Differences in Winter Wheat Productivity and Nitrogen Use Efficiency between the Main Varieties Released in Different Times in Jianghuai Area
|School||Nanjing Agricultural College|
|Keywords||Jianghuai area Winter wheat Productivity N fertilizer efficiency Change characteristic|
To learn the changing trends of crop productivity and N use efficiency among cultivars approved in different times can not only provide scientific proof for comprehensive evaluation on the integral effects of crop productivity but also give important references to cultivar improvement with high yield and high resource use efficiency and cultivation technique development. Therefore, we conducted an experiment (Yanling town, Danyang city, Jiangsu province,2007-2009) to study the actual change characteristics of productivity and N use efficiency of winter wheat in Jianghuai area. Our experiment set up three N application levels and three plant densities with winter wheat cultivars approved from 1950s to the present in this area. The main results were as follows:(1) Under medium N (medium density) level and high N (medium density) level, the yield showed significant rising trend along with cultivar improvement. The average yield of medium N and high N (medium density and high density) of 1960s was lower than which of 1970s,1980s-1990s, and 2000s by 6.59%,8.06%, and 12.47% respectively. In all treatments, the ear length and 1000-grain weight increased obviously with years but the spike number showed decreasing trends. Under different fertilizer levels and plant densities, grain number per spike and spikelet number showed different change trends. Under different N fertilizer treatment, the responses of yield and yield traits of wheat cultivars in 4 times were not influenced by densities. Under different densities treatments, the responses of yield traits of wheat cultivars in 4 times were not influenced by N fertilizer levels but the yield responded differently to densities under different N levels. The N levels and cultivars, cultivars were the key factors to determine yield and 1000-grain weight. The plant densities had certain impacts on spike number, grain number per spike,1000-grain weight and spikelet number. The interactive effects of factors (N×density, N×cultivar, density×cultivar,N×density×cultivar) had little effects on yield and yield traits.(2) The aboveground biomass of winter wheat under three different densities of medium N level decreased significantly along with years. The aboveground biomass of 1960s was higher than which of 1970s,1980s-1990s, and 2000s by 10.84%,25.59%. and 17.23% respectively. The dry matter accumulation, harvest index, dry matter transportation and contribution rates of post-anthesis winter wheat increased significantly with years under different N levels and plant densities. Under different N levels, the responses of biomass and biomass productive rate of cultivars in 4 times were unaffected by densities. However, under different densities, the responses of biomass, biomass transportation and contribution rates of cultivars in 4 times were different with different N levels. The N levels and cultivars, cultivars were the key factors to determine aboveground biomass and harvest index of winter wheat and its interaction with densities influenced dry matter productivity.(3) Along with years, the change characteristics of plant N accumulation and grain N accumulation were almost similar but responded differently under different N levels and plant densities. Along with years, no matter in what N levels or plant densities, the post-anthesis N accumulation increased obviously, N contribution rate decreased as a whole and N transportation rate was insignificant among the 4 times. The N use efficiency and agronomic efficiency were increased significantly with years under medium N (low density and medium density) and high N (low density). Under different N treatments, the N accumulations in aboveground biomass and grain were increased with N increment. But the N harvest index, N use efficiency and N agronomic efficiency decreased significantly. The post-anthesis N accumulation rate, transportation rate and contribution rate were different under different densities. Under different densities, the responses of N transportation rate and N harvest index were insensitive and the responses of N accumulation, N accumulation rate and N contribution rate were different under different N levels. N fertilizer was an important factor that had impact on N accumulation amount, N accumulation rate, N contribution rate and N use efficiency, which contributed above 30% of all the indices.