Effects Of Different Cultivation Models And Fertilizer Placemrent On Uptake And Mobilization Of Carbon, Nitrogen And Phosphorus In Winter Wheat

Both water shortage and nutrient deficiency are the important factors which limit agricultural production in rain-fed area. Rainfall harvesting and the mulching could improve the rainfall use efficiency. Ridge and furrow planting (RF) and ridge film mulching planting (RFM) have been regarded as effective approaches to conserve soil water and increase crop yield in dryland area. But little information was available about the rule of accumulation and mobilization of dry matter in different plant growth stages, and the nitrogen and other nutrients uptake by the plant and mobilization during the filling stage, and the relationship between individual and groups of winter wheat under RF and RFM etc systems. Therefore, the field trials were conducted from 2004 to 2006 at the Agricultural Experimental Station of Northwest A&F University, Yangling, Shaanxi province, China. It is a sub-humid area susceptible to drought, and the soil is classified as Eum-Orthic Anthrosol. The variety of winter wheat, Xiaoyan22, was planted with three cultivation models including conventional cultivation (CC), RF, and RFM systems. Two fertilization methods were adopted under the condition of ridge-furrow. One was conventional method (RFC) and the other was fertilizer placement under ridge (FPR). The objective of this study was to provide the academic and practical bases to higher yield and better quality and more benefit cultivation and optimal fertilization for winter wheat in rain-fed area of north China. The main results obtained from the experiments are as follows:1.In this study, RF could not increase yield due to lower colony density and leaves area index compared with CC and RFM. But it was beneficial to promote plant growth and the nutrients uptake by the plant of winter wheat of RFM. It also delayed senescence of the plant and kept longer duration of photosynthetic function of top three leaves in grain filling stage, so the yield was increased significantly by RFM. In 2004-2005, the outputs were 4743.24 kg hm-2 and 4396.11 kg hm-2 respectively with conventional fertilization and placement under ridge in the RFM, 29% and 8% increase compared with RF, and 10% and 2% compared with CC. In 2005-2006, the yields were 5407.45 kg hm-2 and 5134.32 kg hm-2, 20% and 4 % increase compared with RF, and 10% and 4% increase compared with CC. The output of fertilizer placement under ridge was 11% and 10 % higher than those of conventional fertilization respectively in the RF treats in 2004 and 2005, but they were lower than those of conventional fertilization in the RFM treats in two years'trials.2. The contribution of mobilization of the temporal reserves in vegetative organs before anthesis to seeds was 30%-40%, and the contribution of photosynthate after flower was 60%～70%. Among all organs, stem, leaf sheath , Chaff and rachis had higher dry matter in the anthesis stage, and the contribution of the dry matter stored in stem to grain was largest among all organs, ranged from 14%～21%. N and P fertilization could increase the dry matter accumulation of wheat leaves significantly compared with no fertilizer (CK). The rate of mobilization of three top leaves and their contribution to grain were higher than that of rest leaves. The biomass (Dry matter) of leaves, stems, sheathes of plant with RFM treat were significantly higher than RF, and RFM also increased the grain weight. RFC had a higher assimilation rate than that of FPR under RFM during filling stage. But there was no consistent tendency under CC and RF in two years due to different climate condition.3. Under the conditions of the tests, about 57%～84% of N in the grains came from mobilization of the N accumulated in vegetative organs, and the contribution of N uptake after anthesis were ranges from 16% to 43%. Although the contribution of N mobilization played an important role in grain N, the grain N harvest was related to N uptake after anthesis. The more N uptake by the plant post anthesis, the more grain N harvest. N fertilization increased N accumulation rate in different organs, and so enhanced the total N accumulation in shoot at anthesis and maturity stage. It also stimulated the mobilization of stored N. Leaves were the largest amount of N pool among all vegetative organs, and the contribution of the mobilization of stored N in leaves to grain was also the largest. The N accumulation amount in top second leaf were more than rest leaves. Although N accumulation amount in shoot under RF was significantly lower than CC at anthesis, RF could obviously increase the amount of N accumulation in shoot and grain at maturity compared with CC, largely due to its more N absorption after anthesis. There was more N accumulation in shoot and grain of RFM than that of CC. The contribution of post-anthesis N assimilation to grain N in RF was higher than that in CC, but the amount of N translocation from vegetative organs to grain was lower in RF compared with CC. RFM could not only increase post-anthesis N assimilation, but also stimulate the mobilization of stored N in vegetative organs to grain. Under RFM condition, the grain N harvest of RFC were higher than that of RPF significantly with an increase of 2.87 mg stem-1 and 3.83 mg stem-1 in 2004～2005 and 2005～2006 respectively.4. The contribution of stored P in vegetative organs to grain was about 59%～96%,and the percentage of P absorption after anthesis was 4%～61%. There were more P in stem, chaff and rachis at anthesis, and so the mobilized P of stem or chaff and rachis had higher contribution to the seed. The second leaf had a higher P accumulation and the higher contribution to grain than other leaves. RF decrease P accumulation amount in shoot compared to CC at anthesis stage, but RF could increase the amount of P accumulation in shoot and grain at maturity largely due to the increase of P absorption amount during filling stage. Compared with RF, there was more P accumulation in leaves under RFM, and RFM also stimulated the stored P mobilization in filling stage. P accumulation amount in shoot under RFM was significantly higher than CC and RF at anthesis and maturity stage, and so RFM could remarkably increase the grain P harvest at maturity compared with that in CC and RF. In addition, RFC promoted the mobilization of temporary stored P, but FPR had a higher P assimilation rate and higher contribution to grain than RFC after flowering.5. After winter wheat harvest, residual nitrate were found in 0-200 cm soil profiles. There was no great deal of nitrate leached into deep soil in the most treats, but a small quantity of nitrate accumulated in deep layer in furrow and CC in 2005～2006 due to higher rainfall. The content of residual nitrate decreased as soil depth increases. The different cultivation models resulted in different horizontal distribution of nitrate in soil profiles. The nitrate accumulated in the ridge of soil was significantly higher than that in the furrow through 0-40cm, but there were no significant differences between ridge profile and furrow profile below 60cm. The nitrate content of ridge at the depth of 0-20cm of RFM was higher than that of RF under conventional fertilization, but at the depth of 20-40 cm of RFM was lower than that of RF. It showed that RFM was benefit to reserve the nitrate in the surface layer of soil, but the nitrate of ridge under RF had a trend to leach into deeper layer. 6. There were significant residual effect on summer maize of next season when N and P fertilizers were applied heavily to winter wheat under different cultivation models, and the effect of RPF was greater than RFC under same cultivation models.