| In wheat-maize double cropping system of Huanghuai region, the increase of wheat grain is not proportional to the resource investment nowadays, and it had caused a lot of problems such as the declining nutrient efficiency, eutrophic water, atmospheric pollution, soil acidification, and low utilization level of light and temperature resources. In this research, the main wheat varieties in Huanghuai region, AK 58 and ZM 22, were chosen as the experimental materials. We studied the effects of plant density and nitrogen fertilizer on the growth characters of winter wheat, nitrogen absorption, translocation and utilization to seek the best fertilizer and density combinations to make the best use of nitrogen in farmland ecosystem. The main results were listed as follows:1. During the growth process of wheat, plant density could affect group photosynthetc through changing the structure of crop group, while nitrogen application could improve group quality through the increase in individual quality, which also had a compensation effect on density at late growth stage. When the level of nitrogen was in 0-240 kg·hm-2, plant height, populationsize, ear bearing tiller, population leaf area index, the flag leaf chlorophyll content and net photosynthetic rate of AK 58 and ZM 22 had significantly increased with more nitrogen applicated, and delay the declining rate of population leaf area index, and maintain higher net photosynthetic rate to increase grain yield. When N was 360 kg·hm-2, spike number was higher, and grain number per spike was lower, while the higher spike number could not compensate for the reduction of grain yield caused by lower grain number per spike. The plant height, populationsize, and leaf area index of AK 58 and ZM 22 increased along with the increasing density, while net photosynthetic rate decreased.2. The total N in soil declined along with the wheat growth period. N content in plant increased along with the wheat growing period and also increased with the increasing of nitrogen application. The total N in soil- plant system at mature stage decreased significantly than before, and the largest amount of N loss was in N3(360 kg?hm-2), then N0 followed, the least amount of N loss was in N1(120 kg?hm-2) and N2(240 kg?hm-2). It showed that the N loss of excessive nitrogen or nitrogen deficiency conditions were most serious. N loss became more serious with the increasing of density.3. N accumulation and translocation of leaves and stem sheaths of AK 58 and ZM 22 in flowering and mature period decreased with the decline in canopy and increased along with nitrogen application. N translocation and contribution to grain of leaves and stem sheaths decreased with the decline of wheat canopy level. Nitrogen translocation rates of spike stalk and shell, flag leaf, the 2nd from upper leaf, the 3rd from upper leaf and the first upper internode, the 2nd upper internode, the 3rd upper internode were over 50%. Increasing the amount of nitrogen application could effectively improve the translocation rate of residue internode and residue internode. The N accumulations of bottom leaves(the 4th from flag leaf and residue leaf) and stem sheath(the 4th upper internode and residue internode) of AK 58 and ZM 22 in flowering and mature period were the highest under M3(525×104 basis seedlings·hm-2) and M2(375×104 basis seedlings·hm-2) treatment. Nitrogen translocation capacity, translocation rate and contribution rate of AK 58 were best in M3(525×104 basis seedlings·hm-2) within the level of 0-240 kg?hm-2 and in M2(375×104 basis seedlings·hm-2) under 360 kg?hm-2. While nitrogen translocation capacity, translocation rate and contribution rate of ZM 22 were best in M3(525×104 basis seedlings·hm-2) without N and M2(375×104 basis seedlings·hm-2) within level of 120-360kg?hm-2.4. Appropriate increasing fertilization could significantly improve the translocation of N from vegetative organs to grain and N assimilation after flowers. The N translocation of AK 58 from vegetative organs to grain was the highest in N2(240 kg?hm-2) and N3(360 kg?hm-2), while that of ZM 22 was the highest in N2(240 kg?hm-2). The nitrogen assimilation of AK 58 and ZM 22 after flowers was both the highest in N3(360 kg?hm-2). The contribution rate of accumulated nitrogen before flowering was 54.50%~98.31%. N harvest index of grain was 64.66%~79.90% and decreased as the application of nitrogen increased. The nitrogen nutrient utilization rate, nitrogen partial fertilizer productivity and nitrogen agronomic efficiency were the highest in N1(120 kg?hm-2). The differences of AK 58 and ZM 22 in nitrogen partial fertilizer productivity and nitrogen agronomic efficiency were not significant in different densities.5. The grain yield of AK 58 and ZM 22 with N treatments was 3.76 ~5.60 times of treatments without N. The grain yield and net income of AK 58 and ZM 22 were the biggest in 360 kg N?hm-2、375×104 basis seedlings·hm-2 and 240 kg N?hm-2、225×104 basis seedlings·hm-2, respectively. The maximum grain yield was 10997 kg?hm-2 and 11472 kg?hm-2, respectively.From the perspective of nitrogen utilization and grain yield, the best combination of nitrogen and density of AK 58 and ZM 22 were 360 kg?hm-2、375×104 basis seedlings·hm-2 and 240 kg?hm-2、225×104 basis seedlings·hm-2, respectively. |
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