Effects of planting density on test weight and related indexes of maize

Maize (Zea mays L.) is an important food crop in the world. Reasonably increasing planting density is an important way to increase maize yield. Test weight (TW) determines the classification and affects market price. In order to clarify the influence and mechanism of planting density on TW, in this study, a 2-year field experiment was carried out in Tongliao, Inner Mongolia Autonomous Region in 2019 and 2020. Four widely planted maize hybrids and six planting densities (6.0, 7.5, 9.0, 10.5, 12.0, and 13.5 x 104 plants ha-1) were tested, using drip irrigation water and fertilizer integration. The output parameters measured were grain yield, TW, thousand-kernel weight (TKW), kernel volume, kernel density (KD), kernels per unit volume (KPV), and kernel packing efficiency. The result showed that yields ranged from 12.04 to 16.58 ton ha-1and TW ranged from 751 to 807 kg m-3, which exceeded the requirements for classification as first-grade maize (720 kg m-3). Both yield and TW have a quadratic curve relationship with planting density, but the planting density corresponding to the two indicators is different when they reach the maximum value. With the increase in planting density, the TKW decreased and KPV increased, which made the relationship between TW(y) and planting density (x) and expressed as y = ax2 + bx + c. Planting density had a significant influence on TW and the relationship between TW and planting density was consistent under growth years and maize varieties. Considering the economic benefits, the planting density corresponding to the maximum yield is strongly recommended for future maize production. Both yield and test weight of maize have a quadratic curve relationship with planting density.Decreased thousand-kernel weight (TKW) and increased kernels per unit volume (KPV) cause test weight (TW) to vary with increasing planting density.Growing maize at the planting density corresponding to the highest yield can achieve the greatest benefits.