| By the field experiment and simulated experiment of tube cultivation within three growth years, the temporal and spatial distribution of roots, dry matter accumulation and allocation, relation between roots and canopy of spring wheat mulched with plastic film in semi-arid area, middle of Gansu, and the reason of leaves turned yellow in advance, effect of nitrogen application on the leaves senescence are studied in this paper. The main results are as following:1. Film mulch is favorable to earlier growth and faster development, and increase dry matter weight of roots of spring wheat. Daily growth rate of roots of spring wheat mulched with plastic film was higher 1.34~1.24cm/plant.d than that of spring wheat no mulched with plastic film during pre-jointing period, which is the fast period of roots extension. Dry matter weight of roots of spring wheat with film mulched was higher than that of the contrast spring wheat from beginning to end. Furthermore, the peak period of daily growth of the former was earlier 15d than that of the later. Effect of nitrogenous application on roots growth of the former was quick-acting and short-term. Nitrogen application was favorable to increase of dry roots weight at any stage of spring wheat development. Supplement nitrogen application during the middle and posterior period of spring wheat can increase the whole roots length. Distribution of length and dry weight of roots along profile of soil could be expressed as multinomial y=a+bx+cx2+dx3.2. Effect of the film mulch on the amount of absorption nitrogen, special absorption rate of nitrogen (SARN) and special absorption rate of phosphorus (SARP) was significant. Compared with no mulched wheat, the film mulched wheat was higher 33.20%, 1 6.28% and 6.47% in amount of absorption nitrogen, average SARN and SARP, respectively. Supplement nitrogen application at different wheat development had a different effect on nitrogenous efficiency of spring wheat mulched with film. As supplement nitrogen application at tillering stage, nitrogen use efficiency and the physiological efficiency were the highest. As supplement at jointing stage, nitrogen use rate and agronomic efficiency were the highest. As supplement nitrogen application at booting stage, nitrogen efficiency was the lowest.3. Film mulch was favorable to regulating dry matter allocation between root and crown of spring wheat. The whole biomass of the root-crown of spring wheat mulched with film was obviously higher than that of the spring wheat no mulched with film. Early growth and quick development of the former roots at earlier stage improved the growth of shoot-leave aboveground, which caused the ratio of root to crown decrease 18.87%. An obvious increase of shoot-leave biomass at the middle and posterior stage improved the increase of roots underground, which caused ratio of root to crown increase 1.42~7.34%. Relatively developed roots guaranteed the equilibrium between absorption organ (root) and loss water organ (leave) of crop, coordinated dry matter allocation between root and crown, and improved allocation rate of photosynthetic production in propagation organ. Therefore, grain weight of per spike of spring wheat mulched with film was higher 27.61% than that of the contrast. Nitrogen application at earlier stage for the film-mulched wheat was favorable to improve the growth of shoot and leaves, and decrease the ratio of root to crown. At middle stage, nitrogen application for wheat mulched with film was favorable to roots becoming thick and the ratio of root to crown getting increase.4. Leaf area of the film mulched wheat at earlier stage grew faster, and photosynthetic accumulation was earlier at later stage, net assimilation rate was higher, the continued period of the fast growth was longer. Compared with wheat with no mulched, the largest leaf area of a single plant of film mulched wheat increase 17.16%, the peak value of the largest green leaf area appeared 6d earlier, dry matter accumulation rate was higher 8.97% before anthesis. Increase of...
|
PDF Full Text Request