Effects of integrated agronomic practices management on root growth and development of summer maize

Root growth and development of summer maize (Zea mays L.) is an important process in determining grain yield. In comparison to the information on above ground plant responses only limited knowledge exists on the response of root growth and development to integrated agronomic practices management (defined as a comprehensive management framework consisted of tillage method, plant density, seeding and harvest date, and fertilizer application) under field conditions. Two experiments, integrated agronomic practices management (IAPM) and nitrogen rate testing (NAT) were used to determine the effects on summer maize root system in the course of five years in North China. IAPM consisted of four treatments (CK: local conventional cultivation practices, Opt-1: an optimized combination of cropping system and fertilizer treatment, HY: treatment based on high-yield studies, and Opt-2: a further optimized combination of cropping system and fertilizer treatment). NAT had four treatments of nitrogen rate (0, 129.0, 184.5, and 300.0 kg N ha−1).Individual/population root dry weight, individual/population absorption area, surface, volume, and length density of root and grain yield were measured. Roots were sampled per plot at six-leaf stage (V6), tasseling stage (VT), milk stage (R3) and physiological maturity stage (R6). The results from IAPM revealed that Opt-2 significantly increased dry weight, volume, superficial area, and length density of root across the 0-30 cm soil layer of whole growth period. Root active absorption area of Opt-2 exhibited a significant increase in the 0-30 cm soil layer of whole growth period except V6. In compare with root/shoot ratio of CK, this of Opt-2 increased by 14.5% at VT and 16.3% at R6. Results from NAT revealed that N with a range from 0 to 184.5 kg N ha−1 played a positive role in root growth and development. Dry weight, absorbing area of root, and the root/shoot ratio increased as N rate rise within certain limits and then decreased significantly. Dry weight, the proportion of deeply distributed, absorption area, length density of root, and root/shoot ratio increased due to appropriate population, reasonable fertilizer management, and suitable harvest date, which provided sufficient nutrients and moisture to aboveground parts for growth, development, and high grain yield of summer maize.