| Through the simulated experiment of tube cultivation, this paper studies the effect of fertilizer application depth on root growth, the relations between root and crown,and leaf senescence in spring wheat mulched with plastic film. The major research findings are as follows:(1) Deepening the depth of applying fertilezer of nitrogen and phosphorus results in the changes and differences in root length of different stratification, dry weight root, total root length and total dry weight root of spring wheat mulched with plastic film ?during growing stage. Seen from the changes in root length, dry weight root,in different soil layders in their growing stage, applying fertilizer partly makes the number of roots increase the soil layer where fertilizer is applied. With the relatively deepening of the depth of nitrogen and phosphorus application, the root length and dry weight of the middle and lower stratification exceed that of fertilizer application on surface, and the total root length and dry weight root increases obviously. During anthesis and mature stage, in the soil layer under 70cm, the root lergth of nitrogen application between 20~40cm is 56.95-34.94%, longer than that between 0~20cm, the weight of dry root is 28.32-42.61%, higher, the total root length is 16.1-16.70%; the root length of nitrogen application between 40cm~60cm is 35-52.18% longer than that between 0~20cm. The weight of dry root is 32.29-57.58% heavier, the total root length is 14.96-12.39% longer, the total weight of dry root is 8.88-16.96% heavier, the root length of phosphorus application between 20~40cm is 23.30-15.01% longer than that between 0~20cm; the weight of dry root is 83.32-28.04% heavier; the total root length is 6.18-9.45% longer; the total weight of dry root is 11.53-14.15% heavier; The root length of phosphorus application between 40~60cm is 34.26-21.03% longer that between 0~20cm; the weight of dry root is 56.44-37.8% heavier; the total root length is 7.75-9.29% longer. At the same depth of nitrogen and phosphorus application, the root length and weight of dry root in different soil layer under 70cm which is applied phosphorus are longer and heavier than that is applied nitrogen. So do the total root length and the total weight of dry root.(2)With the relatively deepening of the depth of nitrogen and phosphorus application, their application in deep stratification changes the distribution of root in soil, and makes root grow deeper. So it is good for root to absorb moisture and nutrient from deep soil. And the distribution of root in middle and lower stratification applied phosphorus is wider than that applied nitrogen. Seen from the percentage of the root length in its total root length, during anthesis, root high stratification between 0'40cm, from Ocm to 20m, nitrogen application (50.96%) is more than that (45.84%) from 20~40cm which is more than that (39.58%) from 40cm to 60cm, phosphorus application (45.28%) is more than that (39.57%) from 20cm to 40cm which is more than that (31.34%) from 40cm to 60cm, root of lower stratification between 70-100cm, nitrogen application (21.23%) from 40cm to 60cm is more than that (20.28%) from 20cm to 40cm which is more than that (17.47%) from Ocm to 20cm, phosphorus application (34.65%) from 40cm to 60cm & more than that (31.2%) from 20cm to 40cm which is more than that (25.16%) high stratification from Ocm to 20cm, Nitrogen application is 40.6%, it is more than that (7.23%) from 20cm to 40cm, is more than that (15.92%) from 40cm to 60cm, phosphorus application from Ocm to 20cm is 33.75% it is more than that (3.01%) from 20cm to 40cm, also more than that (9.06%) nitrogen application is 28.33%, it is less than-that (5.52%) from 20cm to 40cm, also less than that (10.04%) from 40cm to 60cm; phosphorus application is 38.35% from Ocm to 20cm, it is less than that (1.95%) from 20cm to 40cm, also less than that (4.12%) from 40cm to 60cm.(3) From the stooling stage to anthesis root-crown ratio on surface nitrogen and phosphorus application is higher than that in deep stratificatio... |
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