is vital for the final maize grain yield planted under high density. To clarify the source and sink characteristics of high yield potential (22.5 Mg ha -1 ), a four-year field experiment was conducted at Qitai Farm in Xinjiang, China. At silking, the maximum leaf area indexes were 5.8, 7.5, and 6.2 for cultivars of high yield level-1 (H1), high yield level-2 (H2), and high yield level-3 (H3) with yield increase of H1 < H2 < H3, which were 2.2, 4.6, and 3.9 at maturity, respectively. The H3 biomass was significantly higher than those of H1 and H2 during post-silking, and the H2 and H3 total kernel numbers were significantly higher than H1’s, although H2 had a significantly higher harvest ear number. While H3’s kernel size was not the largest of the three levels, H3 had a significantly higher thousand kernel weight. The grain filling analysis showed that H1 and H3 had shorter lag period durations (D1) than H2, and H3 had a longer maturation drying period duration (D3) than the other groups did. However, H1 and H3 had significantly higher grain filling rates than H2 in the lag period (D1), and H3’s was the lowest in the maturation drying period (D3). Also, H3’s maximum grain filling rate was significantly higher than H2’s, and H3 had significantly higher biomass/kernel number and kernel weight/leaf area ratios than H1 and H2 did. Based on our findings, three high yield levels were classified into three source-sink types: (1) H1: small source and weak productivity, small sink and short maturation drying period duration (D3); (2) H2: large source but weak productivity, large sink but slow grain filling start, and low maximum grain filling rate; (3) H3: small source but strong productivity, large sink, fast grain filling start, long maturation drying period duration (D3), and high maximum grain filling rate. We achieved an actual high yield of 22.4 Mg ha -1 for H3, which was also the highest yield in China. Therefore, hybrids with H3-type source and sink characteristics should be selected in the future for high-yield cultivation under dense planting. • Maize yield level of more than 22.5 Mg ha -1 has small source and strong biomass productivity under high density. • Large sink with more population kernel number and higher thousand kernel weight are vital for high yield maize. • Fast grain filling start, higher maximum grain filling rate and longer maturation drying period duration are essential.