Effect Of Water And Fertilizer On Relationship Between Competitive Ability And Yield Of Modern And Old Spring Wheat Varieties

The pot experiment and the field experiment were conducted to study the effect of competition on the two spring wheat cultivars ("old" landrace Heshangtou; "modern" cultivar Dingxi-24) and the relationship between relative competitive ability in mixture and grain yield in monoculture along four levels of soil water and fertilizer application at the experiment station of Yuzhong in Lanzhou University, Gansu Province, China. In pot experiment, four soil water and fertilizer application (severe soil water deficit, no fertilizer application; moderate soil water deficit and intermediate fertilizer application; sufficient soil water and fertilizer application) were imposed to investigate the effect of competition on the two spring wheat cultivars. In field experiment, the competitive ability of two spring wheat cultivars were determined by imposing three-level soil water and fertilizer application.The results of pot experiment were:1. The results showed that the landrace Heshangtou had more competitive advantage than the modern variety of Dingxi-24 under a series of soil water and fertilizer conditions. Although the inhibitory effect of the landrace Heshangtou on the modern variety of Ding-24 was weaker along soil water and fertilizer gradients, the modern variety Dingxi-24 had been eventually replaced by old variety Heshangtou.2. At severe soil water deficit, no fertilizer application and sufficient soil water and fertilizer application levels, the modern variety Dingxi-24(29.53 and 59.04g.pof-1) had higher grain yield in monoculture than the old landrace Heshangtou(19.35 and 49.93 g.pot-1) (P<0.05). Under severe soil water deficit and low fertilizer application, the grain production of the old variety Heshangtou (31.27 g.pot-1) almost equaled the grain production of the modern cultivar Dingxi-24 (31.15 g.pot-1). Under moderate soil water deficit and fertilizer application, the old landrace Heshangtou (51.58g.pot-1) had a higher grain yield in monoculture than the modern variety Dingxi-24(43.08 g.pot-1), but the productive performance between them did not show statistically significant differences (P>0.05), this suggested that the old cultivar Heshangtou which had poor productive performance under severe soil water deficit and fertilization conditions did not have low seed yield at the moderate soil water deficit and fertilizer levels.3. A negative relationship between the relative plant competitive ability and seed yield of spring wheat varieties was found at severe water, no fertilizer application and sufficient soil water and fertilizer application levels, i.e. the varieties with higher competitive ability had lower seed yield. A neutral relationship between the relative competitive ability and seed yield of spring wheat varieties occurred under severe soil water deficit and low fertilization conditions. Under moderate soil water deficit and intermediate fertilizer application, a positive relationship between the relative competitive ability and seed yield of wheat varieties was found, i.e. the variety with higher competitive ability had higher seed yield. Our results indicated that a particular relationship did not exist between competitive ability and seed yield, in other words, plant competitive ability of wheat varieties was not definitely relative to seed yield.4. At severe soil water deficit, no fertilizer application and sufficient soil water and fertilizer application levels, the modern variety Dingxi-24(76.79和195.86 g.pot-1) had higher grain yield in monoculture than the old landrace Heshangtou(45.71和156.42 g.pot-1) (P＜0.05). At severe soil water deficit, no fertilizer application level, the modern variety Dingxi-24 (0.38) had higher harvest index in monoculture than the old landrace Heshangtou(0.42)(P＜0.05). With the change of soil water and fertilizer application, both of the harvest index of the old cultivar Heshangtou and the modern variety have been increased.5. When the soil water deficit is severe, the soil water utilization efficiency of the old cultivar Heshangtou (1.00g.L-1) was significantly lower than that of the modern cultivar Dingxi-24 (1.00g.L-1) (P<0.05). With the change of soil water supply, the soil water utilization efficiency of the old cultivar Heshangtou has been significantly increased. However, the water utilization efficiency decreased when soil water was sufficient and no longer a limiting factor for the growth and reproduction the of old cultivar Heshangtou. Therefore, the effect of soil water supply on the utilization efficiency of the old variety Heshangtou is stronger than that of the modern variety Dingxi-24. Therefore, our experiment results suggested that improving the soil water utilization efficiency to a certain extent benefited spring wheat to adapt to the limited soil water environment.The results of pot experiment shown as below,1. At rained treatment, moderate soil water deficit, no fertilizer application and sufficient soil water and fertilizer application levels, the modern variety Dingxi-24 had higher grain yield in monoculture than the old landrace Heshangtou. At the three-level soil water and fertilizer application, the modern variety Dingxi-24 had lower grain yield in the same density than the old landrace Heshangtou.2. At moderate soil water deficit, no fertilizer application, when the seeding ratio of the old landrace Heshantou to the modern variety Dingxi-24 is 1:3, the input ratio and output ratio of the old cultivar, Heshangtou vs. Modern cultivar, Dingxi-24 is at the top of the equilibrium line. when the seeding ratio of the old landrace Heshantou to the modern variety Dingxi-24 is 3:1 and 1:1, the input ratio and output ratio of the old cultivar, Heshangtou vs. Modern cultivar, Dingxi-24 is at the top of the equilibrium line.3. At rained treatment, and sufficient soil water and fertilizer application levels, a negative relationship between the relative plant competitive ability and seed yield of spring wheat varieties was found. i.e. the varieties with higher competitive ability had lower seed yield. At moderate soil water deficit, no fertilizer application, the competitive ability of the old landrace Heshantou to the modern variety Dingxi-24 can not be determined, a negative, positive or neutral relationship between the relative plant competitive ability and seed yield of spring wheat varieties was found.