In order to reveal the impact of various fertilization strategies on carbon（C） and nitrogen（N） accumulation and allocation in corn（Zea mays L.）, corn was grown in the fields where continuous fertilization management had been lasted about 18 years at two sites located in Central and Northeast China（Zhengzhou and Gongzhuling）, and biomass C and N contents in different organs of corn at harvest were analyzed. The fertilization treatments included non-fertilizer（control）, chemical fertilizers of either nitrogen（N）, or nitrogen and phosphorus（NP）, or phosphorus and potassium（PK）, or nitrogen, phosphorus and potassium（NPK）, NPK plus manure（NPKM）, 150% of the NPKM（1.5NPKM）, and NPK plus straw（NPKS）. The results showed that accumulated C in aboveground ranged from 2 550–5 630 kg ha^–1 in the control treatment to 9 300–9 610 kg ha^–1 in the NPKM treatment, of which 57–67% and 43–50% were allocated in the non-grain organs, respectively. Accumulated N in aboveground ranged from 44.8–55.2 kg ha^-1 in the control treatment to 211–222 kg ha^–1 in the NPKM treatment, of which 35–48% and 33–44% were allocated in the non-grain parts, respectively. C allocated to stem and leaf for the PK treatment was 65 and 49% higher than that for the NPKM treatment at the both sites, respectively, while N allocated to the organs for the PK treatment was 18 and 6% higher than that for the NPKM treatment, respectively. This study demonstrated that responses of C and N allocation in corn to fertilization strategies were different, and C allocation was more sensitive to fertilization treatments than N allocation in the area.
Soil organic carbon （SOC） and soil Olsen-P are key soil fertility indexes but information on their relationships is limited particularly under long-term fertilization. We investigated the relationships between SOC and the percentage of soil Olsen-P to total P （PSOPTP） under six different 15-yr （1990-2004） long-term fertilizations at two cropping systems in northern China. These fertilization treatments were （1） unfertilized control （control）; （2） chemical nitrogen （N）; （3） N plus chemical P （NP）; （4） NP plus chemical potassium （NPK）; （5） NPK plus animal manure （NPKM） and （6） high NPKM （hNPKM）. Compared with their initial values in 1989 at both sites, during the 1 lth to 15th fertilization years annual mean SOC contents were significantly increased by 39.4-47.0% and 58.9-93.9% at Gongzhuling, Jilin Province, and Urumqi, Xinjiang, China, under the two NPKM fertilizations, respectively, while no significant changes under the no-P or chemical P fertilization. During the 1 lth to 15th fertilization years, annual mean PSOPTP was respectively increased by 2.6-4.2 and 5.8-14.1 times over the initial values under the two chemical P fertilizations and the two NPKM fertilizations, but was unchanged in their initial levels under the two no-P fertilizations at both sites. Over the 15-yr long-term fertilization SOC significantly positively correlated with PSOPTP （r^2=0.55-0.79, P〈0.01）. We concluded that the combination of chemical P plus manure is an effective way to promote SOC accumulation and the percentage of soil Olsen-P to total P at the two mono-cropping system sites in northern China.
Upland red soils have been identified as major CO2 and N2O sources induced by human activities such as fertilization. To monitor characteristics of soil surface CO2 and N2O fluxes in cropland ecosystems after continuous fertilizer applications over decades and to separate the respective contributions of root and heterotrophic respiration to the total soil CO2 and N2O fluxes, the measurements of soil surface CO2 and N2O fluxes throughout the maize growing season in 2009 were carried out based on a fertilization experiment （from 1990） through of the maize （Zea mays L.） growing season in red soil in southern China. Five fertilization treatments were chosen from the experiment for study： zero-fertilizer application （CK）, nitrogen-phosphorus- potassium （NPK） fertilizer application only, pig manure （M）, NPK plus pig manure （NPKM） and NPK with straw （NPKS）. Six chambers were installed in each plot. Three of them are in the inter-row soil （NR） and the others are in the soil within the row （R）. Each fertilizer treatment received the same amount of N （300 kg ha-1 yr-1）. Results showed that cumulative soil CO2 fluxes in NR or R were both following the order： NPKS〉M, NPKM〉NPK〉CK. The contributions of root respiration to soil CO2 fluxes was 40, 44, 50, 47 and 35% in CK, NPK, NPKM, M and NPKS treatments, respectively, with the mean value of 43%. Cumulative soil N2O fluxes in NR or R were both following the order： NPKS, NPKM〉M〉NPK〉CK, and soil N2O fluxes in R were 18, 20 and 30% higher than that in NR in NPKM, M and NPKS treatments, respectively, but with no difference between NR and R in NPK treatment. Furthermore, combine with soil temperature at -5 cm depth and soil moisWxe （0-20 cm） together could explain 55-70% and 42-59% of soil CO2 and N2O emissions with root interference and 62- 78% and 44-63% of that without root interference, respectively. In addition, soil CO2 and N2O flUXeS per unit yield in NPKM （0.55 and 0.10 kg C t^-1） and M （0.65 and 0.13 g N t^
农田土壤碳库对缓解气候变化、保证粮食安全具有重要作用。日益加剧的气候变化对农田土壤有机碳库演变的潜在影响受到广泛关注。全球气候变化所带来的温度、降雨和大气二氧化碳(CO2)浓度的改变,会通过影响净初级生产力(NPP)、外源碳投入和有机碳分解速率等因素改变生态系统碳循环过程。另外,气候变化也会通过改变土地利用方式和种植制度等农业措施改变生态系统碳循环。综述国内外农田土壤碳库演变对气候变化影响的研究成果表明,到21世纪末,中国气温将会升高3.9—6.0℃,降水有望增加9%—11%。至2050年,气温和降水的变化会造成中国农田系统碳投入相比1980年降低2.3%—10%(小麦、玉米和水稻平均值)。相反,在综合考虑CO2浓度升高的协同作用后,2050年中国农田系统碳投入相比1990年前将会增加13%—22%(平均年增长率0.2%—0.4%)。模型预测显示,至2020、2050和2080年,中国旱地0—30 cm土层有机碳在CO2低排放情景下分别会损失2.7、6.0和7.8 t C·hm-2,在CO2高排放情景下分别会损失2.9、6.8和8.2 t C·hm-2,大概占1980年农田土壤碳的4.5%、10.5%和12.7%。综合碳投入和排放对农田土壤碳库的整体影响来看,21世纪末期中国农田土壤有机碳库含量较1980年会下降10%左右,但如果采取相应的管理措施,可有效抑制农田土壤碳库的降低甚至提高,如农田系统碳投入以每年1%的速度增加时,土壤碳库会在21世纪末增加两倍。目前的研究结果显示,气候变化是否会强烈影响农田土壤碳库依然有很大的不确定因素,其对固碳效应正面和负面影响相互抵消后成为碳源还是碳汇说法不一。因此,在采取缓解气候变化、增加农田土壤固碳的措施的同时,还需加强农田土壤碳库未来变化趋势的研究和探索,为中国政策框架的决定以及未来气候变化谈判提供可靠的科学依据。
