The Effect Of Postponing The N-fertilizer Applying Time On Yield Formation, Growing And Development Characteristics Of Wheat

The effect of postponing the N～ertilizer applying time on yield formation , and growing and development characteristics of wheat was studied for ten years in succession, on the basis of different yield levels, variety types, densities and organic manure applying amounts. The results were as follows: 1. The postponement of N～ertilizer applying time had no effect on wheat growing and developing dates before heading, but the difference appeared after it. Compared with earlier N?fertilizer application, the date of earring and flowering for later N?fertilizer application was unchanged or one day earlier, but the mature date was put off for 1 2d, so the grain filling period of was increased corresponding. The grain filling rate was also higher than ck during one week period before mature, which lead to an increase of 1000ernel weight eventually. This may be attributed to the higher chlorophyll level in flag leaves and the second leaves, and also the higher leafarea coefficient in filling period. 2.At yield level of 400 kg/mu and under 20 kg/mu of N, a certain proportion of N was applied at reviving stage, elongatiop stage or late elongation stage, compared with applying all the N as base fertilizer, could contributed to raise wheat yield, because 2 of the three yield factors increased and the other one kept unchanged or a little decreased. When wheat yield level reached to some 500 kg/mu, the grain yield for applying N at elongation late elongation was higher than that at reviving. This showed that, with the improvement of soil fertility and yield level, the time of applying Nertilizer should be postponed, but better not later than booting stage . If high economic and beneficial result was considered, two times of top application separately in 42 e1ongation and booting were the best. However, in the condition of yie1d1eve1 under 400 kg/mu and fundamenta1 seed1ing 1ess than 0. 1 mi1l ion/mu,the date of app1ying N shou1d be moved up, in order to increase the ears/mu,and then improve grain yie1d.3. When a certain proportion of N--ferti1izer was used as 1atertop dressing, the amount of basic ferti1izer was cut down at the sametime, which cou1d he1p to decrease the high seed1ing popu1ation andinva1 id growth, so the contradiction of fo1 iage shading at e1ongationstage was a11eviated effect ive1y. App1yi ng fert i 1 izer and irri gat ion atthe right moment of midd1e and later growing stage cou1d improve thepercentage of ear bearing ti l lers, steady the ears/mu and increase thegrains/sPike and l000--kernel weight.4. Postponing the time of N top appl ication cou1d shorten tbe firstand second interned 1ength in basa1 portion, prove their so1 id degreeand increase the 1ength of ear interned. I t cou1d a1 so improve the uni formof plant height and ear layer.The resu1t above is applying to both mu1tiple-- and midd1e--sPikevarieties, but not to big --eaI' and b1g kerne1 var1eties.