Comparison Of Root Temporal And Spatial Distribution And NPK Uptake Characteristics Of Maize Varieties Released In Different Years

In order to examine the root temporal and spatial distribution with soil NPK changes, the differences of growth characteristics and NPK accumulation and distribution of maize varieties released in different years in China, field experiment was conducted under the same plant density and fertilization and six maize cultivars released from the 50s in last century until now were employed, e.g. Baimaya, Jinhuanghou, Zhongdan 2, Tangkang 5, Nongda108 and Zhengdan 958.The result showed that newer maize varieties had slower developmental process, longer growth duration, larger total leaf area and slower leaf senescence, compared with those of the older varieties. At V10 stage, there were no differences in plant dry weights and NP contents among different maize varieties. After this stage, however, newer varieties grew quicker and their dry weights and NP contents increased faster than those of the older varieties. The grain dry weights of all varieties were about the same as the dry matter gains of whole plants after silking, indicating that dry matter accumulated in grains was directly from the leaf photosynthesis after silking. At V10 stage, there were no significant differences in plant dry weights and NP contents among the maize varieties released in different years, but K contents had showed differences at this stage, which was higher in the newer varieties than those in the older varieties. Most of K in plants of all maize varieties was taken up before silking. NPK deposited in grains of different maize varieties were gained mainly from the retranslocation from the vegetative organs, especially from leaves.Most of maize roots distribute in the topsoil (0-30cm) and declined substantially with soil depth. Newer released maize varieties, such as Tangkang 5, Nongda 108 and Zhengdan 958, had the greater root length density (RLD) compared to the older varieties. There was a negative relationship between soil N distribution and root growth, and soil N had been significantly depleted where root growth was concentrated, especially in the location closed to the underground stem. With big different from N, although newer maize varieties significantly accumulated more P, soil Olsen-P had not been significantly depleted, even increased at maturity than silking. Different maize varieties and root distribution had no significant influence on soil NH4OAc-K changes. In summary, newer maize varieties had longer growth period, larger leaf area, slower leaf senescence and more NPK accumulation, which was beneficial for grain milking and higher grain yield formation. Newer maize varieties had better root distribution and absorbed more soil NPK. Different with dry weight and NP accumulation, most of K in plants of all maize varieties was taken up before silking, the dry matter, NP and K accumulation in maize plants was not synchronized. Grain dry matter was gained mainly from the photosynthesis after silking, while grain NPK was gained from the retranslocation from the vegetative organs, regardless of the difference in varieties.