Rules Of Nitrogen Absorption And Transportation Under Dry Farming Crop Of Northern Plain

Applying N at high rate year by year in dry farming crop production in China resulted in slightly grain yield increment after N fertilizer application, decreasing nitrogen use effciency and severe environment pollution, etc. Awing at those problems, spring corn as the object crop, field trials comprising of N fertilizer rates were carried in high-yield farmland, in Kangzhung corn field of Yanqing suburb, Beijing City. The ¹⁵N isotope technique was applied in the experiment. From soil-spring corn plant system of view, this experiment studied the rules of N absorption, accumulation, distribution transference, and also the recovery of fertilizer nitrogen by crops and yield by different nitrogen application amount (5 nitrogen rates from 0 to 360kg /hm² N).The following conclusions were drawn from the experimental and simulated studies:1. With the growth of spring corn, the N content in different organs of spring corn descented gradually, then reached the stage of maturity, its order was: kernel>leaf>spike>blade sheath>bract and axle>stalk. The N content in leaves, blade sheath, stalk, spike, bract and axle ranged 1%-4%, 0.6%-2%, 0.3%-3.5%, 0.7%-2.5% and 0.4%-3%.2. During the growing stages of spring corn, N absorption in leaves and blade sheath both showed two peaks: the former is small, the latter is big, and their peaks emerged in stalk growth stage and spike growing stage, respectively. N absorption in stalk was a curve of single-peak during growing stage, and its peak emerged in spike growing stage. N absorption in spike and bract and axle all descended gradually. During the maturing stage, the order of N absorption in different organs is: kernel> spike>blade sheath >bract and axle>stalk> leaf.3. Amount of N absorption in whole spring corn plant showed two peaks, respectively at the stages of bell-mouthed and disperse-pollen, and the second peak is bigger. Speed of N absorption showed a single peak curve in the whole growing stages, and the peak value is at the stage of disperse-pollen. The maximal absorption velocity almost being 0.0653-0.1424 g/plant·d, which provide the base on the theory of that "litter N fertilizer in bell-mouthed stage, but more N fertilizer in spike growing stage".4. N accumulation in leaves, blade sheath and stalk were all single peak curves, and their peak all emerged in disperse-pollen stage. N accumulation in spike and bract and axle both decreased. While the maturing stage, its order is: kernel> leaf >bract and axle >stalk >blade sheath > spike. Then N accumulation in whole spring corn plant accord with curve of S, and under different N fertilizer treatments, their showed: N2>N3>N1>N4>N0.